Kangaroo Island, off of South Australia, is a refuge for a number of threatened and endemic species, has a predominant sheep industry, and hosts a community of approximately 4,500 residents. Landholder reports suggest that the island is a hot-spot for the cat-borne disease, ovine sarcocystosis, compared to the mainland. We asked two questions: (i) are cat-borne diseases truly more prevalent on Kangaroo Island?; and if so, (ii) what ecosystem characteristics facilitate the occurrence of these diseases? We mapped the prevalence of sarcocystosis across South Australia using abattoir surveillance data collected from over 4,200 sheep properties across the last 10 years, and investigated potential associations between sarcocystosis and a range of biotic and abiotic factors.
Results/Conclusions
Sarcocystosis was highly clustered on Kangaroo Island and positively associated with increased rainfall and soil clay content across South Australia. The relative abundance of cats on the island was estimated to be 11 times greater than on the adjacent mainland, which we hypothesise is the main driver of the increased occurrence of sarcocystosis, and raises concerns for other cat-borne diseases with zoonotic potential. Toxoplasmosis is a zoonotic cat-borne disease that has important health, welfare and economic impacts on wildlife, livestock and people. Although data on the prevalence of toxoplasmosis are not readily available, we hypothesise that its prevalence may be similarly driven by rainfall, soil clay content and cat density, as the parasites responsible for causing sarcocystosis are closely related and share similar biology and lifecycles. Our results indicate that the conservation, health, welfare and economic impacts of feral cats and their associated diseases on wildlife, livestock and humans on Kangaroo Island are greater than previously estimated. These findings support the implementation of an intensive cat management program on the island and suggest that intensive cat management will produce substantial reductions in the prevalence and risk of cat-borne diseases.