Experimental infection of redclaw crayfish (Cherax quadricarinatus) with Macrobrachium rosenbergii nodavirus, the aetiological agent of white tail disease

Abstract

Macrobrachium rosenbergii nodavirus (MrNV) or white tail disease has been reported as a new disease of crustacea in western Queensland, Australia. In Australia, Macrobrachium can be hard to source due to their need for a saltwater environment for breeding. No alternative animal experimental model for MrNV has been identified, so redclaw crayfish (Cherax quadricarinatus) were tested as a potential experimental animal in order to study MrNV infection. The highest mortality (35%) was in the groups injected with MrNV and the lowest mortality (0%) was in the control groups. Necrotic muscle and muscle degeneration with haemocytic infiltration were observed in infected crayfish. For the first time, a quantitative real-time polymerase chain reaction (qPCR) on clinical material was developed and it confirmed MrNV infection in infected animals. The mean viral titres (2.73 × 102 copies) and cycle times (Ct = 31.33) lead us to hypothesize that MrNV only poorly replicates in juvenile C. quadricarinatus. However, C. quadricarinatus may be a less than perfect but useable experimental animal model for MrNV infection in the future because of clinical signs, gross lesions, histopathological changes and qPCR titres present in experimentally infected C. quadricarinatus. This study determined that redclaw crayfish (C. quadricarinatus) had low susceptibility and were limited carriers of white tail disease.