Epidemiological monitoring of American tegumentary leishmaniasis: molecular characterization of a peridomestic transmission cycle in the Amazonian lowlands of Bolivia

Abstract

Human-made and environmental changes constitute a major risk factor for the (re-)emergence and spread of leishmaniasis; surveillance of the transmission cycle is essential in this context. This study integrated entomological and molecular parasitological techniques to document the transmission pattern of a peridomestic focus of Leishmania in the Isiboro Secure area of Bolivia. First the spatial distribution and relative density of phlebotomine sand flies, genus Lutzomyia, were established. Lutzomyia shawi was the predominant species in domestic and peridomestic environments (90% from all collections). Second, direct application of the hsp70 PCR to sand fly extracts detected Leishmania infections in Lu. shawi only, and gave an estimated infection rate of 0.21 to 0.38%. The cleavage of the hsp70 amplicon with restriction enzymes (hsp70 PCR-RFLP) allowed identification of Le. (V.) braziliensis and Le. (V.) guyanensis in Lu. shawi captured in the same village. These two parasite species were also found in humans from the study region, supporting the co-existence of two transmission cycles involving the same sand fly species. This study demonstrated the use of PCR-RFLP in the identification of Leishmania in sand fly pools which could lead to the development of methods for screening large sand fly populations in Latin America.

Leishmaniases in Bolivia: Comprehensive Review and Current Status

“…In Bolivia, CL is mostly caused by L. (Viannia) braziliensis (up to 85% cases), [16][17][18][19][20][21][22][23][24][25] L. (Leishmania) amazonensis, 24,26 and L. (V.) lainsoni 22,[27][28][29] ; recently, some cases have also been found to be caused by L. (V.) guyanensis ( Table 1 ). 22 All parasite isolates that have been characterized to species have primarily been reported in the north, center, and east of the country (i.e., Departments of La Paz, Beni, Pando, Santa Cruz, and Cochabamba) ( Figure 1 ).…”

“…22 All parasite isolates that have been characterized to species have primarily been reported in the north, center, and east of the country (i.e., Departments of La Paz, Beni, Pando, Santa Cruz, and Cochabamba) ( Figure 1 ). [16][17][18][19][20][21][22][23][24][25][26][27][28][29] Leishmania (L.) infantum , the causative agent of VL, was isolated from or detected in patients, [31][32][33] dogs, 34,35 and the insect vector Lutzomyia longipalpis 36 in the Yungas region in the Department of La Paz. To our knowledge, VL remains rare in Bolivia and is restricted to this unique focus in the Yungas region in the Beni department, where the first autochthonous case was diagnosed in 1984.…”

“…16,25,33,40,41 Although this still holds true for much of the Bolivian territory, in the past few years, an increasing number of reports emerged of LCL in children and cases contracting the disease in an urban environment rather than in forested areas. 22,25 For better epidemiologic leishmaniases' surveillance in Bolivia, multidisciplinary studies will have to investigate these trends in the future, studying the extent of peridomestic transmission and determining risk factors for infection and disease.…”

“…22,28,29,33,[62][63][64] The sensitivity varies according to the PCR protocol used, but in all cases, PCR proved to be more sensitive and specific in detecting Leishmania parasites compared with culture, microscopy, or clinical diagnosis (especially for ML). Similar to parasite culture, however, the use of PCR in Bolivia is limited to research purposes or epidemiologic studies because of the cost and need for specialized laboratory infrastructure and technically trained staff.…”

“…76 Ideally, to be sustainable in the long term and especially if new evidence corroborates recent reports of domestic transmission of Leishmania spp. in Bolivia, 22,25,33 leishmaniasis case management, prevention, and control should be-inasmuch as possible-integrated in the MoH's overall strategy for other vector-borne diseases, including malaria and Chagas disease. Unfortunately, even these programs suffer from poor funding support and implementation.…”