Seroepidemiology of toxoplasmosis in pregnant women and detection of infection acquired during pregnancy in Cotonou, Benin

Assessing the prevalence of toxoplasmosis in pregnant women and the associated risk factors is the first step in defining policy for the prevention of congenital toxoplasmosis in a given population. An epidemiological study was conducted during prenatal consultations at the CHU-MEL of Cotonou (Benin) between September 2018 and April 2021 and recruited 549 pregnant women to determine the seroprevalence and potential factors associated with Toxoplasma gondii infection. Toxoplasma gondii IgG/IgM antibodies were detected using an enzyme-linked fluorescence assay (ELFA) technique, an IgG avidity test and an IgG/IgM comparative Western blot to diagnose the maternal toxoplasmosis serological status, the possibility of an infection acquired during pregnancy and congenital infection, respectively. Concomitantly, the participants answered a questionnaire investigating potential risk factors. Toxoplasmosis seroprevalence was estimated at 44.4% (95% CI 40.3-48.6) and the factors significantly associated with T. gondii seropositivity were: age over 30 years, multigravid women and contact with cats. The possibility of an infection acquired during the periconceptional period or the first trimester of pregnancy concerned six women [1.1% (95% CI 0.5-2.0)]. However, due to the low rate of serological controls in seronegative women, a significant proportion of women first tested during the 3rd trimester of pregnancy, and an insufficient sample size, the incidence of primary infection during pregnancy could not be determined. No cases of congenital transmission occurred in the newborns from the suspected cases of primary infection.

Serological diagnosis of toxoplasmosis in pregnancy: comparison between a manual commercial ELISA assay and the automated VIDAS® kit

Knowledge of the toxoplasmosis serological status in pregnant women is important to allow adequate management for the prevention of congenital toxoplasmosis of those who are not immunized. Serological screening is generally carried out using commercial kits to determine the presence or absence of immunoglobulins M or G in the maternal blood. Robust results are therefore needed. We evaluated the performances of a commercial ELISA assay composed of several recombinant parasite antigens and of a commercial assay using parasite lysate to determine the serological status against Toxoplasma gondii of African pregnant women. A recruitment of 106 pregnant women during their third trimester of pregnancy was carried out in Benin. Serologies were performed with recomWell Toxoplasma IgM and IgG kits. Subsequently, the serological assays were carried out by an automaton method with the VIDAS^® TOXO IgM and IgG II kits. Here we compared recomWell Toxoplasma to VIDAS^® TOXO results. Reproducibility tests of the recomWell kits were assessed following the discrepancies observed in the results. Of 106 plasmas tested, 47 showed anti-T. gondii IgG (44.3%), including 5 with IgM and high IgG avidity (4.7%). Of the two techniques, VIDAS^® TOXO was more robust and specific for IgG while the recomWell Toxoplasma gave more false positive results. The combination of several techniques for the determination of serological toxoplasmosis status remains relevant. Methods using native proteins are closer to the reality of the environment. Therefore, kits using recombinant proteins should be tested on highly geographically diverse populations to refine their composition.

A hotspot of Toxoplasma gondii Africa 1 lineage in Benin: How new genotypes from West Africa contribute to understand the parasite genetic diversity worldwide

Through international trades, Europe, Africa and South America share a long history of exchanges, potentially of pathogens. We used the worldwide parasite Toxoplasma gondii to test the hypothesis of a historical influence on pathogen genetic diversity in Benin, a West African country with a longstanding sea trade history. In Africa, T. gondii spatial structure is still non-uniformly studied and very few articles have reported strain genetic diversity in fauna and clinical forms of human toxoplasmosis so far, even in African diaspora. Sera from 758 domestic animals (mainly poultry) in two coastal areas (Cotonou and Ouidah) and two inland areas (Parakou and Natitingou) were tested for T. gondii antibodies using a Modified Agglutination Test (MAT). The hearts and brains of 69 seropositive animals were collected for parasite isolation in a mouse bioassay. Forty-five strains were obtained and 39 genotypes could be described via 15-microsatellite genotyping, with a predominance of the autochthonous African lineage Africa 1 (36/39). The remaining genotypes were Africa 4 variant TUB2 (1/39) and two identical isolates (clone) of Type III (2/39). No difference in terms of genotype distribution between inland and coastal sampling sites was found. In particular, contrarily to what has been described in Senegal, no type II (mostly present in Europe) was isolated in poultry from coastal cities. This result seems to refute a possible role of European maritime trade in Benin despite it was one of the most important hubs during the slave trade period. However, the presence of the Africa 1 genotype in Brazil, predominant in Benin, and genetic analyses suggest that the triangular trade was a route for the intercontinental dissemination of genetic strains from Africa to South America. This supports the possibility of contamination in humans and animals with potentially imported virulent strains.

The parasite Toxoplasma gondii is a worldwide-distributed pathogen, able to infect all warm-blooded animals. There are important differences in the clinical expression of the infection in direct relation with the parasite genetic profile. In some regions, the geographical structuration of its genetic diversity points towards a crucial role of human activities in some lineages introduction or sorting. Benin is a West African country with a history of extensive transcontinental exchanges. Our genetic study of Toxoplasma in Benin shows a surprisingly homogeneous and autochthonous diversity, which contrasts with previous studies from other West and Central African countries. In Benin, the absence of European Toxoplasma lineages may be explained by the extreme rarity of the house mouse (Mus musculus), a host species that was previously described as highly susceptible to the mouse-virulent African strains. Might Benin be the origin region for the Africa 1 lineage, our results suggest that Guinean Gulf coasts may be a starting point of this lineage towards South America, especially Brazil, during the slave trade. As a whole, the present study provides further insights into the recent evolutionary history of Toxoplasma gondii and its consequences on human and animal health.

[Seroprevalence of Toxoplasmosis among Pregnant Women in Benin: Meta-Analysis and Meta-Regression]

To assess the seroprevalence of toxoplasmosis among pregnant women in Benin, we conducted a meta-analysis using the PRISMA criteria. Al research published between 1990 and 2018 on toxoplasmosis among pregnant women Benin were eligible. A total of five databases were investigated, and the extracted data were subjected to a meta-analysis under R 3.1 using both random effect model and fixed effect model. The overall prevalence of toxoplasma-specific IgG among pregnant women was 47% (CI 95%: 40-53) and that of specific IgM was 2% (CI 95%: 1-3). The infection rate in urban areas (52%) was significantly higher than in rural areas (33%). The two main risk factors identified by the various eligible studies were the age of the pregnant women and the consumption of raw vegetables. We show that toxoplasmosis is endemic in pregnant women in Benin, implying that primary prevention measures must be put in place by the competent authorities to control this infection.