My area of specialization is clinical protozoology and I practice essentially as a diagnostician; i.e. I detect and study unicellular protozoan parasites infecting vertebrate hosts. I have long been fascinated by their extreme biodiversity as manifest by considerable variation in their structure, function and mode of existence. The prevailing theme of my research is to discover and describe protozoan species in Australian animals. My studies are deliberately parochial as our continent is simply the last great unexplored bastion for micro-fauna. Little is known about protozoa in the gut, blood and tissues of native mammals, birds, reptiles and fish. I seek to define the morphology, biology, historical zoogeography and pathogenicity of endemic protozoan species. I want to know their identity, origins and interactions with their hosts. Despite the diversity of hosts sampled, I confine my studies to four main protozoan assemblages: flagellates, amoebae, ciliates and sporozoa. I have detected a high degree of endemicity of these groups in Australian vertebrates suggesting their evolution in long isolation.
I determine the cellular and subcellular structure of protozoan isolates, explore their developmental cycles and examine their pathogenicity. I employ special techniques in light and electron microscopy, biochemical and immunological assays and protein and nucleic acid analyses. I evaluate morphological and molecular characters for the differential diagnosis of species and to provide reliable markers for biological traits of clinical and epidemiological significance. I determine relationships between the site of infection, parasite pathogenicity, host specificity and mode of transmission. Many protozoan species have fast life-cycles which out-race host immune responses. They invade host tissues, proliferate rapidly and then exit the host as encysted stages infective to other hosts. Resultant diseases are therefore often rapid, acute and severe. Other protozoan species have slow life-cycles where they hide in host tissues to optimize their chances of being taken up by predators or invertebrate vectors. These species cause protracted, chronic diseases often characterized by space-occupying lesions. Effective treatment and control relies on a thorough knowledge of the parasites involved, their effects on their hosts and the epidemiology of infections.