Vector borne diseases have a major impact on human and animal health, but also on society economy. Due to their transmission routes, zoonotic or not, these diseases are very sensitive to climatic changes. Actors, conditions and processes requested for disease transmission are part of a complex and dynamic system whose behavior, influenced by climate but also by other environmental and socio-economic components, drive potential for pathogen transmission and outbreak occurrence. We illustrate this complexity through two examples, ie Rift Valley and West Nile fevers. Rift Valley fever (RVF) is one of the most important viral zoonoses in Africa. Transmitted by mosquitoes and direct contact, RVF affects both livestock and humans. Due to global changes, RVF also threats Northern Africa and Southern Europe (Chevalier, Pépin et al. 2010). Depending on areas, the influence of climate may differ, ranging from determining to insignificant. In Kenyan regions characterized by large depression areas called " Dambos " and a succession of dry and rainy seasons, RVF outbreaks occur every 5-10 years: a strong correlation was shown between outbreak occurrence and heavy rainfall events that favor both massive hatch and development of Aedes mcintoshi and Culex sp mosquitoes that are the main vectors of RVF in that region. Similarly, the Ferlo area located in Northern Senegal is characterized by a Sahelian climate and temporary ponds (small water bodies that are filled during the rainy season and then dry). But in this region, no correlation between outbreaks and extreme rainfall events has ever been demonstrated. However Soti et al (2012) showed that these outbreaks occurred when the abundance of the two main mosquito vectors in this region, namely, Culex poicilipes and Aedes vexans arabiensis, was higher than average: these abundances are directly linked to specific rainfall rhythms now well described (Soti, Tran et al. 2012). Nevertheless, herd management, herd renewal rates and nomad