Veterinary Science - Theses
Permanent URI for this collection
Search Results
1 - 3 of 3
-
Item
-
ItemCestodes of the order Trypanorhyncha Diesing, 1863 from South-east Asia and Australia( 2013)The objective of the present thesis was to carry out a detailed morphological study of trypanorhynch cestodes from the Australasian and Indo-Malayan regions, in order to increase the knowledge of the species diversity of this particular group of tapeworms. Special focus was thereby paid to four key genera, namely Prochristianella Dollfus, 1946, Dollfusiella Campbell & Beveridge, 1994, Otobothrium Linton, 1890 and Parachristianella Dollfus, 1946. Based on newly collected material from taxonomic surveys in Borneo and Australia, it was possible to provide detailed taxonomic descriptions of species new to science, redescriptions of already described species and/or new information on host range and locality records. The geographical distribution of 35 trypanorhynch species from the four key genera that occur in South-east Asia and/or Australia was assessed and possible ecological factors, such as the host specificity and temperature preference, which may have impacts on the distributional patterns were discussed. In conclusion, the present thesis has contributed significantly to our knowledge of the species diversity of trypanorhynchs from Australia and Borneo and furthermore increased the knowledge on the geographical distribution and host range of selected trypanorhynch taxa.
-
ItemHerpesviruses in Australian marsupials( 2013)Herpesviruses are ubiquitous, enveloped DNA viruses that have been identified worldwide in most vertebrate and in several invertebrate species. Within the Marsupialia, several different herpesvirus species have been detected across various macropodid species, and more recently in koalas and antechinus species. Infection may be subclinical, and the capacity to induce lifelong infection with periods of latency and intermittent reactivation is a feature common to all herpesviruses, although the mechanism by which this occurs varies according to the individual herpesvirus species. In macropodids, herpesviruses have been associated with outbreaks of disease and mortality, and clinical signs may include conjunctivitis, oral and/or cloacal ulceration, or sudden death associated with disseminated pathology including widespread visceral necrosis and inflammation. This study sought to evaluate the prevalence and significance of individual herpesvirus species in various free-living and captive populations of Australian marsupials. Swab samples from 397 marsupials principally including eastern grey kangaroos (Macropus giganteus), other members of the Macropodidae and the Potoroididae families, koalas (Phascolarctos cinereus), Tasmanian devil (Sarcophilus harrisii), common wombats (Vombatus ursinus) and bandicoot species were collected and a universal herpesvirus nested PCR protocol utilised to determine the prevalence of active herpesvirus infection in these animals. Serum neutralisation tests and PCR on tissue samples were also performed for some animals, and virological culture on wallaby fibroblast cells and newly developed wombat kidney cells was attempted for several of the novel herpesvirus species identified. Prevalence of active herpesvirus infection varied across the marsupial species, ranging from 0% in some of the wallaby species, to 25% in eastern grey kangaroos, 33.3% in koalas, 34% in Tasmanian devils and 45.5% in the common wombat. Seroprevalence of antibodies against macropodid herpesviruses-1 and -2 was also variable, from 0% prevalence in koalas and some of the wallaby species, 66.7% in common wombats and as high as 92% in the eastern grey kangaroo and 100% in the swamp wallaby. Sequencing of a conserved portion of the DNA polymerase gene identified seven novel herpesvirus species from six marsupial hosts, and phylogenetic analysis classified each of these novel herpesvirus species into their respective subfamily groups, namely the Alphaherpesvirinae (vombatid herpesvirus 3) and the Gammaherpesvirinae (macropodid herpesvirus 5, potoroid herpesvirus 1, dasyurid herpesvirus 2, vombatid herpesvirus 1, vombatid herpesvirus 2 and peramelid herpesvirus 1). Development of a wombat tissue cell culture facilitated the successful isolation of two of the novel wombat herpesviruses, vombatid herpesviruses-1 and -2, in addition to phascolarctid herpesvirus 1, a koala gammaherpesvirus that had not been previously isolated. Epidemiologic analysis was performed where permitted by sample size, and identified various factors in association with active herpesvirus infection. Results varied significantly between the different marsupial species evaluated, and likely reflect differences in the biology of the respective herpesvirus species, biological and ecological differences between marsupial hosts, and environmental factors. The significance of herpesvirus infections identified in marsupial hosts is discussed with respect to the clinical signs observed in infected animals, and the biological and ecological threats facing individual marsupial species including: ongoing habitat destruction as a result of urbanisation, logging and natural disasters; the effects of climate change; predation by introduced mammals; and concurrent diseases of ecological importance. Possible transmission routes for individual herpesvirus species are suggested and scope for further research discussed. This study has broadened the mammalian host range in which natural herpesvirus infections have been found and identified seven novel herpesvirus species. Whilst the significance of these herpesviruses remains unclear, the presence of subclinical infections in a high proportion of individuals suggests that these herpesvirus species are well adapted to their marsupial hosts, likely as a result of an extended period of coevolution, and that severe pathology is unlikely to occur in immunocompetent hosts. Studies investigating the effect of these herpesvirus infections in immunocompromised, immunonaïve or unnatural hosts may be required to determine their pathogenecity and characterise the risk they pose to marsupial populations. Herpesviruses identified in threatened marsupial species should be targeted for these further investigations, as the results of such research may be critical in informing the development and management of species recovery programs.