[Seroprevalence of toxoplasmosis in a rural population in south-west Gabon]

[Serological study on toxoplasmosis among pregnant women from Franceville, Gabon]

The serological prevalence of Toxoplasma gondii was studied among 839 pregnant women in two hospitals from Franceville (Gabon), between May 2007 and December 2007. Specific T gondii IgG and IgM were measured by Enzyme Linked Fluorescent Assay (ELFA). Datation of the infection was carried out by avidity test. Fifty-six percent of women in this study were immunised compare to the 71% who were found as immunised in a previous study carried out fifteen years ago. 2.6% were found to be IgM positive. However, from the avidity test it was found that these infections occurred before pregnancy contact with cats and age increase this prevalence. The lack of information for pregnant women, the lack of continuous training for health personnel and lack of awareness about interpretation of laboratory diagnostic tests like avidity test in these hospitals reduce the level of counselling for women about T gondii.

Additional haplogroups of Toxoplasma gondii out of Africa: population structure and mouse-virulence of strains from Gabon

BACKGROUND

Toxoplasma gondii is found worldwide, but distribution of its genotypes as well as clinical expression of human toxoplasmosis varies across the continents. Several studies in Europe, North America and South America argued for a role of genotypes in the clinical expression of human toxoplasmosis. Genetic data concerning T. gondii isolates from Africa are scarce and not sufficient to investigate the population structure, a fundamental analysis for a better understanding of distribution, circulation, and transmission.

METHODOLOGY/PRINCIPAL FINDINGS

Seropositive animals originating from urban and rural areas in Gabon were analyzed for T. gondii isolation and genotyping. Sixty-eight isolates, including one mixed infection (69 strains), were obtained by bioassay in mice. Genotyping was performed using length polymorphism of 13 microsatellite markers located on 10 different chromosomes. Results were analyzed in terms of population structure by Bayesian statistical modeling, Neighbor-joining trees reconstruction based on genetic distances, F(ST) and linkage disequilibrium. A moderate genetic diversity was detected. Three haplogroups and one single genotype clustered 27 genotypes. The majority of strains belonged to one haplogroup corresponding to the worldwide Type III. The remaining strains were distributed into two haplogroups (Africa 1 and 3) and one single genotype. Mouse virulence at isolation was significantly different between haplogroups. Africa 1 haplogroup was the most virulent.

CONCLUSION

Africa 1 and 3 haplogroups were proposed as being new major haplogroups of T. gondii circulating in Africa. A possible link with strains circulating in South and Central America is discussed. Analysis of population structure demonstrated a local spread within a rural area and strain circulation between the main cities of the country. This circulation, favored by human activity could lead to genetic exchanges. For the first time, key epidemiological questions were addressed for the West African T. gondii population, using the high discriminatory power of microsatellite markers, thus creating a basis for further epidemiological and clinical investigations.