COMPARATIVE SUSCEPTIBILITY OF ANOPHELES STEPHENSI AND ANOPHELES ARABIENSIS COLONIES TO PLASMODIUM FALCIPARUM GAMETOCYTES IN METEHARA, ETHIOPIA

Abstract

The invasive Anopheles stephensi is a newly introduced malaria vectors, while its ability to transmit local Plasmodium falciparum is not well-established.Understanding of the permissiveness of colony An. stephensi to Plasmodium parasites can help infer local malaria epidemiology and determine its relative importance to malaria transmission. Therefore, this study aimed to investigate the relative permissiveness of the An. stephensi and An. arabiensis to the local P. falciparum strains. P. falciparum positive patients with gametocytes attending health centres in Metehara town were asked to donate blood. Then, we conducted a paired membrane feeding assay using the colonies of An. stephensi and An. arabiensis mosquitoes aged 3 to 6 days after being starved for 6-8 hours. In the mosquito midgut, the oocyst development was evaluated at day 10. The 18S qPCR was used to confirm the Plasmodium species and quantify the parasite. RT-qPCR was used to determine the sex ratio of male and female gametocytes on PfMGET and CCP4-based markers, respectively. In 43 paired experiments, 39 patients were P. falciparum mono-infections and four patients were mixed-infections by 18sqPCR. Feeding efficiency was higher in An. arabiensis (media, 85.0%, IQR 80.0 – 89.0) compared to An. stephensi (median, 78.3 %, IQR 73.0- 85.0): P = 0.009). Blood from P. falciparum mono-infected patients, 71% (28/39) were found to be infective for An. stephensi, and 69% (27 out of 39) were infective for An. arabiensis. The infection rates across all experiments were 30.6% (396/1290) for An. arabiensis and 30.7% (387/1259) for An.stephensi with at least one oocyst detected. There was no significance difference in infection rate between An. stephensi and An.arabiensis colonies (P = 0.719). The P. falciparum sporozoite rate was 14.16% in An. stephensi and 10% in An. arabiensis. Our study shows that An. stephensi and An. arabiensis has equivalent permissiveness to local P. falciparum, with comparable oocyst and sporozoite rates, indicating its role as a competent malaria vector.