Phylogeography of foot-and-mouth disease virus serotype O in Ecuador.

Foot-and-mouth disease virus (FMDV) is the causative agent of the most important disease of domestic cattle, foot-and-mouth disease. In Ecuador, FMDV is maintained at an endemic state, with sporadic outbreaks. To unravel the tempo and mode of FMDV spread within the country we conducted a Bayesian phylogeographic analysis using a continuous time Markov chain (CTMC) to model the diffusion of FMDV between Ecuadorian provinces. We implement this framework through Markov chain Monte Carlo available in the BEAST package to study 90 FMDV serotype O isolates from 17 provinces in the period 2002-2010. The Bayesian approach also allowed us to test hypotheses on the mechanisms of viral spread by incorporating environmental and epidemiological data in our prior distributions and perform Bayesian model selection. Our analyses suggest an intense flow of viral strains throughout the country that is possibly coupled to animal movements and ecological factors, since most of inferred viral spread routes were in Coast and Highland regions. Moreover, our results suggest that both short- and long-range spread occur within Ecuador. The province of Esmeraldas, in the border with Colombia and where most animal commerce is done, was found to be the most probable origin of the circulating strains, pointing to a transboundary behavior of FMDV in South America. These findings suggest that uncontrolled animal movements can create a favorable environment for FMDV maintenance and pose a serious threat to control programmes. Also, we show that phylogeographic modeling can be a powerful tool in unraveling the spatial dynamics of viruses and potentially in controlling the spread of these pathogens.