Investigation of a case of Rift Valley fever through the "One Health" approach, Ziguinchor, Senegal, February 2018

Introduction: the first human case of Rift Valley fever (RVF) has occurred in Ziguinchor. We conducted an investigation to describe this epidemic and to investigate factors contributing to its outbreak. Methods: we conducted a cross-sectional survey from February 12 to February 18, 2018. The study population consisted of the inhabitants by communes at risk of developing RVF in the Ziguinchor region. We diagnosed a case based on symptoms including fever and haemorrhagic syndrome or meningoencephalitis associated with possible contact with sick animals. Laboratory tests confirmed the diagnosis. We adopted the "one Health" approach and carried out interviews. We calculated different parameters (median, proportions). Results: in total 433/2318, (18%) patients met the definition of suspect cases. The median was 32 years, the interquartile range was 29-44 years, and the sex-ratio was 0.7. A confirmed case of RVF was identified and died due to bleeding. Factors favoring RVF were: stagnant water inside the home, no use of long-lasting insecticidal mosquito nets. Out of 150 sera collected from small ruminants, none was positive for anti-RVF M immunoglobulins. Among the 1158 mosquitoes collected, possible vectors of RVF accounted for 96.46% of catches. Conclusion: RVF was detected in a patient who did not sleep under impregnated mosquito nets in an environment characterized by the presence of candidate vectors. The actions carried out (vector control, awareness raising, training) enabled the control of the epidemic.