Toxoplasma gondii (Nicolle & Manceaux, 1908)

Hollings, Tracey, Jones, Menna, Mooney, Nick & McCallum, Hamish, 2013, Wildlife disease ecology in changing landscapes: Mesopredator release and toxoplasmosis, International Journal for Parasitology: Parasites and Wildlife 2 (1), pp. 110-118 : 114-115

3.1. Seroprevalence of T. gondii

Toxoplasma seroprevalences are reported in Fig. 3 . Very low T. gondii seroprevalence in brushtail possums (0/14 samples analysed) and Bennetts wallabies (2/25 samples analysed) found in preliminary results would render detection of state-wide regional differences in seroprevalence in these species difficult even with large sample sizes. As a result, we focused subsequent blood sampling on pademelons.

There were significant differences between the three geographic regions in T. gondii seroprevalence (p = 0.035), with the north-west having the lowest seroprevalence (7%), followed by the north-east (15%) and the highest seroprevalence was recorded in the central region (19%) ( Table 1). This regional difference was even stronger when assessing only culled pademelons (p = 0.020; north-west 6%, central 20%, north-east 22%). Cat density over the last eight years was the lowest in the north-west region, and approximately half of that in the central and north-east regions ( Fig. 1 and Table 1).

The seroprevalence of T. gondii in road-kill samples from pademelons was considerably higher (31%, n = 16) than culled animals (11%, n = 212). The Fisher’s exact test indicated significantly different seroprevalence between the two sample sources (p = 0.033). However, the low number of road-kill samples relative to the culling samples means that this result should be interpreted with some caution.

From the GLM analysis using the 10 km zones, there were nine models with a Δ AICc of less than two from the best supported model. Cat density, sample source, geographic region and annual rainfall were all contained within these top models, indicating some influence of these predictor variables on T. gondii seroprevalence in pademelons ( Table 2). The source of the samples and the DFTD region were the two most influential predictor variables with a relative importance of 81% and 64% respectively. Cat density had a relative importance of 47% and rainfall 52%.

Figures

Fig. 3. Prevalence of IgG antibodies of Tasmanian mammals to T. gondii by trophic level; n represents the total number of samples tested. Standard error bars are shown.

Fig. 1. Map of Tasmania showing average cat densities from individual spotlighting districts over 8 years and blood collection sites for the Tasmanian pademelon. Positive T. gondii sites are those where at least one sample tested positive to IgG antibodies. Negative sites are those where no evidence of exposure to T.gondii was found in any sample.