Select bacterial and viral pathogens of potential zoonotic or biosecurity importance in Australian brushtail (Trichosurus spp.) and ringtail (Pseudocheirus peregrinus) possums
Document TypeMasters Research thesis
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© 2018 Anita Tolpinrud
Possums and gliders represent a diverse group of marsupial mammals native to Australia, including multiple vulnerable and endangered species. Common brushtail (Trichosurus vulpecula) and common ringtail (Pseudocheirus peregrinus) possums are two urban adapted species frequently found in gardens and parks throughout eastern Australia. Their presence in urban areas provides opportunities for transfer of zoonotic pathogens through both direct and indirect contact with humans. Diseases affecting possums are relatively poorly understood, as is the role of possums in the maintenance and transmission of zoonotic pathogens. This study aimed to investigate the significance of these possums as host species for a select range of pathogens, particularly in Victoria. Opportunistically collected serum samples from common ringtail, common brushtail and mountain brushtail possums (Trichosurus cunninghami) from Victoria and South Australia were tested for antibodies against Ross River virus (RRV) and flaviviruses. Cloacal swabs from common brushtail and ringtail possums from Victoria and New South Wales were screened for the presence of Mycobacterium ulcerans (the cause of Buruli ulcer), Campylobacter spp. and Salmonella spp. Spleen samples were screened for Francisella tularensis (the cause of tularaemia) and Coxiella burnetii (the cause of Q fever) by PCR. Antibodies to RRV were detected in 6.2% (16/259) of all possum samples, which were sampled during a concurrent epidemic of RRV in humans. Geographical areas with a moderate to high human case rate were associated with a higher seroprevalence rate in sampled possums. There was a significantly lower rate of detection in possums from urban environments compared to rural and mountainous environments. Seroconversion to an unspecified flavivirus was also present in 5.2% (5/97) of common ringtail possums and 6.5% (2/31) of mountain brushtail possums, but not in common brushtail possums (0/137). Two of the seropositive animals displayed clinical signs of encephalitis. Salmonella spp. was detected in 3.1% (7/229) of possums, while Campylobacter spp. Was found in 27.7% (41/229), with a significant predilection for common brushtail possums (38/106). The exact Campylobacter species was not identified, however, the main human pathogens C. jejuni and C. coli were excluded. No samples were positive for F. tularensis (n = 187), C. burnetii (n = 184) or M. ulcerans (n = 229). These findings indicate that, while urban-adapted possums may potentially carry zoonotic pathogens, they are unlikely to represent a high risk to public health, at least in regards to the infectious agents that were the focus of this study in the areas that were investigated. Finally, serum samples from all three possum species were screened for antibodies to Wobbly Possum Disease virus (WPDV), a recently identified virulent nidovirus in common brushtail possums in New Zealand. Although thought to be absent from Australia, antibodies to WPDV, or an antigenically similar nidovirus, were detected in all three species of possum, originating from both Victoria and South Australia. Overall, 16% (30/188) of samples were positive and 11.7% (22/188) were equivocal, with the two brushtail species most commonly affected. This is the first published report of serological evidence of WPDV, or an antigenically similar nidovirus, in Australian possums. However, attempts to detect viral RNA in spleen samples by PCR were unsuccessful.
Keywordspossum; zoonoses; common brushtail possum; common ringtail possum; mountain brushtail possum; Ross River virus; Flavivirus; Wobbly Possum Disease virus; Mycobacterium ulcerans; buruli ulcer; Campylobacter; Salmonella; Francisella tularensis; Coxiella burnetii
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