Toxoplasma gondii Does Not Inhibit the Assisted Colonization of Eastern Barred Bandicoots (Perameles gunnii) to Phillip Island, Victoria, Australia.

Eastern barred bandicoots (Perameles gunnii) are thought to be highly susceptible to disease caused by infection with the protozoan parasite Toxoplasma gondii. This study followed a population of 67 P. gunnii introduced onto the Summerland Peninsula, Phillip Island, Australia, where the prevalence of T. gondii infection in the feral cat population was known to be very high. Prior to release, bandicoots were tested for serologic exposure to T. gondii using the modified agglutination test. A subset of bandicoots was tested on four occasions after release onto the peninsula. No seroconversion was detected at any time point. A subset of bandicoots was radiotracked after release and at two additional trapping sessions to help monitor survival. Toxoplasma gondii DNA was not detected by PCR in eight carcasses recovered for necropsy. Fourteen founder bandicoots (21% of founders) were known to be alive at 500 d post-release. A total of 29 unmarked bandicoots were trapped over the study period, confirming that the bandicoots were successfully reproducing on the island. Body weight, packed cell volume, and total plasma protein were used as measures of individual animal health; population health was inferred from these data. Body weight was significantly associated with trip number, with a general trend of increasing weight after release onto the island. This study showed that eastern barred bandicoots were able to establish a new population despite a probably high environmental load of T. gondii.

Comparison of the modified agglutination test and real-time PCR for detection of Toxoplasma gondii exposure in feral cats from Phillip Island, Australia, and risk factors associated with infection.

Toxoplasma gondii is considered a disease risk for many native Australian species. Feral cats are the key definitive host of T. gondii in Australia and therefore, investigating the epidemiology of T. gondii in cat populations is essential to understanding the risk posed to wildlife. Test sensitivity and specificity are poorly defined for diagnostic tests targeting T. gondii in cats and there is a need for validated techniques. This study focused on the feral cat population on Phillip Island, Victoria, Australia. We compared a novel real-time PCR (qPCR) protocol to the modified agglutination test (MAT) and used a Bayesian latent class modelling approach to assess the diagnostic parameters of each assay and estimate the true prevalence of T. gondii in feral cats. In addition, we performed multivariable logistic regression to determine risk factors associated with T. gondii infection in cats. Overall T. gondii prevalence by qPCR and MAT was 79.5% (95% confidence interval 72.6-85.0) and 91.8% (84.6-95.8), respectively. Bayesian modelling estimated the sensitivity and specificity of the MAT as 96.2% (95% credible interval 91.8-98.8) and 82.1% (64.9-93.6), and qPCR as 90.1% (83.6-95.5) and 96.0% (82.1-99.8), respectively. True prevalence of T. gondii infection in feral cats on Phillip Island was estimated as 90.3% (83.2-95.1). Multivariable logistic regression analysis indicated that T. gondii infection was positively associated with weight and this effect was modified by season. Cats trapped in winter had a high probability of infection, regardless of weight. The present study suggests qPCR applied to tissue is a highly sensitive, specific and logistically feasible tool for T. gondii testing in feral cat populations. Additionally, T. gondii infection is highly prevalent in feral cats on Phillip Island, which may have significant impacts on endemic and introduced marsupial populations.

REPEAT SPILLOVER OF BEAK AND FEATHER DISEASE VIRUS INTO AN ENDANGERED PARROT HIGHLIGHTS THE RISK ASSOCIATED WITH ENDEMIC PATHOGEN LOSS IN ENDANGERED SPECIES.

Conservation efforts for the orange-bellied parrot (Neophema chrysogaster), one of the world's most critically endangered bird species, have been hampered by beak and feather disease virus (BFDV) spillover infection. To understand the vulnerability of orange-bellied parrots to potential reservoirs of infection we investigated geographic versus taxonomic structure in 160 full-genome and 319 partial Rep gene BFDV sequences from captive and wild orange-bellied parrots and other wild parrot species in Australia. We found that Australian BFDV populations are structured by host taxonomy. By identifying genetic stratification of BFDV in reservoir hosts we characterized three separate recent incursions of BFDV into orange-bellied parrots from other wild parrots, which demonstrates the susceptibility of critically endangered species to multiple threats of pathogen re-emergence. Our study highlighted how loss of endemic circulating BFDV in orange-bellied parrots precipitated repeated spillover into an immunologically naïve population, causing significant disease.

Assessing circovirus gene flow in multiple spill-over events.

The establishment of viral pathogens in new host environments following spillover events probably requires adaptive changes within both the new host and pathogen. After many generations, signals for ancient cross-species transmission may become lost and a strictly host-adapted phylogeny may mimic true co-divergence while the virus may retain an inherent ability to jump host species. The mechanistic basis for such processes remains poorly understood. To study the dynamics of virus-host co-divergence and the arbitrary chances of spillover in various reservoir hosts with equal ecological opportunity, we examined structural constraints of capsid protein in extant populations of Beak and feather disease virus (BFDV) during known spillover events. By assessing reservoir-based genotype stratification, we identified co-divergence defying signatures in the evolution BFDV which highlighted primordial processes of cryptic host adaptation and competing forces of host co-divergence and cross-species transmission. We demonstrate that, despite extensive surface plasticity gathered over a longer span of evolution, structural constraints of the capsid protein allow opportunistic host switching in host-adapted populations. This study provides new insights into how small populations of endangered psittacine species may face multidirectional forces of infection from reservoirs with apparently co-diverging genotypes.

Characterization of Beak and Feather Disease Virus Genomes from Wild Musk Lorikeets (Glossopsitta concinna).

Three complete genomes of beak and feather disease virus (BFDV) were recovered from wild musk lorikeets (Glossopsitta concinna). The genomes consisted of 2,008 to 2,010 nucleotides (nt) and encode two major proteins transcribing in opposing directions. This is the first report of BFDV complete genome sequences obtained from this host species.