Comparative permissiveness of Anopheles stephensi colony mosquito with an Anopheles arabiensis colony to Plasmodium falciparum gametocytes in Metehara, Ethiopia.

BACKGROUND

The establishment of Anopheles stephensi in Africa has raised concerns about its potential role in transmitting local Plasmodium falciparum strains relative to native primary vectors. To address this, we evaluated the permissiveness of a newly established An. stephensi colony in comparison with a laboratory-adapted An. arabiensis colony, the principal malaria vector in Ethiopia, using paired direct membrane feeding assay (DMFA).

METHODS

We recruited 43 patients with microscopy-confirmed P. falciparum gametocytes at Metehara Health Center, central Ethiopia. Fresh venous blood samples were used to assess infectivity by feeding 3-5-day-old female An. stephensi and An. arabiensis colony mosquitoes in paired DMFA; 10 days post-feeding, oocyst development was examined microscopically. Vector permissiveness was determined by the proportion of oocyst-positive mosquitoes and the intensity of midgut oocyst infection.

RESULTS

An. arabiensis exhibited higher feeding efficiency (median 85.0%, interquartile range [IQR] 80-89%) compared with An. stephensi (78.3%, IQR 73-85%; P = 0.008). The proportions of feeds resulting in at least one infected mosquito were comparable between An. stephensi (69.7%, n = 30) and An. arabiensis (67.4%, n = 29; P = 0.94). A strong correlation was observed in infection rates between the two colonies (Spearman's ρ = 0.85; P < 0.001). Median oocyst density was similar for An. stephensi (13.5 per infected mosquito, IQR 3.7-44.5) and An. arabiensis (26.3 per infected mosquito, IQR 10.4-89.3; P = 0.083).

CONCLUSIONS

An. stephensi demonstrated permissiveness comparable to An. arabiensis for P. falciparum strains from symptomatic patients in Ethiopia. With the ongoing expansion of An. stephensi in Africa, further investigations are needed to elucidate its role in malaria transmission within newly invaded ecological settings.