Leishmania in phlebotomid sandflies - IV. The transmission of Leishmania mexicana amazonensis to hamsters by the bite of experimentally infected Lutzomyia longipalpis

Abstract

Leishmania mexicana amazonensis was cyclically transmitted in the laboratory from hamster to hamster by single bites of experimentally infected Lutzomyia longipalpis. The sandflies were denied suitable conditions for oviposition and were induced to take a second, infecting, meal while still gravid. In three transmissions, cutaneous lesions developed rapidly on two hamsters, whereas that on the third remained small for 8 months, almost disappeared, and then grew to the usual large size. In some infected flies, parasites migrated to the pharynx and buccal cavity but then died and disintegrated; in others, healthy parasites were attached to the cuticular intima of the oesophagus and pharynx by hemidesmosomes. The common failure of leishmaniae to become established in the foregut of many experimentally infected sandflies may be because parasites die after migration and not because they fail to migrate. One cause of the death may be a lack of plant juices, a food of sandflies in nature. At the second potentially infecting feed, sandflies usually probed many times and took either no blood or only a small meal. It is suggested that parasites in the foregut block the pores of cibarial sensilla which probably control engorgement; such an interference would be an advantage in the evolution of Leishmania.