A comparison of ectoparasite prevalence and occurrence of viral haemorrhagic septicemia virus (VHSV) in whiting Merlangius merlangus euxinus

Seven hundred and eighty-four whiting (Merlangius merlangus euxinus) were individually sampled for virological and parasitological examination to assess the effect of ectoparasite mean intensity on the occurrence of viral haemorrhagic septicemia virus (VHSV) in whiting in the Black Sea. The pooled homogenates of internal organs (kidney, spleen and liver) were inoculated onto BF-2 cells. The cells exhibiting cytopathic effect (CPE) were tested with ELISA to determine the virus species. The mean intensities and prevalence of ectoparasites (Trichodina spp. and Gyrodactylus alviga) were also determined on the gills of the same fish. The whiting infected with VHSV contained similar counts of Trichodina spp. (10.0 +/- 1.8) than VHSV-free whiting (7.2 +/- 1.0). The mean intensities of Gyrodactylus alviga were similar on the VHSV infected (1.8 +/- 0.1) than uninfected fish (3.3 +/- 0.2). The results indicate that ectoparasites were not alone responsible for the observed occurrence of VHSV. Other factors, such as spawning stress, sudden fluctuations in water quality parameters alone or additively to ectoparasites may be responsible for the occurrence of VHSV in whiting.