A malaria surveillance study has reported the first detection of anopheles stephensi in Kenya, an invasive species that can spread very fast to new areas with or without the known malaria mosquitoes.
The study was presented at the 4th Kenya national malaria forum held alongside the 13th Kemri annual scientific and health research conference (13th KASH) in Nairobi.
According to Sylvia Milanoi who presented the study, the Anopheles stephensi mosquito exhibits different behavior from the known malaria mosquitoes in Kenya.
It thrives in urban settings, unlike known malaria vectors that are mainly found in rural settings.
“This mosquito is a competent vector for both Plasmodium falciparum and Plasmodium vivax. It is characterized by a high degree of behavioral plasticity and the ability to reproduce in various types of breeding sites including containers and therefore has the potential to propagate malaria transmission in rapidly urbanizing settings with poor drainage and disposal of waste containers,” Milanoi said.
Currently in Kenya malaria is not transmitted by plasmodium vivax.
Anopheles stephensi, is historically considered an Asian malaria vector and has been one of the major drivers of transmission in cities across India, Iran, and Pakistan, as well as the Arabian Peninsula.
An. stephensi prefers outdoor settings to indoor ones, rendering some conventional methods of mosquito control, such as bed nets and household spraying ineffective.
It is also resistant to common insecticides, such as DDT and pyrethroids.
Methodology
The study was done by entomologists led by Eric Ochomo a principal researcher from Kenya medical research Institute (KEMRI)and researchers from the Division for National Malaria Program, Ministry of Health.
Across the twelve counties surveyed, the new mosquito was found in four different surveillance sites in Marsabit county.
A total of 55 Anopheles larvae were collected and 11 died during transit, of the 11 larvae four were identified as Anopheles stephensi.44 were reared to adults and then killed in a containment facility at KEMRI. forty new adults were tested and nine were identified as Anopheles stephensi.
“We used Polymerase Chain Reaction (PCR) as the primary method of identification and confirmed results using morphological keys and sequencing of the ITS2 region,” Milanoi said.
With the detection of this vector in Kenya, there is an urgent need for intensified surveillance to determine its occurrence and distribution and develop tailored approaches towards control to prevent further spread,” the researchers recommended.
An. stephensi was recently reported in the Horn of Africa countries including Djibouti (2012), Ethiopia, Sudan (2019), Somalia (2019) Nigeria (2020) and recently Kenya.
