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Bull. Eur. Ass. Pathol., 29(5) 2009, 163 Health survey of fish in Swedish pet-shops

T. Hongslo* and E. Jansson

National Veterinary Institute, Department of Health and Antimicrobial Strategies, Uppsala, Sweden

Abstract The aim of this study was to conduct a health survey of aquarium fish in pet-shops in order to identify the main causes for disease. In total 720 fish from 24 Swedish pet- shops (i.e. 30 fish from each shop) were collected for bacteriological and virological investigations from August 2006 to May 2007. Fish were primarily selected according to signs of illness, otherwise fish were randomly chosen. Of the collected fish, 120 fish belonging to various and 23 neon ( innesi) were in addition thoroughly investigated microscopically regarding occurrence of ecto- and endoparasites and pathological organ alterations. Moreover, 51 fish included in the total 720 and belonging to the family , were investigated for the presence of koi herpes virus by real-time PCR. The most commonly occurring reason for illness in the fish was infections caused by parasites and the most frequent parasitic group was Monogenea. Monogenic flukes were not found on the , but were found as frequently as on 77 (64%) of the other 120 fish studied. On the other hand, infection with Pleistophora hyphessobryconis was found especially in the neon tetra. Bacterial infections in the fish were mainly caused by acid-fast . Probable or established infection with acid-fast bacteria was found in 28 (23%) of the 120 fish and in 5 (22%) of the 23 neon tetra studied more in detail. In three fish typical nodules indicative of lymphocystis were observed microscopically, but no other acute or latent virus infections could be demonstrated by virus cultivation of organ material from all 720 fish or by real-time PCR investigation of organ material from the 51 fish of the family Cyprinidae. Oomycete infection was only observed in one swordtail (Xiphophorus hellerii). In conclusion, this health survey carried out on aquarium fish in Swedish pet-shops showed that the most common causes of diseases in the fish were infections with parasites and acid-fast bacteria.

Introduction aquarium fish in Sweden mainly originate Since the beginning of the twentieth century, from Africa, Asia and . In the people in Sweden have kept fish in . last decade, the keeping of koi (Cyprinus Initially, mostly European coldwater fish carpio koi) and goldfish (Carassius auratus species and North American sunfish (Lepomis auratus) in garden ponds also has been very spp.) were kept (Brorsson, 1987), but today popular. In 2002 the number of aquarium fish

* Corresponding author’s E-mail: [email protected] Bull. Eur. Ass. Fish Pathol., 29(5) 2009, 164 in Sweden was estimated to 4.5 million out also held other kinds of for sale. The of total 8.1 million pet animals (Danielsson, numbers of aquariums in the shops varied 2003). Most of these fish are bred in Asia and from 16 to 200. Thirty fish (i.e. 1 fish from 30 Eastern , but there are also wild-caught different aquariums) were collected from each originating from Africa, Asia pet-shop for bacteriological- and virological and South America. Out of total 30 385 fish investigations. In cases where a shop (n=5) species described worldwide in 2008, as had less than 30 aquariums, fish of different many as 3068 (11 %) are commercialized as species were selected from the same aquarium aquarium fish and of these approximately to fulfil the number of 30 fish from each shop. 720 species are bred in captivity (http:// Fish were primarily selected according to signs www..se). Diseases of aquarium of illness such as emaciation, exophthalmia, fish are a common problem for aquarists in fin- and skin erosions, swollen belly, wounds Sweden and in many other countries. Some and/ or a deviant behaviour. Otherwise, fish studies concerning causes for diseases among were randomly collected. Of the collected fish aquarium fish in wholesale business have from each shop, five fish with signs of illness been made (Engelhardt, 1992; Kim et al., 2002; were in addition thoroughly investigated Levsen et al., 2003; Thilakaratne et al., 2003), microscopically regarding occurrence of ecto- but no previous survey has been published and endoparasites and pathological organ that describes the disease-causing agents of alterations, in order to establish diagnosis. aquarium fish exclusively in pet-shops. The These in total 120 (5 x 24) fish were subgrouped aim of this study was therefore to conduct a according to fish species and are described in health survey of aquarium fish in pet-shops Table 1. Additional investigations were also in order to identify the main causes for made on the neon tetra (Paracheirodon innesi) disease such as bacterial-, virus- and parasitic from total 23 shops (1 fish/ shop) (Table 3). infections as well as water quality problems. This information will give indications for Before examination, the majority of fish were prophylactic measures and treatments that euthanized with Tricaine methane sulphonate are possible to reduce the practical and (MS222, Novartis AG, Täby, Sweden, 140-230 financial consequences of the diseases and is mg L-1), followed by a mechanical destruction an important step to improve aquarium fish of the brain. A few larger fish were instead welfare. killed by a blow to the head, followed by mechanical destruction of the brain before Materials and methods examination. Collection of aquarium fish for investigation Freshwater aquarium fish were collected from Microscopic investigation 24 pet-shops randomly chosen from the phone Investigation regarding parasites, oomycete book, located in the middle part of Sweden, and pathological organ alterations was made from August 2006 to May 2007. Twelve of with microscopy directly after the fish were these shops were specialized in selling only put to death through examination of the whole aquarium fish, whereas the other 12 shops surface of the fish and the whole mesentery, Bull. Eur. Ass. Fish Pathol., 29(5) 2009, 165

Group 5. Other fish Family: Callichthyidae Bronze (Corydoras aeneus) Peppered corydoras (Corydoras paleatus) Other corydoras (Corydoras spp.) Family: Black tetra ( ternetzi) axelrodi) (Paracheirodon Colombian tetra ( columbianus) Cuchu´s blue tetra (Boehlkea fredcochui) Glowlight tetra ( erythrozonus) (Hyphessobrycon pulchripinnis) Swegles tetra (Hyphessobrycon sweglesi) Family: Eleotridae Peacook gudgeon ocellicauda) (Tateurdina Family: Melanotaeniidae Rainbow fish ( Melanotaenia sp.) Red rainbow fish (Glossolepis incisus) Family: Pangasiidae Sutchi (Pangasius hypophthalmus) Family: Pictus cat ( pictus) Group 4. Cichlids Family: Cichlidae Altolamprologus compressiceps compressiceps) (Altolamprologus Angelfish scalare) ( Banded cichlid efasciatus) (Heros Demansoni cichlid demansoni) (Pseudotropheus Discus fish (Symphysodon aequifasciatus) Golden mbuna auratus) (Melanochromis Labidochromis yellow caeruleus) (Labidochromis Pseudotropheus liliancinus lombardoi) (Pseudotropheus Rainbow krib pulcher) (Pelvicachromis Ramirez´s dwarf cichlid ramirezi) (Microgeophagus Group 3. Labyrinth fish Family: Helostomatidae Kissing (Helostoma temminkii) Family: Osphronemidae Banded gourami (Colisa fasciata) Blue-, Cosby-, Gold gourami trichopterus) (Trichogaster Dwarf gourami (Colisa lalia) Honey gourami (Colisa chuna) Pearl gourami leeri) (Trichogaster Siamese fighting fish (Betta splendens) Snakeskin gourami pectoralis) (Trichogaster Thick-lipped gourami (Colisa labiosus) ) Family: Cyprinidae Bala shark (Balantiocheilos melanoptereus) Cherry barb (Puntius titteya Comet goldfish/ goldfish (Carassius auratus auratus) Fantail goldfish (Carassius auratus auratus) Glowlight-/ Lampchop hengeli, (Trigonostigma espei) Trigonostigma Goldbarb (Punctius semifasciolatus) Harlequin rasbora heteromorpha) (Trigonostigma Koi (Cyprinus carpio koi) Rosy barb (Puntius conchonius ) barb Tiger (Puntius tetrazona) Zebra fish ( rerio) Group 1. Live bearers Group 2. Cyprinids Family : Poeciliidae Sailfin molly Blackmolly, (Poecilia sphenops, Poecilia latipina) Guppy (Poecilia reticulata) Montezuma swordtail (Xiphophorus montezumae) Platy (Xiphophorus maculatus) Sailfin molly (Poecilia velifera) Swordtail (Xiphophorus hellerii) Table 1. Fish speciesTable examined more thoroughly neon (except tetra). Bull. Eur. Ass. Fish Pathol., 29(5) 2009, 166 or in the case of larger fish, selected parts of chosen. The organ materials from the 30 fish the skin, fins, gills, muscle and viscera (i.e. from each pet-shop were then pooled into three gallbladder, heart, intestine, kidney, liver, samples consisting of organ materials from 10 spleen and stomach). fish in each. The pooled samples were stored in Earle´s Minimal Essential Medium (EMEM) Bacteriological investigation supplemented with 10% calf serum, without Bacteriological investigation was made on antibiotics, at +1°C to +4°C, until virological fish with signs of infection like wounds, investigation. When it was impossible due skin erosions and morphological changes in to practical reasons to start the virological internal organs. Cultivation of tissue samples investigation within 24 hours after collecting were carried out on horse blood (5%) agar and/ the fish, the pooled samples were kept in or Cytophaga agar (Bernardet & Kerouault, -20°C, or if stored longer than a week, in -70°C 1989), TYES agar (Holt et al., 1993) and KDM-C until investigation. The pooled tissue samples agar (Daly & Stevenson, 1985). Agar plates were homogenized in a polytron homogenizer were incubated at 20°C and examined for up (Kinematica AG, Littau, Switzerland) and the to 7 days. Suspected colonies of Aeromonas supernatants, after centrifugation at 2500g sobria, A. hydrophila, Listonella anguillarum and for 20 min, were inoculated on the bluegill Vibrio sp. were verified through their reactions fry-2 (BF-2)-, epithelioma papulosum cyprini in standard biochemical tests. L. anguillarum (EPC)- and rainbow trout gonad (RTG-2) fish were further identified through sensitivity cell lines (Roberts, 1989b), for incubation at for the vibriostatic agent 0129 and by slide 13-14.5°C. Samples were passed on to the agglutination with verified polyclonal rabbit homologous cell lines after seven days and the serum directed to L. anguillarum serotype 01 primary inoculated cells and the passage cells and 02. Either native tissue smears or formalin were regularly red for further seven days. fixed tissue sections from the organs with indications of granuloma formations or lesions In addition, 51 fish of the familyCyprinidae [i.e. were stained with Gram- and Ziehl-Nielsen golden orfe (Leuciscus idus), goldfish and koi] and microscopically investigated. In the cases, and one sutchi catfish (Pangasius hypophtalmus) the granuloma had an appearance typical for of the total 720 fish were investigated for the acid-fast bacteria infection, but no acid-fast presence of koi herpes virus (KHV) by detection bacteria could be detected by means of Gram- of the DNA polymerase gene of the virus by an and Ziehl-Nielsen staining and microscopy, unpublished real-time PCR (M. Y. Engelsma, the granuloma were classified as a granuloma Central Veterinary Institute, Lelystad, The probably due to acid-fast bacteria. Netherlands, personal communication). Briefly, fish tissue samples were grinded with Virological investigation beads in a Qiagen TissueLyser and thereafter Materials for virological investigation were genomic DNA was extracted with the Qiagen taken from parts of the ’ brain, gills, Mag Attrach Virus Mini kit (QIAGEN, Hilden, heart, kidney, liver and spleen, or in the case Germany). Detection of KHV DNA was then of very small fish, the whole mesentery was carried out by real-time Taqman PCR in an Bull. Eur. Ass. Fish Pathol., 29(5) 2009, 167

AmpliTaq Gold system (Applied Biosystems, hydrophila were found in several samples Foster City, CA, USA), using forward primer taken from wounds and gills. In a bile sample 5’-TGC-CCC-GAG-ACC-AAA-CAC-3’, from a Chinese -eater (Gyrinocheilus reverse primer 5’-GCG-TGC-GGT-CAA-AGA- aymonieri) the fish pathogenic gram-negative TGT-C-3’ and probe 6-FAM 5’-TGT-GGA- rod L. anguillarum serotype II was found, and CGG-GCA-GCG-GGT-GTA-3’ BHQ. Tissue in a bile sample from a platy (Xiphophorus samples from the fish were stored at -20°C for maculatus) a Vibrio sp was encountered. 1 to 12 months until investigated. Each tissue Another finding of a Vibrio sp was made sample analysed consisted of 0.1 to 1.6 mg of in a liver sample from a harlequin rasbora gills, and in one case also skin, pooled from (Trigonostigma heteromorpha). 1 to 4 fish. In the group of 120 fish which were more Water investigation thoroughly investigated in order to establish Water samples were collected from selected a diagnosis, acid-fast bacteria were found in aquarium tanks as well as from the tap water 13 (11 %) of the fish (Table 2). Additionally, in 22 of the 24 pet-shops. The water samples granuloma formations probably due to acid- were taken in 50 or 250 mL polyethene (PE- fast bacteria were observed in 15 (13 %) of the LD) bottles (Kautex Textron, GMBH & CO., 120 fish (Table 2). In the separately investigated Bonn, Germany) without air layer at the top. group of neon tetra from total 23 pet-shops, The samples were stored at +4°C for 1 to 14 granuloma formations probably due to acid- days until examination of ammonium (NH4), fast bacteria were observed in 5 (22 %) of the copper (Cu), iron (Fe), nitrate (NO3), nitrite 23 fish (Table 3).

(NO2), phosphate (PO4), carbonate hardness and total hardness by use of conventional Parasitic infections colorimetric aquarium test kits (Sera, Parasitological investigation of the 120 fish Heinsberg, Germany). The detection limits and the 23 neon tetra showed that protozoan were 0.5 mg/L for NH4, 0.1 mg/L for Cu, 0.1 parasites like ciliates and flagellates were mg/L for Fe, 5 mg/L for NO3, 0.9 mg/L for common (Tables 2 and 3). Microsporidia

NO2, 0.1 mg/L for PO4, 1° dKH for carbonate infection with Pleistophora hyphessobryconis hardness and 1° dGH for total hardness. was found only in the neon tetra in which a Measurement of pH was made with a pH total of seven cases were encountered (Table meter [HI 8314], and of conductivity with an 3: 1 [9 %] of 11 fish in specialized shops EC/TDS & Temperature Meter [HI 98311] (both versus 6 [50 %] of 12 fish in non-specialized from Hanna Instruments Inc., Woonsocket, shops were infected, p=0.07, Fisher’s exact Rhode Island, USA). test). Monogenic flukes were not found on the neon tetra, but occurred as frequently as Results on 77 (64 %) of the 120 fish studied (Table 2). Bacterial infections Other metazoan parasites such as nematodes In the group of 720 fish, potentially pathogenic were found in the intestine, liver, stomach gram-negative rods such as A. sobria and A. and other internal organs in 13 (11 %) of the Bull. Eur. Ass. Fish Pathol., 29(5) 2009, 168 1 1 3 1 6 1 2 1 1 3 6 6 1 4 1 6 1 2 9 1 3 15 12 14 with ∑ Fish diagnosis 2 12 1 4 3 2 3 7 13 1 5 1 5 1 3 41 16 7 64 45 32 40 239 Group 5 Other fish (total 24 fish) 1 6 1 2 3 2 1 2 1 1 1 1 2 2 2 1 5 1 9 1 9 2 56 Group 4 Cichlids (total 24 fish) 2 1 1 1 4 4 5 1 3 1 2 1 4 52 11 11 fish Group 3 Labyrinth (total 24 fish) 1 1 3 5 3 3 2 1 1 1 1 1 8 7 38 Group 2 Cyprinids (total 24 fish) 1 3 1 1 1 2 4 1 1 3 1 1 2 3 1 3 5 8 53 11 Group 1 Live bearers (total 24 fish) a spp. spp. spp. sp. sp . spp. spp. spp. sp. spp. adult larvae Centrocestus spp. , metacercaria: Centrocestus , metacercaria: others according to Poppe (1999). according to Poppe Table 2. DiagnosticTable causes for disease in the group fish of 120 studiedmore thoroughly. Diagnostic causes for disease a Bacterial infections sp.) rods ( Vibrio Gram-negative Gram-negative rods (other species) Gram-negative Acid-fast bacteria (rod-/ pleomorphic configured) Parasitic infections parasites Protozoan Ciliophora: Apiosoma Ciliophora: Chilodonella Ciliophora: Ichthyophthirius multifiliis Opalinida: Protopalina Ciliophora: Tetrahymena spp. Ciliophora: Tetrahymena Ciliophora: Trichodina Dinozoa: Piscinoodinium Euglenozoa: Cryptobia Euglenozoa: Ichthyobodo spp. Metamonada: Spironucleus Metazoan parasites Cestoda : Pleurocercoid Monogenea: Dactylogyridae Monogenea: Gyrodactylidae Microspora Myxozoa: Myxidium Myxozoa: Myxobolus Nematoda: Camallanus Nematoda: Trematoda Trematoda Virus infection Virus ( Iridoviridae ) Lymphocystis Oomycete infection Oomycetes Pathological alterations in internal organ Granuloma (probably due to acid-fast bacteria) Granuloma (probably due to parasites) Granuloma (unknown pathogen) Nephrocalcinosis Mechanical injury Trauma Unknown diagnosis Emaciation Gill hyperplasia Others number of diagnoses in all 120 fish Total Bull. Eur. Ass. Fish Pathol., 29(5) 2009, 169 1 1 3 1 6 1 2 1 1 3 6 6 1 4 1 6 1 2 9 1 3 15 12 14 with ∑ Fish diagnosis 2 12 1 4 3 2 3 7 13 1 5 1 5 1 3 41 16 7 64 45 32 40 239 Group 5 Other fish (total 24 fish) 1 6 1 2 3 2 1 2 1 1 1 1 2 2 2 1 5 1 9 1 9 2 56 Group 4 Cichlids (total 24 fish) 2 1 1 1 4 4 5 1 3 1 2 1 4 52 11 11 fish Group 3 Labyrinth (total 24 fish) 1 1 3 5 3 3 2 1 1 1 1 1 8 7 38 Group 2 Cyprinids (total 24 fish) 1 3 1 1 1 2 4 1 1 3 1 1 2 3 1 3 5 8 53 11 Group 1 Live bearers (total 24 fish) a spp. spp. spp. sp. sp . spp. spp. spp. sp. spp. adult larvae Centrocestus spp. , metacercaria: Centrocestus , metacercaria: others according to Poppe (1999). according to Poppe Table 2. DiagnosticTable causes for disease in the group fish of 120 studiedmore thoroughly. Diagnostic causes for disease Microspora Myxozoa: Myxidium Myxozoa: Myxobolus Nematoda: Camallanus Nematoda: a Bacterial infections sp.) rods ( Vibrio Gram-negative Gram-negative rods (other species) Gram-negative Acid-fast bacteria (rod-/ pleomorphic configured) Parasitic infections parasites Protozoan Ciliophora: Apiosoma Ciliophora: Chilodonella Trematoda Ciliophora: Ichthyophthirius multifiliis Opalinida: Protopalina Ciliophora: Tetrahymena spp. Ciliophora: Tetrahymena Ciliophora: Trichodina Trematoda Dinozoa: Piscinoodinium Virus infection Virus ( Iridoviridae ) Lymphocystis Oomycete infection Oomycetes Pathological alterations in internal organ Granuloma (probably due to acid-fast bacteria) Euglenozoa: Cryptobia Granuloma (probably due to parasites) Granuloma (unknown pathogen) Nephrocalcinosis Mechanical injury Trauma Unknown diagnosis Emaciation Gill hyperplasia Others number of diagnoses in all 120 fish Total Euglenozoa: Ichthyobodo spp. Metamonada: Spironucleus Metazoan parasites Cestoda : Pleurocercoid Monogenea: Dactylogyridae Monogenea: Gyrodactylidae Bull. Eur. Ass. Fish Pathol., 29(5) 2009, 170 1 pet-shops randomly Group D: Fish collected from (in total 2 fish) 1 5 3 6 3 1 1 1 1 10 fish) collected from signs of illness pet-shops (in total Group C: Fish with 1 3 fish) Group B: Fish in selling only randomly collected aquarium fish (in total from shops specialized shops from 6 2 1 2 1 1 1 ). (in total 8 fish) shops specialized in Paracheirodon innesi of illness collected from Group A: Fish with signs Group selling only aquarium fish Spironucleus spp . : Spironucleus : Ichthyophthirius multifiliis Table 3. DiagnosticTable causes for disease in neon tetra ( Diagnostic causes for disease Parasitic infections Ciliophora Euglenozoa : Cryptobia spp . Metamonada : Pleistophora hyphessobryconis Microspora Pathological alterations Granuloma (probably due to acid-fast bacteria) Granuloma (unknown pathogen) Nephrocalcinosis Signs with unknown genes Emaciation Malformation of the fins Malformation of the ribs Fin erosion Bull. Eur. Ass. Fish Pathol., 29(5) 2009, 171

120 fish, and infections with trematodes were found in one aquarium tank, in which encountered in the gills and viscera in 7 (6 %) survival problems in the fish population of the 120 fish (Table 2). was reported. Increased levels of NH4 (0.5-5

mg/L, corresponding to 0.015-0.110 mg NH3 Virus infections at present pH) were found in water samples In a total of 720 fish (=72 pooled samples) no from 20 of 153 aquarium tanks. A high level of cases of virus infections were found. Neither NO2 (16.5 mg/L) was found in one aquarium, in the organ material from the 52 selected harbouring neon tetra which showed signs fish investigated with real-time PCR was any of oxygen depletion such as dyspnea and koi herpes nucleic acid detected. However, listless behaviour. Some of these fish were typical nodules indicative of lymphocystis also infected with microsporidia (Pleistophora were observed microscopically on fins hyphessobryconis). and skin of three out of the 720 fish. The affected species were Ramirez’s dwarf cichlid Discussion (Microgeophagus ramirezi), gold gourami This health survey on aquarium fish in Swedish (Trichogaster trichopterus) and pearl gourami pet-shops shows that the most common reason (Trichogaster leeri). for illness in the fish is infections caused by parasites. The most frequent parasitic group Oomycete infections was Monogenea, followed by flagellates and in Oomycete infections were rarely seen in the third place ciliates. Bacterial infections were 120 fish- and neon tetra groups. Only one mainly caused by acid-fast bacteria. In the infection was found in the skin of a swordtail group of 120 fish belonging to 52 different (Xiphophorus hellerii) (Table 2). species that were studied more in detail, established or probable infection with acid- Other findings fast bacteria was found in as many as 28 (23%) Nephrocalcinosis occurred relatively of the fish. Similarly, probable infection with frequently. Fourteen fish (12 %) in the 120 fish acid-fast bacteria was also found in slightly group and one fish in the neon tetra group had more than 20% of the neon tetra. In addition, nephrocalcinosis (Tables 2 and 3). Moreover, in the group of 720 fish, smaller numbers of fin injuries were noted on a comet goldfish, bacterial infections caused by gram-negative probably caused by trauma as a result from an bacteria such as A. hydrophila, A. sobria, L. attack by a turtle living in the same aquarium anguillarum and Vibrio spp were found, of tank (Table 2). which all can cause acute fatal infections in aquarium fish. Water quality parameters Water samples from tap water showed low Concerning virus infections, we cultured Cu content (0.1 mg/L) in seven out of 22 organ material from fish on the cell lines BF-2, pet-shops. In one of these seven shops, low EPC and RTG-2, as these cell lines are sensitive Cu content (0.1 mg/L) in combination with for several viruses belonging to the families low carbonate hardness was in addition aquabirnavirus, iridovirus and rhabdovirus, Bull. Eur. Ass. Fish Pathol., 29(5) 2009, 172 which all are known to cause virus infections out of 11 neon tetra, collected from shops in aquarium fish (Adair & Ferguson, 1981; specialized in aquarium fish. This finding may Hedrick & McDowell, 1995; Betts et al., 2003). suggest that staff working in shops specialized No virus was detected in any of the pooled in aquarium fish have a more pronounced samples investigated including in total 720 fish. experience to identify, handle and treat However, three fish showed microscopically common diseases in aquarium fish, such as the typical cell changes on fins and skin which “Neon Tetra Disease”, as this disease usually were consistent with the iridovirus infection develops slowly and the affected fish in most lymphocystis (Poppe, 1999). The lymphocystis cases exhibit noticeable distinct external signs virus from freshwater fish can be grown in of illness such as fading of the skin coloration the BF-2 cell line (Roberts, 1989a; Hedrick and development of white skin patches. & McDowell, 1995), but only materials from internal organs, and not from the fins and Regarding the finding of survival problems in skin from these three fish were included in the fish population in one aquarium tank with the samples investigated by virus cultivation, a Cu content of 0.1 mg/ L, it has to be noted that which may explain why the iridovirus not Cu can be lethal at concentrations as low as could be isolated. Moreover, using real-time 0.1 mg/L, depending on other water chemistry PCR, no nucleic acid of KHV was detected in parameters ─ for example carbonate hardness organ material from 52 selected fish. (Stoskopf, 1993a). Moreover, the increased

levels of NH4 in the water which were found The selection of fish species in the survey was in 20 of 153 aquarium tanks investigated can done in order to reflect the most commonly be harmful to fish in the long term and cause occurring species of aquarium fish in Swedish gill epithelial hyperplasia (Stoskopf, 1993a; pet-shops. These fish species are also mostly Tomasso, 1993). Furthermore, a NO2 level of cultivated. By now in Sweden, the neon tetra 16.5 mg/L that was found in one aquarium, is the most popular and sold aquarium fish, harbouring neon tetra, is a concentration followed by fantail- and comet goldfish and known to be toxic (Tucker, 1993). live bearers such as guppy (Poecilia reticulata) and platy (Xiphophorus maculatus). In conclusion, this health survey, carried out on aquarium fish in Swedish pet-shops, An interesting question is whether any demonstrated that the most common causes differences exist in regard to the occurrence of of diseases among the fish are infections diseases between fish in pet-shops specialized caused by parasites and acid-fast bacteria. in selling only aquarium fish, and those Improvement of hygiene routines in selling both aquarium fish and other animals. connection with both the handling of fish, We diagnosed “Neon Tetra Disease”, caused and cleaning of the aquariums and their by the microsporidian parasite Pleistophora equipment, are important to avoid infections. hyphessobryconis (Dykowa & Lom, 1980) in Prophylactic treatment against ectoparasitic six out of 12 neon tetra, collected from non- protozoans and monogeneic flukes on specialized shops compared with in only one skin and gills of new fish, and regularly on Bull. Eur. Ass. Fish Pathol., 29(5) 2009, 173

agar, a new growth medium for the fish disease existing fish populations in the shops, will bacterium Renibacterium salmoninarum. Applied also reduce these infections. Fish with signs and Environmental Microbiology 50, 868-871. indicating disease have to be identified and rapidly isolated from healthy fish in order to Danielsson M (2003). The number and importance of pet animals in Europe (Sweden) decrease the risk of spreading the infection. [in Swedish]. PetScandinavia 3, 10-14. Diseased fish should thereafter be treated with appropriate medications in special aquariums Dykova´ I and Lom J (1980). Tissue reactions suitable for the actual treatment (Scott, 1991; to microsporidian infections in fish. Journal of Fish Diseases 3, 265-283. Stoskopf, 1993b). Increasing the knowledge about commonly occurring infections in Engelhardt VA (1992). Causes of diseases and aquarium fish to people working in these mortality in aquarium fishes – frequency and shops will be an important step to improve importance. Berliner Munchener tierärztliche Wochenschrift 105, 187-192. aquarium fish welfare. Hedrick RR and McDowell TS (1995). Acknowledgements Properties of iridoviruses from ornamental We would like to thank Emelie Kjellberg, fish. Veterinary Research 26, 423-427. Susanne Martelius-Walter and Eva Säker for Holt RA, Rohovec JS and Fryer JL (1993). their assistance with skilful laboratory work. Bacterial coldwater disease. In “Bacterial This research was supported by the Swedish diseases of fish” (V. Inglis, R.J. Roberts & N.R. Animal Welfare Agency (grant no. 2005- Bromage, Eds.), pp. 3-23. Blackwell Scientific Publications, Oxford, UK. 1708). Kim J-H, Hayward CJ, Joh S-J and Heo G-J References (2002). Parasitic infections in live freshwater Adair BM and Ferguson HW (1981). Isolation tropical fishes imported to Korea. Diseases of of infectious pancreatic necrosis (IPN) virus Aquatic Organisms 52, 169-173. from non-salmonid fish.Journal of Fish Diseases 4, 69-76. Levsen A, Mo TA and Sterud E (2003). The most common infections in ornamental fish Bernardet J-F and Kerouault B (1989). imported to Norway – a possible threat against Phenotypic and genomic studies of ”Cytophaga Norwegian fauna. Norsk Veterinaertidsskrift psychrophila” isolated from diseased rainbow 115, 639-649. trout (Oncorhynchus mykiss) in France. Applied and Environmental Microbiology 55, 1796-1800. Poppe T (1999). ”Fiskehelse og fiskesykdommer” [in Norwegian]. Betts AM, Stone DM, Way K, Torhy C, Universitetsforlaget, Oslo, Norway. Chilmonczyk S, Benmansour A and de Kinkelin P (2003). Emerging vesiculo-type Roberts RJ (1989a). The virology of teleostas. In virus infections of freshwater fishes in Europe. “Fish Pathology”, 2nd edn. (R.J. Roberts, Ed.), Diseases of Aquatic Organisms 57, 201-212. pp. 192-195. Bailliere Tindall, W.B. Saunders, London, UK. Brorsson E (1987). I remember … [in Swedish]. Akvariet 1, 11. Roberts RJ (1989b). Laboratory methods. In “Fish Pathology”, 2nd edn. (R.J. Roberts, Ed.), Daly JG and Stevenson RM (1985). Charcoal pp. 374-405. Bailliere Tindall, W.B. Saunders, Bull. Eur. Ass. Fish Pathol., 29(5) 2009, 174

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