Description of a presumptive hepatopancreatic reovirus, and a putative gill parvovirus, in the freshwater crayfish Cherax quadricarinatus

Abstract

The redclaw freshwater crayfish Cherax quadricarinatus has a reputation for being hardy and resistant to handling stress. However, in recent years, possibly since 1996, C. quadricarinatus farmers in northern Queensland have noted a decrease in stress resistance in their stock. A presumptive reovirus in the hepatopancreas, and a putative p a~o v i r u s in the gills, were associated with chronic mortalities in C. quadncarinatus at one northern Queensland farm. Hypertrophic nuclei with marginated chromatin were observed in gill epithelium in moribund crayfish which had recently been relocated to a laboratory from the holding tank fachty on the farm. Affected nuclei appeared to be vacant or contained a faint granular basophilia in H&E stained sections. However, toluidine blue staining revealed a homogenously granular appearance of the nuclei. Transmission electron microscopy revealed approximately 20 nm diameter virus-like particles within the nucleus. Eosinophilic, Feulgennegative, cytoplasmic inclusions were observed in distal hepatopancreatocytes in 1 moribund C. quadricarinatus collected from the same on-farm holding tank approximately 6 mo later. This crayfish did not display the gill lesions. Transmission electron microscopy showed that the inclusions contained icosahedral virus particles 35 to 4 0 nm in diameter. The histopathology and preliminary virus morphology of the presumptive hepatopancreatic reovirus, and the histopathology, ultrastructural pathology and preliminary virus morphology of the putative gill pawovirus, are reported herein.

A parvo-like virus in cultured redclaw crayfish Cherax quadricarinatus from Queensland, Australia

“…These were present in crayfish of all the experimental groups. In addition, 1 crayfish had a reo-like viral infection of the hepatopancreas (Edgerton et al 2000).The principal lesions seen in the viral injected crayfish were basophilic, INIBs in cells of the same tissues and tissue types described previously for the farm epizootic. In addition, the retinular, epicorneagenous and proximal cone cells of the eye were occasionally infected.…”

Investigation of an Idiopathic Lesion in Redclaw Crayfish Cherax Quadricarinatus Using Suppression Subtractive Hybridization

“…The affected crayfish had hypertrophic nuclei with rarefied chromatin but without CA intranuclear inclusion bodies in the gill epithelium which resembled histological changes consistent with a putative gill parvovirus reported by Edgerton et al (2000) in this species from northern Queensland. On this basis, it was assumed that these animals were infected with putative gill parvovirus.…”

“…However, genetic characterisation of the viruses has not been carried out and studies on immune-related genes of redclaw crayfish are sparse. Lesions characterised by hypertrophied nuclei with rarefied chromatin but without Cowdry type A (CA) intranuclear inclusion bodies that resemble those associated with putative parvovirus infection previously reported in C. quadricarinatus (Edgerton et al, 2000) were observed in a population, while these changes were not observed in another population of redclaw crayfish in the aquaculture facilities of the School of Veterinary and Biomedical Sciences, James Cook University. Therefore, this study was conducted to profile possible viral genomes and differentially expressed genes from gills of the two populations of crayfish using suppression subtractive hybridization (SSH).…”

“…In addition, a presumptive hepatopancreatic reovirus has been reported to decrease stress resistance in farmed C. quadricarinatus (Edgerton et al, 2000;Hayakijkosol and Owens, 2011). Even though these viruses are not very virulent to redclaw crayfish, they have been shown to cause low level mortalities and growth retardation and are thought to suppress the immunoresponse of animals (Edgerton and Owens, 1999;Hayakijkosol and Owens, 2011).…”

“…Tissue changes and viral morphology have been described using light microscopy and transmission electron microscopy (TEM) (Bowater et al, 2002;Edgerton et al, 2000). However, genetic characterisation of the viruses has not been carried out and studies on immune-related genes of redclaw crayfish are sparse.…”