Abstract. We studied the reservoir competency of canines with distinct clinical presentations of Leishmania chagasi infection. The parasitologic status of asymptomatic and symptomatic dogs was determined by standard culture methods Infectivity was assessed by multiple xenodiagnoses with Lutzomyia longipalpis, over a period of 2-11 months. Asymptomatic dogs were non-infective (0 of 5) while 2 of 7 oligosymptomatic dogs infected L. longipalpis, transmitting the parasites at low rates (range 0.9-5.2% of engorged flies). Polysymptomatic dogs transmitted L. chagasi more frequently (4 of 8 dogs) and reached higher infection rates (range 5.0-22.5% of engorged flies). The skin of the ear tended to be more infective to sand flies than that of the abdomen. Polymerase chain reaction hybridization (PCR-H) was a sensitive method for detection of L. chagasi, yielding the highest positive rate in serum (16 of 17 dogs) with no distinction between clinical groups. No association between skin positivity by PCR-H and infectivity to sand flies was found. The infectivity of dogs from clinically comparable groups from Colombian and Mediterranean foci differed. This may be a reflection of varied nutritional conditions or vector competency of distinct sand fly species.

The effectiveness of bednets and curtains (nylon mesh 64 per cm2) impregnated with deltamethrin at 26 mg a.i./m2 in reducing the biting nuisance caused by three phlebotomine sandfly species: Lutzomyia columbiana, Lu.lichyi and the predominant Lu.youngi (Diptera: Psychodidae), was evaluated at La Guaira, a rural settlement in Valle de Cauca near Cali, Colombia. Pairs of volunteers collected sandflies under impregnated bednets, in rooms protected by impregnated curtains or in unprotected rooms in a randomized matched design. Collections were made in three houses per night on three consecutive nights, so that each house was sampled under each of the three treatments. This routine was repeated at 2-week intervals for 6 months. There was no significant difference between the overall numbers of sandflies collected in rooms with or without impregnated curtains. Only 0.14 sandflies/man-hour were caught on human bait under impregnated bednets, significantly fewer than the numbers collected on human bait outside the nets in the same room (1.91) or in unprotected rooms (3.29). In a second set of experiments carried out in La Guaira and the neighbouring community of Jiguales, the effect of deltamethrin impregnation was evaluated by comparing numbers of sandflies collected on human bait under treated and untreated nets. Significantly fewer were collected under the impregnated nets (0.25 v. 0.69/man-hour). Wild-caught female Lu.youngi exposed to treated netting for 2 min in the laboratory all died with 24 h. The impact of deltamethrin-impregnated bednets was considered to be useful against Lu.youngi and other potential vectors of leishmaniasis in such communities.

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The presence of Leishmania parasites in the unaffected skin and peripheral-blood monocytes of a high proportion of patients even after treatment and the acquisition of infection by sand flies support the plausibility of anthroponotic transmission of American cutaneous leishmaniasis.

We examined changes in the phlebotomine fauna resulting from human intervention in a tropical dry forest of Northern Colombia where visceral and cutaneous leishmaniases are endemic. A natural forest reserve (Colosó) and a highly degraded area (San Andrés de Sotavento [SAS]) were sampled monthly for 8 mo using Shannon traps, sticky traps, and resting-site collections. Overall abundances were higher in Colosó (15,988) than in SAS (2,324). and species richness of phlebotomines was greater in the forest reserve (11 species) than in the degraded habitat (seven species). Fisher alpha, a measure of diversity, reinforced this trend. Both sand fly communities were dominated by Lutzomyia evansi (Nuòez-Tovar), vector of Leishmania chagasi (Cunha & Chagas), representing 92 and 81% of all captures in Colosó and SAS, respectively. Lutzomyia longipalpis (Lutz & Neiva), the common vector of visceral leishmaniasis, accounted for 4-7% of the sand fly community. Lutzornyia panamensis (Shannon) and Lutzomya gomezi (Nitzulescu), putative vectors of Leishmania braziliensis (Vianna), had low abundances at both study sites. The zoophilic species Lutzomyia cayennensis (Floch & Abonneuc) and Lutzomyia trinidadensis (Newstead) were present in variable numbers according to trapping methods and site. Habitat degradation negatively affected sand fly communities, but medically important species were able to exploit modified environments, thereby contributing to Lishmania endemicity.

Abstract. Experimental infection of dogs with Leishmania infantum has yielded heterogeneous clinical, parasitologic, and immunologic results. We studied dogs infected with 10 5 or 10 4 sand fly-derived promastigotes delivered by the intradermal (ID) or intravenous (IV) routes. Total mortality over 1 year post-infection reached 23.8%. The mortality and proportion of sustained polysymptomatic dogs was highest in the IV-10 5 group. The early appearance of polysymptoms was associated with an increased risk of progression to death. Dissemination of the parasite to lymph nodes was faster, and the subsequent infectivity to sand flies higher, in the IV compared with ID-infected dogs. Parasite-specific IgG1 or IgG2 production was similar among the groups, but higher interferon-γ (IFN-γ) and interleukin-10 (IL-10) expression was associated with polysymptomatic dogs. On the basis of the data obtained from this study, a sample size analysis using different endpoints for future vaccine trials is described.