Monitor spread of new mosquito, Kenya advised

Kenya has been urged to increase surveillance of the new, invasive mosquito was found in Marsabit last year.

The mosquito, Anopheles stephensi, is native to the Middle East and South Asia and transmits the two malaria parasites that pose the greatest risk of severe illness and death: Plasmodium falciparum and Plasmodium vivax.

The World Health Organization said the country must increase surveillance in urban areas, where this mosquito poses the greatest threat.

Where this mosquito has been reported in Africa, it has been found to be resistant to many of the insecticides used in public health, posing an added challenge to its control.

“The invasion of An. stephensi in subSaharan Africa — where the burden of malaria is highest and over 40 per cent of the population lives in urban environments — is particularly worrying,” the WHO said in its new initiative to stop the spread of stephensi in Africa.

It said that while the overall contribution of this mosquito to malaria transmission in the region is unclear.

The new initiative aims to increase the collaboration of malaria control programmes in the region and strengthen surveillance to determine the extent of Stephensi’s spread and its role in transmission.

“Where feasible, integration with efforts to control other vector-borne diseases should be explored, as for example in the area of breeding site surveillance in urban and in peri-urban areas,” the WHO said.

Medical entomologist Eunice Owino noted Kenya’s malaria transmission is mainly driven by Anopheles gambie and Anopheles funestus, which do not cope very well with polluted water in urban centres.

Stephensi, on the other hand, can breed in jerrycans, tyres, open tanks, sewers, overhead tanks, underground tanks and polluted environments. It is also invasive, which means it spreads very fast to new areas and can adapt even to cold environments.

Traditional malaria vectors can’t breed in small containers or in water with organic pollution.

“If Anopheles stephensi were to spread in a city like Nairobi, the consequences would be serious,” says Owino, in her article published by the 'Conversation' journal.

Until now, cities such as Nairobi have little or no malaria transmission and their populations may not have acquired immunity against malaria.

Owino, who is from the School of Biological Sciences, University of Nairobi, noted urban development would no longer be assumed to contribute to malaria elimination.

“Urbanisation has added to many health problems. But it has tended to “build out” malaria through better housing and gradual pollution of the landscape,” she said.

According to the Ministry of Health, malaria caused an estimated 4.4 million cases and 12,000 deaths in 2019.

“Despite the progress made, malaria remains a significant health burden in Kenya,” Health CS Susan Nakhumicha said on Tuesday in Nyamira during the World Malaria day event.

She noted the emergence of stephensi threatens increased risk of malaria transmission to urban populations. “Additionally, a reduction in malaria funding and threats of resistance to medicines and insecticides also pose challenges,” she said.

Nakhumicha said the government has distributed more than 16 million mosquito nets, carried out indoor residue spraying of mosquitoes, and ensured that anti-malaria drugs are available in all public health facilities.

Dr Abdourahmane Diallo, WHO Kenya representative, called for the expansion of evidence-based interventions, decentralisation of programmes to the county and community levels, and incorporation of human rights and gender equity.

“To address these challenges, the WHO calls for increased investments in domestic financing, multi-sectoral collaborations, and community engagement and participation,” he said.

(Edited by V. Graham)