Molecular prevalence, genetic characterization and patterns of Toxoplasma gondii infection in domestic small mammals from Cotonou, Benin

Toxoplasmosis, one of the most prevalent parasitic infections in humans and animals, is caused by the intracellular protozoan parasite Toxoplasma gondii. Small mammals play a key role as intermediate reservoir hosts in the maintenance of the T. gondii life cycle. In this study, we estimated the molecular prevalence and provide genetic diversity data for T. gondii in 632 small mammals sampled in four areas of Cotonou city, Benin. Both the brain and heart of each individual were screened through T. gondii-targeting qPCR, and positive samples were then genotyped using a set of 15 T. gondii-specific microsatellites. Prevalence data were statistically analyzed in order to assess the relative impact of individual host characteristics, spatial distribution, composition of small mammal community, and urban landscape features. An overall T. gondii molecular prevalence of 15.2% was found and seven genotypes, all belonging to the Africa 1 lineage, could be retrieved from the invasive black rat Rattus rattus and the native African giant shrew Crocidura olivieri. Statistical analyses did not suggest any significant influence of the environmental parameters used in this study. Rather, depending on the local context, T. gondii prevalence appeared to be associated either with black rat, shrew, or mouse abundance or with the trapping period. Overall, our results highlight the intricate relationships between biotic and abiotic factors involved in T. gondii epidemiology and suggest that R. rattus and C. olivieri are two competent reservoirs for the Africa 1 lineage, a widespread lineage in tropical Africa and the predominant lineage in Benin

Se protéger des tiques

International audienceAcariens des zones boisées, les tiques s’accrochent aux hôtes pour se nourrir de leur sang. C’est lors de ce repas qu’elles peuvent transmettre des pathogènes, potentiellement dangereux, notamment pour l’humain. L’encéphalite à tiques, la fièvre boutonneuse et la très médiatique borréliose de Lyme sont toutes transmises par des tiques. Différents moyens de prévention existent

Phénomènes d’introgression dans la diversité génétique du toxoplasme entre la France et l’Afrique de l’Ouest et Centrale : des influences humaines et environnementales

International audienceLa toxoplasmose, infection due au parasite Toxoplasma gondii, est une zoonose ubiquitaire touchant l’ensemble des espèces homéothermes. La contamination s’effectue principalement par voie orale : ingestion d’oocystes excrétés dans l’environnement par les félidés (hôtes définitifs) ou consommation de kystes présents dans les tissus d’hôtes intermédiaires.Chez l’Homme, un quart de la population mondiale serait concernée par cette zoonose. La variabilité des formes cliniques (d’asymptomatique à mortelle) semble être en lien avec l’état immunitaire du patient mais également avec la souche responsable de l’infection. Géographiquement, une différence génétique est observée entre des souches européennes ou nord-américaines (peu pathogènes pour l’Homme immunocompétent) et des souches isolées en zone tropicale humide (notamment en Amérique du Sud) liées à des manifestations cliniques plus sévères pouvant dans certains cas engager le pronostic vital du patient.En revanche, la diversité génétique du toxoplasme sur d’autres continents comme l’Afrique et l’Asie demeure très peu explorée.Dans le cadre du projet ANR « Introtox », l’objectif principal de cette thèse est d’explorer les voies d’introgression de souches de T. gondii entre la France et l’Afrique de l’Ouest et Centrale au travers des exemples du Sénégal, du Bénin et du Gabon. Cette thèse cherchera à comprendre l’influence des facteurs anthropiques (transport maritime) ou environnementaux (migrations d’oiseaux) sur la structuration génétique des populations de ce parasite à différentes échelles de son génome et leurs conséquences sur l’épidémiologie de l’infection par T. gondii dans ces régions.L’approche méthodologique : La détection de l’infection par T. gondii est faite à l’aide d’un test sérologique (MAT) sur des échantillons sanguins d’animaux. L’isolement du parasite est ensuite réalisé par inoculation à la souris d’organes d’animaux séropositifs prélevés de façon opportuniste. Les tissus des souris infectées (cerveau, ascite…) permettront les analyses génétiques (génotypage, séquençage du génome) et la conservation des souches de T. gondii

Diversity of Toxoplasma gondii strains at the global level and its determinants

International audienceThe population structure of Toxoplasma gondii is characterized by contrasting geographic patterns of strain diversity at different spatial scales: global, regional and even local scales in some regions. The determinants of this diversity pattern and its possible evolutionary mechanisms are still largely unexplored. This review will focus on three main dichotomies observed in the population structure of the parasite: (1) domestic versus wild, (2) South America versus the rest of the world and (3) intercontinental clonal lineages versus regional or local clonal lineages. Here, the impact in terms of public health of this remarkably contrasting geographic diversity of T. gondii populations is discussed, with emphasis on the role of globalization of exchanges that could lead to rapid evolution of T. gondii population spatial structure and new challenges in a One Health context

Toxoplasma and Africa: One Parasite, Two Opposite Population Structures

International audienceExploring the genetic diversity of Toxoplasma gondii is essential for an understanding of its worldwide distribution and the determinants of its evolution. Africa remains one of the least studied areas of the world regarding T. gondii genetic diversity. This review has compiled published data on T. gondii strains from Africa to generate a comprehensive map of their continent-wide geographical distribution. The emerging picture about T. gondii strain distribution in Africa suggests a geographical separation of the parasite populations across the continent. We discuss the potential role of a number of factors in shaping this structure. We finally suggest the next steps towards a better understanding of Toxoplasma epidemiology in Africa in light of the strains circulating on this continent

Epidémiologie moléculaire de Toxoplasma gondii en Nouvelle Aquitaine : évaluation des voies d'introduction de souches exotiques du parasite

International audienc

Fatal toxoplasmosis in wild European brown hares ( Lepus europaeus ) in tularaemia endemic areas of the Czech Republic: Poses risk of infection for humans?

International audienceToxoplasma gondii may cause fatal infection in European brown hares (Lepus europaeus). However, the role of this parasite in terms of mortality rate in tularaemia endemic areas, amount of parasites in affected organs and circulating genotypes, is still unknown. In total, 36 hares (killed or found dead) were submitted for pathomorphological examination as a part of the national tularaemia and brucellosis monitoring. Tissue samples (lung, heart, liver, spleen and kidney) were tested by quantitative real-time PCR targeting 529 bp region of T. gondii. Genotyping was performed by a 15 microsatellite markers method in a single multiplex PCR assay. The same tissues of hares were simultaneously used for the bacteriological cultivation. Toxoplasma gondii was detected by qPCR in the tissues of two hares. Spleen and lungs of one infected hare have been found harbouring up to ~7 millions of T. gondii parasites per gram of tissue. Both positive samples were characterized as T. gondii type II, one archetypal clonal type II and the other one a type II variant (W35 = 244). Bacteria Francisella tularensis was proved in pooled samples of three hares but without coinfection with T. gondii; all hares were negative for Brucella suis. Toxoplasma gondii has significant impact on mortality of European brown hares in tularaemia endemic areas and parasite load within the animal tissues may present high risk of human infection

Combining spatial analysis and host population genetics to gain insights into the mode of transmission of a pathogen: The example of Toxoplasma gondii in mice

International audienceToxoplasma gondii is a ubiquitous highly prevalent zoonotic protozoan. Cats are the definitive hosts, while all other warm-blooded animals are intermediate hosts for this parasite. Commensal rodents, being the main prey of cats, are probably the major reservoir for T. gondii in the domestic environment. Rodents can acquire infection after ingestion of oocysts that have sporulated in the environment. However, experimental evidence shows that vertical transmission can be sufficient for the perpetuation of transmission between generations of mice. In natural settings, the relative epidemiological importance of vertical transmission over oral transmission is a matter of debate and raises the question of the possibility of a T. gondii cycle in the absence of cats. In the present study, we took advantage of an extensive survey of commensal rodents in Dakar, Senegal, where the house mouse is the predominant putative reservoir of T. gondii. Mice genotypes and spatial location through GPS referencing of all trapping localizations were investigated in relation to T. gondii infection in eight sites of the city of Dakar and on Goree Island. In each sampling site, the occurrence of over-prevalence zones of T. gondii infection was investigated through Kulldorf's statistic using SaTScan software. Genetic structure and relatedness between mice were investigated within each over-prevalence zone, in order to find clues of transmission between related mice. Within each of the four over-prevalence zones identified across nine sites, infected mice belonged to more than one genetic group. No association between the degree of relatedness and the occurrence of T. gondii infection could be detected. These findings suggest an environmental source of infection for mice associated with localized putative foci of environmental contamination and support an oral route of infection for mice from Dakar rather than a cycle based on vertical transmission. However, further investigations based on a denser sampling in different epidemiological contexts are recommended

Massive introgressions of Toxoplasma gondii domestic alleles in the Americas coincide with the recent introduction of the domestic cat.

International audienceToxoplasma gondii, a cyst-forming apicomplexan parasite of virtually all warm-blooded species, is the etiologic agent of toxoplasmosis, a disease causing substantial public health burden worldwide. Its wide range of host species and its global occurrence probably complicate the study of its evolutionary history, and conflicting scenarios have been proposed to explain its global spread. By analysis a global set of 156 genomes and by providing the first direct estimate of T. gondii mutation rate, we show that major Old World domestic clonal lineages have spread from Europe and Africa to the Americas in the last few centuries and hybridized with New World specific clades. These events coincide with the recent expansion in the New World of the domestic cat and of a number of rodent species, the main hosts of T. gondii in the domestic environment. By combining environmental and functional data to selection inference tools, we identify the top candidate genes under selection in these hybrid populations of North and South America. We show that a unique domestic allele inherited from the recently introduced Old World lineages has been selected in these emergent domestic populations in the New World. The selection of this domestic allele is most parsimoniously explained by local adaptation to the domestic ecotype and to transmission by domestic cats

Prévalence de Toxoplasma gondii chez les animaux péri-domestiques et sauvages en région Provence-Alpes-Côte d'Azur

International audienc