Ž . Aquaculture 180 1999 23–40 www.elsevier.nlrlocateraqua-online Histopathological surveys of the redclaw freshwater crayfish, Cherax quadricarinatus, in Australia Brett F. Edgerton ) , Leigh Owens Department of Microbiology and Immunology, James Cook UniÕersity, TownsÕille, QLD 4810, Australia Accepted 21 April 1999 Abstract Histopathological surveys on Cherax quadricarinatus from farms in northern Queensland were Ž . conducted in 1992 and 1996. C. quadricarinatus bacilliform virus CqBV and C. GiardiaÕirus-like virus were highly prevalent in both surveys. The prevalence of CqBV in three farms was markedly higher in the 1996 survey than in the 1992 survey. However increased mortalities were not reported by farmers in this period. Bacteraemia and Psorospermium sp. were common in both surveys. Enteric bacterial infections were common at one farm in 1996. Microsporidiosis was observed in two crayfish from one farm in 1992. Haemocytic enteritis was common in two farms in 1996, and black spots were observed on crayfish from one farm in 1992, and from two different farms in 1996. Several other rare idiopathic lesions were observed. The need for more thorough data sets on the prevalence and incidence of disease causing organisms in freshwater crayfish is highlighted. q 1999 Elsevier Science B.V. All rights reserved. Keywords: Cherax quadricarinatus; Redclaw freshwater crayfish; Histopathology; Disease; Surveys 1. Introduction The redclaw freshwater crayfish, Cherax quadricarinatus, has great potential for aquaculture. Consequently the species has been introduced into many countries through- Ž . out the world Medley et al., 1994 . Many proponents have promoted C. quadricarina- ) Corresponding author. Animal Quarantine Policy Branch, Australian Quarantine and Inspection Service, GPO Box 858, Barton ACT 2601, Australia. Tel.: q61-2-6272-4948; fax: q61-2-6272-3399; E-mail: brett.edgerton@aqis.gov.au 0044-8486r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S0044-8486 99 00195-7