No abstract

Objective To describe the clinical signs, gross pathology, serology, bacteriology, histopathology, electron microscopy and immunohistochemistry findings associated with toxoplasmosis in four Indo‐Pacific humpbacked dolphins (Sousa chinensis) that stranded in Queensland in 2000 and 2001. Design Clinical assessment, gross necropsy, and laboratory examinations. Procedure Necropsies were performed on four S chinensis to determine cause of death. Laboratory tests including serology, bacteriology, histopathology and transmission electron microscopy were done on the four dolphins. Immunohistochemistry was done on the brain, heart, liver, lung, spleen and adrenal gland from various dolphins to detect Toxoplasma gondii antigens. Results Necropsies showed all of four S chinensis that stranded in Queensland in 2000 and 2001 had evidence of predatory shark attack and three were extremely emaciated. Histopathological examinations showed all four dolphins had toxoplasmosis with tissue cysts resembling T gondii i n the brain. Tachyzoite stages of T gondii were detected in the lungs, heart, liver, spleen and adrenal gland, variously of all four dolphins. Electron microscopy studies and immunohisto‐chemistry confirmed the tissues cysts were those of T gondii. All four dolphins also had intercurrent disease including pneumonia, three had peritonitis and one had pancreatitis. Conclusion Four S chinensis necropsied in Queensland in 2000 and 2001 were found to be infected with toxoplasmosis. It is uncertain how these dolphins became infected and further studies are needed to determine how S chinensis acquire toxoplasmosis. All four dolphins stranded after periods of heavy rainfall, and coastal freshwater runoff may be a risk factor for T gondii infection in S chinensis. This disease should be of concern to wildlife managers since S chinensis i s a rare species and its numbers appear to be declining.

In the summer of 1999/2000, an epizootic occurred in cultured juvenile redclaw crayfish Cherax quadricarinatus on one commercial crayfish farm in northern Queensland, Australia. Mortalities occurred over 4 wk, with up to 96% cumulative mortalities in 2 earthen ponds stocked with juveniles. The crayfish were weak, anorexic and lethargic. A transmission trial was conducted, using filtered, cell-free extract prepared from infected crayfish as inoculum. The disease was reproduced, with on-going mortalities occurring in inoculated crayfish over 55 d. Experimentally inoculated crayfish showed gross signs of malaise, anorexia and disorientation before dying. Two types of intranuclear inclusion bodies (INIBs) were seen in tissues of endodermal, ectodermal and mesodermal origin by light microscopy with haematoxylin and eosin (H&E) stained sections. 'Early'-stage INIBs were eosinophilic, rounded and located centrally within slightly enlarged nuclei while 'late'-stage INIBs were well-rounded and deeply basophilic. The gills, cuticular epithelium and epithelial cells of the foregut, midgut and hindgut were the most heavily infected tissues. By transmission electron microscopy, virions with an average diameter of 19.5 nm were seen within electron-dense granular inclusion bodies within enlarged nuclei of both naturally and experimentally infected crayfish. The size of the virions and cytopathology are consistent with characteristics of viruses in the Family Parvoviridae. This is the first reported case of mass mortality caused by a parvo-like virus infection in C. quadricarinatus. KEY WORDS:Cherax quadricarinatus · Virus · Parvo-like virus · Disease · Aquaculture · Crayfish · Pathology Resale or republication not permitted without written consent of the publisherDis Aquat Org 50: [79][80][81][82][83][84][85][86] 2002 clinical viral infections have been reported (Edgerton et al. 1994, Edgerton & Owens 1999, but crayfish with these infections have usually been coinfected with bacterial and/or other pathogens. Mass mortalities in pond-reared redclaw have so far been caused by bacterial diseases including vibriosis (Eaves & Ketterer 1994) and those due to infections with rickettsiales-like organisms (Ketterer et al. 1992).In December 1999 and January 2000, 1 redclaw crayfish farm in Queensland, Australia, reported higher than average mortalities in 2 earthen ponds stocked with juvenile crayfish Cherax quadricarinatus. Cumulative mortalities of up to 96% occurred over 2 mo. Histopathological examination of diseased crayfish revealed intra-nuclear inclusion bodies that resembled those associated with parvo-like viral infections. In February 2000, on-going mortalities occurred in other ponds on this farm stocked with adult crayfish. There was an estimated 50% loss in total farm production, due to losses of juvenile and adult crayfish and the farm subsequently closed down for a total destocking and pond disinfection. A detailed disease investigation was carried out to determine the cause of the mortalities.The results an...

ABSTRACT. Basovhilic, Gram-neaative, nucrocolonies of rick- Rickettsia-like organisms (RLO) infect a range of aquahc crustaceans mcludmg amphpods, crabs, prawns and freshwater crayfish (Federici et al. 1974, Bonami & Pappalardo 1980, Johnson 1984, Sparks et al. 1985, Brock et al. 1986, Anderson et al. 1987, Krol et al. 1991, Ketterer et al. 1992, Owens et al. 1992, Bower et al. 1996. The decapod-infecting RLOs are either confined to the hepatopancreatic tubule epithelium, or are systemic. The systemic RLOs never have been observed to infect endodermal enteric tissues. The RLO infecting the redclaw freshwater crayfish Cherax quadricarinatus, and originally described by Ketterer et al. (1992) and Owens et al. (1992), is in the systemic category. A RLO was observed exclusively in the hepatopancreatic tubule epithelium of one moribund C. quadricarinatus during a n investigation of chronic low-grade mortality at a farm in north Queensland. Histopathology, cytopathology and basic morphology of this organism are reported here. Materials and methods. The moribund Cherax'Present address: Animal Quarantine Policy Branch, Australian Quarantine and Inspection Service, GPO Box 858, Canberra, ACT 2601, Australia. E-mail: brett.edgerton@aqis.gov.au ing haematoxylin and eosin staining of sections. Special stains (Culling et al. 1985) included Brown and Brenn Gram, phloxine and tartrazine, and Periodic Acid Schiff (PAS).Unstained, 5 pm thick sections of paraffin embedded tissues were processed for electron microscopy by a method adapted from Bhatnagar et al. (1977). Briefly, lesions were located on the paraffin section. Excess tissue was removed, and the remainder was deparaffinised, rehydrated, refixed in glutaraldehyde, postfixed in osmium tetroxide and dehydrated in a graduated acetone series. Infiltration with increasing concentrations of Spurr's resin was carried out on the slide, using a short section cut from a plastic pipette to create a dam of resin over the section. After overnight polymerisation at 60°C the plastic dam was cut away, the slide gently warmed and the resin stub with attached section eased off the glass slide. Ultrathin sections stained with uranyl acetate and lead citrate were examined with a Philips CM 10 TEM.Results. Basophilic inclusions were observed in the cytoplasm of hepatopancreatocytes in adjacent tubules. Nearly all hepatopancreatocytes in cross-sectioned tubules contained the inclusions (Fig. 1). The inclusions were Gram-negative, moderately PAS positive, intensely phloxophilic, and often had a clear central zone containing faint eosinophilic material. Intracytoplasmic, Gram-negative microcolonies were not observed in any other tissues. Sectioning for special stains went beyond the focus of infection, and the 0 Inter-Research 1999Resale of full a r t~c l e not permitted

No abstract