Background and Objective:
In Senegal seasonal chemoprevention (SMC) is routinely provided to children aged between 3-120 months. During the epidemic season 2018-2019 healthcare workers declared a strike that totally disrupted the SMC services in the regions of Sédhiou and Kolda. The study aimed to investigate the impact of the strike on the malaria epidemic dynamic.

Methods:
Three epidemic seasons (from May to April) were considered, namely pre-strike, strike and post-strike seasons. For each season, monthly numbers of malaria cases occurred in children aged between 3-120 months and 10-day average rainfall data were retrieved from the regional databases. Incidence rates were calculated at regional and district levels and regression analyses using interrupted time series models were performed to evaluate differences in the incidence of malaria among the considered seasons.

Results:
In the strike seasons, only 20 (16%) health centers (out of 124) provided SMC services. During the strike season, a total of 30,522 and 28,129 malaria cases were registered during the pre- and post-strike seasons, respectively, while in the strike season a total of 57,543 cases were observed. The malaria incidence in the strike season was about two times higher than the one registered in the pre-strike season (incidence rate ratio: 1.89, 95% CI 1.56-2.28; p<0.001), this significant increase was observed at regional and sub-district levels. Cumulative seasonal average rainfall was lower in the strike season (Kolda: 906.16 mm, Sédhiou: 971.93 mm) compared to the pre-strike season (Kolda: 978.80 mm, Sédhiou: 1051.66 mm), similar findings were observed at district level.

Conclusion:
Our findings showed that the interruption of the SMC is associated with a significant increase of malaria incidence in children without any significant increase in precipitation. Our findings confirm that SMC is essential to reduce the burden of malaria in children residing in areas of highly seasonal transmission.