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Trypanosomes of the Australian brush-tailed bettong (Bettongia penicillata)- the parasites, the host and their potential vectors

Thompson, Craig (2014) Trypanosomes of the Australian brush-tailed bettong (Bettongia penicillata)- the parasites, the host and their potential vectors. PhD thesis, Murdoch University.

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The brush-tailed bettong (Bettongia penicillata) is known locally as the woylie and is one of two critically endangered potoroids in Australia. At a species level, they have declined by 90% since 1999, with their current distribution occupying a small fraction of their former Australian range. The predation of individuals made more vulnerable by disease is thought to be the primary cause of this decline; however, there may be other, as yet unidentified, stressors. This thesis details research that investigated whether trypanosomes are the causative agent that has reduced the fitness of the woylie and made them more vulnerable to predation.

Woylies and haematophagous insects were sampled from five locations in southern Western Australia. Woylie health checks included the measurement of weight and skeletal morphometrics from adults, sub-adults and pouch young; reproductive observations on adult females; the collection of blood and ectoparasites from adults and sub-adults; and the single collection of tissues from a deceased adult woylie.

During reproductive examinations, the maximum annual breeding potential was observed for the adult female, as to the pouch life, rate of growth, age of independence, sexual maturity and mating of the pouch young. Crown-rump and skeletal measurements of the developing pouch young were adequate predictors of age, with resulting growth curves being incorporated by the Department of Parks and Wildlife during conservation field-work.

During the morphological investigation of trypanosomes from the woylie, a new species was identified and described: Trypanosoma vegrandis sp. nov. Morphological polymorphism was also identified for Trypanosoma copemani, with two different phenotypes described.

Spatially, the prevalence of parasitic infections varied among the five study sites, with contrasting trypanosome prevalence observed from the two declining indigenous populations within the Upper Warren region in southern Western Australia. Parasitaemia associated with trypanosome infection in the peripheral blood of the woylie exhibited a temporal decline as the infection progressed, being indicative of the infection transitioning between the acute and chronic phase.

This thesis addresses host reproductive biology, trypanosome identification, spatial, temporal and transmission dynamics of infections, with relation to acute and chronic health of the woylie. It appears that the chronic intracellular association of trypanosomes with the internal organs of the woylie may be potentially pathogenic and adversely affect the fitness and coordination of the woylie, making them more susceptible to predation. As evident from this thesis, the chronic effect of trypanosome infections requires consideration during future conservation efforts to protect the woylie from extinction.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Veterinary and Life Sciences
Supervisor(s): Thompson, Andrew, Wayne, Adrian and Godfrey, Stephanie
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