Investigation into the pathogenicity of reovirus to juvenile Cherax quadricarinatus

Abstract

Presumptive reoviruses have been visualised in the hepatopancreas of the freshwater redclaw crayfish (Cherax quadricarinatus) in northern Queensland. Transmission electron microscopy of preparations from similar animals revealed approximately 55 nm diameter icosahedral viral particles. Juvenile C. quadricarinatus were challenged orally and by injection with these purified reoviruses. Following the conclusion of the 60 day pathogenicity trial, histological examination was performed on gills and hepatopancreatic tissues of infected crayfish. Reovirus inclusion bodies were seen in hepatopancreatic tubules of the orally infected group more often than inoculated group. The inoculated treatment displayed the highest mortality rate (20%) and the lowest mean weight of 8.2 ± 1.27 g, while the control group had the lowest mortality (0%) and largest mean weight of 13.9 ± 0.53 g. Reoviruses infected a HepG2 cell culture and showed increased light transmission (i.e. less cells) with increasing titre in a viral titration format. This study illustrated the susceptibility of C. quadricarinatus to the Australian isolate of hepatopancreatic reovirus infection.