Leishmania sand fly-transmission is disrupted by Delftia tsuruhatensis TC1 bacteria.

Most human pathogenic Leishmania species are zoonotic agents; therefore, sand fly-based control strategies are essential to prevent parasite circulation. Here, we used the Delftia tsuruhatensis TC1 strain, that inhibits the development of Plasmodium in mosquitoes, but in the context of Leishmania-infected sand flies. We show that D. tsuruhatensis TC1 colonizes the midgut of Phlebotomus duboscqi sand flies and impacts the development of L. major parasites, independently of the colonization timing. This phenotype is likely an indirect consequence of D. tsuruhatensis colonization, related with the induction of sand fly gut dysbiosis. Importantly, Leishmania-infected, D. tsuruhatensis-fed sand flies are less able to transmit L. major parasites and cause disease in mice. Modelling supports the disruption of disease endemicity in the field, highlighting D. tsuruhatensis as a promising agent for the control of leishmaniasis.