Additional Haplogroups of Toxoplasma gondii out of Africa: Population Structure and Mouse-Virulence of Strains from Gabon

Abstract

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 FindingsSeropositive 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.

The Life Cycle of Toxoplasma gondii in the Natural Environment

“…Caribbean genotypes found in the anthropized areas of French Guiana and in several Caribbean Islands, or in Africa, where the same African lineages were found in different countries [169,170,171].…”

Is Predominant Clonal Evolution a Common Evolutionary Adaptation to Parasitism in Pathogenic Parasitic Protozoa, Fungi, Bacteria, and Viruses?

“…The three clonal lineages exhibit phenotypic specificity (virulence) (Boothroyd, 2009;Sibley and Boothroyd, 1992). Additional lineages assimilable to near-clades have been recorded in other cycles and regions of the world (Dubey et al, 2011;Khan et al, 2011;Mercier et al, 2010Mercier et al, , 2011. A classical notion has emerged, namely, that T. gondii undergoes more recombination in South America than in North America and Europe (Lehmann et al, 2004(Lehmann et al, , 2006Su et al, 2010).…”

New Insights into Clonality and Panmixia in Plasmodium and Toxoplasma

“…Identical MLGs have been isolated in French Guiana from humans, cats, dogs, and chickens 50 km apart (Mercier et al, 2011). The "clonal types" I, II, and III, preponderant in Europe and North America, are present in Africa (Mercier et al, 2010) and have been also recorded in Central and South America (Da Silva et al, 2011;Mercier et al, 2011;Rajendra et al, 2012;Su et al, 2012).…”