RESUMO
Introduction: The influence of Wolbachia on mosquito reproduction and vector competence has led to renewed interest in studying the genetic diversity of these bacteria and the phenotypes they induced in mosquito vectors. In this study, we focused on two species of Eretmapodites, namely Eretmapodites quinquevittatus and Eretmapodites subsimplicipes, from three islands in the Comoros archipelago (in the Southwestern Indian Ocean). Methods: Using the COI gene, we examined the mitochondrial genetic diversity of 879 Eretmapodites individuals from 54 sites. Additionally, we investigated the presence and genetic diversity of Wolbachia using the wsp marker and the diversity of five housekeeping genes commonly used for genotyping through Multiple Locus Sequence Typing (MLST). Results and discussion: Overall, Er. quinquevittatus was the most abundant species in the three surveyed islands and both mosquito species occurred in sympatry in most of the investigated sites. We detected a higher mitochondrial genetic diversity in Er. quinquevittatus with 35 reported haplotypes (N = 615 specimens, Hd = 0.481 and π = 0.002) while 13 haplotypes were found in Er. subsimplicipes (N = 205 specimens, Hd = 0.338 and π = 0.001), this difference is likely due to the bias in sampling size between the two species. We report for the first time the presence of Wolbachia in these two Eretmapodites species. The prevalence of Wolbachia infection varied significantly between species, with a low prevalence recorded in Er. quinquevittatus (0.8%, N = 5/627) while infection was close to fixation in Er. subsimplicipes (87.7%, N = 221/252). Both male and female individuals of the two mosquito species appeared to be infected. The analysis of MLST genes revealed the presence of two Wolbachia strains corresponding to two new strain types (STs) within the supergroups A and B, which have been named wEretA and wEretB. These strains were found as mono-infections and are closely related, phylogenetically, to Wolbachia strains previously reported in Drosophila species. Finally, we demonstrate that maternal transmission of Wolbachia is imperfect in Er. subsimplicipes, which could explain the presence of a minority of uninfected individuals in the field.
RESUMO
Mayotte is a French overseas department and one of the 4 islands of the Comoros archipelago in the Indian Ocean, located between Madagascar and the eastern coast of Africa. Malaria, mainly by Plasmodium falciparum, is endemic to the archipelago and remained a major public health problem until recent years. To control and then eliminate the disease, major strategies have been established in Mayotte since 2001. Preventive measures, diagnostic testing, treatment and disease surveillance were introduced or improved.From 2002 to 2021, 4819 autochthonous cases were reported in Mayotte where the annual incidence decreased from 10.3 per 1,000 population in 2002 (1649 cases) to less than 0.01 per 1,000 population in 2020 (2 cases). The incidence has been below 1 per 1,000 population since 2009. In 2013, WHO classified Mayotte as a territory in malaria elimination phase. In 2021, no locally acquired malaria cases were reported on the island. During this period 2002-2021, 1898 imported cases were observed. They mainly came from the Union of Comoros (85.8%), Madagascar (8.6%) and sub-Saharan Africa (5,6%). Since 2017, the annual number of locally acquired cases was less than 10 and decreased steadily (9 cases in 2017, 5 in 2018, 4 in 2019 and 2 in 2020). The distribution of these rare locally acquired cases both in time and space suggests that they were introduced and not indigenous cases. A study of the genotypic profile of the plasmodial strains of these cases observed from 2017 to 2020 (17 cases analysed out of 20 diagnosed) confirms that these were certainly introduced cases related to imported cases from the neighboring Comoros.Malaria indigenous transmission seems to be eliminated in Mayotte, but the island remains under threat of reintroduction via cases imported from neighbouring countries. It is time to develop a local plan to prevent reintroduction and to implement a proactive policy of regional cooperation in the fight against malaria.