Parasite Taxoplasma gondii Found in Scotish Venison Meat

A recently published study looked at the prevalence of Taxoplasma gondii in retail meat samples in Scottland. (Detection of Toxoplasma gondii in retail meat samples in Scotland, FWP 2020).  Results were that "Toxoplasma gondii DNA was detected in 0/39 (0%) beef samples, 1/21 (4.8%) chicken samples, 6/87 (6.9%) lamb samples, 3/71 (4.2%) pork samples and 29/82 (35.4%; Sampling Period 1) and 19/67 (28.4%; Sampling Period 2) venison samples."  The researchers state "This is the first study to report the presence of T. gondii in retail meat products in Scotland and has highlighted venison as a potentially high risk meat."

So, what is the risk for those eating venison?  In 2017, a Wisconsin outbreak was investigated at a hunting camp and in that invesigation, it was believed to be related to undercooked venison.  In this paper, the author points out other outbreaks involving venison, "In 4 other studies of suspected venison-transmitted toxoplasmosis, consumption of undercooked or raw venison was reported [

28–31]. In a follow-up study of the coworkers of the patients in one report, T. gondii seropositivity was significantly associated with having eaten raw or rare venison [31]. Another of the reports describes a toxoplasmosis outbreak among a group of healthy male Canadian hunters who consumed undercooked venison in Illinois, USA [28]. The Canadian outbreak is almost identical to this outbreak in attack rate, incubation period, symptom severity, and the inclusion of one seronegative but presumed exposed individual. As Wisconsin and Illinois share a border, it is possible that similar strains of T. gondii caused the outbreaks. "

Taxoplasma gondii tissue cysts are not overly heat resistance. (link).  "At 61 C (142F) the cysts were generally inac tivated instantaneously as a result of the come up time (2 min) and come-down time (1.5 min)."

But if people follow the recommendation for cooking meats, especially wild meats where the potential for contamination may be higher in that the diet is not controlled, cooking to medium should easily achieve this goal.

However, the biggest risk remains cats.  From a paper published on the topic (Shapiro, 2019):

"Although Toxoplasma gondii infects diverse species of warm-blooded animals, domestic cats (Felis catus) and wild felids are the only known definitive hosts capable of shedding environmentally hardy oocysts in their feces (Dubey et al., 1970; Hutchison et al., 1969; (Jewell et al., 1972; Miller et al., 1972). Domestic cats exist in close association with most human settlements throughout the world (Liberg et al., 2000), and both pet cats and free-ranging stray or feral domestic cats contribute to environmental oocyst burden."

"The epidemiologic importance of whether human toxoplasmosis is transmitted by oocysts or tissue cysts was debated even before the life cycle was determined in the 1970s (Jackson and Hutchison, 1989). The early observation in the 1950s that vegetarians and non-vegetarians had similar prevalence rates (Jacobs, 1957; Rawal, 1959) suggested that carnivorism could not be the only source of infection. Presently, the relative importance of oocyst vs tissue cyst ingestion for Toxoplasma gondii transmission in humans remains unknown for the majority of endemically infected populations."

Food and Waterborne Parasitology
https://www.sciencedirect.com/science/article/pii/S2405676620300159
Detection of Toxoplasma gondii in retail meat samples in Scotland

JacquelinePlazaa1FilipDámekaIsabelleVillenabElisabeth A.InnesaFrankKatzeraClare M.Hamiltona

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https://doi.org/10.1016/j.fawpar.2020.e00086
Highlights

• Toxoplasma gondii DNA was detected in pork, lamb, chicken and venison products.
• None of the beef samples tested were positive for T. gondii DNA.
• Venison could be a high-risk meat for T. gondii infection.
• Non-clonal genotypes may be present in venison products in Scotland.

Abstract
Toxoplasma gondii is a globally important zoonotic parasite ranked as one of the most significant causes of disease burden among the major foodborne pathogens. Consumption of undercooked meat is a well-known risk factor for infection so the aim of this study was to investigate the presence of T. gondii in meat samples from retail outlets in Scotland. In Sampling Period 1, 300 meat samples (39 beef, 21 chicken, 87 lamb, 71 pork and 82 venison) were purchased from butchers', farmers' markets, farm shops and supermarkets, and in Sampling Period 2, 67 pure venison samples only were purchased from farmers' markets, farm shops and supermarkets. DNA was extracted and screened for T. gondii using a quantitative PCR targeting the 529 bp repeat element, and any positive samples were genotyped using PCR-RFLP targeting 10 markers. Meat juice was screened for T. gondii antibodies using a commercial ELISA or modified agglutination assay. Toxoplasma gondii DNA was detected in 0/39 (0%) beef samples, 1/21 (4.8%) chicken samples, 6/87 (6.9%) lamb samples, 3/71 (4.2%) pork samples and 29/82 (35.4%; Sampling Period 1) and 19/67 (28.4%; Sampling Period 2) venison samples. Partial PCR-RFLP genotyping revealed both clonal and non-clonal genotypes. Antibodies to T. gondii were detected in the meat juice of 2/38 (5.3%) beef samples, 3/21 (14.3%) chicken samples, 14/85 (16.5%) lamb samples, 2/68 (2.9%) pork samples and 11/78 (14.1%; Sampling Period 1) and 8/50 (16%; Sampling Period 2) venison samples. This is the first study to report the presence of T. gondii in retail meat products in Scotland and has highlighted venison as a potentially high risk meat. Further work is required to determine viability of parasites in this particular meat product.
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