| Summary: | Intro: Visceral leishmaniasis (VL) is a fatal form of leishmaniasis caused by protozoan parasite Leishmania donovani and transmitted by the bites of blood sucking vector sand fly Phlebotomous argentipes. The spread and severity of infection is exacerbated by its status as an important co-infection of AIDS patients and the overlap in prevalence of HIV and leishmania species. We therefore performed xenodiagnosis to evaluate infectiousness of VL-HIV patients to sand flies in an area endemic for VL. Methods: In this prospective study, we performed direct xenodiagnosis using colonized female P. argentipes sand flies on 14 VL-HIV co-infected patients. During xenodiagnosis, 30 - 35 female flies were exposed for 30 min on each site on the subject's forearm and lower leg. Blood-engorged female flies were held in an environmental cabinet at 28°C and 85% humidity. At 60 -72 hours post- blood meal, flies were dissected and evaluated for L.donovani infection by microscopy as well as by quantitative polymerase chain reaction (qPCR). Findings: A total 732 sand flies were exposed on 14 VL-HIV patients having blood parasitemia roughly 42205 genomes / ml blood. We found that 16.66 % (122/732) of blood fed flies were found positive by microscopy. 92.8% (13 out of 14) HIV-VL patients transmitted infection to flies as reveled by qPCR and or microscopy. We modelled the proportion of flies that get infected based on blood parasitaemia, dividing the VL-HIV patients into three groups defined by qPCR values. We found that the probability of infection in any given blood fed fly correlated with severity of the disease (as defined by blood parasitemia), ranging from 4.92 % (95%CI 1.31 -16.39) in group 1 patients qPCR (0, 1e+04). to 15.39% (95% CI 4.11 – 43.55) in group 3 patients (qPCR 1e+05, 1e+06). Conclusion: Our findings confirm that VL-HIV patients are highly infectious to the vector.
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