Cross-border transhumance movements increase the risk of PPR spreading. | The seasonal migrations of herds in search of available forage and water begin just when climate conditions are increasing the risk of contamination. These migrations are an important factor in the spread of the virus towards disease-free regions. In certain West African countries such as Mauritania, transhumance routes stretch over hundreds of kilometres, with movement from the north towards the south in the direction of agro-pastoral areas where there are high concentrations of animals. The borders of neighboring Mali and Senegal are frequently crossed. A study published in February 2014 in the journal, Emerging Infectious Diseases, confirms this and shows the existence of a gradient of increasing seroprevalence from the north to the south of Mauritania related to herd movements.
In Asia, in a country with very different ecological zones such as Nepal, the return of small ruminant herds from mountain pastures before the start of the cold season contributes to increased epizootic outbreaks in sedentary herds in the plains. In other countries of Africa and Asia, recurrent droughts oblige nomad populations to open new transhumance routes, helping to increase the risk of encounters between healthy and sick animals.
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