Modelling of epidemic cycles of visceral leishmaniasis in the Indian subcontinent

An epidemiological dataset of visceral leishmaniasis (VL) will be spatially analysed. Parsimonious models involving established transmission factors, migration and regional differences will be used to try to describe the reported epidemic cycles of VL. VL has been modelled relatively little and the use of stochastic individual-based models (IBMs) with spatial structure and seasonal migration in this project is original. Research context and modelling considerations Visceral leishmaniasis is a neglected tropical disease targeted by WHO for elimination as a public health problem (<1 case/10K people/year) from the Indian subcontinent by the end of the decade—based on strong intergovernmental commitment, better diagnostic tools, enhanced surveillance, scaling-up sandfly control and faster access to medicines [1]. Falling reported cases in Bihar (India) from 25,222 to 7,615 (2011-2014) support this strategy [2], yet under-reporting, presence of asymptomatics [3] and recurring epidemic cycles present major hurdles to elimination.. This project will use an epidemiological dataset from a community study of VL cases from 5118 households in rural villages in Bangladesh between 2007 and 2010 [4]. It will spatially analyse disease progression within households and across the villages. Understanding these dynamics at a village level may help explain the 10-15 year epidemic cycles seen regionally. Published state-to-state commuter movements can provide seasonal human migration parameters for parameterisation of an IBM. No IBMs have yet been developed for VL [5]. Regional asynchonicity of epidemics and differentiated protective immunity could drive VL recurrence events. Developing metapopulation models with sufficiently simple structures that can produce these effects could help to explain the epidemic cycles of VL. Since epidemic cycles may have existed for centuries, the hypothesis is that parsimonious models, which do not account for modern vector control and chemotherapy activities, are still capable of reproducing this cyclical behaviour.