A new bacilliform virus in Australian Cherax destructor (Decapoda: Parastacidae) with notes on Cherax quadricarinatus bacilliform virus (equals Cherax baculovirus)

Intranuclear lesions were detected in hepatopancreocytes of Cherax destructor by light microscopy. The lesions included nuclear hypertrophy, chromatin margination, a peripherally displaced nucleolus, or nucleolar remnants remaining in the centre of a granular eosinophilic inclusion. The cytoplasm of some infected cells was granular and basophilic. The intensity of the lesions was low in all cases; however, infected nuclei were sloughed from the epithelium. Rod-shaped virions within a granular viroplasm were visualised in these nuclei by electron microscopy. The virions contained a nucleocapsid, consisting of an electron-dense nucleoprotein core and less electron-dense capsid, and a trilaminar envelope. The envelope was closely applied, except that at one end it was laterally expanded to contain a tail-like structure that arose from the nucleocapsid. The nucleocapsid was often bent in this region. Capsids formed unassociated with membranes. A capsid which was partially filled with nucleoprotein was elongated and improperly enveloped. Virions were 68 x 304 nm and nucleocapsids were 49 x 263 nm. Virions of Cherax quadricarinatus bacilliform virus consisted of a rod-shaped nucleocapsid surrounded by a loosely applied trilaminar envelope. A nucleocapsid tail-like structure was visible in several virions. Capsids appeared to form inside of membrane bubbles and capsids that were partially filled with nucleoprotein had a central filament. Virions were 103 x 262 nm and nucleocapsids were 54 x 212 nm. The morphology and development of both viruses is compared to other arthropod bacilliform viruses.