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.
