Systematic review of sporozoite infection rate of Anopheles mosquitoes in Ethiopia, 2001–2021

Abstract

Abstract Background Adult mosquitoes of the genus Anopheles are important vectors of Plasmodium parasites, causative agents of malaria. The aim of this review was to synthesize the overall and species-specific proportion of Anopheles species infected with sporozoites and their geographical distribution in the last 2 decades (2001–2021). Methods A comprehensive search was conducted using databases (PubMed, Google Scholar, Science Direct, Scopus, African Journals OnLine) and manual Google search between January 1 and February 15, 2022. Original articles describing work conducted in Ethiopia, published in English and reporting infection status, were included in the review. All the required data were extracted using a standardized data extraction form, imported to SPSS-24, and analyzed accordingly. The quality of each original study was assessed using a quality assessment tool adapted from the Joanna Briggs Institute critical appraisal checklist. This study was registered on PROSPERO (International Prospective Register of Systematic Reviews; registration no. CRD42022299078). Results A search for published articles produced a total of 3086 articles, of which 34 met the inclusion criteria. Data on mosquito surveillance revealed that a total of 129,410 anophelines comprising 25 species were captured, of which 48,365 comprising 21 species were tested for sporozoites. Anopheles arabiensis was the dominant species followed by An. pharoensis and An. coustani complex. The overall proportion infected with sporozoites over 21 years was 0.87%. Individual proportions included Anopheles arabiensis (1.09), An. pharoensis (0.79), An. coustani complex (0.13), An. funestus (2.71), An. demeilloni (0.31), An. stephensi (0.70), and An. cinereus (0.73). Plasmodium falciparum sporozoites accounted 79.2% of Plasmodium species. Mixed infection of Plasmodium vivax and P. falciparum was only reported from one An. arabiensis sample. Conclusions Anopheles arebiensis was the dominant malaria vector over the years, with the highest sporozoite infection proportion of 2.85% and an average of 0.90% over the years. Other species contributing to malaria transmission in the area were An. pharoensis, An. coustani complex, An. funestus, An. stephensi, and An. coustani. The emergence of new vector species, in particular An. stephensi, is particularly concerning and should be investigated further. Graphical Abstract