Toxoplasma gondii in beef consumed in France: regional variation in seroprevalence and parasite isolation.

Radu Blaga,Vitomir Djokic,Myriam Thomas,Annie Alliot,Lénaïg Halos,Naïma Ortis,Dominique Aubert,Catherine Perret,Régine Geers,Benoît Durand,Isabelle Villena,Aurélien Mercier,Pascal Boireau,Anne Thébault

doi:10.1051/parasite/2019076

Abstract

In France, the consumption of cattle and sheep meat appears to be a risk factor for infection of pregnant women with Toxoplasma gondii. Several nation-wide surveys in France have investigated the prevalence of T. gondii in sheep and pig meat, but little is known at present about the prevalence of the parasite in beef. The main objective of the present cross-sectional survey was to estimate the seroprevalence of T. gondii infection in beef consumed in France. A secondary objective was to attempt to isolate T. gondii from cattle tissues and to study the geographical and age variations of this seroprevalence. The overall estimate of seroprevalence of T. gondii in bovine carcasses (n = 2912), for a threshold of 1:6 was 17.38%. A strong age effect was observed (p < 0.0001) with a seroprevalence of 5.34% for calves (<8 months) and 23.12% for adults (>8 months). Seroprevalence estimates given by area of birth and area of slaughtering for adults showed that the areas with the highest seroprevalence were not the same between these two variables. Only two strains, corresponding to genotype II, were isolated from heart samples, indicating that there is a limited risk of human infection with T. gondii, which needs to be correlated with the food habit of consuming raw or undercook (bleu or saignant) beef. However, new questions have emerged, especially concerning the isolation of parasites from beef and the precise role of bovines, generally described as poor hosts for T. gondii, in human infection.

Highlights

Toxoplasma gondii is an obligate intracellular parasite belonging to the Apicomplexa phylum, with world-wide distribution
Following a previous study and using a sampling plan based on ovine meat production data and innovative testing for antibody detection and parasite isolation [33], the present survey, conducted according to the same principles of sampling and testing, aimed at investigating the national T. gondii seroprevalence in beef consumed in France
The choice of a low threshold was justified in our case by (a) our goal: to isolate viable T. gondii parasites, considering at that time that viable parasites should mostly be present in seropositive animals; (b) the fact that generally in bovines one can find very low titers, in our case the highest titer was observed in only one bovine at a terminal titer of 400, most of the animals (559/598) having a titer lower than 50; and (c) the decision to work on muscle fluid, representing a low-concentration antibody matrix compared to serum

Summary

Introduction

Toxoplasma gondii is an obligate intracellular parasite belonging to the Apicomplexa phylum, with world-wide distribution It has three infectious stages: the tachyzoites, the bradyzoites, and sporulated oocysts (with eight sporozoites). The main route of transmission is oral: humans and animals can become infected by ingesting either tissue cysts containing bradyzoites, from raw or undercooked meat, or sporulated oocysts, from various environmental sources (soil, water, vegetables). Interest in T. gondii in cattle comes mainly from a public health perspective; if cattle carry viable tissue cysts, they may be a source of human infections This might be true in western countries, where eating raw or undercooked beef is, to some extent, related to high standards of living [28]. A few attempts have succeeded in isolating the parasite from various types of bovine tissues, by means of bioassays [7, 23, 25, 50, 51]

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Conclusion