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Visceral leishmaniasis is not endemic in West Africa, but prevalence of canine leishmaniasis and seroprevalence of Leishmania infantum infection in humans are high in the Mont Rolland community (Thiès region, Senegal). Previous studies in this area showed that Sergentomyia schwetzi could be the potential vector of Le. infantum. To precisely describe the biology and population structure of this potential vector, we identified eight novel microsatellite loci to characterize Se. schwetzi populations. We tested these loci in Se. schwetzi populations from five locations at Mont Rolland (Thiès, Senegal). All the loci were polymorphic, with a mean of 17.25 alleles (observed heterozygosity: 0.455). We did not detect any evidence of scoring errors due to stuttering and large allele dropout. Moreover, several of these loci were also amplified in six other sand fly species (Sergentomyia magna, Sergentomyia dubia, Sergentomyia minuta, Phlebotomus duboscqi, Phlebotomus perniciosus, and Phlebotomus ariasi). These preliminary results demonstrate the utility of these microsatellite markers for Se. schwetzi (and for the other sand fly species) population genetic studies.

Visceral leishmaniasis is not endemic in West Africa. However, high seroprevalence of Leishmania infantum infection (one of the Leishmania species that cause visceral leishmaniasis) was detected in dogs and humans in the Mont Rolland community (close to Thiès, Senegal), despite the lack of reports concerning human clinical cases. Our aim was to genetically characterize this L. infantum population and identify its origin. We thus conducted seven field surveys in 25 villages of the Mont Rolland community between 2005 and 2009 and blood samples were collected from 205 dogs. Serological testing indicated that 92 dogs (44.9%) were positive for Leishmania infection. L. infantum was identified as the cause of infection. Analysis of 29 L. infantum isolates from these dogs by multilocus microsatellite typing and multilocus sequence typing indicated that this population had very limited genetic diversity, low level of heterozygosity and only seven different genotypes (79.3% of all isolates had the same genotype). Multilocus sequence typing showed that the Mont Rolland isolates clustered with strains from the Mediterranean basin and were separated from East African and Asian strains. Therefore, our data suggest a quite recent and unique introduction into Senegal of a L. infantum strain from the Mediterranean basin.

Whereas Leishmania infantum, the agent of visceral leishmaniasis (VL), is well known in North Africa, very limited data exist on its spread in West Africa, where mainly cutaneous leishmaniasis has been widely reported. Nevertheless, dogs infected with L. infantum were recently found in the Mont Rolland District in Senegal. To provide a better understanding of L. infantum epidemiology in this area, clinical and serological surveys were carried out to determine the seroprevalence of L. infantum-specific antibodies in the human population. In parallel, an analysis of environmental and individual factors associated with Leishmania antigen seropositivity was conducted to identify potential risk factors for exposure. Although no cases of VL were detected within this study, a large part of the population (73/315; 23%) was exposed to infection, with a strong age effect (being >40 years old increased the risk of being seropositive). Moreover, the presence of Nebedaye trees (Moringa oleifera) and infected dogs in the household were factors increasing the risk of exposure in household members. These results may provide important information to identify the still unknown sandfly species involved in transmission.

Leishmania (L.) infantum is the causative agent in an endemic focus of canine leishmaniasis in the Mont-Rolland district (Thiès, Senegal). In this area, the transmission cycle is well established and more than 30% of dogs and 20% of humans are seropositive for L. infantum. However, the sand fly species involved in L. infantum transmission cycle are still unknown. Between 2007 and 2010, 3654 sand flies were collected from different environments (indoor, peridomestic, farming and sylvatic areas) to identify the main L. infantum vector(s). Nine sand fly species were identified. The Phlebotomus genus (n = 54 specimens; Phlebotomus (Ph) duboscqi and Phlebotomus (Ph). rodhaini) was markedly under-represented in comparison to the Sergentomyia genus (n = 3600 specimens; Sergentomyia (Se) adleri, Se. clydei, Se. antennata, Se. buxtoni, Se. dubia, Se. schwetzi and Se. magna). Se. dubia and Se. schwetzi were the dominant species indoor and in peridomestic environments, near humans and dogs. Blood-meal analysis indicated their anthropophilic behavior. Some Se. schwetzi specimens fed also on dogs. The dissection of females in the field allowed isolating L. infantum from sand flies of the Sergentomyia genus (0.4% of Se. dubia and 0.79% of Se. schwetzi females). It is worth noting that one Se. dubia female not engorged and not gravid revealed highly motile metacyclic of L. infantum in the anterior part of the midgut. PCR-based diagnosis and sequencing targeting Leishmania kinetoplast DNA (kDNA) highlighted a high rate of L. infantum-positive females (5.38% of Se. dubia, 4.19% of Se. schwetzi and 3.64% of Se. magna). More than 2% of these positive females were unfed, suggesting the parasite survival after blood-meal digestion or egg laying. L. infantum prevalence in Se. schwetzi was associated with its seroprevalence in dogs and humans and L. infantum prevalence in Se. dubia was associated with its seroprevalence in humans. These evidences altogether strongly suggest that species of the Sergentomyia genus are probably the vectors of canine leishmaniasis in the Mont-Rolland area and challenge one more time the dogma that in the Old World, leishmaniasis is exclusively transmitted by species of the Phlebotomus genus., Author Summary Leishmaniases, neglected tropical vector-borne diseases, remain today a problem of public health. Classically, the sand flies involved in Leishmania transmission belong either to the Phlebotomus genus (Old World) or to the Lutzomyia genus (New World). In the rural community of Mont-Rolland (Senegal, West Africa), Leishmania infantum is the causative agent in an endemic focus of canine leishmaniasis. Recent surveys revealed more than 30% of dogs and 20% of humans with a positive serological test for Leishmania in this community. However, the sand fly species involved in L. infantum transmission were still unknown. Between 2007 and 2010, we carried out a study in this community to identify the sand fly species responsible for L. infantum transmission. We collected nine species belonging mainly to Sergentomyia genus and in low proportion to Phlebotomus genus. The abundance around dogs and humans, the detection of live and mature parasites in anterior midgut, the high rate of L. infantum-positive females using molecular analyses and the identification of dog and human blood in the fed females incriminates Se. schwetzi and Se. dubia as possible vectors of L. infantum. This hypothesis is strongly supported by statistical analyses performed to compare the prevalence of infected sand flies with the seroprevalence data in humans and dogs.

Background Different epidemiological studies previously indicated that canine leishmaniasis is present in the region of Thies (Senegal). However, the risks to human health, the transmission cycle and particularly the implicated vectors are unknown. Methodology/Principal Findings To improve our knowledge on the population of phlebotomine sand flies and the potential vectors of canine leishmaniasis, sand flies were collected using sticky traps, light traps and indoor spraying method using pyrethroid insecticides in 16 villages of the rural community of Mont Rolland (Thies region) between March and July 2005. The 3788 phlebotomine sand flies we collected (2044 males, 1744 females) were distributed among 9 species of which 2 belonged to the genus Phlebotomus: P. duboscqi (vector of cutaneous leishmaniasis in Senegal) and P. rodhaini. The other species belonged to the genus Sergentomyia: S. adleri, S. clydei, S. antennata, S. buxtoni, S. dubia, S. schwetzi and S. magna. The number of individuals and the species composition differed according to the type of trap, suggesting variable, species-related degrees of endophily or exophily. The two species of the genus Phlebotomus were markedly under-represented in comparison to the species of the genus Sergentomyia. This study also shows a heterogeneous spatial distribution within the rural community that could be explained by the different ecosystems and particularly the soil characteristics of this community. Finally, the presence of the S. dubia species appeared to be significantly associated with canine leishmaniasis seroprevalence in dogs. Conclusions/Significance Our data allow us to hypothesize that the species of the genus Sergentomyia and particularly the species S. dubia and S. schwetzi might be capable of transmitting canine leishmaniasis. These results challenge the dogma that leishmaniasis is exclusively transmitted by species of the genus Phlebotomus in the Old World. This hypothesis should be more thoroughly evaluated.

In the context of global warming and the risk of spreading arthropod-borne diseases, the emergence and reemergence of leishmaniasis should not be neglected. In Senegal, over the past few years, cases of canine leishmaniasis have been observed. We aim to improve the understanding of the transmission cycle of this zoonosis, to determine the responsible species and to evaluate the risk for human health. An epidemiological and serological study on canine and human populations in the community of Mont Rolland (Thies area) was conducted. The data showed a high seroprevalence of canine leishmaniasis (>40%) and more than 30% seropositive people. The dogs' seroprevalence was confirmed by PCR data (concordance > 0.85, Kappa > 0.7). The statistical analysis showed strong statistical associations between the health status of dogs and seropositivity, the number of positive PCRs, clinical signs and the number of Leishmania isolates. For the first time, the discriminative PCRs performed on canine Leishmania strains clearly evidenced that the pathogenic agent is Leishmania infantum. The results obtained show that transmission of this species is well established in this area. That the high incidence of seropositivity in humans may be a consequence of infection with this species is discussed. Published by Elsevier Masson SAS on behalf of the Institut Pasteur.