Toxoplasma gondii seroprevalence in reindeer (Rangifer tarandus tarandus L.) in northern Sweden: a cross-sectional study from 2014

Abstract

Background: Toxoplasma gondii is a parasitic protozoan that can infect a wide range of warm-blooded animals, including humans. The infection with T. gondii, is of particular concern due to its potential impact on human and animal health. In Sweden, semi-domesticated reindeer (Rangifer tarandus tarandus L.) is an important species both economically and culturally, but susceptibility to Toxoplasma infection and seroprevalence in reindeer herds remain relatively understudied.

Results: A total of 528 reindeer, sampled at two slaughterhouses in Sweden in 2014, were investigated for antibodies to T. gondii. Specific antibodies to T. gondii were found in 5 of 209 (2.3%) tested adult reindeer and in 6 of 308 (1.9%) tested calves, giving an apparent total prevalence of 2.1% (95% confidence interval 1.1-3.8%). None of four putative risk factors studied (sex, age, type of grazing area, county) were statistically associated with T. gondii seroprevalence.

Conclusions: Swedish semi-domesticated reindeer are exposed to T. gondii and may harbour infectious tissue cysts. To mitigate the risk of T. gondii infection in consumers, reindeer meat should be frozen or cooked thoroughly before consumption. The global climate change may influence the seroprevalence and possible associated risk factors for T. gondii in reindeer. To be able to manage the risk and get better advice to the consumers there is a need for further investigations covering the whole spectra of herding conditions for reindeer.

Keywords: Cervid; ELISA; Farmed game; Food safety; Meat safety; Toxoplasmosis; Zoonosis.

Fig. 1

Reindeer herding area in Sweden. Slaughterhouse 1 in Västerbotten and Slaughterhouse 2 in Norrbotten. The southern border of the reindeer herding area (the green line) and the 62° latitude indicated. Red line = the borders between counties, Dotted line roughly showing the border between forest and mountain pasture areas

Fig. 2

Toxoplasma gondii-specific IgG antibodies in Swedish reindeer samples (n = 528), expressed as sample to positive ratio percentage (S/P%) (y-axis). Serum samples were considered to test positive at S/P% ≥ 50% (solid line), inconclusive at S/P% values between ≥ 40% (dotted line) and < 50%, and negative at S/P% < 40%