A Comparative Assessment of Visceral Leishmaniasis Burden in Two Eco-epidemiologically Different Countries, India and Sudan

The two hyper–endemic regions for Visceral Leishmaniasis (VL) in the world are located in India and Sudan. These two countries account for more than half of the world’s VL burden. The regional risk factors associated with VL vary drastically per region. A mathematical model of VL transmission dynamics is introduced and parametrized to quantify risk of VL infection in India and Sudan via a careful analysis of VL prevalence level and the control reproductive number,, a metric often used to characterize the degree of endemicity. Parameters, associated with VL-epidemiology for India and Sudan, are estimated using data from health departmental reports, clinical trials, field studies, and surveys in order to assess potential differences between the hyper–endemic regions of India and Sudan. The estimated value of reproduction number for India is found to be 60% higher than that of Sudan (and). It is observed that theis most sensitive to the average biting rate and vector-human transmission rates irrespective of regional differences. The treatment rate is found to be the most sensitive parameter to VL prevalence in humans for both India and Sudan. Although the unexplained higher incidence of VL in India needs to be carefully monitored during long-term empirical follow-up, the risk factors associated with vectors are identified as more critical to dynamics of VL than factors related to humans through this modeling study.Author SummaryThe Visceral Leishmaniasis (VL) is a neglected tropical disease, primarily endemic in five countries, with India and Sudan having the highest burden. The risk factors associated with VL are either unknown in some regions or vary drastically among empirical studies. In this study, we collect VL-related data from multiple sources for the two different countries, India and Sudan, and use techniques from mathematical modeling to understand factors that may be critical in the spread and control of VL. The results suggest that the risk factors associated with disease progression are important in explaining high VL prevalence in both the countries. However, the likelihood of disease outbreak in India is much higher than that in Sudan and the probability of transmission between human and sandfly populations vary significantly between the two. The results have implications towards VL elimination and may require a review of current control priorities.