IMPLICATIONS FOR THE CONSERVATION OF FREE-RANGING POPULATIONS
The impact of T. gondii infection on free-ranging Australian mammal populations and whether species-specific differences in susceptibility to the disease occur are not well understood.
Although there are documented accounts of T. gondii-associated morbidity and mortality in free- ranging populations of native Australian mammals, including bare-nosed wombats (Donahoe et al. 2015), eastern barred bandicoots (Obendorf and Munday 1990; Groenewegen et al. 2017), red-necked wallabies (N. rufog- riseus) and rufous-bellied pademelons (Thylogale billar- dierii) (Obendorf and Munday 1983), eastern (Dasyurus viverrinus) and northern (D. hallucatus) quolls, investigations have demonstrated little evidence that toxoplasmosis contributes to population declines (Oakwood and Pritchard 1999; Fancourt et al. 2014). The situation in brush-tailed bettongs (Bettongia penicillata) is less clear, with some speculation but no clear evidence that T. gondii may contribute to population declines in this species (Smith et al. 2008). Hollings et al. (2013) found a higher seroprevalence of T. gondii antibodies in road-killed versus culled rufous-bellied pademelons. They suggested that infection with T. gondii may have resulted in behavioural changes that predisposed the animals to being killed on roads. Conversely, Taggart et al. (2019) found no significant difference in seroprevalence of T. gondii antibodies in culled versus road-killed western grey kangaroos (Macropus fuliginosus). In another study examining western grey kangaroos, 20% of animals were seropositive without clinical signs of disease or impact on reproductive performance compared with seronegative kangaroos (Mayberry et al. 2014). Toxoplasmosis has been diagnosed in free- raging native rodents, including water rats (Hydromys chrysogaster), but its impact at a population level is unknown. Additionally, there is a growing number of reports of toxoplasmosis in Australian marine mammals, but population level effects are also unknown. Speciesspecific validation of diagnostic tests, appropriate survey sample sizes, minimisation or elimination of sampling bias, cohort studies and control of confounding variables are required to better understand the impact of toxoplasmosis on free-ranging populations of Australian mammals (Hillman et al. 2016).
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