Quantifying the infectiousness of post-kala-azar dermal leishmaniasis towards sandflies

Background In the Indian subcontinent, visceral leishmaniasis (VL) incidence is on track to reach elimination goals by 2020 in nearly all endemic districts. Although not included in official targets, previous data suggest post-kala-azar dermal leishmaniasis (PKDL) patients can act as an infection reservoir. Methods We conducted xenodiagnosis on 47 PKDL patients and 15 VL patients using laboratory-reared Phlebotomus argentipes. In direct xenodiagnosis, flies were allowed to feed on the patient’s skin for 15 minutes. For indirect xenodiagnosis, flies were fed through a membrane on the patient’s blood. Five days later, blood-fed flies were dissected and examined by microscopy and/or PCR. A 3-mm skin snip biopsy (PKDL) or venous blood VL) was processed by quantitative PCR. Results Twenty-seven PKDL patients (57.4%) had positive results by direct and/or indirect xenodiagnosis. Direct was significantly more sensitive than indirect xenodiagnosis (55.3% vs 6.4%, p 1 log10 unit higher than those with negative results (2.88 vs 1.66, p