Epidemiological Situation from 1970 to 2016

Malaria is endemic in the Comoros archipelago. In Mayotte, transmission is carried out by two vectors: Anopheles gambiae and Anopheles funestus. By the late 1970s, the implementation of an integrated control strategy had significantly reduced the number of cases (below the threshold of 100 cases per year until 1990). This strategy was based on controlling mosquito vectors through indoor residual spraying (IRS) of insecticides and larval habitat treatment, combined with chemoprophylaxis and presumptive treatment of all febrile episodes. The reduction in malaria control efforts in Mayotte between 1990 and 2000, particularly the scaling back of systematic vector control, led to an explosion in the number of cases (more than 1,000 cases per year) and an increase in the number of deaths (10 malaria-related deaths in 2001).

Between 2002 and 2010, the reorganization of malaria control efforts—including the resumption of systematic insecticide spraying and larval control, alongside improvements in diagnosis (introduction of rapid diagnostic tests) and changes to the therapeutic arsenal—led to a reduction in the annual number of cases (to fewer than 1,000 cases). Starting in 2011, the annual number of cases dropped sharply, reaching 25 indigenous cases in 2012. A new vector control strategy was adopted in 2012 with the distribution and installation of deltamethrin-treated mosquito nets (MIILD) throughout the territory of Mayotte. The distribution report indicates that more than 140,000 mosquito nets were distributed or installed in 47,000 households, with an average of 3 ITN per household. The coverage rate was 91.4%.

From 2013 to 2015, only 1 or 2 locally acquired cases per year were reported. At the same time, the number of cases imported from the Comoros also decreased due to programs implemented by the Union of the Comoros’ national malaria control program. According to the WHO, Mayotte officially entered the malaria elimination phase in 2014. Given the efforts undertaken in the Union of the Comoros, elimination across the entire archipelago appeared possible if control efforts were sustained. Nevertheless, a worrying resurgence in the number of indigenous malaria cases was observed in Mayotte in 2016, which continued in 2017 and into early 2018 (Figure 1). Furthermore, a marked increase in the number of malaria cases was reported in 2017 on the island of Grande Comore.