Prevalence, genetic diversity and potential clinical impact of blood-borne and enteric protozoan parasites in native mammals from northern Australia.

A molecular survey was conducted to provide baseline information on the prevalence, genetic diversity and potential clinical impacts of blood-borne and enteric protozoans in native wild mammals from the Northern Territory (NT). A total of 209 blood and 167 faecal samples were collected from four target species; the northern brown bandicoot (Isoodon macrourus), common brushtail possum (Trichosurus vulpecula), northern quoll (Dasyurus hallucatus) and brush-tailed rabbit-rat (Conilurus penicillatus). Blood samples were screened by PCR at the 18S rRNA gene for trypanosomes, piroplasms and haemogregarines, with faecal samples tested for Cryptosporidium spp. at the 18S rRNA locus, and for Giardia spp. at the glutamate dehydrogenase (gdh) and 18S rRNA loci. The potential clinical impact was investigated by associating clinical, haematological and biochemical parameters with presence or absence of infection. Overall, 22.5% (95% CI: 17.0-28.8%) of the animals tested were positive for haemoprotozoans. Trypanosomes were found in 26.6% (95% CI: 18.7-35.7%) of the bandicoots and were identified as Trypanosoma vegrandis G6, except for one unique genotype, most similar to T. vegrandis G3 (genetic distance=7%). The prevalence of trypanosomes in possums was 23.7% (95% CI: 11.4-40.2%), and the genotypes identified clustered within the T. noyesi clade. The presence of Babesia sp. and Hepatozoon sp. was confirmed in bandicoots only, both at a prevalence of 9.7% (95% CI: 2.7-9.2%). The total prevalence of intestinal protozoan parasites observed was relatively low (3%; 95% CI: 1.0-6.9%). No evidence of clinical disease associated with protozoan parasitic infection was observed, however bandicoots positive for Trypanosoma exhibited a significantly lower packed cell volume (PCV) compared to negative bandicoots (p=0.046). To the authors' knowledge, this is the first research conducted in the NT to characterise protozoan parasites in threatened native mammals using both molecular and morphological tools; and to assess the potential clinical impacts of these agents. The absence of clear signs of major morbidity in infected animals seems to exclude a direct association between infections with these agents and possible population decline events in northern Australian native mammals. However until the cause(s) of population decline are ascertained for each individual mammal species, further studies are required. The outcome of the present investigation may be used to inform wildlife conservation and zoonotic disease programs.