Risk factors and prevalence of antibodies for Toxoplasma gondii in diaphragmatic fluid in wolverines (Gulo gulo) from the Northwest Territories, Canada

Abstract

Toxoplasma gondii, a zoonotic food borne parasite that can infect almost all warm-blooded animals including people, and ranks 4th among 24 most significant global foodborne parasites listed by the World Health Organization/United Nations Food and Agriculture Organization (FAO/WHO, 2014). Exposure to T. gondii has been reported in wildlife and people in the Canadian North, despite low densities of feline definitive hosts. The ecology of this host-parasite system could be affected by changing climate and landscape in boreal and sub-Arctic regions, and surveillance data are critically needed. Wolverines are an economically and culturally important species in northern Canada due to their valuable fur. Fluid obtained from diaphragmatic muscle of 127 wolverines (Gulo gulo) were tested for antibodies to T. gondii using an enzyme linked immunosorbent assay (ELISA). A seroprevalence of 62% (Confidence Interval (CI): 53-71%) was observed. This result indicates high levels of exposure, likely either through environmental contamination with T. gondii oocysts shed by infected wild felids, or consumption of carcasses/offal of other intermediate hosts containing tissue cysts with bradyzoites in tissues. We examined factors associated with seropositivity, including age, sex, harvest location, harvest location with respect to treeline, and body condition index. Adult (≥2 years) wolverines had 5.2 times higher odds of being sero-positive than juvenile (<1 years) wolverines. The highest seroprevalence was observed in wolverines from Sahtu and South Slave regions. Proportion of sero-positive wolverines harvested above and below the tree line was not significantly different (60% vs 65%). Age was the only significant predictor of T. gondii exposure in wolverines (using logistic regression analysis); further studies should target larger sample sizes. This study is an example of how fluid from diaphragmatic muscle can be used for screening for T. gondii antibodies in wolverines. The diaphragm, commonly collected for screening for another food borne parasite, Trichinella, in wildlife harvested for human consumption, can be used for screening of T. gondii exposure in wildlife. Due to their predatory and scavenging lifestyle and high trophic level, wolverines could serve as a sentinel species for T. gondii.

Keywords: Canada; Northwest Territories; Seroprevalence; Toxoplasma gondii; Wolverines.

Graphical abstract

Fig. 1

Map of the Northwest Territories showing the harvest locations of Toxoplasama gondii seropositive and seronegative wolverines in relation to region and ecoregion.