Experimental transmission of Leishmania (Mundinia) parasites by biting midges (Diptera: Ceratopogonidae)

Leishmaniaparasites, causative agents of leishmaniasis, are currently divided into four subgenera:Leishmania,Viannia,SauroleishmaniaandMundinia. The recently established subgenusMundiniahas a wide geographical distribution and contains five species, three of which have the potential to infect and cause disease in humans. While the otherLeishmaniasubgenera are transmitted exclusively by phlebotomine sand flies (Diptera: Psychodidae), natural vectors ofMundiniaremain uncertain. This study investigates the potential of sand flies and biting midges of the genusCulicoides(Diptera: Ceratopogonidae) to transmitLeishmaniaparasites of the subgenusMundinia. Sand flies (Phlebotomus argentipes,P.duboscqiandLutzomyia migonei) andCulicoidesbiting midges (Culicoides sonorensis) were exposed to fiveMundiniaspecies through a chicken skin membrane and dissected at specific time intervals post bloodmeal. Potentially infected insects were also allowed to feed on ear pinnae of anaesthetized BALB/c mice and the presence ofLeishmaniaDNA was subsequently confirmed in the mice using polymerase chain reaction analyses. InC.sonorensis, allMundiniaspecies tested were able to establish infection at a high rate, successfully colonize the stomodeal valve and produce a higher proportion of metacyclic forms than in sand flies. Subsequently, three parasite species,L.martiniquensis,L.orientalisandL. sp. from Ghana, were transmitted to the host mouse ear byC.sonorensisbite. In contrast, transmission experiments entirely failed withP.argentipes, although colonisation of the stomodeal valve was observed forL.orientalisandL.martiniquensisand metacyclic forms ofL.orientaliswere recorded. This laboratory-based transmission ofMundiniaspecies highlights thatCulicoidesare potential vectors of members of this ancestral subgenus ofLeishmaniaand we suggest further studies in endemic areas to confirm their role in the lifecycles of neglected pathogens.