A meta-population model for the transmission of peste des petits ruminants virus in West Africa

Apolloni Andrea, Coste Caroline, Lancelot Renaud, Hammami Pachka, Gilbert Marius, Nicolas Gaëlle, Ciss Mamadou, Amevoin Yves, Ould Elmamy Bezeid, Yahya Barry, Seck Ismaïla. 2017. A meta-population model for the transmission of peste des petits ruminants virus in West Africa. In : Le pastoralisme dans le courant des changements globaux : Défis, enjeux, perspectives. Livre des résumés P2CG 2017 = Pastoralism in the current of global changes: stakes, challenges and prospects. Book of abstracts P2CG 2017. Diao Camara Astou (ed.), Taubourdeau Simon (ed.). ISRA, CIRAD, PPZS. Dakar : PPZS, Résumé, p. 237. Colloque sur le Pastoralisme dans le courant des changements globaux (P2CG 2017), Dakar, Sénégal, 20 Novembre 2017/24 Novembre 2017.

Résumé : Peste des petits ruminants (PPR) is caused by a Morbillivirus (Paramyxoviridae) that infects mostly goats and sheep. Discovered in Ivory Coast in 1942, this disease is now endemic in most African countries and has spread in Asia as far as India and China1. In immunologically naïve small ruminant populations, mortality rate is around 90% among younger animals, whilst it has milder effects on older ones. PPR has a devastating effect on the economies of low-income families. A live attenuated vaccine was developed in the 1980's, providing a life-long immunity after a single injection. The global eradication of PPR is now on the agenda of the Food and Agricultural Organization of the United Nations (FAO) and World Animal Health Organization (OIE) who play a pivotal role as they aim to reach this goal before 2030 ². Mobility of live animals is the most important factors in the diffusion and in maintaining the disease endemic in West Africa. It is a complex phenomenon involving different types of movements: small ruminants' trade among Western Africa countries (http://faostat.fao.org/); transhumance from arid areas of the North to greener areas in the South and sometimes crossing frontiers; religious festivity, like Tabaski during which millions of sheep are slaughtered. With this respect, Senegal and Mauritania have developed a system of animal health certificates to track livestock movements. These data allow researchers to re-construct the mobility network at the country level, and provides hint about animal movements across their borders. To describe PPR diffusion patterns, estimate its infectious burden, and assess the effects of PPR vaccination strategies we have been developing a metapopulation model for PPR in Mauritania and Senegal. We consider a network whose nodes correspond to administrative districts, and whose links represent the animal movements between two of them. The model couples the virus transmission and small ruminant population dynamics occurring at the local (within-district) level, with the virus diffusion due to livestock mobility. The model uses different data sources. The mobility network is built on the data collected by the Mauritanian and Senegalese Veterinarian Services. Small ruminant population dynamics is calibrated on the data from previous follow-up studies implemented in Senegal 3. PPR prevalence and epidemiological data are taken from the VACNADA project (http://au-ibar.org/vacnada). We briefly present the analysis of the different data sources to provide a panoramic view of the situation in West Africa. We then present some of the results of the model, focusing on the conditions that could lead to PPR outbreaks, maintain its endemicity, or stop the epidemics.

Auteurs et affiliations

• Apolloni Andrea, CIRAD-BIOS-UMR ASTRE (FRA) ORCID: 0000-0002-0228-2086
• Coste Caroline, CIRAD-BIOS-UMR ASTRE (FRA)
• Lancelot Renaud, CIRAD-BIOS-UMR ASTRE (FRA)
• Hammami Pachka, CIRAD-BIOS-UMR ASTRE (FRA)
• Gilbert Marius, ULB (BEL)
• Nicolas Gaëlle, ULB (BEL)
• Ciss Mamadou, ISRA (SEN)
• Amevoin Yves, CNERV (MRT)
• Ould Elmamy Bezeid, FAO (SEN)
• Yahya Barry, FAO (SEN)
• Seck Ismaïla, FAO (GHA)

Source : Cirad-Agritrop (https://agritrop.cirad.fr/604574/)

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