Abstract
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.
Highlights
Leishmaniases are vector-borne diseases with complex ecology and epidemiology
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
Summary
Leishmaniases are vector-borne diseases with complex ecology and epidemiology In humans, they are caused by more than 20 species of Leishmania parasites that live in a wide range of ecosystems and may have different clinical manifestations (mainly cutaneous, mucocutaneous or visceral) [1]. To our knowledge, only one human clinical case has been recorded: one child with several cutaneous lesions [6]. This L. infantum canine leishmaniasis focus is interesting because of its unusual location (i.e., outside the Mediterranean basin, Central and Southwest Asia, China, Middle East, Central and South America etc.) [7, 8] and because of the absence of the usual vectors (Phlebotomus sand flies) for this parasite
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