In Australia, wild deer, including Fallow, Sambar, Red, Rusa, Chital and Hog deer, can feed on agricultural landscapes and, therefore, pose a biosecurity risk to the agricultural sector as potential carriers of important livestock diseases such as foot-and-mouth disease (FMD).
FMD is highly contagious and is the exotic disease of greatest significance to Australian agriculture. A large multi-state outbreak of FMD in Australia will result in an estimated direct economic loss of AU$52 billion over 10 years, with a current FMD freedom status underpinning a nationally significant annual trade in live animal and meat exports.
A spatially explicit, multi-species model has been developed (Australian Animal Disease Spread Model; AADIS) to predict the movement of FMD virus through various Australian agricultural industries. However, this model currently does not include virus transmission between livestock and wildlife populations, including deer. The role of wildlife in the transmission of FMD has been demonstrated overseas, but has not been evaluated against wild deer populations within the unique farming systems and environment of Australia.
This project will directly investigate the risk posed by deer to the livestock industry as hosts for exotic disease, using the transmission of endemic viral disease(s) between deer and livestock as an example. This project will also evaluate the effectiveness of possible mitigation strategies should an outbreak occur. This will be achieved by estimating deer population density adjacent to farms, quantifying their level of interactions with livestock, the level of connectivity between local deer populations and by estimating the cross-species infection rate between deer and livestock species.
Faecal, blood and DNA samples have been collected from deer species across Australia and analysis undertaken to confirm species.
Serum (blood) samples were screened for the presence of antigens and antibodies against Pestivirus and Bovine herpesvirus-1 using commercial serological tests. Antigens and antibodies against Pestivirus were detected in a very small number of the samples, while no serological evidence of Bovine herpesvirus-1 were detected in the samples.
For a subset of the blood samples collected, blood smears were performed on site at the time of blood collection. Microscopy examination of 50 blood smears revealed the presence of several morphological forms, possibly compatible with blood-protozoan. The corresponding blood samples were screened by PCR for known blood parasites. Published primers targeting conserved regions of seven parasitic genera commonly infecting livestock species were selected for molecular identification. PCR conditions and protocols were optimised to enable large scale screening, and analysis is currently ongoing.
Cripps, J. K., Pacioni, C., Scroggie, M. P., Woolnough, A. P., & Ramsey, D. S. (2019). Introduced deer and their potential role in disease transmission to livestock in Australia. Mammal Review, 49(1), 60-77. https://doi.org/10.1111/mam.12142
August 2019 update:
A high-throughput sequencing system (Illumina Hiseq) was used to analyse five serum samples from wild Fallow deer. The sequencing depth was increased five-fold from initial sequencing analysis to provide a greater scope of detection. Preliminary evidence of viral genetic material was found in some samples with confirmation and further analysis ongoing.
Microscopic examination of blood smears from NSW has revealed the presence of several morphological forms, possibly compatible with blood-protozoa. DNA from each blood sample was tested for seven parasitic genera using PCR, returning a negative result for these parasite groups. Analysis of additional blood samples is ongoing.
Deeper analysis of the viral sequences found in the last trial of metagenomics is necessary. This will allow the development of specific primers to detect individual viruses using PCR. PCR analysis of the blood samples from NSW revealed negative results, despite microscopic analysis revealing evidence of possible presence of some microorganisms. Metagenomics analysis of a specific RNA region will help identify the microorganism and provide information to develop a screening tool.