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

Abstract

ObjectiveThe 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.DesignToxoplasma 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.MethodsAliquots 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. Results: 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.ConclusionResults provide evidence that suggests N. caninum oocysts may have different survival characteristics, such as varying tolerances to low relative humidity, than T. gondii oocysts.

Infection Pressure is Necessary, but not Sufficient by Itself, to Explain Toxoplasma gondii Seroprevalence in Intermediate Host Species

“…We, therefore, assumed the Fleurieu Peninsula to be a region of low T. gondii infection pressure and Kangaroo Island to be a region of high T. gondii infection pressure. This assumption is supported by previous work, which has shown a lower seroprevalence of T. gondii in sheep (10%) on the South Australian mainland relative to that on Kangaroo Island (sheep 23%) and a low seroprevalence of T. gondii in rabbits from this region as well (O'Donoghue et al, 1987;McKenny et al, 2020;Taggart et al, 2020b). Hereafter, we refer to the Fleurieu Peninsula on the South Australian mainland as a region of low T. gondii infection pressure (low cat abundance, expected low seroprevalence in cats) and Kangaroo Island as a region of high T.…”

PCR Detection of Toxoplasma gondii in European Wild Rabbit (Oryctolagus cuniculus) from Portugal

“…In wild rabbits, T. gondii infection has been documented as a subclinical disease [8,16,19], in contrast to domestic rabbits, in which fatal cases of toxoplasmosis have been described [9,31]. However, parasitic infection has detrimental effects on host health and fitness, and debilitated animals become easy prey for their predators [32].…”

“…In Portugal, the European wild rabbit may be an important source of T. gondii infection for the Iberian lynx and other wild carnivores such as foxes, and therefore can compromise wildlife conservation. As an herbivorous animal, infection with T. gondii in wild rabbits may also be a marker of environmental contamination by sporulated oocysts [8,9,13].…”

“…The European wild rabbit is an important reservoir of pathogens, including parasites, which can infect domestic animals and even humans [7]. The species is also an excellent choice as a sentinel for evaluating the pathogens circulation in the environment [8].…”

“…The studies found on T. gondii in European wild rabbit have been based only on serological analysis. The presence of antibodies for T. gondii has been reported in wild rabbits from Spain (14.2%) [16], Norway and Sweden (21%) [17], the Czech Republic (8%) [18], Scotland (3.3%) [19], and Australia (9.9%) [8]. The current T. gondii infection levels in European wild rabbit in Portugal are not really known.…”