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چکیده
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In Brazil, koi (Cyprinus carpio) and goldfish (Carassius auratus) are the most important species reared for ornamental aquaculture. In 2014, one of the largest koi and goldfish producers in Brazil experienced substantial mortality in yearling koi (< 5 cm in total length) being reared in earthen ponds. The young koi were noted to be stratified in the upper layers of the ponds and in obvious respiratory distress. The mortality was estimated between 50-70% over a two week period in some affected ponds. During the outbreak, water temperature was around 22°C with other water quality parameters within normal limits. Wet mounts of affected fish revealed high levels of trichodinid parasites which were also observed upon histologic examination of external tissues. The most significant histologic lesions were observed in the gills where severe hyperplasia of the respiratory epithelium was noted leading to fusion of adjacent secondary lamellae and an associated inflammatory response. Gill tissue from moribund koi tested negative for koi herpesvirus (KHV) and positive for Carp Edema Virus (CEV) by conventional PCR. This study is the first detection of CEV in South America and further confirms the global spread of this lethal disease of koi.
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