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Risks related to Toxoplasma gondii infection in humans remain poorly known in Senegal. Although rodent surveys could help to assess the circulation of T. gondii, they have seldom been set up in sub-Saharan Africa. The aim of this study was to examine Toxoplasma seroprevalence in rodents from villages and towns across Senegal. Rodents were sampled in 40 localities using a standardised trapping protocol. Detection of T. gondii antibodies was performed on 1205 rodents, using a modified agglutination test (MAT) technique. Seroprevalence data were analysed depending on geography, the local rodent community, and individual characteristics of the rodent hosts. We found 44 seropositive rodents from four different species (Mastomys erythroleucus, Mastomys natalensis, Mus musculus domesticus, Rattus rattus). Toxoplasma seroprevalence was low, averaging 4% in the localities. Higher Toxoplasma seroprevalence (up to 24%) was found in northern Senegal, a region known to be the heart of pastoral herding in the country.

In sub-Saharan Africa, few studies have addressed the environmental determinants of the incidence of Toxoplasma gondii infection. Free-range chickens are regarded as sensitive indicators for environmental contamination with T. gondii oocysts due to their ground-feeding behavior and have been used as sentinels. A cross-sectional study was conducted from January to April 2018 to estimate the seroprevalence of T. gondii infection in free-range chickens from Senegal, West Africa, using the modified agglutination test. Sampling was performed in two regions of the country: Saint-Louis, a Sahelian area in the North, and Kedougou, a forest and rainy area in the South. A questionnaire was administered to chicken owners to assess potential risk factors for T. gondii seropositivity, and univariable and multivariable logistic regression analyses were used to determine the statistical significance of risk factors. The seroprevalence in chickens was 7.67% (51/665; 95% confidence interval [CI]: 5.51–9.52). The multivariable logistic regression model indicated that the odds to test T. gondii seropositive was higher in chickens provided well water (odds ratio [OR] = 3.17, 95% CI: 1.45–6.93; p = 0.004) than in chickens provided tap water, and in hens having chicks (OR = 80.15, 95% CI: 22.79–281.95; p < 0.001) than in chickens (male or female) not having chicks. The possible role of contaminated well water in the acquisition of infection in chickens—and hence in human—merits consideration and should be addressed in future studies. [ABSTRACT FROM AUTHOR]

Toxoplasma gondii is a zoonotic protozoan with a worldwide occurrence, but the determinants of the current pattern in the geographical distribution of T. gondii lineages and strains remain poorly understood. To test the influence of human trade on T. gondii populations, we conducted a population genetic study of 72 T. gondii animal isolates from Senegal, a West African country in which the ongoing inland progress of invasive murine hosts (introduced in port cities of Senegal since the 16th century by European sailors) is well described. Isolates were mainly collected on free-range poultry, which are considered as relevant bioindicators of T. gondii strain diversity in the domestic environment. Sampling was conducted in two port cities of Senegal (Dakar and Saint-Louis) and in one inland region (Kedougou). Population genetic analyses using 15 microsatellite markers revealed different patterns between port cities where lineages non-virulent for mice (type II, type III, and Africa 4) were predominant, and Kedougou where the mouse-virulent Africa 1 lineage was the most common. By considering the current spatial pattern in the inland progress of invasive rodents in Senegal, our results suggest that the invasive house mouse Mus musculus domesticus counter-selects the Africa 1 lineage in the invaded areas. The comparison of the microsatellite alleles of type II strains from Senegal to type II strains from other areas in Africa and Western Europe, using discriminant analysis of principal components and Network analysis, point to a mainly Western European origin of the type II lineage in Senegal. Collectively, these findings suggest that human-mediated intercontinental migrations of murine hosts are important vectors of T. gondii strains. Differential susceptibility of endemic and introduced murine hosts to various T. gondii strains probably determines the persistence of these strains in the environment, and therefore their availability for human and animal infection. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The modified agglutination test (MAT) should not be used for Toxoplasma gondii detection in wild Mus musculus domesticus. • Prevalence of T. gondii infection varies significantly between species. • Both transcontinental and African lineages of T. gondii are found in Senegal. • The African T. gondii lineage Africa 1 was only found in native African small mammals. Abstract Commensal rodent species are key reservoirs for Toxoplasma gondii in the domestic environment. In rodents, different T. gondii strains show variable patterns of virulence according to host species. Toxoplasma gondii strains causing non-lethal chronic infections in local hosts will be more likely to persist in a given environment, but few studies have addressed the possible role of these interactions in shaping the T. gondii population structure. In addition, the absence of validated techniques for upstream detection of T. gondii chronic infection in wild rodents hinders exploration of this issue under natural conditions. In this study, we took advantage of an extensive survey of commensal small mammals in three coastal localities of Senegal, with a species assemblage constituted of both native African species and invasive species. We tested 828 individuals for T. gondii chronic infection using the modified agglutination test for antibody detection in serum samples and a quantitative PCR assay for detection of T. gondii DNA in brain samples. The infecting T. gondii strains were genotyped whenever possible by the analysis of 15 microsatellite markers. We found (i) a very poor concordance between molecular detection and serology in the invasive house mouse, (ii) significantly different levels of prevalence by species and (iii) the autochthonous T. gondii Africa 1 lineage strains, which are lethal for laboratory mice, only in the native African species of commensal small mammals. Overall, this study highlights the need to reconsider the use of MAT serology in natural populations of house mice and provides the first known data about T. gondii genetic diversity in invasive and native species of small mammals from Africa. In light of these results, we discuss the role of invasive and native species, with their variable adaptations to different T. gondii strains, in shaping the spatial structure of T. gondii genetic diversity in Africa. [ABSTRACT FROM AUTHOR]