Phlebotomine vector ecology in the domestic transmission of American cutaneous leishmaniasis in Chaparral, Colombia

Abstract

Phlebotomine vector ecology was studied in the largest recorded outbreak of American cutaneous leishmaniasis in Colombia in 2004. In two rural townships that had experienced contrasting patterns of case incidence, this study evaluated phlebotomine species composition, seasonal abundance, nocturnal activity, blood source, prevalence of Leishmania infection, and species identification. CDC miniature light traps were used to trap the phlebotomines. Traps were set indoors, peridomestically, and in woodlands. Natural infection was determined in pools by polymerase chain reaction-Southern blot, and blood sources and species identification were determined by sequencing. Large differences were observed in population abundance between the two townships evaluated. Lutzomyia longiflocosa was the most abundant species (83.1%). Abundance was higher during months with lower precipitation. Nocturnal activity was associated with human domestic activity. Blood sources identified were mainly human (85%). A high prevalence of infection was found in L. longiflocosa indoors (2.7%) and the peridomestic setting (2.5%). L. longiflocosa was responsible for domestic transmission in Chaparral.

Figure 1.

Map of Chaparral, Tolima, Colombia, showing the townships (grey areas) affected by the CL outbreak and locations of Agua Bonita (high CL case prevalence) and Irco Dos Aguas (low CL prevalence).

Figure 2.

Densities of females/trap per night and monthly standard error. (A) L. longiflocosa and (B) L. columbiana captured indoors, peridomestically, and in woodland in Agua Bonita were related to total precipitation. Each left vertical axis has a break to facilitate visualization of low values.

Figure 3.

Phlebotomine nocturnal activity of L. longiflocosa and L. columbiana in (A) peridomestic and (B) indoor environment.

Figure 4.

Leishmania species identification by SNP typing of the 7SL RNA gene region in Colombia. 7SLRNA PCR (430 bp) products from L. (V.) reference strains (L. V. braziliensis M2903, L. V. guyanensis M4147, and L. V. panamensis LS94), L. guyanensis strains from Chaparral patients (isolates 3), Lutzomyia infected by xenodiagnostic, and five L. longiflocosa samples (Blood21TOCHAB005, Blood66TOCHAB011, NonBlood16, NonBlood17, and NonBlood4) were sequenced, and species identification was determined by SNP analysis. Species-specific SNPs used for typing within the L. (V.) subgenus, which were previously reported by Stevenson and others, are as follows: braziliensis 80A, 91G, 98A, 124T, 161G, 164C, 167T, 341C panamensis 80T, 91A, 98G, 124A, 161A, 164A, 167A, 341C guyanensis 80T, 91A, 98A, 124A, 161A, 164A, 167T, and 341T.