Toxoplasma gondii and related Sarcocystidae parasites in harvested caribou from Nunavik, Canada

Current and potential future impacts of food- and water-borne parasites in a changing world: A Norwegian perspective

In 2021, the Norwegian Scientific Committee for Food and Environment published a multi-criteria risk ranking of 20 potentially food-borne pathogens in Norway. The pathogens ranked included five parasite taxa (3 species, one genus, one family): Toxoplasma gondii, Echinococcus multilocularis, Giardia duodenalis, Cryptosporidium spp., and Anisakidae. Two of these, T. gondii and E. multilocularis, scored very highly (1st and 3rd place, respectively), Cryptosporidium was about midway (9th place), and G. duodenalis and Anisakidae ranked relatively low (15th and 20th place, respectively). Parasites were found, on average, more likely to present an increasing food-borne disease burden in the future than the other pathogens. Here, we review the current impact of these five potentially food-borne parasites in Norway, and factors of potential importance in increasing their future food-borne disease burden. Climate change may affect the contamination of water and fresh produce with transmission stages of the first four parasites, potentially leading to increased infection risk. Alterations in host distribution (potentially due to climate change, but also other factors) may affect the occurrence and distribution of Toxoplasma, Echinococcus, and Anisakidae, and these, coupled with changes in food consumption patterns, could also affect infection likelihood. Transmission of food-borne pathogens is complex, and the relative importance of different pathogens is affected by many factors and will not remain static. Further investigation in, for example, ten-years' time, could provide a different picture of the relative importance of different pathogens. Nevertheless, there is clearly the potential for parasites to exert a greater risk to public health in Norway than currently occurs.

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

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.