Temporal lagged relationship between a vegetation index and cutaneous leishmaniasis cases in Colombia: an analysis implementing a distributed lag nonlinear model.

Cutaneous leishmaniasis is a neglected tropical disease with a strong environmental component. The aim of this research was to implement a distributed lag nonlinear model to explore the temporal lagged relationship between a vegetation index and cutaneous leishmaniasis cases. In this ecological study, a time series of weekly cases of cutaneous leishmaniasis reported between 2007 and 2016 in the five municipalities in Colombia with the most cases of the disease and a vegetation index was analyzed. During the study period, a total of 16,321 cases were reported in these five municipalities. Two municipalities showed a lagged nonlinear positive association between the risk of occurrence of new cases and the magnitude of the vegetation index; two municipalities showed a negative association; and in the remaining municipality, the risk was associated with the vegetation index but its confidence interval was not significant. Our results show different patterns and magnitudes of the lagged relationship between the vegetation index and cutaneous leishmaniasis cases and suggest the possibility of using the lag pattern of the vegetation index in the development of an early warning system where a lagged positive relationship is identified.