Experimental Acquisition, Development, and Transmission of Leishmania tropica by Phlebotomus duboscqi
NAVAL MEDICAL RESEARCH UNIT NO 3 CAIRO (EGYPT) DEPT OF MEDICAL ZOOLOGY
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We report experimental infection and transmission of Leishmania tropica Wright, by the blood-feeding sand fly Phlebotomus duboscqi Neveu-Lemaire. Groups of laboratory-reared female sand flies that fed naturally on L. tropica-infected hamsters, or artificially, via membrane feeding device, on a suspension of L. tropica amastigotes, were dissected at progressive time points post-feeding. Acquisition, retention and development of L. tropica through procyclic, nectomonad, and leptomonad stages to the infective metacyclic promastigote stage, and anterior progression of the parasites from abdominal midgut bloodmeal to the thoracic midgut were demonstrated in both groups. Membrane feeding on the concentrated amastigote suspension led to metacyclic promastigote infections in 60 of sand flies, whereas only 3 of P. duboscqi that fed naturally on an infected hamster developed metacyclics. Sand flies from both groups re-fed on naive hamsters, but despite infections in 25-50 of membrane-fed and 2-3.5 of naturally fed flies, no skin lesions developed in the hamsters. After four months of observation these animals were euthanized and necropsied. Screening of the organs and tissue by polymerase chain reaction PCR that targeted the small subunit RNA gene, amplified generic Leishmania DNA from liver, spleen, bone marrow and blood, but only from hamsters bitten by membrane-infected P. duboscqi. These results are notable in demonstrating the ability of P. duboscqi, originating from Kenya, to acquire, retain, develop, and transmit a Turkish strain of L. tropica originally isolated from a human case of cutaneous leishmaniasis. This marks the first demonstration of complete development and transmission of L. tropica by a member of the Phlebotomus subgenus of sand flies.