The First Report Of Diplostomiasis From Cultured Rainbow Trout (Oncorhynchus Mykiss) In Turkey

Metacercariae of the Diplostomum spp., the cause of Larval Eye Diplostomiasis (LED), are located in the lenses of the eyes of fresh water fish and cause degeneration, lens opacity and blindness as disease progresses. Feed uptake is hindered in fish with failing eyesight causing loss of apetite and mortality becomes inevitable with the onset of secondary diseases. Freshwater molluscs and waterfowl have an important role in the fast spread of the disease to nearby farms. In this work, a total of 534 trout samples obtained from 24 farms located in southeastern Turkey were examined for LED. Histopathological findings were evaluated in thirty fish with lens opacity in varying degrees. Also these fish were examined in terms of bacterial agents as well. As a result of this work, Diplostomum spp. metacercariae were found to be prevalent in the lenses of fish. In fish with marked lens opacity, focal to extensive subcapsular cataract was observed. Cataract lesions included abnormal proliferation of the lens epithelium at the site of capsular rupture, often followed by degeneration, fragmentation and liquefaction of adjacent cortical lens fibers. Additionally, Lactococcus garvieae was also isolated in 10 of 24 farms.