Color profile: Disabled Composite Default screen

3 Infectious Diseases of Coldwater Fish in Marine and Brackish Water

Michael L. Kent1,* and Trygve T. Poppe2 1Department of Fisheries and Oceans, Biological Sciences Branch, Pacific Biological Station, Nanaimo, British Columbia V9R 5K6, Canada; 2Department of Morphology, Genetics and Aquatic Biology, The Norwegian School of Veterinary Science, PO Box 8196 Dep., N-0033 Oslo, Norway

Introduction transferred with them to sea cages. Brown and Bruno (Chapter 4) deal with these Salmonids are the primary fishes reared in freshwater diseases, and our emphasis is cold seawater netpens. This component of infectious diseases that are contracted after the industry produces approximately transfer to sea cages. − 500,000 t year 1 on a worldwide basis. The principle species reared in netpens are Atlantic salmon (Salmo salar), coho Viral Diseases salmon (Oncorhynchus kisutch), chinook salmon (Oncorhynchus tshawytscha) and Several viruses are important pathogens of rainbow trout (Oncorhynchus mykiss). salmonid fishes, particularly during their Additional species include minor produc- early development in fresh water (Wolf, tion of Arctic char (Salvelinus alpinus), 1988). Viral diseases of fishes have histori- Atlantic cod (Gadus morhua), haddock cally been of great concern to fish health (Melanogrammus aeglefinus), Atlantic managers because they can cause high mor- halibut (Hippoglossus hippoglossus) and tality. In addition, the presence of certain Atlantic wolffish (Anarhichas lupus). The viruses in a fish population causes eco- purpose of this chapter is to review the most nomic hardships to fish farmers due to important infectious diseases affecting fish restrictions on transfer or sale of these fish. reared in cold seawater netpens. At least six viral diseases are of concern for The problems in controlling water pen-reared salmon: these include infectious flow make it difficult, if not impossible, to haematopoietic necrosis (IHN), infectious exclude pathogens in the water column from pancreatic necrosis (IPN), salmon pancreas netpens. Therefore, marine pathogens are disease (SPD), infectious salmon anaemia among the most important causes of diseases (ISA), salmonid herpesvirus 2 infections in seawater netpens. As salmonids are and erythrocytic inclusion body syndrome reared in fresh water before they are held (EIBS). The erythrocytic necrosis virus has in seawater, freshwater pathogens may be the potential to infect salmon in seawater,

* Current address: Center for Fish Disease Research, Department of Microbiology, Oregon State University, Corvallis, OR 97331, USA. ©CAB International 2002. Diseases and Disorders of Finfish in Cage Culture (eds P.T.K. Woo, D.W. Bruno and L.H.S. Lim) 61

71 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 12, 2002 3:08:47 PM Color profile: Disabled Composite Default screen

62 M.L. Kent and T.T. Poppe

but has yet to be recognized as a serious are much larger than their counterparts in problem. At least one form of plasmacytoid fresh water, IHN in Atlantic salmon reared in leukaemia is associated with a retrovirus, seawater is usually chronic. Infected salmon but this disease is described under the also often exhibit frank haemorrhages in the section on Nucleospora salmonis. Cardiac visceral cavity. As with the freshwater form myopathy syndrome (CMS) has recently of the disease, IHN is best managed by avoid- been associated with a nodavirus, and is ance. There is circumstantial evidence to thus covered in this section. IHN, IPN and suggest a marine reservoir is the primary EIBS are also important diseases in fresh source of the infection for outbreaks in sea- water, and are dealt with in more depth water netpens. If this were the case, then in Chapter 4. However, the manifestations avoidance of the infection in netpens would of IHN and IPN as they occur in seawater be very difficult. Marine-phase chinook are described. Furthermore, viruses have salmon may harbour the virus for several caused disease in farmed Atlantic halibut months with no signs of the disease, and the and turbot larvae, resulting in considerable virus has been found in healthy chinook losses (Bloch et al., 1991; Grotmol et al., reared at netpen farms that have experienced 1995; Wood et al., 1996). However, to date, IHN outbreaks in Atlantic salmon (St-Hilaire specific viral diseases of non-salmonids et al., 2001). Therefore, chinook salmon may reared in coldwater sea cages have not been act as a subclinical reservoir for the virus identified as serious problems. Vacuolating when they are reared with Atlantic salmon. encephalopathy and retinopathy (VER) is a disease primarily of larval or juvenile marine fishes, but may be carried into Infectious pancreatic necrosis cage-cultured flatfish. This nodavirus is dealt with in Chapter 9. This is a freshwater viral disease (see Chapter 4) that causes mortality in sea cage culture. The infection is prevalent in Infectious haematopoietic necrosis in netpens pen-reared Atlantic salmon in Norway (Krogsrud et al., 1989). For many years, The first confirmed report of IHN in pen- the virus was extremely widespread in reared Atlantic salmon occurred in 1992 in Norwegian sea sites (Melby et al., 1991) British Columbia (Armstrong et al., 1993; without causing clinical disease. However, Traxler et al., 1993). Since this initial find- in recent years clinical IPN has impacted ing, IHN has been reported at many netpen on sea-farmed Atlantic salmon culture and farm sites and has become a major disease is considered as an emerging problem in concern on Atlantic salmon farms in the Chapter 9. Most outbreaks occur from a Quadra Island region of British Columbia. few weeks up to a couple of months after The existence or establishment of marine transfer to seawater (Jarp et al., 1994), but hosts or reservoirs of IHN virus (IHNV) that outbreaks up to 1 year after transfer to sea- may serve as sources of the virus at sea water may also occur (Smail et al., 1992, cage sites, and the reports of virus in 1995). IPNV may be the most important non-salmonids around netpens during an infectious disease of farmed fish in Norway, outbreak is of concern (Traxler and Richard, accounting for losses of approximately − 1996). In addition, IHNV has been found in Nkr 400 million year 1 (Christie, 1996). Pacific herring (Clupea herningus pallasi) In Scotland, significant mortality has been collected well away from infected farms associated with the infection, particularly (Kent et al., 1998). in combination with SPD. Clinical signs of IHN in Atlantic salmon Clinical signs of IPN in post-smolt in netpens are often similar to those seen Atlantic salmon may be minimal, but in infected salmonids in fresh water (see some fish stop feeding and show nervous Chapter 4). However, because affected fish distress. The most significant losses may

72 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:04 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 63

sometimes be attributed to the long-term Elston, 1987), and rarely in British effects of reduced or completely ceased feed- Columbia. ing. Fish show hyperaemia and petechial A toga-like virus has been isolated from haemorrhage in the visceral fat and in the fish with SPD (Nelson et al., 1995), and pyloric caeca. McLoughlin et al. (1996) experimentally An epizootiological study of IPN in reproduced the disease with the virus. post-smolts has shown that the risk of Therefore, the evidence is essentially con- clinical disease was related to the mixing clusive that the cause of pancreas disease is of smolts from several suppliers at the same this virus, referred to as salmon pancreas sea site (Jarp et al., 1994). A way to avoid disease virus (SPDV). SPD is contracted after this would therefore be to buy smolts from smolts are transferred to seawater. Although as few producers as possible. Smolts with not specifically associated with fresh water no history of IPN in fresh water, but with (McVicar, 1987), a similar toga-like virus has specific humoral immunity against IPNV been isolated from rainbow trout (Boucher prior to smoltification, were protected et al., 1994). against clinical IPN for up to 4 months after Fish usually exhibit clinical signs of transfer to seawater (Jarp et al., 1996). SPD about 6–12 weeks after introduction to Because IPNV can be vertically trans- netpens, but fish that have been in pens for mitted and infected fish can excrete virus as long as 2 years may be affected (McVicar, for the rest of their life, the only effective 1987). Mortality associated with the disease control method is avoidance. The use of is low. Nevertheless, surviving fish often IPNV-free broodstock, rearing progeny in show poor growth and are more susceptible virus-free water and restricting the move- to other diseases (McVicar and Munro, ment of fish are measures that can reduce 1987). the spread of IPNV. A multivalent vaccine, which includes Escherichia coli-expressed Clinical and gross pathological changes. IPNV proteins, protects pre-smolt Atlantic Affected fish are anorexic, dark in colour, salmon against natural exposure to IPN lethargic, and usually at the sides of cages (Christie, 1996). This vaccine is now and near the surface. Fish with SPD are licensed in Norway, and results from the usually emaciated (Fig. 3.1). Internal signs 1996 season were promising, as mortalities include haemorrhage in the pancreatic due to IPN were reduced considerably. tissue and fat between the pyloric caeca, or the tissue between the pyloric caeca may be severely atrophied. Salmon pancreas disease Diagnosis. Haemorrhage in tissues associ- SPD of pen-reared Atlantic salmon is an ated with the pyloric caeca in emaciated important disease in Scotland, Ireland and Atlantic salmon smolts, along with the Norway (Munro et al., 1984; Ferguson et al., absence of other infectious agents (e.g. IHN 1986; McVicar, 1987; Menzies et al., 1996). or IPN viruses, Aeromonas salmonicida or Hisological changes consistent with SPD Vibrio spp.), is indicative of SPD. Confirma- have been observed in pen-reared Atlantic tion of the disease is based on histological salmon in Washington State (Kent and changes or by isolation of SPDV from

Fig. 3.1. Emaciated Atlantic salmon post-smolts with pancreas disease.

73 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:04 AM Color profile: Disabled Composite Default screen

64 M.L. Kent and T.T. Poppe

affected fish. Isolation of the virus can be Clinical signs and gross pathology. Most achieved by co-cultivation of kidney tissues clinical cases occur during rapid tempera- on CHSE-214 cells at 15°C, and cultures are ture increases in the spring, but outbreaks blind passed after 28 days (Nelson et al., may also occur in the late autumn. Fish 1995) where the cytopathic effect (CPE) may are anorexic, lethargic, and tend to stay at be observed after about 10 days. the bottom or rest near the edges of cages. Mortality may vary from 15 to 100%. Out- Control and treatment. No treatment is breaks are usually chronic (lasting several known for pancreas disease. Reports from months), but are more acute if water tem- ° Scotland indicate that reducing stressors peratures are above 10–12 C. Affected fish (e.g. transport and handling) during the show a distended abdomen, exophthalmos, acute phase of the disease may enhance oedema and haemorrhage of the skin. Fish recovery. In addition, some farmers have are anaemic, and the gills and heart may reported that keeping fish on a smaller be extremely pale. The visceral organs are pellet size reduces anorexia and the overall congested and haemorrhage occurs in mortality associated with SPD. Recovered the perivisceral fat. In some cases the fish exhibit strong protection against rein- liver may appear extremely congested fection (Houghton, 1994), indicating that a and almost black in colour (Evensen et al., vaccine could be produced against the virus. 1991b).

Diagnosis. A diagnosis is based upon Infectious salmon anaemia characteristic gross pathology and light microscopy, anaemia and absence of patho- ISA was first observed in southwest Norway genic bacteria. Supporting diagnosis of the in 1984. During the following 10 years, the virus is achieved by culture on the salmon disease spread to most fish-farming areas head kidney cell line (SHK-1) (Dannevig along the coast, but only seawater farms et al., 1995), a polymerase chain reaction and freshwater farms that use some sea- (PCR) test (Mjaaland et al., 1997) or water have experienced natural outbreaks an enzyme-linked immunosorbent assay (Thorud and Djupvik, 1988). However, ISA (ELISA) test. can be experimentally transmitted to fish in fresh water and therefore might pose a Control and treatment. To control ISA, threat to these stocks. A virus typical of Norway has implemented strategies, includ- orthomyxoviruses has been shown to be the ing mandatory health control in smolt cause of ISA (Dannevig et al., 1995). The farms, disinfection of processing water virus is shed from infected carriers before from slaughtering facilities, separation of they develop clinical signs of the disease different year classes, isolation of infected through skin mucus, urine and faeces. Early sites from unaffected sites and fallowing of colonization of the causative virus occurs sites after infected stocks are removed. In in the pillar cells of the gills and the endo- Canada, commercially developed vaccines cardium, indicating that the gills are the to control ISA virus have been deployed. most likely port of entry (Totland et al., Recently, Jones et al. (1999) demonstrated a 1996). Natural outbreaks in fish farms are reduction in vaccinate mortality (P < 0.01) restricted to Atlantic salmon, but other using viral antigen emulsified in mineral salmonids may harbour the virus and oil in Atlantic salmon parr. Although trails may act as reservoirs (Nylund and Jakob- and licensing may be incomplete, under sen, 1995). ISA virus has been considered Canadian Regulatory Guidelines the release a Norwegian problem, but recently has of some vaccine for use in the industry is been found in Scotland, Canada and possible. Under current UKand Norwegian the USA. ISA as an emerging disease is legislation there is a restriction on the use of reviewed in Chapter 9. vaccines for ISA.

74 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:05 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 65

Salmonid herpesvirus 2 infections smolts from contaminated hatcheries; and (iv) examine fish for virus shortly after Several members of the family Herpesviri- introduction to seawater. dae are recognized as fish pathogens (Wolf, Kimura et al. (1983) reported that daily 1988). In Japan, a herpesvirus type 2 (SH-2) immersion of chum salmon in the anti- infection has caused up to 30% mortality viral compound acyclovir suppressed the in pen-reared coho salmon (Kumagai et al., growth of OMV-associated tumours. They 1994). The disease affects fish from less also found that oral treatment with another than 100 g to 1 kg, and epizootics usually anti-viral drug, IUdR, decreased mortality last from 30 to 80 days. due to the infection. Surface tumours are Certain strains of salmon herpesvirus often removed manually at harvest from fish 2 (e.g. Oncorhynchus masou virus (OMV) before they are sent to market. and yamame tumour virus (YTV)), cause liver damage in young fish in fresh water. Fish that survive the infection may later Cardiomyopathy syndrome in cage culture develop epithelial tumours in sea cages (Kimura et al., 1981a,b; Sano et al., 1983; This chronic, progressive disease has been Kimura and Yoshimizu, 1991; Yoshimizu observed since 1984 in farmed Atlantic et al., 1995). salmon in Norway and a few cases have been diagnosed in the Faroe Islands (Bruno Clinical signs and gross pathology. Affected and Poppe, 1996). The cause(s) has not been fish are dark in colour, and often have determined, but recently Grotmol et al. skin ulcers and erosion of the fins. The liver (1997) reported a nodavirus-like agent in exhibits focal pale areas, and the intestinal affected heart tissue. Although transmission tract shows erythema. Surface tumours experiments have been negative, viral appear as whitish papillomatous masses particles have been observed using elec- around the mouth, eyes, fins or gills. These tron microscopy and the lesions and tumours may also occur in the visceral epizootiology are consistent with a viral cavity (Kimura et al., 1981a,b). aetiology. The most serious losses typically occur in the autumn, 12–18 months after Diagnosis. Focal necrosis of the liver in transfer to seawater. coho salmon reared in Japan is presumptive diagnosis for the disease. Diagnosis is Clinical signs and gross pathology. Fish in achieved by isolation of the virus from the terminal stages of the disease are often affected livers on CHSE-214 or RTG-2 cell in good body condition, showing no or few lines. Syncytia formation occurs in the latter clinical signs before death. They may go (Sano et al., 1983). off their feed and swim sluggishly around for a few days before they die. Such fish Control and treatment. As with other viral frequently develop skin haemorrhage and diseases, the best method to control the oedema, exophthalmia and ascites. Typical infection is avoidance. The occurrence of findings at necropsy are fibrinous peritoni- the disease is associated with previous tis, ascitic fluid and blood clots surrounding infections at freshwater hatcheries, although the heart. The atrium and sinus venosus pen-to-pen transmission in seawater is are usually dilated and may contain blood negligible (Kumagai et al., 1997). Rainbow clots. Sometimes clotted blood may also be trout may have subclinical infections and found on the dorsocranial surface of the liver serve as reservoir hosts. Kumagai et al. (Ferguson et al., 1990). (1997) recommended the following to control the infection: (i) do not rear other Diagnosis. The diagnosis is based on the salmonids with coho salmon; (ii) disinfect characteristic gross and pathognomonic facilities after out-planting stocks; (iii) avoid histopathological lesions. Characteristic

75 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:05 AM Color profile: Disabled Composite Default screen

66 M.L. Kent and T.T. Poppe

lesions are found in the spongious myo- whereas furunculosis and myxobacteriosis cardium of the atrium and ventricle (Amin represent an increased problem for Atlantic and Trasti, 1988; Ferguson et al., 1990). salmon compared with Pacific salmon These lesions are comprised of muscular species. Almost all non-salmonid marine degeneration, proliferation of the endo- fishes are susceptible to vibriosis and furun- cardial cells with macrophage infiltration culosis. Typical furunculosis is caused and lymphocytes subendocardially and in by A. salmonicida subsp. salmonicida. The the degenerated muscle. Blood clots are fre- atypical strain of A. salmonicida is usually quently found in the atrium. Focal necrosis the aetiological agent of furnuculosis in in the hepatic parenchyma may also occur. non-salmonid marine fishes. Diseased fish may also be diagnosed by means of ultrasound imaging (Sande and Poppe, 1995). CMS bears little resemblance Vibriosis to other diseases, but haemopericardium may be observed in fish dying from other Vibriosis is a systemic disease that affects diseases. many marine fishes and invertebrates (Anderson and Conroy, 1970; Colwell and Control and treatment. There are differ- Grimes, 1984; Egidius, 1987). Frerichs and ences in susceptibility to CMS between fish Roberts (1989) considered vibriosis to be families, and selective breeding may be a the most significant disease in wild and possibility for controlling this infection in cultured marine and brackish water fishes. the future. Fallowing of sites for a year or two V. anguillarum accounts for most of the before new fish are introduced into problem outbreaks of vibriosis in farmed salmon areas has reduced the problem considerably. worldwide, and also causes disease in Atlantic cod. V. ordalii occasionally causes disease in salmonids reared in the Pacific Bacterial Diseases Northwest and in New Zealand (Evelyn, 1971; Harrell et al., 1976; Novotny, 1978; A number of bacterial diseases cause Schiewe et al., 1981; Wards et al., 1991). serious and recurring losses in pen-reared Diseases caused by other Vibrio spp. salmon and other coldwater fishes. Some include coldwater vibriosis or Hitra disease, important bacterial diseases, such as bacte- caused by V. salmonicida, and winter ulcer rial kidney disease (BKD), furunculosis and disease caused by M. viscosa. The latter is yersiniosis, primarily occur in fresh water considered as an emerging problem and is and are dealt with in Chapter 4. Important discussed in Chapter 9. bacterial infections on sea pens include: V. anguillarum strains show hetero- typical vibriosis, caused by Vibrio geneity in both phenotypic (Tajima et al., anguillarum and Vibrio ordalii; coldwater 1985) and serotypic (Kitao et al., 1984; vibriosis or Hitra disease caused by Vibrio Tajima et al., 1985; Sorensen and Larsen, salmonicida; ‘winters ulcers’ caused by 1986) characteristics. The strains of V. Moritella viscosa (Vibrio viscosus); anguillarum that cause vibriosis in pen- myxobacteriosis, caused by Cytophaga– reared salmon worldwide represent only Flexibacter spp.; and salmonid rickettsial one or two serotypes (based on the ‘O’ septicaemia or piscirickettsiosis, caused by antigens present), which simplifies the Piscirickettsia salmonis. All salmon species formulation of anti-vibriosis vaccines for reared in netpens are susceptible to these controlling the disease. Vibriosis caused bacterial diseases, but some diseases are by V. anguillarum usually occurs between more problematic in certain species and 15 and 21°C, and most outbreaks occur in particular areas. For example, chinook, smolts during their first summer in seawater. coho and sockeye salmon appear to be more Vibriosis in the Pacific Northwest is mainly susceptible to BKD than Atlantic salmon, a problem of Pacific salmon (e.g. chinook

76 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:05 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 67

and coho), although Atlantic salmon are also Clinical signs and gross pathology. In small susceptible to the infection. Interestingly, fish, mortality caused by vibriosis may be all cases of vibriosis due to V. ordalii in high and rapid, and these fish may exhibit pen-reared salmon reported to date have no gross pathological changes other than involved Pacific salmon in Japan and the darkening and lethargy. Typical of bacterial Pacific coast of the USA (Schiewe et al., septicaemias, fish with vibriosis may exhibit 1981). erythema at the base of the fins, petechiae Coldwater vibriosis is a bacterial in the skin and haemorrhage on the body septicaemia caused by the psychrophilic surface. Fish may also exhibit bilateral bacterium V. salmonicida. Since its first exophthalmia and frayed fins. Haemor- occurrence in farmed Atlantic salmon in rhagic abscesses in the muscle are often seen northern Norway in 1977 (Egidius et al., in Atlantic salmon with vibriosis in Europe. 1981), coldwater vibriosis has been diag- Congestion and petechiae are usually nosed in most fish-farming areas, as well as evident in visceral organs, particularly in in salmon-producing countries surrounding the gut and liver. Large multiple coalescing the North Atlantic (Bruno et al., 1986), haematomas in the liver (peliosis hepatis) including eastern Canada and the USA are often seen in vibriosis caused by V. (O’Halloran and Henry, 1993). The condi- anguillarum. Affected fish also exhibit tion is also known as ‘Hitra disease’ after pallor of the gills (due to anaemia) and severe outbreaks occurred in the Hitra region enlargement of the spleen and kidney. of Norway in the early 1980s. The disease is Clinical signs of coldwater vibriosis usually most severe at low temperatures may be non-specific, but usually include during the winter months, but may occur lethargy and cessation of feeding. Affected throughout the year. Environmental stress- fish turn dark, exhibit exophthalmos, a ors and poor nutrition may predispose swollen vent and pinpoint haemorrhage fish to coldwater vibriosis. Although the along the belly and at the base of the pecto- bacterium may cause disease in other ral, pelvic and anal fins. The gills are usually fish, such as Atlantic cod (Jøtorgensen et al., pale. Internally, ascites and petechial haem- 1989), serious losses occur mainly in Atlan- orrhage in the perivisceral fat, pyloric caeca, tic salmon. Schroder et al. (1992) showed peritoneal surfaces, liver and swimbladder in experimental studies that cod are more are typical findings (Figs 3.2 and 3.3). The resistant to the bacterium than salmon. latter may be filled with a blood-tinged fluid

Fig. 3.2. Atlantic salmon with coldwater vibriosis. Note multiple haemorrhage in the liver.

77 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:06 AM Color profile: Disabled Composite Default screen

68 M.L. Kent and T.T. Poppe

Fig. 3.3. Vibrio salmonicida infection in Atlantic salmon. Note petechial haemorrhage in the perivisceral fat between the pyloric caeca.

and the liver typically has a yellowish dis- 22°C. In contrast, V. anguillarum and V. coloration. In chronic cases, skin ulceration, ordalii will grow at about 25°C. The bacteria fin rot, a pseudomembranous peritonitis and can be distinguished using biochemical tests epicarditis may also be found. The spleen (Schiewe et al., 1981; Holm et al., 1985; usually has a colour slightly lighter than nor- Tajima et al., 1985; Scalati and Kusuda, mal. In cod, the pathological changes are 1986). API-20E test strips (Analytab Co., rather diffuse and non-specific, but keratitis Plainview, New York, USA) can be used for is frequently seen. rapid identification of marine vibrios from fish (Kent, 1982; Grisez et al., 1991). These Diagnosis. For typical vibriosis, presump- bacteria can also be identified serologically tive diagnosis is by macroscopic examina- using slide agglutination tests. tion if the characteristic haematomas in With V. salmonicida, microscopical the liver are present. The causative Gram- demonstration of the bacterium in Giemsa- negative bacilli are usually easy to detect stained smears or paraffin sections, or by in Gram-stained kidney smears. The highly immunohistochemistry (Evensen et al., motile bacteria are also detectable in fresh 1991a) is useful for locating the organism in preparations of blood or in wet mounts of tissues. However, immunofluorescence tests the kidney or spleen, or in lesions. The other applied directly to tissues infected with V. gross and clinical changes are not specific to anguillarum are not useful for rapid diagno- vibriosis and are associated with a number of sis of this bacterium. Apparently salmonid bacterial or viral systemic diseases. tissues contain substances that block recep- A diagnosis is based on culture and tor sites on the vibrios that would normally identification of the causative organism react with the vibrio-specific antibodies from the kidney of infected fish. Both in the diagnostic antisera (T.P.T. Evelyn, V. anguillarum and V. ordalii are easily cul- Pacific Biological Station, Nanaimo, British tured on tryptic soy agar with 1.5% NaCl or Columbia, personal communication). on marine agar (Difco) at room temperature. Bacterial colonies are round, raised and Control and treatment. Vibriosis is best off-white in colour. V. ordalii and V. salmon- conrolled by prevention, and commercial icida grow more slowly than V. anguillarum vaccines are available. With salmonids, and form smaller colonies. Optimum growth vaccination is best carried out on fish that temperature for V. salmonicida is from 12 to have attained immunocompetent size (at 16°C and growth will occur between 0 and least 5–10 g) and before they are introduced

78 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:06 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 69

to netpens. The vaccines are conveniently outbreaks and it is therefore important to administered by immersion methods, and isolate diseased fish from healthy fish (Enger if applied properly, they afford excellent et al., 1989) and to remove dead and mori- protection (Evelyn, 1984, 1988). Some farms bund fish from the cages. revaccinate fish shortly after introduction to netpens, and results with revaccination in seawater have been promising. Revaccina- tion should, however, be conducted with Marine myxobacteriosis caution because the handling of fish shortly after their introduction to seawater is Cytophaga and Flexibacter spp. (commonly very stressful. The most recent trend is to referred to as ‘myxobacteria’ or ‘gliding administer the vaccine by intraperitoneal bacteria’) are important bacterial pathogens injection, usually in combination with other of cultured fishes and usually cause vaccines, e.g. with furunculosis vaccines, external lesions in freshwater and marine which are most effective when injected. species (Anderson and Conroy, 1969; Pacha Vaccines for controlling vibriosis in cod and Ordal, 1970). In marine aquaculture, are also promising for protecting against V. infections by Flexibacter maritimus have anguillarum (Espelid et al., 1991; Groman been observed in Japanese flounder et al., 1992) and V. salmonicida (Schroder (Paralichthys olivaceous) and seabreams et al., 1992). (family Sparidae) in Japan (Masumura and Antibacterial drugs (e.g. oxytetracy- Wakabayashi, 1977; Hikida et al., 1979; cline, potentiated sulphonamides, quino- Wakabayashi et al., 1984, 1986; Baxa et al., lones and florfenicol) incorporated in feed 1986, 1987) and Europe (Bernardet et al., are available for treating vibriosis. Treat- 1990). In Tasmania, Handlinger et al. (1997) ment is usually efficacious if the infection is identified F. maritimus associated with skin recognized early when fish are still actively and gill lesions in pen-reared Atlantic feeding, and if care is taken to select a drug to salmon and rainbow trout. Myxobacteria which the pathogen is sensitive. However, in that have not been precisely identified have some countries not all of the drugs have been been associated with skin lesions in sea- approved for use in fish intended for human water-reared salmonids for many years consumption. Thus, control of vibriosis (Borg, 1960; Rucker et al., 1963; Anderson should be conducted primarily through a and Conroy, 1969; Wood, 1974; Sawyer, vaccination programme. 1976). These bacteria have at times been V. salmonicida is not considered to be a identified as Sporocytophaga spp. How- highly pathogenic bacterium and significant ever, the presence of microcysts (an impor- exposure is required to infect fish. As with tant diagnostic feature of this genus) has not other diseases, optimization of the environ- been clearly demonstrated in these isolates. ment and reduction of stressors, particularly Proper taxonomic identifications have during the winter months, are important not been conducted on many Cytophaga and measures to avoid outbreaks. Multivalent Flexibacter spp. that have been associated vaccines protecting against furunculosis, with disease in marine fishes. However, to vibriosis and coldwater vibriosis give date, marine Cytophaga and Flexibacter excellent protection provided the vaccina- species have not been transferred to Flavo- tion programmes are carried out in a proper bacterium (Bernardet et al., 1996), as was manner (e.g. fish are vaccinated at an proposed for certain freshwater species. Fish appropriate size and given adequate time health workers and aquaculturists usually to develop immunity before exposure). Nev- refer to these bacteria as ‘myxobacteria’. ertheless, outbreaks do occur in properly This is technically incorrect because these vaccinated fish, particularly in northern bacteria belong to the order Cytophagales, Norway. Although the bacterium occurs and not to the order Myxobacteria. It would, commonly in the water and sediments close therefore, be more appropriate to refer to to cages, its numbers escalate during the marine forms using collective terms such

79 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:07 AM Color profile: Disabled Composite Default screen

70 M.L. Kent and T.T. Poppe

as ‘cytophaga–flexibacter-like bacteria’ or appears to be a seasonality, and fish ‘gliding bacteria’. However, to remain con- introduced later in the spring and summer sistent with the common terminology and to usually exhibit fewer body lesions. Infec- avoid confusion, reference is made to these tions are restricted to the skin and muscle. bacteria as myxobacteria in this review. Fish with large lesions apparently die from Two types of myxobacterial infections osmotic imbalance (Kent et al., 1988a). have been associated with high mortality in A particularly lethal form of myxobac- pen-reared Atlantic salmon in the Pacific teriosis occurs in the mouth of pen-reared Northwest; one type causes large body Atlantic salmon, referred to as ‘mouth rot’ ulcers, and the other causes lesions primar- by fish farmers. Infections of the mouth ily in the mouth. Myxobacteria infections and snout by myxobacteria are observed are also seen in pen-reared Pacific salmon, in post-smolt Atlantic salmon during their but are not usually associated with severe first summer in seawater. The condition has epizootics. In Pacific salmon, myxobacteria occurred at many netpen sites in the Pacific are usually associated with frayed fins and Northwest, and is often associated with erosion of the tail. high mortalities (Hicks, 1989; Frelier et al., A Cytophaga sp. causes large skin 1994). Pen-reared Arctic char have also been lesions in Atlantic salmon smolts (Fig. 3.4) afflicted with the infection. The infection shortly after transfer to seawater (Kent et al., appears to begin around the teeth. It has been 1988). Very similar skin lesions associated suggested that the infection is initiated in with F. maritimus infections were observed periodontal tissue that has been abraded by in pen-reared Atlantic salmon and rainbow feeding on spiny crustaceans such as crab trout in Tasmania (Handlinger et al., 1997). larvae and Caprella spp. amphipods. Other Lesions and associated mortalities usually potential predisposing factors suggested by peak at about 1–3 weeks after introduction, farmers that may lead to the infection are: (i) and based on our observations, the infection feeding on hard pellets; (ii) fish biting net subsides after about 3–4 weeks. There surfaces; and (iii) stress-induced lesions in

Fig. 3.4. Atlantic salmon with Cytophaga-associated skin lesions. Note severe lesion with exposure of underlying muscle.

80 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:08 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 71

the mouth. Fish farmers in British Columbia, Diagnosis. Diagnosis of myxobacterial Canada report that the condition is par- infections can usually be accomplished ticularly troublesome in waters with high by observing large numbers of filamentous salinity. Based on preliminary culture analy- bacteria in wet-mount preparations from sis, the myxobacterium from mouth lesions the lesions (Fig. 3.5). Isolation of the bacteria appears to be different from the myxo- can be accomplished by culture on either bacterium causing skin lesions. A similar Cytophaga medium made with 50% sterile myxobacterial stomatitis has been observed seawater or marine agar (Difco). Isolation in wild Atlantic cod in the North Sea (Hilger of myxobacteria in pure culture may be et al., 1991). difficult from skin lesions due to contam- ination with other faster-growing bacteria Clinical signs and gross pathology. Skin (e.g. vibrios). However, the lesions usually lesions are large, white patches on the contain large numbers of the myxobacteria caudal peduncle and the posterior region of and serial dilutions of affected tissue in the flanks when the dermis is intact. Fish sterile 50% seawater facilitates the isolation with more severe lesions have areas of the of the myxobacteria in pure culture. skin completely destroyed and the under- Reichenbach (1988) has described the lying muscle exposed (Fig. 3.4). Fish with general characteristics of Cytophaga and mouth myxobacteriosis are often lethargic, Flexibacter spp. emaciated and anorexic, and some affected fish may exhibit flashing or head shaking. Treatment and control. External treatments Early in the infection, examination of the with antibiotics are often used to control mouth reveals focal, yellow bacterial mats myxobacterial infections in fresh water, around the palate and teeth, including the but such treatments are not usually vomer. The lesions may be single, but the practical in seawater netpens. These opposing surface is often affected (Frelier bacterial infections are often initiated in et al., 1994). As the disease progresses, the skin where there are abrasions. Physical affected fish show multiple ulcers in the trauma during transport of smolts may mouth with large bacterial mats overlying allow the bacteria to establish an infection. the lesions. The lesions may extend to the According to fish farmers, improved trans- branchial arches and proximal oesophagus, port techniques and careful handling of and the lower and upper jaw may be com- fish greatly reduces the prevalence of the pletely eroded in severe cases. Severely disease. There are unconfirmed reports that affected fish do not feed and hence the treating fish with oxytetracycline can con- stomach is devoid of food. trol mouth rot.

Fig. 3.5. Cytophaga bacteria in wet mount of skin lesions showing ‘myxobacteria’. Bar, 5 µm.

81 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:08 AM Color profile: Disabled Composite Default screen

72 M.L. Kent and T.T. Poppe

Salmonid rickettsial septicaemia crustaceans and molluscs around netpens, based on histology and serology. Neverthe- Piscirickettsia salmonis causes a severe less, P. salmonis survives well in seawater septicaemia in pen-reared salmon, par- (Almendras, 1996) and is easily transmitted ticularly in Chile (Branson and Neito Diaz- directly from fish to fish. Munoz, 1991; Cvitanich et al., 1991; Garcés The disease may also occur in brackish et al., 1991; Fryer et al., 1992; Almendras water, and the infection has recently been and Carmeu Fuentealba, 1997). In British reported in rainbow trout and coho salmon Columbia, the disease was first observed held in fresh water (Bravo, 1994; Cvitanich in seawater-reared pink salmon (Oncorhyn- et al., 1995; Gaggaro et al., 1995). However, chus gorbuscha), held for experimental P. salmonis does not survive in fresh water purposes, at the Pacific Biological Station away from the host (Lannan and Fryer, on Vancouver Island in 1970. More 1994). Bustos et al. (1994) conducted field recently, infections of Atlantic salmon trials that suggested that vertical transmis- with rickettsia-like organisms have been sion may occur naturally, and Larenas et al. reported from Norway (Olsen et al., 1997), (1996) detected the infection in 10% of fertil- Ireland (Rodger and Drinan, 1993) and ized ova from infected fish. This may explain Scotland (Grant et al., 1996). A PCR method its occurrence in fresh water. However, the developed by Mauel et al. (1996) for detect- poor survivability of the organism in fresh ing and identifying the pathogen showed water may explain the rarity of the infection that the isolates from Norway, Ireland, before fish are introduced to seawater. Canada and Chile were all P. salmonis;it was clear that at least two variants of the Clinical signs and gross pathology. Clinical pathogen occurred in Chile. House et al. and gross pathological changes associated (1998) showed that the strain from Chile with P. salmonis infections have been out- was more pathogenic than common strains lined by Cvitanich et al. (1991), Branson and from British Columbia and Norway. Nieto Diaz-Munoz (1991) and Brocklebank In British Columbia, the infection is et al. (1992). Affected fish are lethargic, usually coincidental with other infectious anorexic, exhibit pallor of the gills due to diseases (e.g. bacterial kidney disease) in the anaemia, are dark in colour and may swim population, but may occasionally cause near the surface. There are marked differ- epizootics in which it is the primary cause ences in clinical signs between salmonid of mortality. In contrast, piscirickettsiosis species. For example, infected rainbow trout is the most important infectious disease often do not accumulate near the surface of pen-reared salmonids in Chile, where it before they die. In Atlantic and coho salmon caused losses of around US$48 million in the nervous system is often affected, with 1995. In Chile, the disease was first recog- flashing and side swimming being common nized as a serious problem in coho salmon, in the former. Ulceration often occurs on the but it now is also common in both rainbow skin with coho salmon and rainbow trout, trout and Atlantic salmon. Several outbreaks whereas this is rare with Atlantic salmon in of the disease may occur in the same popula- Chile. However, in Norway, Atlantic salmon tion of fish during their seawater grow-out with the disease occasionally show skin period, particularly with coho salmon. lesions, e.g. raised nodules or white spots Information to date on the epizootiology (Olsen et al., 1997). of the organism suggests that it is normally The liver of affected fish may have large, acquired in seawater from a marine source. whitish or yellow, multifocal, crater-like However, a marine reservoir has yet to be lesions or nodules (Fig. 3.6). These lesions identified, although certain salmon ecto- often rupture, resulting in shallow crater- parasites may be involved in the trans- like cavities in the liver. Fish may have mission, perhaps serving as vectors (Garcés ascites, an enlarged spleen and a grey, et al., 1994). Furthermore, Cvitanich et al. enlarged kidney. The spleen is extremely (1991) found evidence of the organism in enlarged in infected pink salmon. Pallor and

82 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:08 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 73

petechiae are observed in the visceral organs (Lannan and Fryer, 1991). Further confirma- and muscle, and a whitish pseudomembrane tion includes the isolation of the organism in may cover the heart. culture using CHSE-214 cells (Fryer et al., 1990; Cvitanich et al., 1991), an indirect Diagnosis. Presumptive diagnosis can be fluorescent-antibody test (Lannan et al., achieved by observing the distinctive 1991) or using specific primers with PCR crater-like lesions and nodules in the liver, (Mauel et al., 1996). A commercial ELISA but they may not occur in many infected test for P. salmonis was developed by fish. Definitive diagnosis can be achieved by Microtek Ltd-Bayer (Sidney, British Colum- observing the organism within phagocytic bia) and used extensively by Chilean farmers cells in liver or kidney imprints stained in brood stock segregation programmes. with Giemsa, Gram or methylene blue stains (Fig. 3.7A), or in macrophages in tissue sec- Control and treatment. Various antibiotics, tions (Fig. 3.7B) along with the distinctive such as oxolinic acid, flumequine and histological changes described above. oxytetracycline, have been used to treat Acridine orange-stained tissue smears are the infection, often with limited success. In also useful for demonstrating the organism extreme cases some Chilean farmers have

Fig. 3.6. Piscirickettsiosis in salmon. Multiple, white, crater-like lesions in the liver (courtesy of P. Bustos).

Fig. 3.7. Piscirickettsia salmonis. (A) Gram-stained kidney imprint. (B) Organisms in macrophages from kidney section, stained with H&E. Bar, 10 µm.

83 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 12, 2002 3:09:08 PM Color profile: Disabled Composite Default screen

74 M.L. Kent and T.T. Poppe

had success with employing injectable treat- pen-reared rainbow trout and Atlantic ments with fluoroquinolones. The micro- salmon in Tasmania (Roubal et al., 1989; organism is intracellular, and this probably Munday et al., 1993) and Europe (Rodger contributes to the difficulties of treating and McArdle, 1996). A similar (if not identi- the disease with antibiotics. Although the cal) amoeba (identified as P. pemaquiden- role of vertical transmission is unknown, sis) was associated with severe gill disease the techniques used for preventing vertical in coho salmon reared in netpens in Wash- transmission of bacterial kidney disease (e.g. ington State and land-based seawater tanks brood stock screening) are being employed in California (Kent et al., 1988b). This in Chile with some success. species is an opportunistic pathogen that is normally free-living in seawater. Intensity and prevalence of the amoeba on fish gills Protozoa and Myxozoa varied from year to year, with infections being most prevalent in the late summer Protozoans and myxosporeans (phylum and autumn. The exact environmental Myxozoa) are some of the most important conditions or health status of the fish that pathogens of cage-reared fishes. For exam- allow the organism to proliferate on fish ple, the amoeba Paramoeba pemaquidensis gills are unknown. Presumably fish already is an important gill pathogen in cage- compromised by other diseases are more reared salmon in Australia, and the susceptible to the infection, and in Wash- flagellate Ichthyobodo (= Costia) spp. ington State many of the infected fish (see Chapter 4) and trichodinid ciliates had pre-existing diseases or smoltification infect gill surfaces of salmon and some problems (Kent et al., 1988b). marine fishes. Systemic infections by Cryptobia salmositica (see Chapter 9) and a Clinical signs and gross pathology. Heavily diplomonad flagellate similar to Hexamita infected fish are lethargic, accumulate at salmonis have caused disease in chinook the surface and have flared opercula. Exces- salmon in British Columbia. Another sive mucus is often observed on heavily diplomonad (Spironucleus barkhanus) infected gills. Focal, whitish patches may be has caused extra-intestinal infections in observed on heavily infected fish. Atlantic salmon in Norway. Four myxo- sporeans (Parvicapsula sp., M. aeglefini, Diagnosis. Paramoebiasis of salmon is diag- Kudoa thyrsites and Chloromyxum nosed by the detection of large numbers of truttae) and three microsporidians (Loma the amoebae on the gills. The organisms are salmonae, N. salmonis and Microsporidium best identified in fresh wet-mount prepara- cerebralis) infect internal organs or gills. tions of the gills. Floating and transitional Some protozoan infections are contracted forms of the amoeba on the gills are in fresh water (e.g. Cryptobia, Ichthyobodo) 20–30 µm in diameter and have several and are dealt with in Chapter 4. In the pres- digitiform pseudopodia. In wet mounts, ent chapter, the most important marine pro- amoebae will attach to the slide after about tozoan and myxosporean parasites affecting an hour, resulting in a locomotive form coldwater marine netpen culture, i.e. measuring about 20 × 25 µm. Paramoeba Paramoeba sp., K. thyrsites, extraintestinal spp. possess a unique organelle, called a diplomonads, L. salmonae and N. salmonis, parasome or Nebenkörper, which is adjacent are discussed. to the nucleus (Fig. 3.8). The parasome can be observed in wet mounts of locomotive forms, and is readily visible with Feulgen Paramoeba pemaquidensis gill infections DNA stains. Amoebae can also be identified on gill surfaces in histological preparations, Paramoeba sp. (Sarcomastigophora: Para- but many detach during processing. The moebidae) has caused devastating losses in amoebae can also be identified with specific

84 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:10 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 75

Fig. 3.8. Paramoeba pemaquidensis from coho salmon gill. The parasome (arrowhead) is adjacent to the nucleus. Bar, 10 µm.

polyclonal antibodies in tissue sections or (Cameron, 1993; Johnson et al., 1993; Bruno imprints (Howard and Carson, 1993a). and Raynard, 1994).

Treatment and control. Most compounds typically used as external treatments (e.g. Diplomonad flagellates formalin, chelated copper, diquat, malachite green and chloramine T) are not effective Extra-intestinal infections by diplomonad against the organism (Munday et al., 1993), flagellates have cause disease in caged- but the amoeba is readily eradicated from reared salmon in Norway and British fish gills with freshwater bath treatments. Columbia. One outbreak of a severe sys- Kent et al. (1988b) confirmed that the para- temic infection by a diplomonad flagel- site survives poorly in low salinity water. late (family Hexamitidae) resembling H. Cameron (1993) reported that reducing sea- salmonis caused close to 50% mortality in water concentrations to 4 ppt was needed chinook at one netpen site in the Sechelt for effective treatment. Reducing the salinity area, British Columbia (Kent et al., 1992). has been effective for eradicating infections The fish were introduced to seawater in the in fish held in land-based tanks, but this spring of 1990 and showed high mortality treatment is usually difficult to apply and starting in September 1991. Interestingly, impractical in netpens. Hydrogen peroxide about the same time, extra-intestinal infec- bath treatments at concentrations between tions by a similar parasite were reported in 200 and 400 ppm are moderately effective post-smolt to adult Atlantic salmon reared at controlling the infection (Cameron, 1993). at netpen farms in northern Norway (Mo Howard and Carson (1993b) reported that et al., 1990; Poppe et al., 1992). 100 ppm hydrogen peroxide for 2 h killed Whereas gut infections in fish by all the amoeba. However, Cameron (1994) diplomonads are common (Woo and found that hydrogen peroxide did control Poynton, 1995), systemic infections by the infection in field situations, even when diplomonad parasites in fish are rare. Only used at 300 ppm. Hydrogen peroxide treat- one other report of such infections is known, ments should be applied with caution and Ferguson and Moccia (1980) reported because of potential toxic effects to the a similar disease in Siamese fighting fish fish, particularly at higher temperatures (Beta splendens). Although the flagellates

85 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:11 AM Color profile: Disabled Composite Default screen

76 M.L. Kent and T.T. Poppe

observed in pen-reared salmon are morpho- detected in DifQuick or Giemsa-stained logically indistinguishable from the rela- imprints (Fig. 3.9B), where they appear as tively non-pathogenic H. salmonis that dark-staining, oval bodies with two clear infects the intestinal tract of salmonids in bands, representing the flagella pocket, run- fresh water, they probably represent new, ning the length of the organism. The two highly invasive strains or species. Sterud nuclei at the anterior end of the parasite may et al. (1997) recently named the organism be visible. from pen-reared Atlantic salmon and Arctic grayling (Thymallus arcticus) from fresh Control and treatment. Several drugs, most water as S. barkhanus. of which are added to the diet, have been Water-borne exposure of the fish to recommended for the control of H. salmonis infected blood and viscera, or cohabitation infections in the gut of salmonids (Yasutake with infected fish in either fresh or seawater et al., 1961; McElwain and Post, 1968; (Kent et al., 1992) can reproduce the sys- Hoffman and Meyer, 1974; Becker, 1977). temic disease in chinook salmon. However, However, presently, none of these com- the parasite of Atlantic salmon from Norway pounds is approved for treatment of food could not be transmitted to healthy fish by fish in Canada or the USA. cohabitation. Although it has been determined that the disease is transmissible in seawater, it is Clinical and gross pathology. In chinook not established whether salmon contracted salmon from British Columbia, infected fish the infection in seawater, or were subclini- appeared normal except that some fish had a cally infected when they were transferred to distended abdomen. The gills were pale due netpens. At present, the best guess is that to anaemia. The hallmark gross pathological infections in both Norway and Canada are change of the disease is an extremely contracted in seawater. In addition, Poppe enlarged liver. In some fish, the liver was and Mo (1993) suggested that fish could also mottled and had petechial haemorrhage become infected by exposure to untreated and whitish, friable areas. Affected fish water from fish processing plants. An under- consistently had serosanguinous ascites and standing of the source of the infection would blood clots in the visceral cavity. The spleen be helpful for implementing effective con- and kidney were moderately enlarged, and trol strategies. petechiae occurred throughout the skeletal muscle (Kent et al., 1992). In Atlantic salmon, the infection dif- Kudoa thyrsites (Myxozoa) fered in that the parasite caused large, multifocal, white, lesions in the muscula- Myxosporeans of the genus Kudoa and ture, liver, spleen and kidney (Poppe et al., related genera infect the muscle of many 1992). Yellow or white cysts filled with the marine fishes, and heavy infections can parasite were also in the fins, and infected cause unsightly white cysts or soft texture fish often had exophthalmia (Poppe and Mo, in fillets (Kabata and Whitaker, 1981; 1993). Patashnik et al., 1982). These parasites can lower the market value of the infected Diagnosis. The infection is identified by fish, although they seldom cause morbidity. wet-mount preparations or Giemsa-stained K. thyrsites is a cosmopolitan parasite that imprints of the gut or other visceral organs. infects many species of marine fishes Because the parasite is highly motile, it may (Whitaker et al., 1994). Infections in be easier to identify the parasites in wet- pen-reared Atlantic salmon have been mount examination. Wet-mount prepara- reported from the Pacific Northwest tions of the visceral organs reveal massive (Harrell and Scott, 1985; Whitaker and × µ numbers of flagellates that are 10 5 m Kent, 1991), Spain (Barja and Toranzo, (Fig. 3.9A). The parasites are also readily 1993) and Ireland (Palmer, 1994). In one

86 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:11 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 77

Fig. 3.9. Systemic diplomonad flagellates (arrowheads) from chinook salmon. (A) Phase-contrast wet mount. (B) Blood smear, Giemsa stain. Bar, 20 µm.

instance, Harrell and Scott (1985) attributed grilse (i.e. fish that have reabsorbed their mortalities in Atlantic salmon smolts to gonads and do not exhibit external signs of this parasite. More importantly, heavy sexual maturation) than in market-size fish infections are associated with soft flesh in that have not undergone sexual maturation pen-reared Atlantic salmon that are either (St-Hilaire et al., 1998). For example, infec- held on ice for 3–6 days or cold-smoked. tion in grilse may reach 70%, whereas K. thyrsites infections and associated soft market-size fish that are not sexually mature flesh have also been observed in farmed usually show infections below 10%. There is coho salmon (Whitaker and Kent, 1992) a positive correlation between intensity and brown trout (Baudin-Laurencin and of infection and severity of soft flesh in Bennassr, 1993). Atlantic salmon held on ice (St-Hilaire et al., The infection is much more prevalent 1997a). Heavily infected fish always have in Atlantic salmon grilse or reconditioned soft flesh, whereas lightly infected fish (i.e.

87 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:13 AM Color profile: Disabled Composite Default screen

78 M.L. Kent and T.T. Poppe

− fewer than 20,000 spores g 1) usually do not transferred to seawater. An infectious stage have the condition. Soft flesh is not noticed of the parasite occurs in the blood. Moran on the processing line, and only becomes et al. (1999b) showed that direct per os apparent after fish are held for about 3–6 exposure of Atlantic salmon with heavily days on ice or when fillets are smoked. In infected tissue did not cause infections. As an investigation of K. thyrsites infections in with other myxosporeans, an annelid alter- Pacific hake (Merluccius productus), the native host is probably involved in the life flesh softening was apparently caused by a cycle. proteolytic enzyme produced by the parasite Analysis using small subunit ribosomal (Tsuyuki et al., 1982). This enzyme remains rDNA (SSU rDNA) suggests that Kudoa active below 70°C. Therefore, tissue break- species are phylogenetically different from down will continue through cold-smoking other myxosporean genera examined (i.e. processes, which are normally conducted at Myxobolus, Henneguya and Myxidium), and about 50°C or less. Seymour et al. (1994) that K. thyrsites in Atlantic salmon is indis- suggested that the flesh degradation is due tinguishable from that infecting tubesnout to cathepsin L from the host inflammatory (Aulorhynchus flavidus) and probably other response to the parasite, instead of a marine fishes in the Pacific Northwest proteolytic enzyme from the parasite. (Hervio et al., 1997). Very little is known about development and transmission of K. thyrsites in fish. It Clinical signs and gross pathology. Heavily takes about 5–6 months after infection before infected fish held on ice for 3–6 days may spores are detected in the flesh and a high develop extreme softening of the flesh prevalence occurs in post-smolts (Moran texture. Occasionally discrete white patches et al., 1999a). As the infection progresses in are visible with the naked eye. The soft Atlantic salmon, pseudocysts in the muscle flesh also will occur following smoking at fibres enlarge and ultimately rupture. A pro- cool temperatures (below 70°C) where white minent inflammatory response is associated patches in the muscle are readily seen. with ruptured pseudocysts, and fish elimi- nate the detectable infections after about a year in seawater (Moran et al., 1999a). Diagnosis. Diagnosis is based on the obser- It is not known if the high prevalence of vation of the characteristic stellate spores the infection in grilse is due to reinfection, of the parasite, which are about 13 µmin or proliferation of a cryptic infection that diameter (Fig. 3.10). The spores are best originally occurred shortly after fish were detected by microscopic examination of

Fig. 3.10. Wet mount of Kudoa thyrsites spores. Bar, 15 µm.

88 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:14 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 79

fluid collected from the freshly cut surface infections by a Loma sp. (presumably L. of a fillet or by crushing a small piece salmonae). of muscle. The parasite shows up well Infections can persist after fish are in Giemsa-stained histological sections. transferred to seawater, and the associated Detection of the parasite in whole fish is a lesions in the gills can become severe in the problem that is, as yet, unresolved. pen-reared salmon (Kent et al., 1989; Speare Wet-mount examination of the hyoid et al., 1989). Although the gills are the muscle in the underside of the operculum is primary site of infection, parasites and a relatively sensitive and specific method for associated lesions can occur in the heart, detecting the infection without damaging spleen, kidney and pseudobranch. Infection the body musculature (St-Hilaire et al., can originate in fresh water, but there is a 1997b). Although this method may miss high prevalence of L. salmonae in chinook a few light infections, this is not a great salmon from netpens that have been reared concern because light infections do not solely on ground water during the fresh- cause soft flesh. water phase (Kent et al., 1995). Furthermore, Many copies of the rDNA sequence infection has been reported in ocean-caught occur within an individual eukaryotic adult salmon (Kent et al., 1998). Potential cell, and thus this sequence is useful for vertical transmission of microsporeans via developing very sensitive PCR-based tests. the ova has been reported by Vaney and Hervio et al. (1997) developed a sensitive Conte (1901) and Summerfelt and Warner PCR test for K. thyrsites, which will be used (1970). Vertical transmission of L. salmonae to identify the source of infection for salmon. from infected females to progeny should also be considered as a possibility. L. salmonae Control and treatment. There are no com- occurs in the ovaries, but not in the eggs, mercially available drugs against myxo- of sexually mature salmon (Docker et al., sporeans. Fish become infected in seawater, 1997a). Therefore, the progeny of infected so it would be very difficult to eliminate females could become exposed to the para- exposure to infections. Because sexually site through contaminated ovarian fluid. mature fish and reconditioned grilse are Furthermore, spores of L. salmonae can more prone to the infection, removing survive iodine treatment at 100 ppm for such fish from the population before 15 min (Shaw et al., 1999), a dose typically harvest (e.g. by thorough screening for used for disinfecting salmonid eggs after grilse in the winter) will greatly minimize spawning. the problem. Although other Loma species infect non-salmonid fish, it is doubtful whether these fish are reservoirs for L. salmonae. Shaw et al. (1997) demonstrated that a Loma salmonae (Microsporidia) Loma sp. from shiner perch, Cytmatogaster aggregata (a common fish found around sea L. salmonae is an obligate intracellular cages in British Columbia), was a different microsporidian and infects the gills and species from L. salmonae. Although the other vascularized tissues of salmonids two microsporeans were morphologically reared in fresh water (Putz et al., 1965; indistinguishable, Shaw et al. (1997) Putz and McLaughlin, 1970; Morrison and showed that the parasite from shiner perch Sprague, 1981, 1983; Hauck, 1984; Poynton, could not infect salmon. 1986; Markey et al., 1994; Bruno et al., Loma morhua is a common gill parasite 1995). Severe gill infections have been of Atlantic cod (Morrison, 1983), and causes reported in rainbow trout, steelhead trout similar gill lesions to those induced by L. and kokanee salmon (Wales and Wolf, salmonae in salmon. Therefore, this parasite 1955), and Hauck (1984) observed high also has potential to cause disease in farmed mortality in chinook due to systemic cod.

89 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:14 AM Color profile: Disabled Composite Default screen

80 M.L. Kent and T.T. Poppe

Clinical signs and gross pathology. Fish parasite–host cell complexes, xenomas, with heavy gill infections are usually appear more opaque than the surrounding lethargic, and small white cysts may be seen tissue, and high magnification reveals in the gills (Fig. 3.11). A consistent finding masses of the spores within the xenoma in pen-reared salmon is the presence of (Fig. 3.12). Individual xenomas may occlude multiple petechiae in an otherwise pale blood vessels, and rupture results in a gill. Infected gills may also appear nodular. marked inflammatory response by the Systemic infections in chinook may cause host as spores are released (Kent et al., 1989). enlargement of the spleen and kidney. In The spores are bean-shaped and are about Atlantic cod, obvious white cysts are also 5 × 3 µm. Spores in infected tissue are apparent in the gills and visceral organs Gram-positive. (Morrison, 1983). A sensitive PCR test for L. salmonae using an rDNA sequence has been described Diagnosis. Spores of Loma spp. can be (Docker et al., 1997a). This may be useful easily detected in wet-mount preparations for screening fish (i.e. broodstock) for of moderately to heavily infected gills. The subclinical infections. Furthermore, these

Fig. 3.11. Salmon gill with Loma salmonae infection. Note the mottled appearance of the gills and numerous xenomas (arrowheads).

Fig. 3.12. Wet mount of a gill infected with Loma showing a ruptured xenoma releasing spores (arrowheads). Bar, 10 µm.

90 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:15 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 81

specific primers can differentiate L. This microsporidium was originally salmonae from other Loma species. described as N. salmonis (cf. Hedrick et al., 1991a), but was described shortly there- Control and treatment. Currently, there are after as Enterocytozoon salmonis by no licensed pharmacological agents or Chilmonczyk et al. (1991). Rules of zoo- vaccines (Speare et al., 1998). In laboratory logical nomenclature, morphological data − studies, feeding fumagillin at 10 mg kg 1 fish and rDNA sequence data support the − day 1 for 30 days (Kent and Dawe, 1994) validity of the genus Nucleospora, and its prevented infections in chinook salmon. placement in the family Enterocytozooidae Our recent experiments demonstrated that (see Desportes-Livae et al., 1996; Docker infections can be controlled with lower et al., 1997b). Similar intranuclear micro- − doses of fumagillin, i.e. 2 or 4 mg kg 1 fish sporidia were reported in Atlantic lumpfish (Kent and Poppe, 1998). (Cyclopterus lumpus) (Mullins et al., 1994) The synthetic analogue of fumagillin, and Atlantic halibut (Nilsen et al., 1995). TNP-470 (Takeda Chemical Industries, Ltd, N. salmonis infections are usually asso- Japan), can also be effective in reducing ciated with a concurrent neoplastic condi- L. salmonae infections (Higgins et al., tion involving massive lymphoproliferation, 1998). Oral treatment with this compound at known as plasmacytoid leukaemia (PL) in − 0.1 or 1.0 mg kg 1 fish for 4 weeks greatly chinook salmon in British Columbia (Kent reduced the intensity of infections, with no et al., 1990). However, the actual cause of apparent clinical toxic side effects. Speare PL is controversial. Laboratory transmission et al. (1998) showed that rainbow trout studies indicated that N. salmonis may have strong protection against reinfection, not be the primary cause of all cases of which suggests that L. salmonae infections PL (Kent and Dawe, 1990; Newbound and may be prevented by vaccines. Kent, 1991), and Eaton and Kent (1992) The susceptibility of Pacific salmon described a retrovirus associated with the strains to L. salmonae infection using condition. feeding trails was examined by Shaw et al. It is possible that PL actually represents (2000). Differences in strain susceptibility two separate diseases; one caused by the were noted and this may assist with future virus and one caused by the micro- breeding experiments. sporidium. Studies with fumagillin and TNP-470 (Hedrick et al., 1991b; Higgins et al., 1998) support the microsporidian hypothesis, i.e. treatment with these Nucleospora salmonis anti-microsporidian compounds prevented N. salmonis infections and PL. Moreover, N. salmonis is an unusual microsporidium in contrast to the late 1980s and early 1990s, that infects the nuclei of haemoblasts, par- N. salmonis is consistently observed in the ticularly lymphoblasts or plasmablasts, in proliferating plasmablasts in essentially all salmonid fishes (Chilmonczyk et al., 1991). cases that have been investigated in recent This microsporidium was first observed in years in British Columbia. pen-reared chinook in Washington State, N. salmonis is transmitted by co- where it was associated with anaemia habitation or feeding infected tissues to (Elston et al., 1987). The parasite has also fish in fresh water (Baxa-Antonio et al., been reported in freshwater-reared chinook, 1992). These findings have been reported kokanee (Oncorhynchus nerka) and steel- in our laboratory, but we were unable to head trout (O. mykiss) (Hedrick et al., 1990, transmit the infection by cohabitation in 1991b; Morrison et al., 1990) The infection seawater. Circumstantial evidence (e.g. the is common in caged-reared chinook salmon occurrence of the parasite in Chile) suggests in British Columbia and in Atlantic salmon that the parasite may be transmitted via in Chile (Bravo, 1996). eggs.

91 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:15 AM Color profile: Disabled Composite Default screen

82 M.L. Kent and T.T. Poppe

Clinical signs and gross pathology. Heavily ascites consisting of a clear or sero- infected fish are anaemic. Fish with PL are sanguinous fluid. often dark, lethargic and may swim near the surface. Many of the of fish with PL exhibit Diagnosis. This microsporidium is small severe bilateral exophthalmos (Fig. 3.13). (about 2 µm) and is identified by careful The exophthalmos is due to massive accu- examination of nuclei of haemoblasts in mulation of white or hyperaemic tissue in histological sections or in Gram-stained the orbit of the eye. The spleen and kidney imprints (Fig. 3.14). Following Gram stain, are enlarged when systemic infections the spores stain Gram-positive. They have occur. Petechiae may occur in the liver, a characteristic bean shape, and measure mesenteric fat, pancreas, heart and skeletal about 2 × 1 µm. Sensitive and specific PCR muscle. The lower intestinal wall may tests have been developed for the detection be markedly thickened. Some fish have of N. salmonis based on a rDNA sequence

Fig. 3.13. Severe exophthalmos in chinook salmon with plasmacytoid leukaemia associated with Nucleospora salmonis infection.

Fig. 3.14. Gram-stained kidney imprint of Nucleospora salmonis showing spores (arrowhead) in a remnant of a nucleus. Bar, 10 µm.

92 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:16 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 83

from the small subunit region (Barlough Sea lice have ten developmental stages: et al., 1995) or internal transcribed spacer two free-living planktonic nauplius stages, region (Docker et al., 1997b). one free-swimming infectious copepodid stage, four attached chalimus stages, Treatment and control. There is no com- two pre-adult stages and one adult stage mercially available drug for treating N. (Johnson and Albright, 1991; Schram, 1993). salmonis infections. However, Hedrick et al. The copepodid, chalimus, pre-adult and (1991b) controlled the infection in experi- adult stages all feed on mucus, skin and mentally infected chinook by oral treatment blood of fish (Kabata, 1970; Brandal et al., − − with fumagillin at 1.0 mg kg 1 fish day 1 for 1976). 2 weeks. Higgins et al. (1998) found that the fumagillin analogue, TNP-470 (Takeda Clinical signs and gross pathology. Pre-adult Chemical Industries Ltd), was very effective and adult parasites actively move on the at controlling experimental infections when surface of fish, and lesions caused by these fish received an oral treatment at either 0.1 stages may be severe and widespread. − − or 1.0 mg kg 1 fish day 1 for 4 weeks. In contrast, damage by the non-motile copepodid and chalimus larvae is generally focal (Bron et al., 1991; Johnson and Crustacean Parasites Albright, 1992). Infected salmon commonly have grey patches (extensive areas of skin Sea lice – caligid copepods (family Caligidae) erosion) and haemorrhaging on the head and back. They often exhibit distinct areas of Sea lice are the most economically impor- erosion, dark coloration and subepidermal tant parasites afflicting salmon in cage haemorrhage in the perianal region culture. ‘Sea lice’ refer to several species of (Wootten et al., 1982; Urawa and Kato, 1991; marine ectoparasitic copepods of the genera Nagasawa and Sakamoto, 1993; Johnson Lepeophtheirus and Caligus of the family et al., 1996). Severely infected salmon have Caligidae that infect marine fishes, particu- ulcers in which the epidermis is breached larly salmonids (Costello, 1993; Johnson, and the underlying tissues exposed. These 1998). Lepeophtheirus salmonis has a cir- lesions often occur on the head and behind cumpolar distribution and is restricted to the dorsal fin (Jónsdóttir et al., 1992). salmonids, except as a result of accidental transfer from salmonids (Kabata, 1979). In Diagnosis. Copepodids and chalimus contrast, Caligus species that infect salmon larvae of sea lice are small (< 4 mm in length) have broad host ranges that include both and can occur on the body surface and fins non-salmonid teleost and elasmobranch as well as in the buccal cavity and on the hosts. gills. Their small size requires the use of a Heavy infections greatly reduce the magnifying glass or dissecting microscope to market value of the fish and ultimately result detect their presence. in death. Mortality may occur due to the Pre-adult and adult sea lice are visible to development of secondary diseases (e.g. the naked eye. They are on the body surface, vibriosis, furunculosis) exacerbated by the especially on the head, back and in the high levels of accompanying stress. In severe perianal region. It is these stages that usually cases where the epidermis is breached, cause the most damage to the fish. Pre-adult death may be due to a loss of physiological and adult stages of Caligus species can be homeostasis including osmotic stress, anae- distinguished from Lepeophtheirus species mia and hypoproteinaemia (Wootten et al., by the presence of lunules on their anterior 1982; Tully et al., 1993). Sea lice may also margin (Fig. 3.15). There is a key to aid function as vectors of bacteria and viruses in the identification of adult sea lice of such as infectious salmon anaemia virus the northern hemisphere (Johnson and (Nylund et al., 1994). Margolis, 1994).

93 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:17 AM Color profile: Disabled Composite Default screen

84 M.L. Kent and T.T. Poppe

Fig. 3.15. Caligus (a) and Lepeophtheirus (b). Note lunules (arrow) on Caligus. (From Kabata, 1988.)

Control and treatment. There are excellent Costello, 1993; Johnson et al., 1993; Roth reviews on the control and treatment of sea et al., 1993a,b; Thomassen, 1993a,b). These lice (Costello, 1993; Johnson et al., 1993; treatments have mainly been developed for Roth et al., 1993a; Johnson, 1998). Manage- treatingAtlantic salmon, and caution should ment strategies are useful for reducing the be used when applyingthem to other impact of sea lice in cage farms. Farms species, as they often vary in their ability to should be located in areas with strongwater tolerate sea lice treatments (see Johnson and currents to flush away copepodid stages and Margolis, 1993; Johnson et al., 1993). in areas where wild fish reservoir hosts are The organophosphorus insecticides, not numerous. Fallowingof sites between dichlorvos, marketed as ‘Nuvan 500EC’ production cycles and maintainingonly or ‘Aquaguard SLT’, or in its related single year classes at sites can also signifi- trichlorphon form as ‘Neguvon’, were the cantly reduce the need for treatments for first chemicals widely used to control sea L. salmonis (Bron et al., 1993; Grant and lice (Brandal and Egidius, 1977; Grave et al., Treasurer, 1993). This approach may be 1991a,b). Dichlorvos and trichlorphon have applied to several sites within a common been used since the 1960s as a bath treatment area. In cases where farms belonging to for parasites in pond fish culture (reviewed different companies are in close proximity to in Schmahl et al., 1989). These treatments each other, cooperative agreements between effectively remove both the pre-adult and companies with respect to single-year class adult stages of sea lice, but not the chalimus stocking, periods of fallowing and timing larvae, from salmon (Brandal and Egidius, of sea lice treatments have been effective 1979). Therefore, successive treatments, for controllingsea lice outbreaks (Grant and usually at 2–4 week intervals, are required Treasurer, 1993). to control infections (Wootten et al., 1982). Chemotherapy has played a significant Repeated treatment with dichlorovos may role in attempts at controllingsea lice. Bath induce resistance in sea lice (Jones et al., treatments with dichlorvos, trichlorfon, 1992). azamethiphos, cypermethrin, carbaryl, Another organophosphate, azamethi- pyrethroids and hydrogen peroxide have phos (marketed as Salmosan® and Alfa- been employed (Brandal and Egidius, 1979; cron®), is presently used in Europe and

94 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 12:32:03 PM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 85

Canada for sea lice control. It is administered Raynard, 1994). With respect to L. salmonis, as a bath treatment, and like the other these stages are less likely to reinfect the organophosphates shows little efficacy treated hosts. Pre-adults and adults of against the attached chalimus stages (Roth species of Caligus are generally more et al., 1996). This chemical is efficacious active swimmers and reinfection is possible against L. salmonis, has a wider therapeutic if they recover. The use of hydrogen per- margin and appears to be more tolerated oxide is rather impractical and it has been than the other organophosphates by Atlantic essentially abandoned in Norway. Further- salmon (Hodneland et al., 1993; Roth et al., more, caution should be used when apply- 1993a, 1996). ing hydrogen peroxide treatments, particu- A drawback with these organophos- larly at higher temperatures (Johnson et al., phates is that they may be toxic to a wide 1993; Roth et al., 1993a; Bruno and Raynard, variety of marine organisms when they are 1994). Fortunately, Atlantic salmon are less released into the surrounding waters after sensitive to hydrogen peroxide than Pacific treatment. However, their impact on non- salmon species, such as chinook salmon target species may be minimal due to dilu- (Johnson et al., 1993). tion and the rapid breakdown of these pesti- Application of external treatments in cides (Egidius and Moster, 1987; Cusack and netpens is often expensive and difficult. Johnson, 1990; Dobson and Tack, 1991). Therefore, considerable effort has been Pyrethrin and pyrethroid compounds directed toward development of oral are currently being used for sea lice control treatments for sea lice. Palmer et al. (1987) (Boxaspen and Holm, 1991a,b; Roth et al., reported the results of preliminary studies 1993b). The synthetic pyrethroid cyper- on the efficacy of oral doses of ivermectin for methrin is believed to be more efficacious the control of sea lice on Atlantic salmon. than azamethiphos for the control of L. Ivermectin has been demonstrated to be salmonis on Atlantic salmon. Clinical field effective in controlling all developmental trials are ongoing in Maine, USA, using stages of sea lice (Smith et al., 1993; Johnson cypermethrin (under the market name and Margolis, 1993). Although this drug was Excis®). Presently this is the most widely found to be effective in reducing popu- used bath treatment against sea lice in lations of sea lice, it had a relatively Norway. narrow margin of safety with salmon. Bath treatments with hydrogen Johnson et al. (1993) showed that ivermectin peroxide may also be another effective can be very toxic to Atlantic salmon, and that method for treating sea lice (Bruno, 1992; the level of toxicity varied between salmon − Thomassen, 1993a,b; Bruno and Raynard, species. Atlantic salmon fed 0.05 mg kg 1 1994). Thomassen (1993a,b) reported that on alternate days became anorexic after bath treatments of hydrogen peroxide at a 20 days, and ivermectin was lethal to fish − concentration 1.5 g l 1 for 20 min effectively fed at higher doses (Johnson et al., 1993). removes from 85 to 100% of the pre-adult Fish suffering from ivermectin toxicity are and adult stages of sea lice without being listless, show ataxia and then die in a few toxic to Atlantic salmon. The market name of days. Due to long tissue withdrawal times hydrogen peroxide for use in fish farming is and concerns about the impact of ivermectin Salartect 500 FLT®. Twenty minute bath residues in the sediments beneath the − treatments of 1.5 g l 1 hydrogen peroxide at netpens, this drug may never be licensed or 11°C effectively removed approximately registered for use in aquaculture (Burridge 80% of the pre-adult and adult stages of and Haya, 1993; Costello, 1993). L. salmonis, but had no significant effect on Oral administration of diflubenzuron the intensity of infection with the attached (a chemical that inhibits chitin synthesis) chalimus stages. In addition, a high pro- reduces infections by both adult and larval portion of the pre-adult and adult stages stages of sea lice (Roth et al., 1993a). removed from the fish recovered after Treatments using Lepsidon (containing treatment (Johnson et al., 1993; Bruno and diflubenzuron) and Ektobann (containing

95 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:18 AM Color profile: Disabled Composite Default screen

86 M.L. Kent and T.T. Poppe

teflubenzuron) are being conducted on a when exposed under laboratory conditions limited scale in Norway and the Faroe (Grayson et al., 1995). Islands under special permit. These compounds are highly effective against the copepodid, chalimus and pre-adult Family Pennellidae stages. However, they have no efficacy against the adult stages because they no Members of the family Pennellidae may longer moult. A concern with these drugs is cause problems in netpen aquaculture. the possible detrimental effects on non- Haemobaphes disphaerocephalus has been target arthropods that dwell around sea reported in pen-reared Atlantic salmon cages. Licensing of these compounds in (Kent et al., 1997). This parasitic copepod some areas, such as the USA, may be very normally infects eulachon (Thaleichthys difficult due to laws that limit the use of pacificus) and this was the first report of diflubenzuron within 5 km of the coast a Haemobaphes species infecting salmon. (Roth et al., 1993a). The parasite penetrates the branchial vascu- Cleaner-fishes (i.e. wrasse species in the lature and causes anaemia. Fortunately, the family Labridae) are used in Norway, the infection has been observed in only a few Shetland Isles, Scotland and Ireland to con- Atlantic salmon reared in British Columbia. trol sea lice (reviewed in Costello, 1993; In contrast, Lernaeocera branchialis is a Kvenseth, 1993; Treasurer, 1993; Tully et al., common parasite of Atlantic cod (Kabata, 1996). In laboratory and field studies, wrasse 1984). The parasite causes reduced growth remove sea lice from salmonids but not and anaemia (Khan, 1988), and Khan et al. always in a predictable manner. A survey (1990) concluded that it is a potential threat of fish farmers in Scotland who have tried to cod farming. wrasses to control sea lice showed that the majority felt that their use was beneficial, particularly when used in conjunction Clinical disease and gross pathology. Fish with dichlorvos treatments (Anon., 1991). infected with either Haemobaphes or Lern- Wrasses are also useful for reducing fouling aeocera are usually anaemic and may be on cages. The disadvantages of using wrasse lethargic. Examination of the opercula cav- to control sea lice include the requirement ity reveals the coiled egg sacs and blood- for smaller mesh size in nets to prevent their engorged body of the parasite penetrating escape, intimidation by larger salmon and the gill (Fig. 3.16). The long neck and ante- a tendency not to clean them, aggressive rior holdfast are internal within the gill arch. behaviour and infliction of scale and eye damage to the salmon (Anon., 1991). In Diagnosis. Haemobaphes and Lernaeocera addition, wrasse exhibit high over-winter spp. are characterized by attachment at the mortalities, their supply is limited and their gill arch and coiled egg sacs. Specific identi- cost is usually high. Nevertheless, wrasse fication requires examination of the anterior are used in over half of the fish farms in holdfast (see Kabata, 1988), which must be Norway. very carefully dissected from tissues. Atlan- A vaccine for sea lice would be useful. tic lumpfish (C. lumpus) is an intermediate Although Atlantic salmon can produce anti- host of L. branchialis, and thus simultaneous bodies to sea lice extracts in controlled rearing of this fish with cod should be studies (Grayson et al., 1991), salmon natu- discouraged. rally infected with L. salmonis and Caligus elongatus fail to produce an antibody Control and treatment. There is no suitable response (Grayson et al., 1991; MacKinnon, drug available for treating this infection. The 1991). Furthermore, there was no difference infective larvae are free-swimming and it in the number of copepods carried on would be difficult to prevent the infection in control and immunized Atlantic salmon netpens.

96 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:18 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 87

Fig. 3.16. Haemobaphes disphaerocephalus infecting the gills of an Atlantic salmon.

Isopods – Ceratothoa gaudichaudii

Four species of isopods, Ceratothoa gaudichaudii, Rocinela maculata, Rocinela belliceps pugettensis and Gnathia sp., have been reported from seawater-reared salmonids (Novotny and Mahnken, 1971; Awakura, 1980, 1983; Drinan and Rodger, 1990; Inostroza et al., 1993). The only economically important isopod parasite of marine coldwater netpen-reared fish has been C. gauchichaudii. In Chile, C. gaudichaudii has been reported from a wide variety of native hosts. This low Fig. 3.17. Ceratothoa gaudichaudii on the gills of host specificity has allowed this parasite Atlantic salmon (courtesy of R. Inostroza). to successfully infect coho and Atlantic salmon. Disease caused by this parasite has Atlantic salmon. Sixty-minute bath been a serious problem at certain farm sites treatments with the organophosphates, in Chile (Inostroza et al., 1993). trichlorfon (Neguvon) and dichlorvos (Nuvan 1000) at concentrations of 300 Clinical signs and gross pathology. C. gaudi- and 3 ppm, respectively, were found to be chaudii feeds on host blood, attaching to 100% effective against this parasite without the inner mouth surfaces and less frequently toxicity to the fish. to the gills (Sievers et al., 1995). Disease is caused by their attachment and feeding activities. Damage to the host includes Helminth Parasites severe erosion of gill lamellae and ulcers on the gill arch and inside the mouth. Fish are infected with a wide variety of parasitic worms, collectively referred to Diagnosis. Ceratothoa is readily identified as helminth parasites. Although these on the fish by examination of the mouth and parasites are very common in wild fish, gills (Fig. 3.17). and occasionally infect cultured species, generally they do not cause severe disease. Control and treatment. Sievers et al. (1995) However, certain helminths can cause evaluated the efficacy of eight commercial damage when infections are heavy or when insecticides against C. gaudichaudii on they infect a critical organ. In addition,

97 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:19 AM Color profile: Disabled Composite Default screen

88 M.L. Kent and T.T. Poppe

some helminth parasites of fish can infect Atlantic salmon in Norway have been humans or cause unsightly lesions. The associated with reduced growth and, occa- following are helminth parasites of impor- sionally, mortality (Bristow and Berland, tance in coldwater marine netpen-reared 1991a,b; Håstein and Lindstad, 1991). The fish. weight of infected market-size farmed Atlantic salmon in Norway is 10–15% less than uninfected salmon (Berland and Cestodes (tapeworms) Bristow, 1994). It has been noted that a similar infection occurs in the cestodes Two life stages of cestodes are found in of broodstock from pen-reared chinook fish: adults infect the digestive tract and salmon in British Columbia. metacestodes (juveniles) are usually on the The fish acquire infections of internal organs or muscle. The first interme- Eubothrium species by ingesting first inter- diate hosts of tapeworms that infect fish are mediate hosts (presumably copepods) usually crustaceans (e.g. copepods). Fish infected with the procercoid stage, or may also be the second intermediate hosts possibly transport hosts infected with for tapeworms, and a fish-eating mammal or plerocercoids. The life cycle of this bird, or another fish, are definitive hosts. tapeworm in marine fishes has not been Therefore, fish usually acquire metacestode elucidated, but its freshwater counterpart, infections by eating infected crustaceans. Eubothrium salvelini, uses copepods Metacestodes in fish tissues often cause an (Cyclops spp.) as its intermediate host. inflammatory response to the encapsulated Procercoids that develop in Cyclops are or migrating parasite. The only reported directly infective for juvenile salmon significant metacestode disease of salmon (Boyce, 1974). E. salvelini is known to affect reared in marine netpens is caused by survival, growth and stamina, and to have Gilquinia squali, which infects the eyes of other debilitating effects on juvenile sockeye chinook salmon (Kent et al., 1991). salmon (Boyce and Behrens-Yamada, 1977; Boyce, 1979; Boyce and Clarke, 1983). Adult cestodes – Eubothrium spp. Clinical signs and gross pathology. Heavily Eubothrium spp. are common cestode para- infected fish are often smaller than aver- sites of salmonid fish in both fresh and salt age. Dissection of the gut will reveal num- water, in which adults develop in the gut. erous, white, flat, ‘tape-like’ worms in the Infections with one species in pen-reared intestine and pyloric caeca (Fig. 3.18). Heavy

Fig. 3.18. Adult Eubothrium cestodes in the gut of Atlantic salmon (courtesy of B. Berland).

98 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:19 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 89

infections may induce anaemia, and when netpens presumably acquire the infection by extremely severe the cestodes may cause eating this crustacean. death due to blockage of the intestinal tract (Mitchell, 1993). Clinical signs and gross pathology. Mori- bund fish are lethargic and remain near the Diagnosis. Adult cestodes are usually long, bottom of the pen. The fish can easily be flat, whitish and segmented. Identification captured by hand, suggesting that they are as a cestode is based on a segmented body, a blind. However, fish are not usually emaci- scolex (anterior end), and on the structure ated and contain food in their stomachs, and arrangement of the reproductive system which indicates that they continue to feed. within the segments (Schmidt, 1986; Khalil The lens often appears normal, whereas et al., 1994). Eubothrium lacks hooks on the the iris and vitreous chamber may be white scolex, which is elongate with two shallow and opaque and occasionally haemorrhagic. grooves – one dorsal and the other ventral. The lens in more severely affected eyes is also opaque, suggesting cataracts. In extreme cases, the globe is ruptured and the lens is Control and treatment. Oral treatment for extruded. However, many fish die with the adult tapeworms with anthelmintic drugs, globe of the eye still intact. The eye lesions such as praziquantel, may be effective are often bilateral. (Mitchell, 1993). Avoiding cestode infec- tions is difficult because infected inter- Diagnosis. mediate hosts (i.e. crustaceans) move freely The infection is identified by throughout netpens. detecting trypanorhynch metacestodes in the vitreous humour. Trypanorhynch ces- todes are identified by the presence of four Gilquinia squali metacestodes reversible, spiny tentacles, which emerge from the apex of the scolex (Fig. 3.19). Eye infections by metacestodes of G. squali (order Trypanorhyncha) have been associ- ated with mortality of young chinook Control and treatment. There is no known salmon at netpen sites in British Columbia treatment for Gilquinia infection in fish. (Kent et al., 1991). The definitive host for Infestation can only be controlled by pre- G. squali is the spiny dogfish (Squalus venting infection. Fish that are feeding well acanthus). The metacestode is common in on commercial diets and thus feed less on the eyes of North Sea whiting, Merlangius natural biota appear to have lower infec- merlangus (MacKenzie, 1965, 1975). Wild tions. The complete life cycle of the parasite salmon are probably not a normal inter- is unknown, so precise recommendations mediate host for the worm as this infection for avoiding infection are not available. has only been seen in cage-reared salmon Furthermore, preventing transmission of (Kent et al., 1991). the parasite from dogfish to salmon via The adult worms are prevalent in the arthropod first intermediate hosts would dogfish throughout marine waters in British be difficult because of uncontrolled water Columbia, and gravid adult worms are movement into netpens and unrestricted commonly found in dogfish in the spring. movement of dogfish around netpens. Dogfish are frequently found in or around netpens at this time, thus providing infective coracidia for the first intermediate host near Digenetic trematodes (flukes) the pens. Based on trypanorhynchs whose life cycles have been investigated (Mundry As with cestodes, fish can be intermediate and Dailey, 1971; Overstreet, 1978; Mattis, hosts or definitive hosts for digenetic 1986; Sakanari and Moser, 1989), it is likely trematodes. Almost all flukes have either that a crustacean is the first intermediate a two-host or three-host life cycle, but host for G. squali. Chinook salmon in there is a wide variety of life cycle patterns

99 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:20 AM Color profile: Disabled Composite Default screen

90 M.L. Kent and T.T. Poppe

Fig. 3.19. Gilquinia squali metacestode from the eye of a chinook salmon. Semichon’s acetocarmine. Bar, 0.2 mm.

(Williams and Jones, 1994). With a few ‘neascus’-type, Diplostomum sp., Crypto- exceptions among the marine fish blood cotyle lingua and Stephanostomum tenue. flukes of the family Sanguinicolidae, molluscs (either snails or bivalves) are the Skin diseases caused by digenean trematodes first intermediate hosts of digeneans and second intermediate hosts may be an inver- Black grub (larval type neascus) is the tebrate or a fish. Except in occasional metacercarial stage of certain species of circumstances where the life cycle has been the family Diplostomatidae, which includes foreshortened, the definitive hosts are verte- several genera (Gibson, 1996). This parasite brates. The species of concern in marine infects a wide variety of freshwater fishes, farming of salmon use either birds or fish as including salmonids. Freshwater snails are definitive hosts, with the fish serving as the the first intermediate hosts, and cercariae second intermediate host. Cercariae of these released from infected snails penetrate species emerge from molluscs and infect beneath the scales in the dermis of the fish the salmonid host by direct penetration of host. Fish-eating birds serve as the defini- the skin or gills, subsequently developing tive hosts. These infections can persist after into a resting stage known as a metacercaria, fish are transferred to seawater. The prob- which may be encysted or unencysted lem has been recorded in pen-reared coho depending upon the final site of infection in salmon in British Columbia. A condition the fish. similar to black grub in coho salmon is Heavy infections by metacercariae are of ‘black spot disease’ in Atlantic salmon concern because they can cause morbidity. caused by metacercariae of C. lingua.In In addition, metacercarial infections of the contrast to the former condition, this para- skin or muscle can be important because site has a marine life cycle, which involves they may reduce the aesthetic quality of the a definitive (adult) stage in fish-eating fish. Except for blood flukes and a group of birds and a cercarial stage in snails. A tissue parasites of the family Didymozoidae Cryptocotyle sp. has also caused similar found mainly in scombroid fishes, most infections in cage-reared Atlantic cod adult flukes of fish infect the alimentary tract (Lysne et al., 1994). and seldom cause significant tissue damage. The metacercariae of four digenean Clinical signs and gross pathology. Infected trematodes have caused problems in fish exhibit few to numerous raised black seawater pen-reared salmonid fishes: spots up to 1 mm in diameter in the skin,

100 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:20 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 91

Fig. 3.20. Cryptocotyle (black spot) metacercariae in the skin of a Atlantic salmon.

fins, cornea and gills (Fig. 3.20). Occa- sionally, encysted metacercariae may be found in internal organs. Fish seldom become clinically affected unless they are heavily infected.

Diagnosis. Diagnosis of metacercarial infections in general is relatively easy using wet mounts or histological sections. How- ever, more precise identification to the genus or species level usually requires careful preparations of the metacercariae in stained whole mounts and examination of the internal anatomy (Fig. 3.21). Information on the first occurrence of the infection (i.e. marine vs. freshwater) is useful for differentiating neascus from Cryptocotyle.

Control and treatment. As the cercarial stage of Cryptocotyle is common in the periwinkle (Littorina littorea), cages located in shallowwaterand close to the shore are more prone to the infection. There is no known treatment for this infection. With neascus, fish become infected in fresh water by exposure to surface water containing infected snails. Disinfection of the water supply or using ground water Fig. 3.21. Cryptocotyle metacercaria. (From should eliminate or greatly reduce the Gibson, 1996.) infection. Based on reports from one fish farm in British Columbia, removing fish from freshwater hatcheries and introducing Stephanostomum heart infections them to netpens before June or July may reduce the intensity and prevalence of the Heart (pericardial cavity) infections by infection. metacercariae of S. tenue caused high

101 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 12, 2002 3:09:30 PM Color profile: Disabled Composite Default screen

92 M.L. Kent and T.T. Poppe

mortalities in pen-reared rainbow trout in (Berland, 1987). Intestinal infections of Atlantic Canada (McGladdery et al., 1990). seapen-reared coho salmon and rainbow Rainbow trout are accidental hosts for this trout with Hysterothylacium spp. have marine fluke, which normally infects also been observed in Chile (González and mummichog (Fundulus heteroclitus)or Carvajal, 1994). silverside (Menidia menidia) as second Calanoid copepods are the first interme- intermediate hosts. Teleost fish, such as diate host of H. aduncum, whereas fish and the American eel (Anguilla rostrata), are various invertebrates, such as polychaetes, the definitive host for the parasite in the barnacles and amphipods, act as second vicinity of the affected netpen sites. The intermediate hosts (Svendsen, 1990). first intermediate host is the mud dog whelk (Nassarius obsoletus), which is common Clinical signs and gross pathology. Carvajal around the affected netpens. et al. (1990) suggested that heavily infected fish exhibit poor growth, and Berland and Clinical signs and gross pathology. The Egidius (1980) have attributed mortalities infection was associated with high mor- in pen-reared rainbow trout in Norway talities in the summer months when water to heavy intestinal infections with H. temperatures increase, presumably due to aduncum. cardiac dysfunction (McGladdery et al., 1990). Diagnosis. Diagnosis is based on the identi- fication of the worm. Presumptive diagnosis Control and treatment. Maintaining is based on the observation of nematodes netpens in water with over 7 m clearance in gut lumen. The worms are whitish and from the bottom may reduce the intensity of cylindrical, and adults are about 40–80 mm infection (McGladdery et al., 1990). in length (Gonzáles and Carvajal, 1994). Confirmation of identification requires microscopical examination of cleared or Nematodes dissected worms for certain pathognomonic anatomical features of the worm’s digestive Nematodes (roundworms) are common tract (Möller and Anders, 1986; Berland, parasites of fish, and occasionally infect 1989). Hysterothylacium and Anisakis pen-reared salmon. As with cestodes and spp. can be differentiated from Pseudo- digenetic trematodes, fish can be either terranova and Contracaecum in that they definitive or intermediate hosts for nema- have straight digestive tracts, without a todes. Crustaceans and, less frequently, ventricular appendix or intestinal caecum. other invertebrates are the first intermediate Hysterothylacium can be separated from hosts for nematodes that infect fish. Anisakis in that the former has the excretory Members of the family Anisakidae are pore at the level of the nerve ring, whereas the only important (and reported) nema- it occurs near the anterior tip with Anisakis. todes of pen-reared salmon. The nematode that has been associated with disease in Control and treatment. To prevent infec- salmon netpens is Hysterothylacium tions with Hysterothylacium or Contracae- aduncum, which in its adult stage infects the cum spp., or to keep infection low, the use of fish digestive tract. fresh wild marine fish or fish offal as feed for Large numbers of adult Hysterothy- farmed fish should be avoided (Berland and lacium (= Thynnascaris) aduncum were Egidius, 1980; Vismanis et al., 1984). These found blocking the anterior part of the intes- fish are intermediate or paratenic (transport) tine of pen-reared rainbow trout in Norway hosts for the nematodes. González and some months after the trout were fed fresh Carvajal (1994) also referred to use of anthel- wild sprat (Sprattus sprattus) that contained mintics to reduce infections but did not juvenile H. aduncum in their viscera specify the anthelmintics they employed.

102 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:22 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 93

Acknowledgements Awakura, T. (1983) Fish disease in Hokkaido – 23. Rocinellosis of coho salmon. Uo to Mizu 21, We thank our colleagues with specific 28–29 (in Japanese). Barja, J.L. and Toranzo, A.E. (1993) Myolique- expertise in the following subjects for their faction post-mortem caused by the myxo- advice: Dr P. Bustos, ADL Diagnostics Chile sporean Kudoa thyrsites in reared Atlantic Ltda, for the P. salmonis information for salmon in Spain. Bulletin of the European Chile; Dr T.P.T. Evelyn, Canada Fisheries Association of Fish Pathologists 13, 86–88. and Oceans, for general information on Barlough, J.E., McDowell, T.S., Milani, A., bacterial diseases; and Dr S.C. Johnson, Bigornia, L., Slemenda, S.B., Pieniazek, N.J. Canadian National Research Council, for and Hedrick, R.P. (1995) Nested polymerase sea lice information. chain reaction for detection of Enterocytozoon salmonis genomic DNA in chinook salmon Oncorhynchus tshawytscha. References Diseases of Aquatic Organisms 23, 17–23. Baudin-Laurencin, F. and Bennassr, N. (1993) Post-mortem liquefaction of seawater farmed Almendras, F.E. (1996) Transmission and brown trout Salmo trutta resulting from pathogenesis of Piscirickettsia salmonis in Kudoa infections. In: Diseases of Fish and Atlantic salmon (Salmo salar). MSc Thesis, Shellfish. Book of Abstracts, Sixth Interna- Atlantic Veterinary College, Charlottetown, tional Conference of the European Associa- Prince Edward Island, Canada. tion of Fish Pathologists, 5–10 September Almendras, F.E. and Carmen Fuentealba, I. (1997) 1993, Brest, France, p. 60. Salmonid rickettsial septicaemia caused by Baxa, D.V., Kawai, K. and Kusuda, R. (1986) Char- Piscirickettsia salmonis: a review. Diseases acteristics of gliding bacteria isolated from of Aquatic Organisms 29, 137–144. diseased cultured flounder, Paralichthys Amin, A. and Trasti, J. (1988) Endomyocarditis olivaceus. Fish Pathology 21, 251–258. in Atlantic salmon in Norwegian seafarms. Baxa, D.V., Kawai, K. and Kusuda, R. (1987) Exper- A case report. Bulletin of the European imental infection of Flexibacter maritimus Association of Fish Pathologists 8, 70–71. in black seabream (Acanthopagrus schlegeli) Anderson, J.I.W. and Conroy, D.A. (1969) fry. Fish Pathology 22, 105–109. The pathogenic myxobacteria with special Baxa-Antonio, D., Groff, J.M. and Hedrick, R.P. reference to fish diseases. Journal of Applied (1992) Experimental horizontal transmission Bacteriology 32, 30–39. of Enterocytozoon salmonis to chinook Anderson, J.W. and Conroy, D.A. (1970) Vibrio salmon, Oncorhynchus tshawytscha. Journal disease in fishes. In: Snieszko, S.F. (ed.) Dis- of Protozoology 39, 699–702. eases of Fishes and Shellfishes. American Becker, C.D. (1977) Flagellate parasites of fish. Fisheries Society Special Publication 5, In: Kreier, J.P. (ed.) Parasitic Protozoa, Vol. 1 Washington, DC, pp. 266–272. Academic Press, New York, pp. 358–416. Anon. (1991) Scottish farmers take a long view on Berland, B. (1987) Helminth problems in louse control. Fish Farming International 14, sea-water aquaculture. In: Stenmark, A. and 45. Malmberg, G. (eds) Parasites and Diseases Anon. (1996) Proceedings of the Mouthrot in Natural Waters and Aquaculture in Workshop, 12 October 1995, Campbell River, Nordic Countries. Zoo-Tax, Naturhistoriska British Columbia. BC Ministry of Agri- Riksmuseet, Stockholm, pp. 56–62. culture, Fisheries, and Food, Commerical Berland, B. (1989) Identification of larval Fisheries Branch, Seafood Industry Develop- nematodes from fish. In: Moller, H. (ed.) ment Report 96-01, 26 pp. Nematode Problems in North Atlantic Fish. Armstrong, R., Robinson, J., Rymes, C. and Report from a Workshop in Kiel, 3–4 April Needham, T. (1993) Infectious haemato- 1989. International Council for the Explora- poietic necrosis in Atlantic salmon in British tion of the Sea C.M./F:6, pp. 16–22. Columbia. Canadian Veterinary Journal 34, Berland, B. and Bristow, G.A. (1994) The cestode 312–313. Eubothrium sp. in farmed marine salmon. In: Awakura, T. (1980) On the parasites and parasitic Abstracts of the 8th International Congress of disease of salmonid fish in Hokkaido. Fish Parasitology, Vol. 1, 10–14 October 1994, Pathology 14, 207–209 (in Japanese). Izmir, Turkey, p. 53.

103 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:22 AM Color profile: Disabled Composite Default screen

94 M.L. Kent and T.T. Poppe

Berland, B. and Egidius, E. (1980) Rundmark i Boyce, N.P. and Clarke, W.C. (1983) Eubothrium oppdrettsfisk – større problem enn antatt? salvelini (Cestoda: Pseudophyllidea) impairs Norsk Fiskeoppdret. Medlemsblad for seawater adaptation of migrant sockeye year- Norske Fiskeoppdretteres Forening 5, 16 lings (Oncorhynchus nerka) from Babine (in Norwegian). Lake, British Columbia. Canadian Journal of Bernardet, J.F., Campbell, A.C. and Buswell, J.A. Fisheries and Aquatic Sciences 40, 821–824. (1990) Flexibacter maritimus is the agent Brandal, P.O. and Egidius, E. (1977) Preliminary of ‘black patch necrosis’ in Dover sole in report on oral treatments against salmon lice Scotland. Diseases of Aquatic Organisms 8, Lepeophtheirus salmonis, with Neguvon. 233–237. Aquaculture 18, 177–178. Bernardet, J.-F., Segers, P., Vancanneyt, M., Brandal, P.O. and Egidius, E. (1979) Treatment Berthe, F., Kersters, K. and Vandamme, P. of salmon lice (Lepeophtheirus salmonis (1996) Cutting a Gordian knot: emended Krøyer, 1838) with Neguvon® – description classification and description of the genus of method and equipment. Aquaculture 18, Flavobacreium, emended description of the 183–188. family Flavobacteriaceae, and proposal of Brandal, P.O., Egidius, E. and Romslo, I. (1976) Flavobacterium hydatis nom. nov. (basonym, Host blood: a major food component for Cytophaga aquatilis Strohl and Tait 1978). the parasitic copepod Lepeophtheirus International Journal of Systematic Bacteri- salmonis Krøyer, 1838 (Crustacea: ology 46, 128–148. Caligidae). Norwegian Journal of Biology 24, Bloch, B., Gravningen, K. and Larsen, J.L. (1991) 341–343. Encephalomyelitis among turbot associated Branson, E.J. and Nieto Diaz-Munoz, D. (1991) with a picornavirus-like agent. Diseases of Description of a new disease condition occur- Aquatic Organisms 10, 65–70. ring in farmed coho salmon, Oncorhynchus Borg, A. (1960) Studies on myxobacteria kisutch (Walbaum), in South America. associated with diseases in salmonid Journal of Fish Diseases 14, 147–156. fishes. Wildlife Diseases (microfiche) 8, 1–85 Bravo, S. (1994) First report of Piscirickettsia (2 microcards). salmonis in freshwater. Fish Health Section/ Boxaspen, K. and Holm, J.C. (1991a) New biocides American Fisheries Society Newsletter 22, 6. used against sea lice compared to organo- Bravo, S. (1996) Enterocytozoon salmonis in phosphorous compounds. In: De Pauw, Chile. Fish Health Section/American N. and Joyce, J. (eds) Aquaculture and Fisheries Society Newsletter 24, 12–13. the Environment. European Aquaculture Bristow, G.A. and Berland, B. (1991a) A report Society Special Publication No. 16, Belgium, on some metazoan parasites of wild marine pp. 393–402. salmon (Salmo salar L.) from the west coast of Boxaspen, K. and Holm, J.C. (1991b) Norway with comments on their interactions Blomsterekstrakt som avslusingsmiddel for with farmed salmon. Aquaculture 98, laks [Extract from chrysanthemum flowers 311–318. as a delousing agent against salmon lice]. Bristow, G.A. and Berland, B. (1991b) The effect Fiskets Gang 77, 17–19. of long term, low level Eubothrium sp. Boyce, N.P.J. (1974) Biology of Eubothrium (Cestoda: Pseudophyllidea) infection on salvelini (Cestoda: Pseudophyllidae), a growth of farmed salmon (Salmo salar L.). parasite of juvenile sockeye salmon Aquaculture 98, 325–330. (Oncorhynchus nerka) of Babine Lake, Brocklebank, J.R., Speare, D.J., Armstrong, R.D. British Columbia. Journal of the Fisheries and Evelyn, T.P.T. (1992) Septicemia in Research Board of Canada 31, 1735–1742. farmed Atlantic salmon and chinook salmon Boyce, N.P. (1979) Effects of Eubothrium salvelini due to a rickettsia-like agent. Canadian (Cestoda: Pseudophyllidea) on the growth Veterinary Journal 34, 745–748. and vitality of sockeye salmon, Oncor- Bron, J.E., Sommerville, C., Jones, M. and Rae, hynchus nerka. Canadian Journal of Zoology G.H. (1991) The settlement and attachment 57, 597–602. of early stages of the salmon louse, Boyce, N.P. and Behrens-Yamada, B. (1977) Lepeophtheirus salmonis (Copepoda: Effects of a parasite, Eubothrium salvelini Caligidae) on the salmon host Salmo salar. (Cestoda: Pseudophyllidea), on the resis- Journal of Zoology 224, 201–212. tance of juvenile sockeye salmon, Oncorhyn- Bron, J.E., Sommerville, C., Wootten, R. and Rae, chus nerka, to zinc. Journal of the Fisheries G.H. (1993) Fallowing of marine Atlantic Research Board of Canada 34, 706–709. salmon, Salmo salar L., farms as a method for

104 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:22 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 95

the control of sea lice, Lepeophtheirus Christie, K.E. (1996) Immunization with viral salmonis (Krøyer, 1837). Journal of Fish and parasite antigens: infectious pancreatic Diseases 16, 487–493. necrosis. In: Book of Abstracts, International Bruno, D.W. (1992) The use of hydrogen peroxide Symposium of Fish Vaccinology, 5–7 June

(H2O2) to remove sea lice from farmed 1996, Oslo. Atlantic salmon. In: First European Con- Colwell, R.R. and Grimes, D.J. (1984) Vibrio ference on Crustacea, September 1992, diseases of marine fish populations. Paris, p.19. Helgolaender Wissenschaftliche Meeresun- Bruno, D.W. and Raynard, R.S. (1994) Studies on tersuchungen 37, 265–287. the use of hydrogen peroxide as a method for Costello, M.J. (1993) Review of methods to control the control of sea lice on Atlantic salmon. sea lice (Caligidae: Crustacea) infestations of Aquaculture International 2, 10–18. salmon (Salmo salar) farms. In: Boxshall, Bruno, D. and Poppe, T.T. (1996) A Colour Atlas G.A. and DeFaye, D. (eds) Pathogens of Wild of Salmonid Diseases. Academic Press, and Farmed Fish: Sea Lice. Ellis Horwood, London, 194 pp. Chichester, UK, pp. 219–252. Bruno, D.W., Hastings, T.S. and Ellis, A.E. (1986) Cusack, R. and Johnson, G. (1990) A study Histology, bacteriology, and experimental. of dichlorvos (Nuvan, 22,dichloro- transmission of cold water vibriosis in ethenyldimethyl phosphate) a therapeutic Atlantic salmon Salmo salar. Diseases of agent for the treatment of salmonid infected Aquatic Organisms 1, 163–168. with sea lice (Lepeophtheirus salmonis). Bruno, D.W., Collins, R.O. and Morrison, C.M. Aquaculture 90, 101–112. (1995) The occurrence of Loma salmonae sp., Cvitanich, J.D., Garate, O. and Smith, C.E. (1991) (Protozoa: Microspora) in farmed rainbow The isolation of a rickettsia-like organism trout, Oncorhynchus mykiss Walbaum, in causing disease and mortality in Chilean Scotland. Aquaculture 133, 341–344. salmonids and its confirmation by Koch’s Burridge, L.E. and Haya, K. (1993) The lethality of postulate. Journal of Fish Diseases 14, ivermectin, a potential agent for treatment of 121–145. salmonids against sea lice, to the shrimp Cvitanich, J.D., Gárate, N.O., Silva, P.C., Andrade, Cragnon septemspinosa. Aquaculture 117, V.M., Figueroa, P.C. and Smith, C.E. (1995) 9–14. Isolation of a new rickettsia-like organism Bustos, P., Entrala, P., Montana, J. and from Atlantic salmon in Chile. Fish Calbuyahue, J. (1994) Septicemia rickettsial Health Section/American Fisheries Society salmonídea (SRS): éstudio de transmisión Newsletter 23, 1–3. vertical en salmón coho (Oncorhynchus Dannevig, B.H., Falk, K. and Namork, E. (1995) kistuch). Seminario Internacional, Patología Isolation of the causal virus of infectious y Nutrición en el desarrollo de la salmon anaemia (ISA) in a long-term cell line Acuicultura: Factores de éxito, Fundación from Atlantic salmon head kidney. Journal of Chile, 3–7 October 1994, Puerto Montt, Chile. General Virology 76, 1353–1359. Cameron, D.E. (1993) Amoebic gill disease Desportes-Livae, I., Chilmonczyk, S., Hedrick, R., field research 1992/93. In: Proceedings of the Ombrouck, C., Monge, D., Maiga, I. and Saltas Research Review Seminar, 29 April Gentilini, M. (1996) Comparative develop- 1993, Hobart, Australia, pp. 89–102. ment of two microsporidian species: Entero- Cameron, D.E. (1994) AGD Field Research cytozoon bieneusi and Enterocytozoon 1993–94. III. Field testing of hydrogen per- salmonis, reported from AIDS patients and oxide with AGD-infected Atlantic salmon: salmonid fish, respectively. Journal of – efficacy and toxicity. In: Report of the Eukaryotic Microbiology 43, 49–60. Saltas 1993/94 Reseach and Development Dobson, D.P. and Tack, T.J. (1991) Evaluation Programme, Hobart, Australia, pp. 119–120. of the dispersal of treatment solutions of Carvajal, J., Ruiz, G. and González, L. (1990) dichlorvos from marine salmon pens. Presencia de Hysterothylacium sp. Aquaculture 95, 15–32. (Nematoda: Anisakidae) en salmón coho de Docker, M.F., Devlin, R.H., Richard, J. and Kent, Chiloé cultivado en jaulas. Revista Chilena M.L. (1997a) Sensitive and specific polymer- de Historia Natural 63, 165–168. ase chain reaction assay for detection of Loma Chilmonczyk, S., Cox, W.T. and Hedrick, R.P. salmonae (Microsporea). Diseases of Aquatic (1991) Enterocytozoon salmonis n. sp.: an Organisms 29, 13–20. intranuclear microsporidium from salmonid Docker, M.F., Kent, M.L., Hervio, D.M.L., Weiss, fish. Journal of Protozoology 38, 264–269. L., Cali, A. and Devlin, R.H. (1997b)

105 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:22 AM Color profile: Disabled Composite Default screen

96 M.L. Kent and T.T. Poppe

Ribosomal DNA sequence of Nucleospora Evensen, Ø., Espelid, S. and Håstein, T. salmonis Hedrick, Groff, and Baxa, 1991 (1991a) Immunohistochemical identification (Microsporea: Enterocytozooidae): implica- of Vibrio salmonicida in stored tissues of tions for phylogeny and nomenclature. Jour- Atlantic salmon, Salmo salar, from the nal of Eukaryotic Microbiology 44, 55–60. first known outbreak of coldwater vibriosis Drinan, E.M. and Rodger, H.D. (1990) An occur- (‘Hitra disease’). Diseases of Aquatic Organ- rence of Gnathia sp., ectoparasitic isopods, isms 10, 185–189. on caged Atlantic salmon. Bulletin of the Evensen, Ø., Thorud, K.E. and Olsen, Y.A. (1991b) European Association of Fish Pathologists A morphological study of the gross and light 10, 141–142. microscopic lesions of infectious salmon Eaton, W.D. and Kent, M.L. (1992) A retrovirus anaemia in Atlantic salmon (Salmo salar). in chinook salmon (Oncorhynchus Research in Veterinary Science 51, 215–222. tshawytscha) with plasmacytoid leukemia Ferguson, H.W. and Moccia, R.D. (1980) Dissemi- and evidence for the aetiology of the disease. nated hexamitiasis in siamese fighting fish. Cancer Research 52, 6496–6500. Journal of the American Veterinary Medical Egidius, E. (1987) Vibriosis: pathogenicity and Association 177, 854–857. pathology. A review. Aquaculture 67, 15–28. Ferguson, H.W., Poppe, T. and Speare, D. (1990) Egidius, E., Andersen, K., Clausen, E. and Raa, J. Cardiomyopathy in farmed Norwegian (1981) Cold-water vibriosis or ‘Hitra disease’ salmon. Diseases of Aquatic Organisms 8, in Norwegian salmonid farming. Journal of 225–231. Fish Diseases 4, 353–354. Ferguson, H.W., Roberts, R.J., Richards, R.H., Col- Egidius, E. and Moster, B. (1987) Effect of lins, R.O. and Rice, D.A. (1986) Severe degen- Neguvon® and Nuvan® on crabs (Cancer erative cardiomyopathy associated with pan- pagurus), lobster (Homarus americanus) and creas disease in Atlantic salmon, Salmo salar blue mussel (Mytilus edulis). Aquaculture L. Journal of Fish Diseases 20, 95–98. 60, 165–168. Frelier, P., Elston, R.A., Loy, J.K. and Mincher, C. Elston, R.A., Kent, M.L. and Harrell, L.H. (1987) (1994) Macroscopic and microscopic fea- An intranuclear microsporidium associated tures of ulcerative stomatitis in farmed with acute anaemia in chinook salmon, Atlantic salmon Salmo salar. Diseases of Oncorhynchus tshawytscha. Journal of Aquatic Organisms 18, 227–231. Protozoology 34, 274–277. Frerichs, G.N. and Roberts, R.J. (1989) The Enger, Ø., Husevåg, B. and Goksøyr, J. (1989) bacteriology of teleosts. In: Roberts, R.J. (ed.) Presence of Vibrio salmonicida in fish farm Fish Pathology. Baillière Tindall, London, sediments. Applied Environmental Micro- pp. 289–319. biology 55, 2815–2818. Fryer, J.L., Lannan, C.N., Garcés, L.H., Larenas, J.J. Espelid, S., Roedseth, O.M. and Jørgensen, T.O. and Smith, P.A. (1990) Isolation of a (1991) Vaccine experiments and studies of rickettsiales-like organism from diseased the humoral immune responses in cod, coho salmon (Oncorhynchus kisutch)in Gadus morhua L., to four strains of Chile. Fish Pathology 25, 107–114. monoclonal-defined Vibrio anguillarum. Fryer, J.L., Lannan, C.N., Giovannoni, S.J. and Journal of Fish Diseases 14, 185–197. Wood, N.D. (1992) Piscirickettsia salmonis Evelyn, T.P.T. (1971) First records of vibriosis gen. nov., sp. nov., the causative agent of an in Pacific salmon cultured in Canada, epizootic disease in salmonid fishes. Inter- and taxonomic status of the responsible national Journal of Systematic Bacteriology bacterium, Vibrio anguillarum. Journal of the 42, 120–126. Fisheries Research Board of Canada 28, Gaggero, A., Castro, H. and Sandino, A.M. (1995) 517–525. First isolation of Piscirickettsia salmonis Evelyn, T.P.T. (1984) Immunization against from coho salmon, Oncorhynchus kisutch pathogenic vibrios. In: de Kinkelin, P. and (Walbaum), and rainbow trout, Oncor- Michel, C. (eds) Symposium on Fish Vaccina- hynchus mykiss (Walbaum), during the tion. OIE Fish Diseases Commission, Paris, freshwater phase of their cycle. Journal of pp. 121–150. Fish Diseases 18, 277–279. Evelyn, T.P.T. (1988) Vibrio vaccines for Garcés, L.H., Larenas, J.J., Smith, P.A., Sandino, salmonids. In: Congress Proceedings, S., Lannan, C.N. and Fryer, J.L. (1991) Aquaculture International Congress and Infectivity of a rickettsia isolated from coho Exposition, 6–9 September 1988, Vancouver, salmon Oncorhynchus kisutch. Diseases of British Columbia, Canada, pp. 459–469. Aquatic Organisms 11, 93–97.

106 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:23 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 97

Garcés, L.H., Correal, P., Larenas, J., Contreras, J., Groman, D., Tweedie, D. and Shaw, D. (1992) Oyanadel, S., Fryer, J.L. and Smith-Shuster, Experiences with atypical furunculosis in P.A. (1994) Finding of Piscirickettsia Newfoundland: an overview. Bulletin of the salmonis on Ceratothoa gaudichadii. In: Aquaculture Association of Canada 92–1, Abstracts of the International Symposium 36–39. on Aquatic Animal Health, 4–8 September Grotmol, S., Totland, G.K., Kvellestad, A., Fjell, K. 1994, Seattle, Washington, p. 109. and Olsen, A.B. (1995) Mass mortality of Gibson, D.I. (1996) Trematoda. In: Margolis, L. and larval and juvenile hatchery-reared halibut Kabata, Z. (eds) Guide to the Parasites of (Hippoglossus hippoglossus L.) associated Fishes of Canada, Part IV. Canadian Special with the presence of virus-like particles in Publication of Fisheries and Aquatic Sci- vacuolated lesions in the central nervous ences 124, 373 pp. system and retina. Bulletin of the European González, L. and Carvajal, G.J. (1994) Parásitos en Association of Fish Pathologists 15, 176–180. los cultivos marinos de salmónidos en el sur Grotmol, S., Totland, G.K. and Kryvi, H. (1997) de Chile. Investigacion Pesquera (Chile) 38, Detection of a nodavirus-like agent in heart 87–96. tissue from reared Atlantic salmon Salmo Grant, A.N. and Treasurer, J.W. (1993) The effects salar suffering from cardiac myopathy syn- of fallowing on caligid infestations on farmed drome (CMS). Diseases of Aquatic Organisms Atlantic salmon (Salmo salar L.) in Scotland. 29, 79–84. In: Boxshall, G.A. and DeFaye, D. (eds) Patho- Handlinger, J., Soltani, M. and Percival, S. (1997) gens of Wild and Farmed Fish: Sea Lice. Ellis The pathology of Flexibacter maritimus in Horwood, Chichester, UK, pp. 255–260. aquaculture. Journal of Fish Diseases 20, Grant, A.N., Brown, A.G., Cox, D.I., Birkbeck, 159–168. T.H. and Griffen, A.A. (1996) Rickettsia-like Harrell, L.W. and Scott, T.M. (1985) Kudoa organism in farmed salmon. Veterinary thyrsitis (Gilchrist) (Myxosporea: Multi- Record 138, 423 pp. (correspondence). valvulida) in Atlantic salmon, Salmo salar L. Grave, K., Engelstad, M. and Sóli, N.E. (1991a) Journal of Fish Diseases 8, 329–332. Utilization of dichlorvos and trichlorfon Harrell, L.W., Novotny, A.J., Schiewe, M.H. in salmonid farming in Norway during and Hodgins, H.O. (1976) Isolation and 1981–1988. Acta Veterinaria Scandinavica description of two vibrios pathogenic to 32, 1–7. Pacific salmon in Puget Sound, Washington. Grave, K., Engelstad, M., Sóli, N.E. and Toverud, Fisheries Bulletin (US) 74, 447–449. E.-L. (1991b) Clinical use of dichlorvos Håstein, T. and Lindstad, T. (1991) Diseases (Nuvan®) and trichlorfon (Neguvon®)inthe in wild and cultured salmon: possible inter- treatment of salmon louse, Lepeophtheirus action. Aquaculture 98, 277–288. salmonis: compliance with the recommen- Hauck, A.K. (1984) A mortality and associated ded treatment procedures. Acta Veterinaria tissue reactions of chinook salmon, Scandinavica 32, 9–14. Oncorhynchus tshawytscha (Walbaum), Grayson, T.H., Jenkins, P.G., Wrathmell, A.B. and caused by the microsporidan Loma sp. Jour- Harris, J.E. (1991) Serum responses to the nal of Fish Diseases 7, 217–229. salmon louse, Lepeophtheirus salmonis Hedrick, R.P., Groff, J.M., McDowell, T.S., Willis, (Krøyer, 1838), in naturally infected M. and Cox, W.T. (1990) Haematopoietic salmonids and immunized rainbow trout, intranuclear microsporidian infections with Oncorhynchus mykiss (Walbaum), and features of leukemia in chinook salmon rabbits. Fish and Shellfish Immunology 1, Oncorhynchus tshawytscha. Diseases of 141–155. Aquatic Organisms 8, 189–197. Grayson, T.H., John, R.J., Wadsworth, S., Greaves, Hedrick, R.P., Groff, J.M. and Baxa, D.V. (1991a) K., Cox, D., Roper, J., Wrathmell, A.B., Gilpin, Experimental infections with Nucleospora M.L. and Harris, J.E. (1995) Immunization of salmonis n.g. n.sp.: an intranuclear micro- Atlantic salmon against the salmon louse: sporidium from chinook salmon (Oncor- identification of antigens and effects on louse hynchus tshawytscha). Fish Health Section/ fecundity. Journal of Fish Biology 47 (Suppl. American Fisheries Society Newsletter 19, 5. A), 85–94. Hedrick, R.P., Groff, J.M. and Baxa, D.V. Grisez, L., Ceusters, R. and Ollevier, F. (1991) The (1991b) Experimental infections with use of API 20E for the identification of Vibrio Enterocytozoon salmonis Chilmonczyk, Cox, anguillarum and V. ordalii. Journal of Fish Hedrick (Microsporea): an intranuclear Diseases 14, 351–365. microsporidium from chinook salmon

107 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:23 AM Color profile: Disabled Composite Default screen

98 M.L. Kent and T.T. Poppe

Oncorhynchus tshawytscha. Diseases of Howard, T. and Carson, J. (1993b) Are there Aquatic Organisms 10, 103–108. alternatives to freshwater treatment of AGD? Hervio, D.M.L., Kent, M.L., Khattra, J., Sakanari, J., In: Proceedings of the Saltas Research Review Yokoyama, H. and Devlin, R.H. (1997) Seminar, 29 April 1993, Hobart, Australia, Taxonomy of Kudoa species (Myxosporea: pp. 81–87. Multivalvulida) using small subunit ribo- Inostroza, R., Sievers, G., Roa, J. and Aguirrebena, somal DNA sequence. Canadian Journal of R. (1993) Prevalencia e intensidad de infecc- Zoology 75, 2112–2119. ion estacional por Ceratothoa gaudichaudii Hicks, B. (1989) British Columbia Salmonid en salmones (Salmo salar) cutlivados en aqua Disease Handbook. Province of British de mar en el sur de Chile. Archivos de Columbia, Ministry of Agriculture and Medicina Veterinaria (Valdivia) 25, 173–179. Fisheries, Victoria, British Columbia, 40 pp. Jarp, J., Gjevre, A.G., Olsen, A.B. and Bruheim, T. Higgins, M., Dawe, S.C. and Kent, M.L. (1998) Effi- (1994) Risk factors associated with furun- cacy of the fumagillin analog TNP-470, for culosis, infectious pancreatic necrosis and Nucleospora salmonis and Loma salmonae mortality in post-smolt of Atlantic salmon, infections in chinook salmon Oncorhynchus Salmo salar L. Journal of Fish Diseases 18, tshawytscha. Diseases of Aquatic Organisms 67–78. 34, 45–49. Jarp, J., Taksdal, T. and Trøud, B. (1996) Infectious Hikida, M., Wakabayashi, H., Egusa, S. and pancreatic necrosis in Atlantic salmon Salmo Masumura, K. (1979) Flexibacter sp., a salar in relation to specific antibodies, smol- gliding bacterium pathogenic to some marine tification, and infection with erythrocytic fishes in Japan. Bulletin of the Japanese Soci- inclusion body syndrome (EIBS). Diseases of ety of Scientific Fisheries 45, 421–428. Aquatic Organisms 27, 81–88. Hilger, I., Ulrich, S. and Anders, K. (1991) A new Johnson, S.C. and Albright, L.J. (1991) The devel- ulcerative flexibacteriosis-like disease (‘yel- opmental stages of Lepeophtheirus salmonis low pest’) affecting young Atlantic cod Gadus (Krøyer, 1837) (Copepoda: Caligidae). Cana- morhua from the German Wadden Sea. Dis- dian Journal of Zoology 69, 929–950. eases of Aquatic Organisms 11, 19–29. Johnson, S.C. and Albright, L.J. (1992) The effects Hodneland, K., Nylund, A., Nilsen, F. and of cortisol implants on the susceptibility and Midttun, B. (1993) The effect of nuvan, histopathology of the responses of naive coho azamethiphos and hydrogen peroxide on salmon Oncorhynchus kisutch to experi- salmon lice (Lepeophtheirus salmonis). mental infection with Lepeophtheirus Bulletin of the European Association of Fish salmonis (Copepoda: Caligidae). Diseases of Pathologists 13, 203–206. Aquatic Organisms 14, 195–205. Hoffman, G.L. and Meyer, F.P. (1974) Parasites of Johnson, S.C. and Margolis, L. (1993) The efficacy Freshwater Fish. TFH Publishers, Neptune of ivermectin for the control of sea lice City, New Jersey, 224 pp. on sea-farmed Atlantic salmon. Diseases Holm, K.O., Strøm, E., Stensvåg, K., Raa, J. of Aquatic Organisms 17, 107–112. and Jørgensen, T. (1985) Characteristics of a Johnson, S.C. and Margolis, L. (1994) Sea lice. Vibrio sp. associated with the ‘Hitra Disease’ In: Thoesen, J.C. (ed.) Suggested Procedures of Atlantic salmon in Norwegian fish farms. for the Detection and Identification of Fish Pathology 20, 125–129. Certain Finfish and Shellfish Pathogens, 4th Houghton, G. (1994) Acquired protection in edn. Fish Health Section, American Fisheries Atlantic salmon Salmo salar parr and post- Society, 10 pp. smolts against pancreas disease. Diseases of Johnson, S.C., Constible, J.M. and Richard, J. Aquatic Organisms 18, 109–118. (1993) Laboratory investigations of the House, M.L., Bartholomew, J.L., Winton, J.R. and toxicological and histopathological effects of Fryer, J.L. (1998) Relative virulence of three hydrogen peroxide to salmon and its efficacy isolates of Piscirickettsia salmonis for coho against the salmon louse Lepeophtheirus salmon Oncorhynchus kisutch. Diseases of salmonis. Diseases of Aquatic Organisms 17, Aquatic Organisms 35, 107–113. 197–204. Howard, T. and Carson, J. (1993a) Verification Johnson, S.C., Blaylock, R.B., Elphick, J. and that Paramoeba species are consistently Hyatt, K. (1996) Disease caused by the salmon associated with gill damage in fish affected louse Lepeophtheirus salmonis (Copepoda: with amoebic gill disease. In: Proceedings Caligidae) in wild sockeye salmon of the Saltas Research Review Seminar,29 (Oncorhynchus nerka) stocks of Alberni April 1993, Hobart, Australia, pp. 69–80. Inlet, British Columbia. Canadian Journal

108 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:23 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 99

of Fisheries and Aquatic Sciences 53, Kent, M.L. and Dawe, S.C. (1994) Efficacy of 2888–2897. Fumagillin DCH against experimentally- Jones, M.W., Sommerville, C. and Wootten, R. induced Loma salmonae (Microsporea) (1992) Reduced sensitivity of the salmon infections in chinook salmon Oncorhynchus louse, Lepeophtheirus salmonis,tothe tshawytscha. Diseases of Aquatic Organisms organophosphate dichlorvos. Journal of Fish 20, 231–233. Diseases 15, 197–202. Kent, M.L. and Elston, R.A. (1987) Diseases of Jones, S.R.M., MacKinnon, A.M. and Groman, seawater reared salmon in Washington State. D.B. (1999) Virulence and pathogenicity of In: Proceedings of the Fourth Alaska infectious salmon anemia virus isolated from Aquaculture Conference. Alaska Sea Grant farmed salmon in Atlantic Canada. Journal of Report No. 88 4, pp. 161–163. Aquatic Animal Health 11, 400–405. Kent, M.L. and Poppe, T.T. (1998) Diseases of Jónsdóttir, H., Bron, J.E., Wootten, R. and Seawater Netpen-reared Salmonids. Pacific Turnbull, J.F. (1992) The histopathology Biological Station Press, Nanaimo, British associated with the pre-adult and adult stages Columbia, Canada, 138 pp. of Lepeophtheirus salmonis on the Atlantic Kent, M.L., Dungan, C.F., Elston, R.A. and Holt, salmon, Salmo salar L. Journal of Fish R.A. (1988a) Cytophaga sp. (Cytophagales) Diseases 15, 521–527. infection in seawater pen-reared Atlantic Jørgensen, T., Midling, K., Espelid, S., Nilsen, R. salmon Salmo salar. Diseases of Aquatic and Stensvåg, K. (1989) Vibrio salmonicida, Organisms 4, 173–179. previously registered as a pathogen in Kent, M.L., Sawyer, T.K. and Hedrick, R.P. salmonids, does also cause mortality in (1988b) Paramoeba pemaquidensis (Sarco- netpen captured cod (Gadus morhua). mastigophora: Paramoebidae) infestation of Bulletin of the European Association of Fish the gills of coho salmon Oncorhynchus Pathologists 9, 42–44. kisutch reared in seawater. Diseases of Kabata, Z. (1970) Crustacea as Enemies of Fishes. Aquatic Organisms 5, 163–169. In: Snieszko, S.F. and Axelrod, H.R. (series Kent, M.L., Elliot, D.G., Groff, J.M. and Hedrick, eds) Diseases of Fish. TFH Publications, R.P. (1989) Loma salmonae (Protozoa: Jersey City, New Jersey. Microspora) infections in seawater reared Kabata, Z. (1979) Parasitic Copepoda of British coho salmon (Oncorhynchus kisutch). Fishes. The Ray Society, London, 468 pp. Aquaculture 80, 211–222. Kabata, Z. (1984) Diseases caused by metazoans: Kent, M.L., Groff, J.M., Traxler, G.S., Zinkl, J.G. crustaceans. In: Kinne, O. (ed.) Diseases of and Bagshaw, J.W. (1990) Plasmacytoid Marine Animals, Vol. 4, Part 1. Biologische leukemia in seawater reared chinook salmon Anstalt Helgoland Hamburg, pp. 321–399. Oncorhynchus tshawytscha. Diseases of Kabata, Z. (1988) Copepoda and Branchiura. Aquatic Organisms 8, 199–209. In: Margolis, L. and Kabata, Z. (eds) Guide to Kent, M.L., Margolis, L. and Fournie, J.W. (1991) the Parasites of Fishes of Canada. Part II. A new eye disease in pen-reared chinook Crustacea. Canadian Special Publication caused by metacestodes of Gilquinia squali of Fisheries and Aquatic Sciences 101, (Trypanorhyncha). Journal of Aquatic Ani- pp. 3–127. mal Health 3, 134–140. Kabata, Z. and Whitaker, D.J. (1981) Two species Kent, M.L., Ellis, J., Fournie, J.W., Dawe, S.C., of Kudoa (Myxosporea: Multivalvulida) Bagshaw, J.W. and Whitaker, D. (1992) parasitic in the flesh of Merluccius productus Systemic hexamitid infection in seawater (Ayres, 1855) (Pisces: Teleostei) in the pen-reared chinook salmon Oncorhynchus Canadian Pacific. Canadian Journal of tshawytscha. Diseases of Aquatic Organisms Zoology 59, 2085–2091. 14, 81–89. Kent, M.L. (1982) Characteristics and identifica- Kent, M.L., Dawe, S.C. and Speare, D.J. (1995) tion of Pasteurella and Vibrio species patho- Transmission of Loma salmonae (Micro- genic to fishes using API-20E (Analytab sporea) to chinook salmon in seawater. Products) Multitube Test Strips. Canadian Canadian Veterinary Journal 36, 98–102. Journal of Fisheries and Aquatic Sciences 39, Kent, M.L., Whitaker, D.J., Moran, J. and Kabata, Z. 1725–1729. (1997) Haemobaphes disphaerocephalus Kent, M.L. and Dawe, S.C. (1990) Transmission (Pennellidae: Copepoda), an accidental of a plasmacytoid leukemia of chinook parasite of seawater pen-reared Atlantic salmon Oncorhynchus tshawytscha. Cancer salmon. Canadian Veterinary Journal 38, Research (Suppl.) 50, 5679s–5681s. 110–111.

109 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:23 AM Color profile: Disabled Composite Default screen

100 M.L. Kent and T.T. Poppe

Kent, M.L., Traxler, G.S., Kieser, D., Richard, J., Lannan, C.N. and Fryer, J.L. (1991) Recommended Dawe, S.C., Shaw, R.W., Prosperi-Porta, G., methods for inspection of fish for the Ketcheson, J. and Evelyn, T.P.T. (1998) Sur- salmonid ricketttsia. Bulletin of the Euro- vey of salmonid pathogens in ocean-caught pean Association of Fish Pathologists 11, fishes in British Columbia, Canada. Journal 135–136. of Aquatic Animal Health 10, 211–219. Lannan, C.N. and Fryer, J.L. (1994) Extracellular Khalil, L.F., Jones, A. and Bray, R.A. (eds) (1994) survival of Piscirickettsia salmonis. Journal Keys to the Cestode Parasites of Vertebrates. of Fish Diseases 17, 545–548. CAB International, Wallingford, UK, 751 pp. Lannan, C.N., Ewing, S.A. and Fryer, J.L. (1991) Khan, R.A. (1988) Experimental transmission, A fluorescent antibody test for detection development, and effects of a parasitic of the rickettsia causing disease in Chilean copepod, Lernaeocera branchialis,on salmonids. Journal of Aquatic Animal Health Atlantic cod, Gadus morhua. Journal of 3, 229–234. Parasitology 74, 586–599. Larenas, J.J., Astroga, C., Contreras, J. and Smith, P. Khan, R.A., Lee, E.M. and Barker, D. (1990) (1996) Detección de Piscirickettsia salmonis Lernaeocera branchialis: a potential patho- en ovas fertilizadas provenientes de trucha gen to cod ranching. Journal of Parasitology arco iris (Oncorhynchus mykiss) experimen- 76, 913–917. talemente infectadas. Archivo di Medicina Kimura, T. and Yoshimizu, M. (1991) Viral Veterinaria (Valdivia) 28, Communicaciones diseases of fish in Japan. Annual Review No. 2. of Fish Diseases 1, 67–82. Lysne, D.A., Hemmingsen, W. and Skorping, A. Kimura, T., Yoshimizu, M. and Tanaka, M. (1981a) (1994) The distribution of Cryptocotyle spp. Studies on a new virus (OMV) from Oncor- metacercariae in the skin of caged Atlantic hynchus masou. II. Oncogenic nature. Fish cod (Gadus morhua). Journal of Fish Biology Pathology 15, 149–153. 45, 352–355. Kimura, T., Yoshimizu, M., Tanaka, M. and MacKenzie, K. (1965) The plerocercoid of Sannohe, H. (1981b) Studies on a new Gilquinia squali Fabricius, 1794. Parasit- virus (OMV) from Oncorhynchus masou. ology 55, 607–615. I. Characteristics and pathogenicity. Fish MacKenzie, K. (1975) Some aspects of the biology Pathology 15, 149–153. of the plerocercoid of Gilquinia squali Kimura, T., Suzuki, S. and Yoshimizu, M. Fabricius 1794 (Cestoda: Trypanorhyncha). (1983) In vitro antiviral effect of 9-(2hydroxy- Journal of Fish Biology 7, 321–327. ethoxymethyl) guanine on the fish herpes MacKinnon, B.M. (1991) Sea lice and Atlantic virus (OMV). Antiviral Research 3, 103–108. salmon: absence of immunoprotection in Kitao, I., Aoki, I. and Muroga, K. (1984) Three new Salmo salar to Caligus elongatus. Bulletin of O-serotypes of Vibrio anguillarum. Bulletin the Aquaculture Association of Canada 91, of the Japanese Society of Scientific Fisheries 58–60. 50, 1955. Markey, P.T., Blazer, V.S., Ewing, M.S. and Kocan, Krogsrud, J., Håstein, T. and Ronningen, K. (1989) K.M. (1994) Loma sp. in salmonids from Infectious pancreatic necrosis virus in eastern United States: associated lesions in Norwegian fish farms. In: Ahne, W. and rainbow trout. Journal of Aquatic Animal Kurstak, E. (eds) Viruses of Lower Verte- Health 6, 318–328. brates. Springer-Verlag, Berlin, pp. 284–291. Masumura, K. and Wakabayashi, H. (1977) An Kumagai, A., Takahashi, K. and Fukuda, H. (1994) outbreak of gliding bacterial disease in Epizootics caused by salmonid herpesvirus hatchery-born red seabream (Pagrus major) type 2 infection in maricultured coho and gilthead (Acanthopagrus schlegeli) fry in salmon. Fish Pathology 29, 127–134. Hiroshima. Fish Pathology 12, 171–177. Kumagai, A., Takahashi, K. and Fukuda, H. (1997) Mattis, T.E. (1986) Development of two tetrarhyn- Infection source of herpesvirus disease in chidean cestodes from the northern Gulf coho salmon culture and its control. Fish of Mexico. PhD dissertation. University of Pathology 32, 103–108. Southern Mississippi, Mississippi, 172 pp. Kvenseth, P.G. (1993) Use of wrasse to control Mauel, M.J., Giovannoni, S.J. and Fryer, J.L. (1996) sea lice. In: Reinersten, H., Dahle, L.A., Development of polymerase chain reaction Jørgensen, T.L. and Tvinnereim, K. (eds) Fish assays for detection, identification, and Farming Technology. Balkema, Rotterdam, differentiation of Piscirickettsia salmonis. pp. 227–232. Diseases of Aquatic Organisms 26, 189–195.

110 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:23 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 101

McElwain, I.B. and Post, G. (1968) Efficacy Moran, J.D.W., Margolis, L., Webster, J.M. and of cyzine for trout hexamitiasis. The Pro- Kent, M.L. (1999a) Sequential development gressive Fish-Culturist 30, 84–91. of Kudoa thyrsites (Myxozoe: Myxosporea) in McGladdery, S.E., Murphy, L., Hicks, B.D. and netpen-reared Atlantic salmon determined Wagner, S.K. (1990) The effects of Stephano- by light microscopy and a polymerase chain stomum tenue (Digenea: Acanthocolpidae) reaction test.. Diseases of Aquatic Organisms on marine aquaculture of rainbow trout, 37, 185–193. Salmo gairdneri. In: Perkins, F.O. and Cheng, Moran, J.D.W., Whitaker, D.J. and Kent, M.L. T.C. (eds) Pathology in Marine Science. (1999b) Natural and laboratory transmission Academic Press, San Diego, California, of the marine myxosporean parasite Kudoa pp. 305–315. thyrsites to Atlantic salmon. Journal of McLoughlin, M.F., Nelson, R.T., Rowley, H.M., Aquatic Animal Health 11, 110–115. Cox, D.I. and Grant, A.N. (1996) Experi- Morrison, C.M. (1983) The distribution of the mental pancreas disease in Atlantic salmon microsporidian Loma morhua in tissues of Salmo salar post-smolts induced by salmon the cod Gadus morhua L. Canadian Journal pancreas disease virus (SPDV). Diseases of of Zoology 61, 2155–2161. Aquatic Organisms 26, 117–124. Morrison, C.M. and Sprague, V. (1981) Micro- McVicar, A.H. (1987) Pancreas disease of farmed sporidian parasites in the gills of salmonid Atlantic salmon, Salmo salar, in Scotland: fishes. Journal of Fish Diseases 4, 371–386. epidemiology and early pathology. Aqua- Morrison, C.M. and Sprague, V. (1983) Loma culture 67, 71–78. salmonae (Putz, Hoffman and Dunbar 1965) McVicar, A.H. and Munro, A.L.S. (1987) Pancreas in the rainbow trout, Salmo gairdneri Disease in Farmed Atlantic Salmon: Evi- Richardson, and L. fontinalis sp. nov. dence for an Infectious Aetiology. Inter- (Microsporida) in the brook trout, Salvelinus national Council for the Exploration of the fontinalis (Mitchell). Journal of Fish Diseases Sea – CM 1987/F:6 Mariculture Committee. 6, 345–353. Melby, H.P., Krogsrud, J., Håstein, T. and Stenwig, Morrison, J.K., MacConnell, E., Chapman, P.F. and H. (1991) All commercial Atlantic salmon Westgard, R.L. (1990) A microsporidium- seawater farms in Norway harbour carriers of induced lymphoblastosis in chinook salmon infectious pancreatic necrosis virus (IPNV). Oncorhynchus tshawytscha. Diseases of In: Fryer, J.L. (ed.) Proceedings of the 2nd Aquatic Organisms 8, 99–104. International Symposium on Viruses of Mullins, J.E., Powell, M., Speare, D.J. and Lower Vertebrates. Oregon State University, Cawthorn, R. (1994) An intranuclear micro- Corvallis, Oregon, pp. 211–217. sporidian in lumpfish Cyclopterus lumpus. Menzies, F.D., Wheatley, S.B., Goodall, E.A. and Diseases of Aquatic Organisms 20, 7–13. McLoughlin, M.F. (1996) Development of a Munday, B.L., Lange, K., Foster, C., Lester, R.J.G. computerised information retrieval system and Handlinger, J. (1993) Amoebic gill dis- for Atlantic salmon (Salmo salar). Aqua- ease of sea-caged salmonids in Tasmanian culture Research 27, 183–190. waters. Tasmanian Fisheries Research 28, Mitchell, C.G. (1993) Eubothrium. Aquaculture 14–19. Information Series 14, Scottish Office Mundry, D.R. and Dailey, M.D. (1971) Agriculture and Fisheries for Scotland, Postembryonic development of certain Aberdeen, UK. tetraphyllidean and trypanorhynchan Mjaaland, S., Rimstad, E., Falk, K. and Dannevig, cestodes with a possible alternative life B.H. (1997) Genomic characterization of the cycle for the order Trypanorhyncha. Cana- virus causing infectious salmon anaemia dian Journal of Zoology 49, 1249–1253. in Atlantic salmon (Salmo salar L.): an Munro, A.L.S., Ellis, A.E., McVicar, A.H., McLay, orthomyxo-like virus in a teleost. Journal of A.H. and Needham, E.A. (1984) An exocrine Virology 71, 7681–7686. pancreas disease of farmed Atlantic salmon Mo, T.A., Poppe, T.T. and Iversen, L. (1990) in Scotland. Helgolaender Meeresunterssu- Systemic hexamitosis in salt-water reared chungen 37, 571–586. Atlantic salmon. Bulletin of the European Nagasawa, K. and Sakamoto, S. (1993) Infection of Association of Fish Pathologists 10, 69–70. the salmon louse Lepeophtheirus salmonis Möller, H. and Anders, K. (1986) Diseases and (Copepoda: Caligidae) on seawater-farmed Parasites of Marine Fishes. Verlag Möller, salmonids in Northern Honshu, Japan. Kiel, Germany, 365 pp. Grobyo Kenkyu 28, 143–144.

111 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:24 AM Color profile: Disabled Composite Default screen

102 M.L. Kent and T.T. Poppe

Nelson, R.T., McLouglin, M.F., Rowley, H.M., of British Columbia, Ministry of Agricul- Platten, M.A. and McCormick, J.I. (1995) ture, Fisheries and Food, Victoria, British Isolation of a toga-like virus from farmed Columbia, Canada. Atlantic salmon Salmo salar with pancreas Palmer, R., Rodger, H., Drian, E., Dwyer, C. disease. Diseases of Aquatic Organisms 22, and Smith, P.R. (1987) Preliminary trials on 25–32. the efficacy of Ivermectin against parasitic Newbound, G.C. and Kent, M.L. (1991) copepods of Atlantic salmon. Bulletin of the Experimental interspecies transmission of European Association of Fish Pathologists 7, plasmacytoid leukemia in salmonid fishes. 47–54. Diseases of Aquatic Organisms 10, 159–166. Patashnik, M., Groninger, H.S., Barnett, H., Nilsen, F., Ness, A. and Nylund, A. (1995) Obser- Kudo, G. and Koury, B. (1982) Pacific vations on an intranuclear microsporidian in whiting, Merluccius productus. I. Abnormal lymphoblasts from farmed Atlantic halibut muscle texture caused by myxosporidian- larvae (Hippoglossus hippoglossus L.). Jour- induced proteolysis. Marine Fisheries nal of Eukaryotic Microbiology 42, 131–135. Review 44, 1–12. Novotny, A.J. (1978) Vibriosis and furunculosis Poppe, T.T. and Mo, T.A. (1993) Systemic, in marine cultured salmon in Puget Sound, granulomatous hexamitosis of farmed Washington. Marine Fisheries Review 40, Atlantic salmon: interaction with wild fish. 52–55. Fisheries Research 17, 147–152. Novotny, A.J. and Mahnken, C.V.W. (1971) Poppe, T.T., Mo, T.A. and Iversen, L. (1992) Predation on juvenile Pacific salmon by a Disseminated hexamitosis in sea-caged marine isopod Rocinela belliceps pugettensis Atlantic salmon Salmo salar. Diseases of (Crustacea, Isopoda). US National Marine Aquatic Organisms 14, 91–97. Fisheries Service Fishery Bulletin 69, Poynton, S.L. (1986) Distribution of the flagellate 699–701. Hexamita salmonis Moore, 1922 and the Nylund, A. and Jakobsen, P. (1995) Sea trout as a microsporidian Loma salmonae Putz, carrier of infectious salmon anaemia virus. Hoffman and Dunbar, 1965 in brown trout, Journal of Fish Biology 47, 174–176. Salmo trutta L., and rainbow trout, Salmo Nylund, A., Hovland, T., Hodneland, K., Nilsen, F. gairdneri Richardson, in the River Itchen and Løvik, P. (1994) Mechanisms for trans- (UK) and three of its fish farms. Journal of mission of infectious salmon anaemia (ISA). Fish Biology 29, 417–429. Diseases of Aquatic Organisms 19, 95–100. Putz, R.E. and McLaughlin, J.J.A. (1970) The O’Halloran, J. and Henry, R. (1993) Vibrio biology of Nosematidae (Microsporida) salmonicida (Hitra disease) in New Bruns- from freshwater and euryhaline fishes. wick. Bulletin of the Aquaculture Associa- In: Snieszko, S.F. (ed.) A Symposium on tion of Canada 4, 96–98. Diseases of Fishes and Shellfishes. Special Olsen, A.B., Melby, H.P., Speilberg, L., Eversen, Publication No. 5, American Fisheries Soci- Ø. and Håstein, T. (1997) Piscirickettsia ety, Washington, DC, pp. 124–132. salmonis infection in Atlantic salmon Salmo Putz, R.E., Hoffman, G.L. and Dunbar, C.E. (1965) salar in Norway – epidemiological, patholog- Two new species of Plistophora (Micro- ical and microbiological findings. Diseases of sporidea) from North American fish with a Aquatic Organisms 31, 35–48. synopsis of Microsporidea of freshwater and Overstreet, R.M. (1978) Marine Maladies? Worms, euryhaline fishes. Journal of Protozoology 12, Germs and Other Symbionts From the North- 228–236. ern Gulf of Mexico. Blossman Printing, Ocean Reichenbach, H. (1988) Order Cytophagales. Springs, Mississippi, 140 pp. In: Holt, J.G., Staley, J.T., Bryant, M.P. Pacha, R.E. and Ordal, E.J. (1970) Myxobacterial and Pfennig, N. (eds) Bergey’s Manual diseases of salmonids. In: Snieszko, S.F. (ed.) of Systematic Bacteriology, Vol. 3, A Symposium on Diseases of Fishes and Williams & Wilkins, Baltimore, Maryland, Shellfishes. Special Publication No.5, pp. 2011–2066. American Fisheries Society, Washington, Rodger, H.D. and Drinan, E.M. (1993) Observa- DC, pp. 243–247. tions on a rickettsia-like organism in Atlantic Palmer, R. (1994) Kudoa – the Irish experience. salmon, Salmo salar L., in Ireland. Journal of In: Conley, D.C. (ed.) Kudoa Workshop Pro- Fish Diseases 16, 361–369. ceedings, 17–18 February 1994, Nanaimo, Rodger, H.D. and McArdle, J.F. (1996) An outbreak British Columbia. Aquaculture Industry of amoebic gill disease in Ireland. The Development Report 94-01: 18-21, Province Veterinary Record 139, 348–349.

112 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:24 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 103

Roth, M., Richards, R.H. and Sommerville, C. of vibriosis in fish. Current Microbiology (1993a) Current practices in the chemo- 6, 343–348. therapeutic control of sea lice infestations Schmahl, G., Taraschewski, H. and Mehlhorn, in aquaculture: a review. Journal of Fish H. (1989) Chemotherapy of fish parasites. Diseases 16, 1–21. Parasitology Research 75, 503–511. Roth, M., Richards, R.H. and Sommerville, C. Schmidt, G.D. (1986) Handbook of Tapeworm (1993b) Preliminary studies on the efficacy of Identification. CRC Press, Boca Raton, two pyrethroid compounds, resmethrin and Florida, 675 pp. lambdacyhalothrin, for the treatment of sea Schram, T.A. (1993) Supplementary descriptions lice (Lepeophtheirus salmonis) infestations of the developmental stages of Lepeoph- of farmed Atlantic salmon (Salmo salar). In: theirus salmonis (Krøyer, 1837) (Copepoda: Boxshall, G.A. and DeFaye, D. (eds) Patho- Caligidae). In: Boxshall, G.A. and DeFaye, D. gens of Wild and Farmed Fish: Sea Lice. Ellis (eds) Pathogens of Wild and Farmed Fish: Horwood, Chichester, UK, pp. 275–289. Sea Lice. Ellis Horwood, Chichester, UK, Roth, M., Richards, R.H., Dobson, D.P. and pp. 30–47. Rae, G.H. (1996) Field trials on the efficacy Schroder, M.B., Espelid, S. and Jørgensen, T.O. of the organophosphorous compound (1992) Two serotypes of Vibrio salmonicida azamethiphos for the control of sea lice isolated from diseased cod (Gadus morhua (Copepoda: Caligidae) infestations of farmed L.): virulence, immunological studies and Atlantic salmon (Salmo salar). Aquaculture vaccination experiments. Fish and Shellfish 140, 197–217. Immunology 2, 211–221. Roubal, F.R., Lester, R.J.G. and Foster, C.K. (1989) Seymour, T.A., Morrissey, M.T., Peters, M.Y. Studies on cultured and gill-attached and An, H. (1994) Purification and character- Paramoeba sp. (Gymnamoebae: Paramoe- ization of Pacific whiting proteases. Journal bidae) and the cytopathology of paramoebic of Agricultural and Food Chemistry 42, gill disease in Atlantic salmon, Salmo salar 2421–2427. L., from Tasmania. Journal of Fish Diseases Shaw, R.W., Kent, M.L., Docker, M.F., Devlin, 12, 481–492. R.H., Brown, A. and Adamson, M.L. (1997) A Rucker, R.R. (1963) Status of fish diseases new Loma species (Microsporea) in shiner and relation to production. In: Report of perch (Cymatogaster aggregata). Journal of the 2nd Governor’s Conference on Pacific Parasitology 83, 296–301. Salmon, January 1963, Seattle, Washington, Shaw, R.W., Kent, M.L. and Adamson, M.L. (1999) pp. 98–101. Iodophor treatment is not completely Sakanari, J.A. and Moser, M. (1989) Complete efficacious in preventing Loma salmonae life cycle of the elasmobranch cestode, (Microsporidia) transmission in experi- Lacistorhynchus dollfusi Beveridge and mentally challenged chinook salmon, Sakanari, 1987 (Trypanorhyncha). Journal of Oncorhynchus tshawytscha (Walbaum). Parasitology 75, 806–808. Journal of Fish Diseases 22, 1–3. Sande, R.D. and Poppe, T.T. (1995) Diagnostic Shaw, R.W., Kent, M.L. and Adamson, M.L. (2000) ultrasound examination and echocardio- Innate susceptibility differences in chinook graphy in Atlantic salmon (Salmo salar). salmon Oncorhynchus tshawytscha to Loma Veterinary Radiology and Ultrasound 36, salmonae (Micrsporidia). Diseases of 551–558. Aquatic Organisms 43, 49–53. Sano, T., Fukuda, H., Okamoto, N. and Kaneko, F. Sievers, G., Palacios, P., Inostroza, R. and (1983) Yamame tumor virus: lethality Dolz, H. (1995) Evaluation of the toxicity and oncogenicity. Bulletin of the Japanese of 8 insecticides in Salmo salar and the Society of Scientific Fisheries 49, 1159–1163. in vitro effects against the isopod parasite, Sawyer, E.S. (1976) An outbreak of myxobacterial Ceratothoa gaudichaudii. Aquaculture 143, disease in coho salmon (Oncorhynchus 9–16. kisutch) reared in a Maine estuary. Journal of Smail, D.A., Bruno, D.W., Dear, G., McFarlane, L. Wildlife Diseases 12, 575–578. and Ross, K. (1992) Infectious pancreatic Scalati, F. and Kusuda, R. (1986) Chemical necrosis (IPN) virus Sp serotype in farmed composition of the lipopolysaccharides from Atlantic salmon post-smolts associated with Vibrio anguillarum and Vibrio ordalii. Fish mortality and clinical disease. Journal of Fish Pathology 21, 193–199. Diseases 15, 77–83. Schiewe, M.H., Trust, T.J. and Crosa, J.H. (1981) Smail, D.A., McFarlane, L., Bruno, D.W. and Vibrio ordalii sp. nov.: a causative agent McVicar, A.H. (1995) The pathology of an

113 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:24 AM Color profile: Disabled Composite Default screen

104 M.L. Kent and T.T. Poppe

IPN-Sp subtype (Sh) in farmed Atlantic Summerfelt, R.C. and Warner, M.C. (1970) salmon, Salmo salar in the Shetland Isles, Incidence and intensity of infection of Scotland. Journal of Fish Diseases 18, Plistophora ovariae, a microsporidian 631–638. parasite of golden shiner, Notemigonus Smith, P.R., Moloney, M., McElligott, A., Clarke, crysoleucas. In: Snieszko, S.F. (ed.) A Sympo- S., Palmer, R., O’Kelly, J. and O’Brien, J. sium on Diseases of Fishes and Shellfishes. (1993) The efficacy of oral ivermectin in the Special Publication No. 5, American Fish- control of sea lice infections of farmed Atlan- eries Society, Washington, DC, pp. 142–160. tic salmon. In: Boxshall, G.A. and DeFaye, D. Svendsen, Y.S. (1990) Hosts of third stage (eds) Pathogens of Wild and Farmed Fish: larvae of Hysterothylacium sp. (Nematoda: Sea Lice. Ellis Horwood, Chichester, UK, Anisakidae) in zooplankton from outer pp. 296–307. Oslofjord, Norway. Sarsia 75, 161–167. Sorensen, U.B.S. and Larsen, J.L. (1986) Sero- Tajima, K., Ezura, Y. and Kimura, T. (1985) typing of Vibrio anguillarum. Applied and Studies on the taxonomy and serology of Environmental Microbiology 51, 593–597. causative organisms of fish vibriosis. Fish Speare, D.J., Brackett, J. and Ferguson, H.W. (1989) Pathology 20, 131–142. Sequential pathology of the gills of coho Thomassen, J.M. (1993a) Hydrogen peroxide as salmon with a combined diatom and a delousing agent for Atlantic salmon. In: microsporidian gill infection. Canadian Boxshall, G.A. and DeFaye, D. (eds) Patho- Veterinary Journal 30, 571–575. gens of Wild and Farmed Fish: Sea Lice. Ellis Speare, D.J., Beaman, H.J., Jones, S.R.M., Horwood, Chichester, UK, pp. 290–295. Markham, R.J.F. and Arsenault, G.J. (1998) Thomassen, J.M. (1993b) A new method for the Induced resistance in rainbow trout, control of salmon lice. In: Reinersten, H., Oncorhynchus mykiss (Walbaum), to gill Dahle, L.A., Jørgensen, L. and Tvinnereim, K. disease associated with the microsporidian (eds) Fish Farming Technology. Balkema, gill parasite Loma salmonae. Journal of Fish Rotterdam, pp. 233–236. Diseases 21, 93–100. Thorud, K. and Djupvik, H.O. (1988) Infectious St-Hilaire, S., Hill, M., Kent, M.L., Whitaker, D.J. anaemia in Atlantic salmon (Salmo salar L.). and Ribble, C.S. (1997a) A comparative study Bulletin of the European Association of Fish of muscle texture and intensity of Kudoa Pathologists 8, 109–111. thyrsites infection in pen-reared Atlantic Totland, G.K., Hjeltnes, B.K. and Flood, P.R. salmon. Diseases of Aquatic Organisms 31, (1996) Transmission of infectious salmon 221–225. anaemia (ISA) through natural secretions and St-Hilaire, S., Ribble, C., Whitaker, D.J. and Kent, excretions from infected smolts of Atlantic M.L. (1997b) Evaluation of a nondestructive salmon Salmo salar during their presympto- diagnostic test for Kudoa thyrsites in farmed matic phase. Diseases of Aquatic Organisms Atlantic salmon (Salmo salar). Aquaculture 26, 25–31. 156, 139–144. Traxler, G.S. and Richard, J. (1996) First detection St-Hilaire, S., Ribble, C., Whitaker, D.J. and Kent, of infectious haematopoietic necrosis virus M. (1998) Prevalence of Kudoa thyrsites in in marine fishes. Fish Health Section/ sexually mature and immature pen-reared American Fisheries Society Newsletter 24, 7. Atlantic salmon (Salmo salar) in British Traxler, G.S., Roome, J.R. and Kent, M.L. (1993) Columbia, Canada. Aquaculture 162, 69–77. Transmission of infectious hematopoietic St-Hilaire, S., Ribble, C., Traxler, G.S., Davies, T. necrosis virus in seawater. Diseases of and Kent, M.L. (2001) Evidence for a carrier Aquatic Organisms 16, 111–114. state of infectious hematopoietic necrosis Treasurer, J.W. (1993) Management of sea lice virus in chinook salmon (Oncorhynchus (Caligidae) with wrasse (Labridae) on tshawytascha). Diseases of Aquatic Organ- Atlantic salmon (Salmo salar L.) farms. In: isms 46, 173–179. Boxshall, G.A. and DeFaye, D. (eds) Patho- Sterud, E., Mo, T.A. and Poppe, T.T. (1997) gens of Wild and Farmed Fish: Sea Lice. Ellis Ultrastucture of Spironucleus barkhanus Horwood, Chichester, UK, pp. 335–345. n.sp. (Diplomodadida: Hexamitidae) from Tsuyuki, H., Williscroft, S.N., Kabata, Z. and grayling Thymallus thymallus (L.) Whitaker, D.J. (1982) The relationship (Salmonidae) and Atlantic salmon Salmo between acid and neutral protease activities salar L. (Salmonidae). Journal of Eukaryotic and the incidence of soft cooked texture in Microbiology 44, 399–407. the muscle tissue of Pacific hake Merluccius

114 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:24 AM Color profile: Disabled Composite Default screen

Infectious Diseases of Coldwater Fish in Salt Water 105

productus infected with Kudoa paniformis Whitaker, D.J. and Kent, M.L. (1991) Kudoa and/or K. thyrsites, and held for varying times thrysites (Myxosporea): a cause of soft flesh under different pre-freeze chilled storage in farm-reared Atlantic salmon (Salmo salar). conditions. Canadian Technical Report of Journal of Aquatic Animal Health 3, Fisheries and Aquatic Sciences 1130, 39 pp. 291–294. Tully, O., Poole, W.R., Whelan, K.F. and Whitaker, D.J. and Kent, M.L. (1992) Kudoa Merigoux, S. (1993) Parameters and possible thyrsites (Myxosporea) and soft flesh in pen- causes of epizootics of Lepeophtheirus reared coho salmon. Fish Health Section/ salmonis (Krøyer) infesting sea trout (Salmo American Fisheries Society Newsletter 20, trutta L.) off the west coast of Ireland. In: 4–5. Boxshall, G.A. and DeFaye, D. (eds) Patho- Whitaker, D.J., Kent, M.L. and Margolis, L. (1994) gens of Wild and Farmed Fish: Sea Lice. Ellis Myxosporean parasites and their potential. Horwood, Chichester, UK, pp. 202–213. impact on the aquaculture industry, with Tully, O., Daly, P., Lysaght, S., Deady, S. and emphasis on Kudoa species. In: Conley, Varian, S.J.A. (1996) Use of cleaner-wrasse D.C. (ed.) Kudoa Workshop Proceedings, (Ctenolabrus exoletus (L.) and Ctenolabrus 17–18 February 1994, Nanaimo, British rupestris (L.)) to control infestation of Caligus Columbia. Aquaculture Industry Develop- elongatus Nordmann on farmed Atlantic ment Report 94-01, Province of British salmon. Aquaculture 142, 11–24. Columbia, Ministry of Agriculture, Fisheries Urawa, S. and Kato, T. (1991) Heavy infections of and Food, Victoria, British Columbia Caligus orientalis (Copepoda: Caligidae) on pp. 2–7. caged rainbow trout Oncorhynchus mykiss in Williams, H. and Jones, A. (1994) Parasitic Worms brackish water. Gyobyo Kenkyu 26, 161–162. of Fish. Taylor & Francis, London, 593 pp. Vaney, C. and Conte, A. (1901) Sur une nouvelle Wolf, K. (1988) Fish Viruses and Fish Viral microsporidie, Pleistophora mirandellae, Diseases. Cornell University Press, Ithaca, parasite de l’ovaire d’Alburnus mirandella New York, 476 pp. Blanch. Comptes Rendus de l’Academie des Woo, P.T.K. and Poynton, S.L. (1995) Diplo- Sciences 133, 644–646. monadida, Kinetoplastida and Amoebida Vismanis, K.O., Lullu, A.V., Inglis, V.A., (phylum Sarcomastigophora). In: Woo, Turovskii, A.M. and Yun, A.I. (1984) P.T.K. (ed.) Fish Diseases and Disorders, Diseases of Salmonidae in the marine fish Vol. 1. Protozoan and Metazoan Infections. farms on the Baltic coast and their preven- CAB International, Wallingford, UK, pp. tion. In: Bauer, O.N., Musselius, V.A. and 27–96. Skryabina, E.S. (eds) Biologicheskie Osnovy Wood, B.P., Bruno, D.W. and Ross, K. (1996) Rybovodstva: Parazity i Bolezni Ryb, ‘Nauka’, Infectious pancreatic necrosis virus (IPNV) Moscow, pp. 56–63 (in Russian). mortalities among farmed Atlantic halibut, Wakabayashi, H., Hikida, M. and Masumura, K. Hippoglossus hippoglossus L., in Scotland. (1984) Flexibacter infection in cultured Bulletin of the European Association of Fish marine fish in Japan. Helgolaender Meere- Pathologists 16, 214–216. suntersuchungen 38, 1–8. Wood, J. (1974) Diseases of Pacific Salmon: Their Wakabayashi, H., Hikida, M. and Masumura, K. Prevention and Treatment. Washington (1986) Flexibacter maritimus sp. nov., a State Department of Fisheries, Olympia, pathogen of marine fishes. International Washington, 82 pp. Journal of Systematic Bacteriology 36, Wootten, R., Smith, J.W. and Needham, E.A. 396–398. (1982) Aspects of the biology of the parasitic Wales, J.H. and Wolf, H. (1955) Three protozoan copepods Lepeophtheirus salmonis and diseases of trout in California. California Fish Caligus elongatus on farmed salmonids, and and Game 41, 183–187. their treatment. Proceedings of the Royal Wards, B.J., Patel, H.H., Andersen, C.D. and Society of Edinburgh, Section B (Biological de Lisle, G.W. (1991) Characterization by Sciences) 81, 185–197. restriction endonuclease analysis and Yasutake, W.T., Buhler, D.R. and Shanks, W.E. plasmid profiling of Vibrio ordalii strains (1961) Chemotherapy of hexamitiasis in fish. from salmon (Oncorhynchus tshawytscha Journal of Parasitology 47, 81–86. and Oncorhynchus nerka) with vibriosis Yoshimizu, M., Fukuda, H., Sano, T. and in New Zealand. New Zealand Journal Kimura, T. (1995) Salmonid herpevirus 2. of Marine and Freshwater Research 25, Epizootiology and serological relationship. 345–350. Veterinary Research 26, 486–492.

115 Z:\Customer\CABI\A4337 - Woo\A4419 - Woo Vouchers.vp Tuesday, November 05, 2002 11:34:24 AM