North-to-south increasing gradient in Toxoplasma gondii seroprevalence and no serological evidence of exposure to Neospora caninum in semi-domesticated Eurasian tundra reindeer (Rangifer tarandus tarandus) in Finland and northern Norway in 2015.

BACKGROUND: While the coccidian parasites Toxoplasma gondii and Neospora caninum have a worldwide distribution and wide host ranges, relatively few studies have investigated these parasites in Eurasian tundra reindeer (Rangifer tarandus tarandus). The aim of this study was to estimate prevalence of antibodies against T. gondii and N. caninum in semi-domesticated Eurasian tundra reindeer in Finland and northern Norway.

RESULTS: Blood samples from 635 semi-domesticated reindeer were collected in 2015 and tested with commercial indirect enzyme-linked immunosorbent assays. Altogether 35 (5.5%; 95% confidence interval 3.9-7.5) of the reindeer were seropositive for T. gondii, while none of the reindeer tested seropositive for N. caninum (95% confidence interval 0.0-0.5). The seroprevalence for T. gondii was higher in adult animals (over 18 months) compared to calves, and there was a geographical north-to-south increasing gradient in seroprevalence.

CONCLUSIONS: We detected serological evidence of exposure of semi-domesticated Eurasian tundra reindeer from Finland and northern Norway to the zoonotic parasite T. gondii, but not to N. caninum. The north-to-south increasing gradient in T. gondii seroprevalence may suggest that there is a gradient in environmental contamination with oocysts.