Visceral Leishmaniasis-HIV coinfection as a predictor of increased leishmania transmission at the village level in Bihar, India

ABSTRACT BackgroundVisceral leishmaniasis (VL) is on the verge of being eliminated as a public health problem in the Indian subcontinent. Although Post-kala-azar dermal leishmaniasis (PKDL) is recognized as an important reservoir of transmission, we hypothesized that patients with VL co-infected with Human Immunodeficiency Virus (HIV) may also be important reservoirs of sustained leishmania transmission. We therefore investigated to what extent cases of PKDL or VL-HIV are associated with VL incidence at the village level in Bihar, India. MethodsVL, VL-HIV, and PKDL case data from six districts within the highly VL-endemic state of Bihar, India were collected through the Kala-Azar Management Information System for the years 2014 – 2019. Multivariate analysis was done using negative binomial regression controlling for year as a fixed effect and block (subdistrict) as a random effect. FindingsPresence of VL-HIV and PKDL cases were both associated with a more than twofold increase in VL incidence at village level, with Incidence Rate Ratios (IRR) of 2.16 (95% CI 1.81 – 2.58) and 2.37 (95% CI 2.01 – 2.81) for VL-HIV and PKDL cases respectively. A sensitivity analysis showed the strength of the association to be similar in each of the six included subdistricts. ConclusionsThese findings indicate the importance of VL-HIV patients as infectious reservoirs, and suggest that they represent a threat equivalent to PKDL patients towards the VL elimination initiative on the Indian subcontinent, therefore warranting a similar focus. CONTRIBUTION TO THE FIELDVisceral leishmaniasis (VL) – also called kala azar on the Indian subcontinent - is a parasitic disease which is fatal if not treated timely. Since the elimination initiative was launched in 2005 in the Indian subcontinent, the number of cases has come down drastically in this region. However, with the regional incidence of VL decreasing, understanding the role of potentially highly infectious subgroups in maintaining refractory Leishmania transmission is becoming increasingly important. Patients with Post-Kala-Azar Dermal Leishmaniasis (PKDL) are recognized as an important reservoir of transmission. We hypothesized that VL patients co-infected with Human Immunodeficiency Virus (HIV) may also be important reservoirs of sustained leishmania transmission. In this study, we found that the presence of VL-HIV and PKDL patients are both associated with a twofold increase incidence of VL at village level, suggesting they are equally important reservoirs for leishmania transmission. Our paper suggests that VL-HIV patients pose a threat equivalent to PKDL patients towards the VL elimination initiative and that therefore they should receive a similar focus.