INVESTIGATION INTO THE PATHOGENESIS OF BLUE CATFISH ALLOHERPESVIRUS (BCAHV)

 Blue catfish alloherpesvirus (BCAHV) is a strain of Ictalurid herpesvirus 1 (IcHV1)  genetically similar  (94%) to channel catfish virus (CCV). Limited information on the pathogenesis of this virus combined with its potential to cause damages at the production facilities  warranted  a detailed study of BCAHV. To determine the host-specificity and potential host range of BCAHV, the virus was inoculated onto  fish cell lines belonging to families Ictaluridae, Cyprinidae, Centrarchidae, and Clariidae. The virus replication and exhibition of cytopathic effects (CPEs) were restricted to cell lines from family Ictaluridae indicating the host preference of BCAHV. Subsequently, fish challenge trials were carried out to evaluate intrinsic and extrinsic factors influencing BCAHV infection. Mortality due to BCAHV infection was significantly high in blue catfish and low in channel catfish further specifying the host preference of the virus (Figure 1). Clinical symptoms of BCAHV infection included ascites  and  exophthalmia.  Histopathological alterations of the BCAHV infected fish revealed prominent splenitis with severe erythrophagia.  Host susceptibility to BCAHV differed with age and fish at 60 days post hatch were  more susceptible. Temperature had a significant role in the activation and pathogenesis of BCAHV. Fish exposed to BCAHV at a sustained high temperature had significantly low mortality suggesting the likelihood of virus inactivation. In another  fish challenge simulating crowding, mortality was found to be significantly higher in densely  stocked tanks, indicating the role of horizontal transmission in BCAHV pathogenesis. The heightened pathogenicity of BCAHV towards blue and hybrid catfish as observed in this study points to the potential of this virus to cause significant concern in catfish production.