Anopheles Stephensi expanding its geographic range over the last decade; may derail Kenya's progress against malaria control
A deadly malaria vector from Asia has been detected in Kenya, raising alarms. Kenya is now the sixth and latest country in Africa to report an invasion of the deadly malaria species.
Transmitter Anopheles Stephensi was detected in the drylands of northern Kenya during routine mosquito surveillance, Kenya Medical Research Institute (KEMRI) acting Director General Samuel Kariuki recently announced in a press statement.
“Kemri and the Health Ministry have put in place efforts in research activities in Laimsamis and Saku sub-counties of Marsabit County, where the Anopheles Stephensi vector samples were first detected,” read a report by KEMRI.
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The discovery is likely to stifle Kenya’s massive progress in the fight against malaria, due to the species’ strong adaptive qualities, according to KEMRI researchers.
Anopheles Stephensi originated in Southeast Asia, West Asia and the Arabian Peninsula. The species has been expanding its geographic range over the last decade, with detections in Africa first reported in Djibouti (2012), Ethiopia and Sudan (2016), Somalia (2019), and Nigeria (2020), according to KEMRI.
The deadly vector could also be silently wreaking havoc and killing people in other arid African jurisdictions, especially those with low or zero surveillance, the release by KEMRI said.
“There is a risk of Anopheles Stephensi spreading further south and west from its original foci of detection in the Horn of Africa region, as has been observed in Nigeria in West Africa in 2020,” the KEMRI statement said.
There is scanty information regarding how the vector expanded its geographic range. But scientists are calling for expanded investigations, especially in countries serviced by the Indian Ocean trade routes, to establish the full extent and future trajectories of the problem.
The species is reported to spread faster in different climatic conditions, especially in countries experiencing rapid urban development through devolution, like Kenya, with spiralling population growth rates in towns and concentration of malaria control programmes in rural areas.
It also poses a significant threat because, unlike other main malaria-causing mosquito vectors that primarily breed in rural areas, Anopheles Stephensi is highly adaptive and can thrive in urban environments.
“Our surveillance studies indicate the new vector, unlike the traditional malaria-causing mosquitoes, Anopheles Gambie and Anopheles Funfest, is not only invasive. It can spread quickly to new areas and adapt to different climatic and environmental conditions,” KEMRI said.
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In 2019, the World Health Organization issued a threat notice, warning public health authorities about the deadly vector in the Horn of Africa. Though issued seven years after the first reported case in Africa in Djibouti, this warning was critical in addressing the threat, but only for some time.
Besides countries like Kenya, where malaria control has made some significant progress, little has been going on in most African countries. Challenges such as insecticide resistance, antimalarial drugs resistance, sociocultural hindrances and surges in imported cases have contributed significantly to the upsurge in infections.
Following the discovery of Anopheles Stephensi in Kenya and previously in other select countries across the Horn of Africa, there are serious concerns that the species may already be present in, or is spreading to, western and southern parts of Africa.
Besides KEMRI projections, other geostatistical models have predicted that the species will likely spread to many other African countries, putting at least 126 million people at risk for malaria.
“More recent surveys in Sudan have confirmed extensive geographical spread of the vector, including observations in districts bordering six other countries without any prior evidence of the species,” read a report in the Malaria Journal.
The discovery is happening against Kenya’s significant progress in reducing malaria incidences, with prevalence rates dropping from eight per cent to five per cent in the last five years, according to the latest Kenya Malaria indicator survey. An estimated 3.5 million new malaria cases and 10,700 deaths are reported across Kenya annually.
Africa requires a more integrated response to the vector because most countries lack the capacity and resources for effective entomological assessments, including understanding insecticide resistance, the Malaria Journal report said.
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Africa accounts for at least 95 per cent of all malaria cases world over and 96 per cent of deaths, according to WHO. African children bear the brunt of the disease, with an estimated 80 per cent of all malaria deaths.
Increasing collaborations, improving data and information exchange, strengthening surveillance, developing guidance and prioritising research are needed to stop the spread of the vector, said Damaris Matoke-Muhia, research scientist at KEMRI and Programme Manager at Pan Africa Mosquito Control Association (PAMCA).
Besides campaigns to ensure citizens sleep under treated mosquito nets, Kenya is administering malaria vaccine piloted in the country alongside Malawi and Ghana, among other measures to fight the killer disease.
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Anopheles Stephensi is reported to spread faster in different climatic conditions due to its strong adaptive qualities. Photo: iStock.png)
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