Studies of Mycoses in farmed estuarine crocodiles (Crocodylus porosus Schneider 1801)
thesisposted on 06.12.2017, 00:00 by Elspeth Hibberd
Project aims to investigate the epidemiology of systemic mycotic disease in juvenile farmed estuarine crocodiles and to describe the histopathology of the infection.. The ubiquitous fungus, Fusarium solani (Mart.) Sacc., (teleomorph Nectria haematococca Berk and Broome) was frequently isolated, both superficially and systemically, from diseased juvenile farmed crocodiles, Crocodylus porosus Schneider 1801. At autopsy, various internal tissues sllowed granulomatous inflammations from which the .same fungal pathogen was readily isolated. Asymptomatic tissues were also shown to be infected. Other fungi isolated with less frequency from the animals were Paecilomyces lilacinus, Cladosporium sp. and Aspergillus sp. Infection rates at a commercial crocodile farm had reached epidemic proportions with mortality and morbidity in excess of 50% of each year's eggs and 50% of each year's hatchlings. Environmental samples showed that the pathogen was widely distributed in the farm environment. Contamination of freshly laid eggs by the pathogen was determined as the probable primary cause of infection, along with subsequent physical trauma in juveniles. Natural nesting material was implicated as a major source of egg contamination. To prevent infection of eggs, changes to procedures in the artificial incubation techniques used at the fann were carried out and a significant increase in hatchability was achieved. Treatments of diseased animals met with varying degrees of success. Attempts weremade to control the incidence of the disease by modifying husbandry practices afterinvestigation of environmental parameters. Hatchling survival was significantly improved. Standard autopsy, histological and mycological procedures were used to isolate andidentify the pathogens. Various environmental monitoring methods were employedwith a view to minimising stress on the animals. Scanning electron microscopy wasused to determine the method of access by the fungi into the eggs.