Some sandfly food is a Leishmania poison.

The studies summarized suggest that some of the diverse diets of sandfly vectors can adversely affect the Leishmania parasites in their gut. Phlebotomus papatasi in the vicinity of turkey sheds in the Jordan Valley (Israel) were free of L. major, in contrast to the commonly high infection rate elsewhere in the endemic region. Experiments demonstrated that sandfly meals of turkey or chicken blood are lethal to L. major infections. Furthermore, such meals reduce the potential of uninfected flies to harbour L. major. Plant feeding of sandflies in nature was demonstrated by identification of plant-tissue residues in the gut. Experimental feeding of Leishmania-infected flies on some plant species (Ricinus communis, Capparis spinosa and Solanum luteum, but not Malva nicaeensis or the honeydew of Icerya purchasi) caused parasite death in a high proportion of flies. The mortality of Leishmania parasites found in field-collected flies could therefore result from the sandflies' plant diet. Bacterial gut contaminations are harmful to sandflies and their Leishmania parasites. Their prevention is attributed to an antibacterial agent in the sandfly crop, which is a temporary store of contaminated sugary food, ingested from the surface of plants. Bacterial gut infections of sandflies are rare in the arid Jordan Valley where contaminating food is scarce and they are probably more common in temperate or tropical climates.