Variation in Toxoplasma gondii seroprevalence: effects of site, sex, species and behaviour between insular and mainland macropods

Abstract

<p><b>Context:</b> Feral cats threaten wildlife conservation through a range of direct and indirect effects. However, most studies that have evaluated the impacts of feral cats on species of conservation significance have focussed on direct impacts such as predation; few studies have considered the indirect impacts of cat-borne disease. <I>Toxoplasma gondii</I>, a cat-borne parasite, causes both acute and latent disease in a range of wildlife species, and macropods are particularly susceptible. Kangaroo Island is Australia’s third largest island and supports a high density of feral cats and high seroprevalence of <I>T. gondii</I> in multiple species, relative to the mainland. This suggests that Kangaroo Island has a high environmental contamination with the parasite and a high risk of infection for other species.</p><p> <p> <b>Aims:</b> We aimed to describe <I>T. gondii</I> seroprevalence in culled and road-killed macropods, so as to assess the effects of island versus mainland location, sex, species and behaviour.</p><p>

<b>Methods:</b> Macropod sera were tested for <I>T. gondii</I> IgG antibodies using a commercially available modified agglutination test.</p><p>

<b>Key results:</b> The seroprevalence of <I>T. gondii</I> in culled western grey kangaroos (<I>Macropus fuliginosus</I>) was significantly higher on the island (20%, 11/54 positive) than on the mainland (0%, 0/61 positive). There was no difference in <I>T. gondii</I> seroprevalence between culled and road-killed (21%, 21/102 positive) kangaroos from the island. The seroprevalence of <I>T. gondii</I> was significantly higher in female (32%, 12/38 positive) than in male (13%, 8/60 positive) kangaroos, but we observed no sex effect in tammar wallabies (<I>Macropus eugenii</I>), and no effect of species.</p><p>

<b>Conclusions:</b> The higher <I>T. gondii</I> seroprevalence in insular macropods supports previous reports of higher <I>T. gondii</I> exposure in other Kangaroo Island fauna. The lack of difference in <I>T. gondii</I> seroprevalence between culled and road-killed kangaroos suggests that <I>T. gondii</I>-positive animals are not more vulnerable to road mortality, in contrast to that suggested previously.</p><p>

<b>Implications:</b> Our findings suggest greater potential adverse conservation impacts owing to toxoplasmosis on the island than on the mainland. In light of a recent study demonstrating higher cat abundance on the island than on the mainland, the higher observed <I>T. gondii</I> seroprevalence in insular macropods is likely to be a consequence of higher cat density.</p><p></p>