Species-specific identification of Leishmania in naturally infected sand flies captured in Mato Grosso do Sul State, Brazil.

An increase in cutaneous and visceral leishmaniasis cases has been reported in recent years in the state of Mato Grosso do Sul, Brazil, and little is known to date about their etiological agents. An investigation into natural Leishmania infection of sand flies captured in this state between December 2003 and August 2004 was carried out. Mini-exon sequences were used as targets to identify Leishmania, and an RFLP technique was employed for those identified as belonging to the Viannia subgenus. Calculation of the minimal infection rate (MR) revealed that 1.6% of sand flies captured in the forest, peridomicile and intradomicile were positive. Six species were found to be infected by Leishmania (V.) braziliensis. Interestingly, two of the six species, Lutzomyia longipalpis and Nyssomyia whitmani, were captured in anthropic environments. The findings of this study constitute a useful tool for planning control measures against this disease in the State of Mato Grosso do Sul.

Detection and identification of Leishmania species in field-captured phlebotomine sandflies based on mini-exon gene PCR.

Leishmaniasis is one of the most diverse and complex of all vector-borne diseases. Because it involves several overlapping species and sandfly vectors, the disease has a complex ecology and epidemiology. Adequate therapy and follow-up depend on parasitological diagnosis, but classical methods present several constraints when identifying species. We describe a polymerase chain reaction (PCR) which uses primers designed from mini-exon repetitive sequences that are specific for subgenus LeishmaniaViannia (PV), as well as sequences with specificity for genus (PG) that can distinguish between Leishmania species from other insect flagellates with minor differences in PCR products. For standardization, these PCR were tested in experimentally infected sandflies, and Leishmania infection in these insects was successfully confirmed. This methodology identified a 3.9% infection rate in field-captured phlebotomine sandflies from an endemic region in Brazil. Natural infection by Leishmania species was identified in three samples of Lutzomyia longipalpis, of which two were Leishmania (L.) chagasi and one Leishmania (L.) amazonensis. Irrespective of specific epidemiological conclusions, the method used in this study was able to identify Leishmania infections both in experimentally infected and field-captured phlebotomine sandflies, and could be a useful tool in epidemiological studies and strategic planning for the control of human leishmaniasis.