United States Department of the Interior, Fred A , Seaton, Se.::rctary Fish and Wildlife Service, Arnie J. Suomela. Commi ssioncr

Fishery Leaflet 459

Washington 25, D. C. July I~ ,'ili

FRESHWATER FISH DISEASES CAUSED BY BACTERIA BELONGING TO THE GENERA AEROMONAS AND PSEUDOMONAS

By 1/ S. F. Snieszko_ Bacteriologist Branch of Fishery Research Bureau of Sport Fisheries and Wildlife

INTRODUCTION 5 , Red ~ disease in frogs ,

Bacterial fish diseases caused by pseudo­ Fish furunculosis should also be In ­ monas-like bacteria which are now classified eluded hut because of its importan,,:c il IS (it: as belonging to the genus Aeromonas are very scribed in a separate ka !let, common among warmwater pond fishes. Here ~ belong the economically most important pond­ This outline ..:ontains more dL'lallt:d Ill' fish diseases in Europe. There is increasing formation than other similar outlllH'S beL';IlISt' evidence that also in the United States and Can­ of palk"lty of referen..:e material )[1 tIll" 1-.n;..:ll"h ada fish diseases caused by bacteria belonging language, to this genus are of considerable economh.: Sig­ nificance. Fish diseases caused by bacteria IDENTIFICA liON belonging to the apparently related genus Pseudomonas are less common. Diseases Most of the uist:ases listed Jhn\l' .. rl' caused by bacteria of this group have been de­ caused by badena whl..:h are c llllL'r Hit-ill 1-,1 i scribed by various investigators as: with AcroTlwnas lIquefaC:lvns or rt"iatnl III II , In some instanc:es fIsh dlsL'asL's of sIllJIlJr Il.H I IfI' 1. Infectious abdominal dropsy may be ..:aused by pseudoTllonads Wlll,: 11 prfJlllkc (Bauchwassersucht in Germany) . fluorescent pigments 111 spedal Illt'tll;I, In ;.!t'n eral, all these diseases are sePtkl' ll11- .In

nlL' most tYPI..:al external ,; :.mptllll," ,I!"<" !! Headquarters: Eastern Fish Disease Lab" superfidal shallow graYish or red ..:n;lJiar " f Leetown (P.O. Kearneysville) irregular ukers, Thl' mU; I)u!' ll IL'n :hrant.'s ; !nl ~ West Virginia. .::artila~Tjnous tisSUL' In and around the rT , .. ,:rtl r" ,.", be inflamed and even eroded as in the" red are believed to be the most frequently used (~ mouth" disease in rainbow trout. Fish may have synonyms: Bacillus punctatus distended abdomen filled with slightly opaque e)r Bacterium punctatum bloody fluid. Some fish may have protruding Pseudomonas punctata~/ eyes (exophthalmus) and behind the eyeball an Pseudomonas hydrophila opaque fluid may accumulate. Some fish, cy­ Proteus hydrophilus prinids in particular, may have furuncles simi- Bac il b s nnicida 1ar to those in furunculosis, which may break Aeromonas punctata out to the surface producing deep necrotic cra­ Aeromonas hydrophila ters lined with red or grayish muscle tissue. In some instances these lesions can heal leaving U a bacterium is isolated in pure culture scars. Fins may be inflamed. from a lesion or blood of diseased fish, the following characteristics can be used for a Internally, in addition to the presence of presumptive test: gram -negative, motile, opaque or purulent fluid in the abdominal ca vity, single polar flagellum, will grow well from the kidney may be swollen and soft, liver pale 10 to 35° C (optimum about 30· C, 86· F), with or without necrotic areas and petechiae liquefies ge latin, acid and gas produced in dex­ (small hemorrhages) may be present in the trose' sucrose, and mannitol; in lactose no peritoneum and in the musculature. Lower in­ fermentation or slow fermentation after 2 to 4 testine and vent are usually swollen, inflamed, weeks of incubation. With paper discs contain­ and may contain bloody contents or discharge. ing antibiotics and sulfonamides (medium con­ The mortalities may be low or high and the epi­ centration) and using petri plates with Trypticase zootics may have a rapid or a slow course. Soy Agar (Baltimore Biological Laboratory), the follOWing results .::an be anticipated: In frogs the main symptom of the disease is distended capillaries on the undersidl' e)f legs Clear zones present Clear zones absent and abdomen giving them a deep red color from ( which the name of the disease, "red leg," ori­ Chloromycetin +++ Carbomycin ginated. Terramycin ++ Bacitracin Aureomycin ++ Polymyxin Outbreaks of this disease among the Tetra.:: yc line ++ Penicillin warmwater pond fishes and frogs usually occur Streptomycin + Viomycin in spring and coincide with the increase in the Neomycin + Magnamycin temperature of water. It is believed that at Sulfonamides + or - this time of the year fish have a decreased dis­ ease resistance owing to winter dormancy and Aeromonas liquefaciens is a bacterium starvation which usually results in some anemia common in water containing organic matter. It and a decrease in the blood proteins. is most likely a saprophytic bacterium which under certain conditions can be highly pathogenic CAUSE OF THE DISEASE to lower vertebrates. It is also pathogenic to mammals if injected into tissues or blood stream. There is a con siderable confu sion re­ garding the taxonomy of bacteria involved in On occasions typical water:.inhabiting this disease or diseases. Apparently identical pseudomonads, as for example Pseudomonas or very closely related cultures isolated from fluorescens, can cause epizootics among pond diseased fish and frogs and pond water were de­ fishes. Pseudomonas fluorescens in contrast to scribed under different generic and specific names. The writer's opinion is that bacteria '!:./ See the 7th Edition of the Bergey's Manual of causing most of the outbreaks of infectious Determinative Bacteriology, pp. 189-193, 1957. dropsy, hemorrhagic septicemia, red mouth and red leg diseases should be classified as ~/ Name used most frequently during the past Aeromonas liquefaciens 2/. The following names 20 years.

2 9 ~. liquefaciens slightly ferment some sugars RANGE with production of some acid but no gas. It produces brilliant fluorescence if grown on Apparently all over the world. tryptose phosphate agar and exposed to ultra­ violet illumination. It also produces green OCCURRENCE pigment in media containing glycerol ~ The greatest epizootics were described SOURCE AND RESERVOIR OF INFECTION in Europe. Disease is common in warmwater pond fish in the United States, in rainbow trout Pond water, diseased fish, diseased in the western states and Europe, in northern frogs, as well as fish which have recovered pike in Canada, and in aquarium fishes. from the disease and are immune or resistant carriers (fish and frogs). METHODS OF CONTROL

MODE OF TRANSMISSION A. Preventive measures.

Through intestinal tract and external a . Avoidance of transfer of fish from lesions. External parasites as trematodes ponds or hatcheries in which fish (Gyrodactylus), copepods and leeches which have or recently had this disease to fed on infected fish were found to contain this hatcheries free from it. pathogen in their intestinal tract. Therefore b. Wherever this disease breaks out external parasites may be responsible at least frequently the pond fish should not for some outbreaks of this disease. be handled and transferred in spring of the year until fish become active INCUBATION PERIOD and the temperature of water is high enough for fish to feed normally. ~ Depends on the species of fish, their c. Very substantial reductions of mor­ --; resistance, external conditions and the season talities amounting to from 80 to 90 of the year. percent were obtained in Europe if fish at the time of spring transfer PERIOD OF COMMUNICABILITY were given intraperitoneal injections of 2 to 5 milligrams of Chloromycetin Adult resistant fish and frogs as well as dissolved in water per 100 grams of animals which recovered may serve as carriers fish (10 to 25 milligrams per pound). for an indefinite period of time. This is a practice which is becoming a standard procedure in Germany SUSCEPTmILlTY AND RESISTANCE (Schliperclaus 1956). d. If warmwater fish are held in tanks, In general the warmwater fish are most shipped in trucks or in plastic bags susceptible in the spring in the climatic zones the value of addition of antibiotics or in which fish are inactive during winter. It is disinfectants should be tested. The believed that infe:::tion frequently occurs during most promising substances are winter with the disease breaking out in the spring. chloramphenicol, Terramycin, Aquarium fishes can develop this disease at any Aureomycin and a mixture of peni­ time of the year. Of salmonid fishes, the rain­ cillin and streptomycin added to bow trout seems to be most susceptible to in­ water at a rate of 10 to 50 milligrams fections with these bacteria. German investi­ per liter (40 to 200 milligrams per gators were able to breed strains of carp having gallon). van DJijn (1956) recommends increased resistance to infectious abdominal addition of acriflavine and phenoxye­ dropsy (hemorrhagic septicaemia). Handling thanol to aquarium water. According and crowding of fish can cause severe outbreaks. to his recommentations, acri- flavine should be used as a stock

3 solution containing 10 p. p. m. This ANNOTATED BffiLIOGRAPHY should be added at a rate of 8 milli­ liters per gallon. Phenoxyethanol Bibliography of these diseases contain should be used as a 1 percent stock many paper s which were published in German, solution; 38 -75 milliliters of this Russian and French. The reference material solution should be used per gallon. available in the English language is compara­ Other authors recommend use of tively small. Therefore some foreign language much stronger concentrations of papers of highest importance are listed for acriflavine, namely 10 p. p. m. in persons who can use them. None of the foreign water containing fish. papers which were reviewed and listed by e. Selective breeding of stocks of fish Griffin and Snieszko in the "Symposium" on resistant to this disease. This is fish diseases (1954) are here included. one of the most promising long­ range control measures. Ambrus, J.L., C.M. Ambrus andJ.W.E. Harrison B. Therapy. 1951. Prevention of Proteus hydrophilus infections (red leg disease) in frog a. If fish are regularly being fed any colonies. Amer. Journ. Pharrn., diet which is taken promptly so that Vol. 123, p. 129. the drugs cannot be leached out com­ Addition of 50 milligrams of chloram­ pletely, drugs can be incorporated phenicol to water in which frogs were with the diet. This is particularly kept protected frog colonies from red true with salmonid fishes raised in leg disease. hatcheries, minnows and aquarium fishes raised in ponds, and aquarium Besse, P. fishes. In such cases the drugs of 1954. L 'hydropisie des truites arc -en­ choice are Chloromycetin ( chloram­ ciel ou exophthalmie epizootique. ( phenicol) and Terramycin (oxytetra­ Bull. Franc. de Pisciculture, No. cycline). They should be used at a 172, pp. 113-115. rate of 50 to 75 milligrams of pure A bacterial infection of rainbow trout in antibiotic activity per kilogram of Switzerland. Infected fish have exoph­ fish per day (2.5 to 3.5 grams per thalmia, photophobia, lack of appetite, 100 pounds). Sulfonamides, such as pale gills, distention of abdomen with sulfamerazine, sulfamethazine, accumulation of abdominal fluid, gut sulfadiazine, or sulfisoxazole, can filled with yellow gelatinous mass. be also used but they are less likely to be ef!ecti ve. They should be in­ Curran, H. Wesley corporated in the diet and given at a 1947. A biological survey of Lake Opinicon. rate of 10 grams per 100 pounds of Progress Report, Queens University fish per day. Nitrofurans should be Biological Station, Ontario. pp. 47- tried as very promising. 48. b. Addition of drugs to water is less Infection of sunfish with Aeromonas lique­ effective in treatment than in prophy­ faciens (Proteus hydrophilus). The dis· laxis. If drugs cannot be given orally ease is characterized externally by in­ they should be used as described fected areas which range from small red under Preventive Measures in para­ spots to open necrotic lesions of the skin graphs c and d. or any part of the body or fins. In ad­ vanced cases in the red, slimy necrotic areas scales are displaced and the lesion penetrates the skin.

4 ~ van Dlijn, C., Jr. Schttperclaus, W. 1956. Diseases of Fishes. Dorset Hous~ 1954. Fischkrankheiten. Berlin, London. Fish Dropsy is described Germany. on pp. 97-1Ol. Infectious dropsy and similar diseases Symptoms, cause and treatment of are excellently described. Manyex­ aquarium fishes are described. cellent photographs, pp. 447 -524.

*Griffin, P.J. and S . F. Snieszko 1956. Bekttmphfung der infektitlsen 1951 . A unique bacterium pathogenic Bauchwassersucht der Karpfens for warm -blooded and cold­ durch Antibiotika. Zeitschr. f. blooded animals. U.S. Fish and Fischerei, Vol. 5(1-2), pp. 3-59. Wildlife Service, Fish. Bull. 68, Results of extensive experiments on the pp. 187-190. prophylaxis of infectious abdominal A bacterium which caused infection and dropsy in carp by single intraperitoneal death in several species of aquarium injection of antibiotics. Chlorampheni­ fishes was isolated. It is identical with col and streptom ycin are best. The or very similar to Aeromonas lique­ former last longer in fish and in a faciens. Chara.:teristics of the bac­ solution and can be used in smaller terium are described in detail. quantities. Single injection of about 2 milligrams per 100 grams of carp *Reed, G.B. and G.C. Toner during the spring transfer increased 1941 . Red sore disease of pike. Canad. the fish survival manyfold for the entire Journ. Res., Sect. D. Zool. ScL, growth period in summer. Author gives Vol. 19 (5), pp. 139-143. extensive review of German and Russian This disease is common in northern pike bibliography. American publications (Esox lucius). It is characterized by were not listed. shallow ulcers, gray in appearance. It is caused by Proteus hydrophilus Seaman, W. R . (Aeromonas liquefaciens). 1951. Notes on a bacterial disease of rainbow trout in a Colorado 1942. Proteus hydrophilus infections of hatchery. Progr. F ish -Cult., pike, trout and frogs. Canad. Vol. 13(3), 139-141. Journ. Res., Vol. 20, Sect. D, An outbreak, symptoms and successful pp. 16 1 - 166 . treatment with sulfonamides of a bac­ The "red sore" disease in trout and terial disease which is probably identical pike usually coincided with the outbreaks with the "red mouth" disease. Treat­ of "red leg" disease in frogs. Proteus ment with 15 grams of sulfamerazine hydrophilus (Aeromonas liquefaciens) given orally with food per 100 pounds of was regularly isolated from the lesions trout per day gave excellent results. The and frequently from the internal organs identity of the pathogen was not definitely of diseased fish or frogs. Since methods established except that it was most likely for the isolation of Hemophilus piscium a pseudomonad. were not known at that time, it is im­ possible to determine now if the disease *Snieszko, S. F . in brook trout was not the typical ulcer 1940. A bacterial disease of carp in cen­ disease with !:. liquefaciens present as tral Europe. Progr. Fish -Cult., the secondary invader. No. 52, pp. 12-15. A review of the problem.

5 ·Symposium: Research on Fish Diseases ·Wagner, E.D. and C.L. Perkins ( 1954. Trans. Am. Fish. Soc., Vol .. 83 1952. Pseudomonas hydrophila, the cause ' (for 1935). of "red mouth" disease in rainbow See the papers by Griffin, pp. 246-248 trout. Progr. Fish -Cult., Vol. and by Snieszko pp. 317-318. 14(3), pp. 127-128. Pseudomonas hydrophila (Aeromonas liquefaciens) has been found to be the cause of "red mouth" disease in rainbow trout and "red leg" disease in frogs.

• Papers indicated by an asterisk are of special importance to fish culturists.

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INT.-DlIP . SIC .• lASH .• D.C. J9 2 2J 6