By Sylvia Chebet
A deadly mosquito species that transmits two parasites has been found in two northern Kenya counties bordering Ethiopia,
The Centers for Disease Control (CDC) is concerned that it could spread even further, having been found in Turkana County's Lodwar town, which is on a major land transport corridor. The species has also been detected in Marsabit county.
At a glance
The species, scientifically known as Anopheles stephensi (An. Stephensi), is capable of transmitting both Plasmodium falciparum and P. vivax malaria parasites.
While Plasmodium falciparum is responsible for more deaths, Plasmodium vivax is the most widespread of all of the malaria species and can cause severe and fatal infections, according to the World Health Organization (WHO).
Unlike other mosquitoes, An. Stephensi thrives in human-made containers and in clean or contaminated water.
Those traits have enabled the species to thrive in more urban settings in addition to their native rural habitats. Poor drainage and waste disposal systems also create conducive larval habitats.
Origins
Originally native to parts of South Asia and the Arabian Peninsula, An. stephensi has been detected, to date, in seven African countries.
The An. stephensi mosquito was first reported in Djibouti in the Horn of Africa in 2012.
Since then, it has been reported in multiple urban and rural settings in Ethiopia and Sudan (2016), Somalia (2019), Nigeria (2020) and Ghana and Kenya (2022). It remains unclear via which route it got to these countries.
WHO has called on African countries to increase surveillance efforts to detect and report this vector and institute control mechanisms.
In Kenya, health authorities have collected both larval and adult mosquito samples for study at the Kenya Medical Research Institute (KEMRI) to understand its arrival.
“The An. stephensi isolated in Kenya matched closely with isolates from India, Iraq, Yemen, Iran and Nigeria, but were more distant from the isolates from Ethiopia,” the Division of National Malaria Program and KEMRI said.
Resistance
The species has been found to be resistant to many of the insecticides used in public health, posing an added challenge to its control, experts say.
While the overall contribution of the species to malaria transmission in Africa is unclear, health experts are concerned that the rapid growth of many African cities, coupled with the invasion and spread of the highly adaptable malaria vector, could undermine the gains made in reducing the burden of the disease.
The detection of An. stephensi in Sub-Saharan Africa, where the burden of malaria is highest, is particularly worrying, WHO said.
In 2021, 95% of global malaria cases and 96% of deaths were found in the WHO African Region. Nearly 80% of all malaria deaths in the region are among children under the age of 5, the global health agency said.
