سال انتشار: ۱۳۸۷

محل انتشار: اولین کنگره بین المللی مدیریت بهداشتی و بیماریهای آبزیان

تعداد صفحات: ۱

نویسنده(ها):

M Alishahi – Faculty of veterinary Medicine, Shahid Chamran University, Ahvaz, Iran
M Mesbah –
N Moori Bakhtiari –

چکیده:

Objective: Warm water fish farming is based on cultivation of 4 species of cyprinid family in earthen farms in Iran. Big head (Aristichtys nobilis) as an zooplanktonphage species is one of the important species among cyprinid family economically and biologically. It can control zooplanktons and copepodid stage of some crustacean parasites (e.g., Lernea) in polyculture systems. Aeromonads infection is one of the important and common bacterial infections in cyprinid farms particularly after environmental stress and immune suppression. In this study, infection of big head carp with Aeromonas sobria like bacteria is reported.
Method & Materials: In the February 2008, we are informed about a mass mortality of big head carp (mean weight= 50g) in one of the farms in Ahvaz, Khouzestan. In visit of the farms, nothing unusual was observed, however, net fishing showed lots of dead, nearly dead and moribund big head with surprisingly wide open mouth. Water biochemical factors were nearly normal. Water temperature was 18° and there were no significant differences between this farm and neighboring healthy farms. It is notable that the fish intensity in this farm was 50% higher than usual.
Results & Conclusion: 50 moribund fish were captured and transported to the laboratory. External visual signs composed of: exophthalmia and cataract, spread petechiae in skin, dropsy, general skin darkening, emaciation and necroses in gill filaments. These symptoms could be observed in most of fish but, wide open mouth was a general sign in all fish. Internal sign include empty digestive tract, swelling and pare liver, kidney and spleen swelling and presence of black spot on them and abnormal darken ascetic fluid in ventral cavity. Histopathological study showed some pathological change in gill, liver, kidney and spleen. Parasitical assay showed nothing except few monogeneans in gills. Bacterial study showed a very severe infection to Aeromonas sobria like bacteria in about 85% of fishes. This bacteria was isolated from kidney (65%), liver (45%), ascitic fluid (60%) and spleen (40%) of infected fish. Regarding to environmental, biochemical and historical aspects of mass mortality, symptoms and lake of parasitic agents it can be concluded that Aeromonas sobria is a causative organism of this mortality. Neurotoxic effects of bacterial endotoxines can be the reason of wide open mouth in all moribund fish. The role of viruses or unknown factors as a primary cause of mortality can not be denied.