Molecular surveillance leads to the first detection of Anopheles stephensi in Kenya

Abstract

Anopheles stephensi is an invasive malaria vector that is endemic to south Asia and the Arabian Peninsula. It was recently reported in the Horn of Africa countries including Djibouti (2012), Ethiopia, Sudan (2019), Somalia (2019) and most recently Nigeria (2020). This mosquito is a competent vector for both Plasmodium falciparum and P. 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. The World Health Organization (WHO) has called on all countries to scale up surveillance efforts to detect and report invasion by this vector and institute appropriate and effective control mechanisms. In Kenya, the Division for National Malaria Program (DNMP) and its partners have been conducting entomological surveillance in all coastal and northern counties that are suspected to be at risk of An. stephensi invasion as well as in all counties at risk of malaria. These efforts were supported by molecular surveillance of all unidentified Anopheles mosquitoes from other studies conducted by the Kenya Medical Research Institute (KEMRI) to try and identify An. stephensi. In this article, we report the first detection of An. stephensi in two sub counties of Marsabit County, Kenya in December 2022. We used Polymerase Chain Reaction (PCR) as the primary method of identification and confirmed results using morphological keys and sequencing of the ITS2 region. 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.

Identification of two insecticide resistance markers in Ethiopian Anopheles stephensi mosquitoes using a multiplex amplicon sequencing assay

“…Ethiopian samples shared haplotypes with samples of Pakistan origin, as previously reported 53 , but also shared haplotypes with samples from neighbouring countries (Sudan, Djibouti), supporting evidence of the spread of this vector across the Horn of Africa. It is possible that this vector is already present in other regions in Africa, as recently reported in Nigeria and Kenya (year 2020) 54 , 55 . Strengthening the surveillance activities of this species, through large-scale genetic characterisation of this vector, is urgently needed to rapidly implement targeted control strategies.…”

High prevalence and risk of malaria among asymptomatic individuals from villages with high rates of artemisinin partial resistance in Kyerwa district, North-western Tanzania

“…Tanzania faces biological and other threats which may compromise its progress and prospects to eliminate malaria by 2030 [26]. Of the biological threats, Tanzania has reported high prevalence of mosquitoes with resistance to multiple insecticides [10] and it is at high risk of the invasive Anopheles stephensi vectors which have been reported in Kenya and the Horn of Africa [27]. In addition, artemisinin partial resistance has been reported in some parts of Kagera region near the border with Rwanda and these parasites can potentially spread to other regions if not curtailed (Giesbretch D and Ishengoma D, Unpublished data).…”

Malaria prevalence, transmission potential and efficacy of Artemisinin Combination Therapy in the Kenyan Central highlands - a zone previously characterized as malaria free

“…(Eric O. Ochomo, 2023) Globally, there were an estimated 247 million malaria cases in 2021, with 228 million (95%) in the African region according to the World Malaria Report, 2022. Malaria claimed the lives of over 619,000 in the same year, mostly in sub-Saharan Africa with children below the age of 5 years being especially vulnerable to the disease (WHO, 2022).…”