Evidence of infection with Toxoplasma gondii and Neospora caninum in South Australia: using wild rabbits as a sentinel species.

Abstract

The aim of this study was to utilise wild rabbits (Oryctolagus cuniculus) as a sentinel species to study levels of environmental contamination with N. caninum and T. gondii in South Australia, and to examine associations with rainfall, climate and land use. Toxoplasma gondii (T. gondii), an apicomplexan parasite, causes the clinical disease toxoplasmosis, which can affect sheep as well as humans and many other animals. Neosporosis, the clinical disease caused by closely related Neospora caninum (N. caninum), causes abortions in cattle, with large economic impacts to cattle industries. Aliquots of wild rabbit (Oryctolagus cuniculus) serum were obtained from twelve sites across South Australia over a period of eighteen years, with a total of 2114 samples. An in-house Modified Agglutination Test (MAT) was developed, and samples were screened for the specific antibodies against both T.gondii and N. caninum. Overall, 9.9% of samples screened for T. gondii tested positive and 6.1% of samples screened for N. caninum tested positive. There was no difference observed in seroprevalence of T.gondii specific antibodies between samples collected throughout summer, autumn, winter or spring. By contrast, a significantly higher (p=0.030) seroprevalence of N. caninum specific antibodies was observed in spring than any other season. T. gondii and N. caninum antibodies were discovered at sites across a broad area of South Australia, indicating these environments maybe infected with both parasites. Results provide evidence that suggests N. caninum oocysts may have different survival characteristics, such as varying tolerances to low relative humidity, than T. gondii oocysts.