Suchergebnisse

Abstract Context Disease is increasingly becoming a driver of wildlife population declines and an extinction risk. Vaccines are one of the most successful health interventions in human history, but few have been tested for mitigating wildlife disease. The transmissible cancer, devil facial tumour disease (DFTD), triggered the Tasmanian devil's (Sarcophilus harrisii) inclusion on the international endangered species list. In 2016, 33 devils from a DFTD-free insurance population were given an experimental DFTD vaccination before their wild release on the Tasmanian northern coast. Aim To determine the efficacy of the vaccination protocol and the longevity of the induced responses. Method Six trapping trips took place over the 2.5 years following release, and both vaccinated and incumbent devils had blood samples and tumour biopsies collected. Key results In all, 8 of the 33 vaccinated devils were re-trapped, and six of those developed DFTD within the monitoring period. Despite the lack of protection provided by the vaccine, we observed signs of immune activation not usually found in unvaccinated devils. First, sera collected from the eight devils showed that anti-DFTD antibodies persisted for up to 2 years post-vaccination. Second, tumour-infiltrating lymphocytes were found in three of four biopsies collected from vaccinated devils, which contrasts with the 'immune deserts' typical of DFTs; only 1 of the 20 incumbent devils with DFTD had a tumour biopsy exhibiting immune-cell infiltrate. Third, immunohistochemical analysis of the vaccinated devils' tumour biopsies identified the functional immune molecules associated with antigen-presenting cells (MHC-II) and T-cells (CD3), and the immune checkpoint molecule PD-1, all being associated with anti-tumour immunity in other species. Conclusions These results correlate with our previous study on captive devils in which a prophylactic vaccine primed the devil immune system and, following DFTD challenge and tumour growth, immunotherapy induced complete tumour regressions. The field trial results presented here provide further evidence that the devil immune system can be primed to recognise DFTD cells, but additional immune manipulation could be needed for complete protection or induction of tumour regressions. Implications A protective DFTD vaccine would provide a valuable management approach for conservation of the Tasmanian devil.

Context Diseases are increasingly contributing to wildlife population declines. Tasmanian devil (Sarcophilus harrisii) populations have locally declined by 82%, largely owing to the morbidity and mortality associated with two independent transmissible devil facial tumours (DFT1 and DFT2). Toxic baits are often used as a management tool for controlling vertebrate pest populations in Australia, but in other areas of the world, oral baits are also used to deliver vaccines or pharmaceuticals to wildlife. Aim Our goal was to evaluate the potential use of edible baits as vehicles for vaccine delivery to Tasmanian devils. Method We first tested bait palatability with captive devils. Bait interactions were recorded, and consumption and bait interaction behaviours were quantified. We next trialled baits containing inert capsules as potential vaccine containers in captivity. After confirming bait palatability in captivity, ground baiting was trialled at six field sites and monitored using camera traps. Finally, an automated bait dispenser was trialled at field sites to attempt to limit bait consumption by non-target species. Key results Captive devils consumed all types of placebo baits, but consumed a higher percentage of ruminant- and fish-based baits than cereal-based baits. Captive devils also consumed inert capsules inserted into placebo baits. Ground-baiting trials in the field showed that 53% of baits were removed from bait stations, with 76% of the removals occurring on the first night. Devils were suspected or confirmed to remove about 7% of baits compared with 93% by non-target species. We also evaluated an automated bait dispenser, which reduced bait removal by non-target species and resulted in over 50% of the baits being removed by devils. Conclusions This study demonstrated that captive and wild devils will accept and consume placebo versions of commercial baits. Bait dispensers or modified baits or baiting strategies are needed to increase bait uptake by devils. Implications Bait dispensers can be used at a regional scale to deliver baits to devils. These could potentially be used as vaccine-delivery vehicles to mitigate the impacts of disease on devil populations.