Susceptibility of the Anopheles coustani complex to Plasmodium vivax and Plasmodium falciparum infection in Ethiopia

Abstract Background Insecticide-based vector control interventions along with case management with artemisinin-based combination therapy (ACT) reduced malaria incidence and prevalence worldwide. The current control methods focus on the primary malaria vector, Anopheles gambiae s.l., however, the role of secondary and suspected vectors has been either sidelined or limited. Determining the susceptibility of secondary and suspected vector species to different parasites in time and space is important in malaria control and elimination programs. Thus, this study aimed at assessing the susceptibility of Anopheles gambiea s. l., An. coustani complex and An. pharoensis to Plasmodium vivax and P. falciparum infection in Ethiopia. Methods Larvae of Anopheles were collected from different breeding sites and reared to adult under controlled conditions. The adult female mosquitoes were identified to species as An. gambiea s.l, An. coustani complex and An. pharoensis. The three species were allowed to feed in parallel on the same infected blood with gametocytes drawn from P.vivax and P. falciparum gametocemic patients by Indirect Membrane Feeding Assays (IDMFA). Fed mosquitoes were kept under controlled laboratory conditions. After seven days, all survived mosquitoes were dissected to detect mid-gut oocyst using microscopy and enumeration. Data were analyzed using R statistical software package version 4.2.0. Results Out of a total 5,915 female Anopheles mosquitoes exposed to gametocyte infected blood, 2,106 (35.60%) mosquitoes fed successfully in the 32 independent infection experiments. There was a significant variation in feeding rates among An. gambiae s l, An. pharoensis and An. coustani complex (G = 48.43, p < 0.0001). All the three exposed Anopheles species were susceptible to P. vivax and P. falciparum infection. The proportion of infected mosquitoes following engorgement on an infected blood meal was significantly different among species (G = 6.49, p < 0.05). The median intensity of infection for An. coustani complex, An. gambiae s.l. and An. pharoensis was 1.16, 2.00 and 1.25, respectively. Even though, the proportion of infected mosquitoes significantly differed in intensity of infection, infection rate and mean oocysts among the species, gametocyte density was highly correlated to infection rate and mean oocyst of infection all tests (p < 0.001). Conclusion Anopheles coustani complex were susceptible to both P. vivax and P. falciparum infection. An effective malaria elimination program might include tools that target outdoor vector surveillance and control, which reduce focal malaria transmission.