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Diseases of Aquatic Organisms

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DAO 41:83-90 (2000)  -  doi:10.3354/dao041083

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

Brett F. Edgerton1,*, Richard Webb2, Ian G. Anderson1, Elizabeth C. Kulpa1

1Queensland Department of Primary Industries, Oonoonba Veterinary Laboratory, PO Box 1085, Townsville, Queensland 4810, Australia
2Department of Microbiology and Centre for Microscopy and Microanalysis, University of Queensland, St Lucia, Queensland 4072, Australia
*Present address: Animal Quarantine Policy Branch, Australian Quarantine and Inspection Service, GPO Box 858, Barton, Australian Capital Territory 2604, Australia. E-mail:

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 parvovirus in the gills, were associated with chronic mortalities in C. quadricarinatus 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 facility 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, Feulgen-negative, 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 40 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 parvovirus, are reported herein.

KEY WORDS: Freshwater crayfish · Cherax quadricarinatus · Crustacea · Aquaculture · Reovirus · Parvovirus · Disease · Pathology

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