Histopathological surveys of the redclaw freshwater crayfish, Cherax quadricarinatus, in Australia

Histopathological surveys on Cherax quadricarinatus from farms in northern Queensland were conducted in 1992 and 1996. C. quadricarinatus bacilliform virus (CqBV) and C. Giardiavirus-like virus were highly prevalent in both s urveys. The prevalence of CqBV in three farms was markedly higher in the 19 96 survey than in the 1992 survey. However increased mortalities were not r eported by farmers in this period. Bacteraemia and Psorospermium sp. were c ommon in both surveys. Enteric bacterial infections were common at one farm in 1996. Microsporidiosis was observed in two crayfish from one farm in 19 92. Haemocytic enteritis was common in two farms in 1996, and black spots w ere observed on crayfish from one farm in 1992, and from two different farm s in 1996. Several other rare idiopathic lesions were observed. The need fo r more thorough data sets on the prevalence and incidence of disease causin g organisms in freshwater crayfish is highlighted. (C) 1999 Elsevier Scienc e B.V. All rights reserved.