Health and disease status of Australia's most critically endangered mammal the Gilbert's potoroo (Potorous gilbertii)

The Gilbert's potoroo (Potorous gilbertii) is a small marsupial endemic to the Two Peoples Bay Nature Reserve in the south-west of Western Australia. The Gilbert's potoroo is classified as Australia's most critically endangered mammal (IUCN 2006) with an estimated population of only 35 individuals. This thesis examines the health and disease status of the Gilbert's potoroo, presenting a strong case for the relatively new concept of disease as a potential threatening factor and modifier of population decline. Specific diseases, including Cryptococcus, ectoparasitism, endoparasitism, haemoparasitism, Toxoplasma and a novel Treponema organism are extensively studied. An assessment of the clinical significance of these diseases is made, and management strategies are recommended to minimise the impact of these diseases on both the wild and captive population. The novel Treponema organism which clinically presents with tenacious, green discharge and an associated balanoposthitis in males is molecularly characterized. Epidemiological studies show the effects of this agent on reproductive function and a penicillin-based treatment regime is trialled in the analogous long-nosed potoroo (Potorous tridactylus) with a recommendation to then trial this treatment regime in the critically endangered Gilbert's potoroo. Standard haematological and urinalysis findings are tabulated to form reference ranges for this species. A treatment regime for Cryptococcus in the analogous long-nosed potoroo is reported and parasitological findings, including the identification of a novel tick species are discussed. This thesis addresses key health issues, which have subsequently been incorporated into the Recovery Plan of the Gilbert's potoroo. A document encompassing multiple disciplines and expertise to support the recovery of this critically endangered marsupial in its current environment. In addition, this thesis outlines a recommended health monitoring and treatment protocol for future translocation procedures and provides a working example of the emerging importance of health monitoring in threatened species recovery programs

The Ecology and Transmission of the Raccoon Roundworm, Baylisascaris procyonis.

Emerging infections in both humans and wildlife can often be traced back to human mediated changes in host densities, host communities, and the environment. In Chapter 1, I reviewed how humans affect wildlife nematodes. Nematode responses to human actions vary, thus knowing host and parasite natural history, and the mechanisms underlying disease dynamics are critical for predicting parasite responses and managing disease.Among wildlife nematodes, raccoon roundworm (Baylisascaris procyonis) is infamous for its ability to cause fatal disease in both humans and wildlife. This parasite infects millions of raccoons in North America. Although adult worms cause little pathology in raccoons, larval worms undergo extensive tissue migrations in other hosts, often causing neurological damage. Disease risk is driven by environmental egg contamination, which increases with raccoon density, worm intensity, and worm prevalence. In Chapter 2, I examined 189 raccoons from southern California to investigate how host age and season affect parasite abundance, demography, and fecundity. Roundworm infected 90% of Santa Barbara County raccoons, juveniles hosted more worms than adults, and more heavily infected raccoons released more eggs.In Chapter 3, I investigated whether animals can avoid raccoon roundworm contaminated sites, and if such avoidance balances disease costs and foraging preferences. Using wildlife cameras, I monitored animal behavior at raccoon latrines — sites that concentrate both seeds and pathogenic parasite eggs, and found that latrine contact rates reflected background activity, diet preferences and disease risk. Disease-tolerant raccoons and rats displayed significant site attraction, while susceptible birds and small mammals avoided these high-risk sites.The introduced black rat, Rattus rattus, occurs throughout the native range of the raccoon roundworm, Baylisascaris procyonis, and frequently forages in latrines. In Chapter 4, I examined the role of these rats and other California rodents in B. procyonis transmission. I surveyed wild rodents for B. procyonis and found that B. procyonis infected R. rattus at intensities more than 100 times greater than loads in co-occurring native Reithrodotomys megalotis and Peromyscus maniculatus. I also conducted scavenger trials using motion activated cameras and found that rodent carcasses were scavenged by opossums, skunks and raccoons, suggesting that these infected rodents, particularly R. rattus, contribute to B. procyonis transmission in this coastal California ecosystem.Raccoon roundworm infects both rodents and raccoons in southern California, but we know little about infection risk for other species. In Chapter 5, I used information on animal time allocation and behavior to build a model for predicting community-wide exposure risk for raccoon roundworm. This model suggests that larval worms are likely widespread in the animal community and provides a novel non-invasive method for identifying “at-risk” species.Raccoon roundworm infection can cause devastating pathology in humans, but there is growing evidence that subclinical cases also occur. As there is limited information on the frequency of these subclinical human infections, in Chapter 6 I surveyed 150 adults from California for B. procyonis antibodies. Eleven participants were seropositive suggesting that subclinical infection does occur and that previously undetectable infections warrant further study

Immunity to teladorsagia circumcincta infection in Scottish blackface sheep: an investigation into the kinetics of the immune response, antigen recognition and the MHC

The kinetics of the host's immune responses to challenge infection were studied and identified clear patterns in plasma IgA activity, peripheral eosinophil counts, faecal egg counts and plasma pepsinogen concentrations but not in plasma IgG activity. It was determined that when used in parallel and when tested at multiple time points, these parameters have much greater potential as markers of resistance than when used individually or more importantly if only assessed on a single occasion. Further work investigated the recognition of stage specific parasite antigens by host plasma IgA by Western blotting. After adjusting for differences in the activity of IgA in each plasma sample the work in this thesis identified that preferential recognition of a different set of antigens was associated with resistance in the group of experimentally challenged animals compared to previous publications. Additionally, and for the first time this investigation was also carried out on naturally infected animals. There was little correlation in the patterns of antigen recognition between the experimentally challenged and naturally infected animals. Finally, the role of MHC was investigated and it was determined that MHC heterozygotes produced significantly more plasma IgA then MHC homozygotes but did not harbour significantly shorter worms. The analysis also confirmed in naturally infected sheep that there was no obvious relationship between MHC polymorphism and antigen recognition. The results suggested that resistance was due to the recognition of several molecules rather than a single molecule. The work detailed in this thesis has further increased our understanding of the complex host/parasite relationship and has confirmed that selective breeding using the various phenotypic and genetic markers studied is possible. However, this will only be viable if the tests involved in assessing these traits become cheaper and easier to perform, especially if they are to be carried out by the farmer, on the farm

The Molecular Diversity of Strains of Ostertagia ostertagi

Increasing evidence for the occurrence of intraspecific variation of nematodes prompted this study of Ostertagia ostertagi, a parasite of the bovine abomasum which causes gastroenteritis. Parasites recovered from calves with ostertagiosis have shown differences in their morphology, pattern of development and drug susceptibility. These factors led to experimental work to assess the degree of variation detectable at a molecular and structural level. The techniques applied examined the genetic products of different isolates of O. ostertasi and also compared them to other trichostrongyle species. In addition, the stages of the parasite life cycle were followed

Faculty Impact Statements, 2009

Each issue [in the Research Series] has a distinctive titl

Faculty Impact Statements, 2009

Each issue [in the Research Series] has a distinctive titl

Dictionary of Invertebrate Zoology

An exhaustive dictionary of over 13,000 terms relating to invertebrate zoology, including etymologies, word derivations and taxonomic classification. Entries cover parasitology, nematology, marine invertebrates, insects, and anatomy, biology, and reproductive processes for the following phyla: Acanthocephala Annelida Arthropoda Brachiopoda Bryozoa Chaetognatha Cnidaria Ctenophora Echinodermata Echiura Entoprocta Gastrotricha Gnathostomulida Kinorhyncha Loricifera Mesozoa Mollusca Nemata Nematomorpha Nemertea Onychophora Pentastoma Phoronida Placozoa Platyhelminthes Pogonophora Porifera Priapula Rotifera Sipuncula Tardigrada.https://digitalcommons.unl.edu/zeabook/1061/thumbnail.jp