Detection of a Nonoccluded Baculovirus in the Freshwater CrayfishCherax quadricarinatusin North America

Abstract

A nonoccluded baculovirus was detected during a routine health examination of the tropical freshwater blue crayfish Cherax quadricarinatus reared in a farm in California, USA. The crayfish were progeny of captive-reared adults imported from Australia. There were no external or internal signs of disease in infected crayfish, but histological examination revealed eosinophilic to amphophilic intranuclear inclusions within the tubular epithelial cells of the hepatopancreas. The infected cells occurred throughout the hepatopancreas but never exceeded 10% of the cells constituting the tubule epithelium. Electron microscopy revealed numerous loosely enveloped, rod-shaped baculoviruses. The enveloped virions had a length of 292 ± 15 nm and a diameter of 102 ± 7 nm (mean ± SD). The cylindrical nucleocapsids often possessed squared ends and were 216 ± 13 nm in length by 47 ± 3 nm in width. There was no evidence of occlusion body formation similar to that known for certain other crustacean baculoviruses. The origin of the virus is uncertain, although a similar or identical agent has recently been detected among C. quadricarinatus in Australia.