Progress towards understanding the ecology and epidemiology of malaria in the western Kenya highlands: Opportunities and challenges for control under climate change risk

Abstract

Following severe malaria epidemics in the western Kenya highlands after the late 1980s it became imperative to undertake eco-epidemiological assessments of the disease and determine its drivers, spatial-temporal distribution and control strategies. Extensive research has indicated that the major biophysical drivers of the disease are climate change and variability, terrain, topography, hydrology and immunity. Vector distribution is focalized at valley bottoms and abundance is closely related with drainage efficiency, habitat availability, stability and productivity of the ecosystems. Early epidemic prediction models have been developed and they can be used to assess climate risks that warrant extra interventions with a lead time of 2–4 months. Targeted integrated vector management strategies can significantly reduce the cost on the indoor residual spraying by targeting the foci of transmission in transmission hotspots. Malaria control in the highlands has reduced vector population by 90%, infections by 50–90% in humans and in some cases transmission has been interrupted. Insecticide resistance is increasing and as transmission decreases so will immunity. Active surveillance will be required to monitor and contain emerging threats. More studies on eco-stratification of the disease, based on its major drivers, are required so that interventions are tailored for specific ecosystems. New and innovative control interventions such as house modification with a one-application strategy may reduce the threat from insecticide resistance and low compliance associated with the use of ITNs.

Hydrological and geomorphological controls of malaria transmission

“…Dobson, 1989;Staedke et al, 2003;Ernst et al, 2009). In the western Kenya highlands, anopheline larval habitats are generally restricted to the valley bottoms, especially during the dry season (Minakawa et al, 2005b;Mushinzimana et al, 2006;Githeko et al, 2012). Githeko et al (2006) classified study villages as 'valley-bottom', 'mid-hill' and 'hill-top' and found that vector density, EIR and malaria prevalence all decreased upslope.…”

Early biting of the Anopheles gambiae s.s. and its challenges to vector control using insecticide treated nets in western Kenya highlands

“…Whereas malaria transmission declined significantly it continued to occur at an unacceptable level with the A. arabiensis predominating transmission. Similarly, the proportion of A. arabiensis in western Kenya highlands has been increasing from nil to about 20% since 2005 (Githeko et al, 2012).…”

Spatial modelling of malaria risk factors in Ruhuha sector in the east of Rwanda

“…The increase of malaria with household size is realistic in the study area because if a household contains many individuals, when one of them is infected, he could serve as a reservoir for other (Mboera et al, 2014;Nagasaki University, 2007;Ngom & Siegmund, 2010). In general, more people in the study area are low income population and large families with bad quality houses and are therefore prone to malaria (Githeko et al, 2012;Nagasaki University, 2007).…”