High mortality among laboratory cultured Iberian toothcarp Aphanius iberus occurred in February 1997 in Valencia (Spain). The main signs of the &sease were external haemorrhage and tail rot. Bacteria isolated from internal organs of infected fish were biochemically hon~ogeneous and identified as Vibrio parahaemolyticus. The bacteria were haemolytic against erythrocytes from eel AnguilIa anguilla, ambe j a c k Seriola dumerili, toothcarp A. iberus and humans, and were Kanagawa-phenomenon-negative. Infectivity tests showed that the virulence for A. iberus was dependent on salinity. Finally, all strains were virulent for ambejack and eel. 1993). These species cause haemorrhagic septicaemia in marine fish and may lead to substantial mortalities in cultured populations (Wong et al. 1990). Among the genus Vibrio, the species V. parahaemolyticus is a marine bacterium which causes acute gastroenteritis and food poisoning in humans who consume raw or improperly cooked seafood (Hlady & Montz 1996, Pan et al. 1997.The Iberian toothcarp Aphanius iberus is a cyprinodontid native to the Iberian peninsula. This fish is euryhaline and found in salt marshes and coastal lagoons (Sanz 1985). It is considered an endangered species (Blanco & Gonzalez 1992), with decreasing numbers attributed to pollution and destruction of its habitats, as well as competition from allochthonous species such as eastern mosquitofish Gambusia holbrooki. In 1996 work began on the reproduction of Iberian toothcarp at different salinities. During February-March 1997, an infectious disease occurred in the fish maintained in laboratory culture tanks. Diseased fish first appeared in tanks with 30%0 salinity, and later in the tanks maintained at 5 and 15%0 salinities. The affected fish showed tail rot, red spots on the head and a swollen intestine containing ascitic fluid. Fish held in tanks at 45 and 60%0 salinities were not affected. Mortality was high and all fish in the affected tanks died within 7 d. Pure cultures of a bacterium identified as V. parahaemolyticus were isolated from internal organs of all moribund fish. In this paper the authors report on the isolation and characterization of V. parahaemolyticus from diseased Iberian toothcarp for the first time.Material and methods. Microbiological analysis: Diseased fish were 3 mo old and the water temperature was above 25°C when the outbreak was registered. Samples from the surface and liver of moribund fish were analysed. Each sample was streaked on thiosulphate citrate bile salt agar and tryptone soy agar supplemented with 3 % NaCl (TCBS-3 and TSA-3 respectively). All plates were incubated at 25°C for 24 to 48 h. Isolates were characterized by morphological tests and API 20E strips (BioMerieux). Similar analysis was made of the water from the tanks in which the fish were held as well as the food supply. Further characterization of the isolates was carried out by additional biochemical tests (Table 1) and type strain Vibrio parahaemolyticus ATCC 17802 was included as a control.Enzymatic and ...

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