Emerging malaria in pastoralist communities

Northern Kenya is a prototypical example of the convergence of changing ecosystem and parasite importation. Historically, large swathes of northern Kenya were considered outside of the malaria risk map. These arid and semi-arid regions are unsuitable for cultivation and are populated by nomadic and semi-nomadic peoples. Recently, these groups are creating more settled, permanent communities than ever before and changing the landscape as a result.

In the far north-west of Kenya around Lake Turkana, this increased pattern of settlement and changing lifestyle can be attributed in large part to oil discovery and the influx of people, money, and infrastructure that accompanies resource extraction. Migrants from all regions of Kenya, east Africa, and beyond have become the new nomads of this region; they work with oil companies, non-governmental organizations, and charities and stay for short periods of time. Prior to the establishment of weekly flights, travel was by a long, arduous land route and the number of visitors was relatively few. Now an estimated 30 flights arrive and depart each week. Many of these visitors originate from malaria-endemic areas as flights connect from western and coastal Kenya to Turkana via Nairobi.

Our work in Turkana demonstrated that malaria transmission is startling high — 30% of household members had parasites detected by PCR. Although we were able to identify genetic signatures of malaria importation from visitors and economic migrants, these importation events are not substantially contributing to persistent transmission.

It is not known whether the current levels of infection are a result of increasing transmission or reflect historical levels. However, we were able to show that infection rates are high in both urban and rural communities and do not seem to track with rainfall, suggesting that seasonal pools and streams are not the primary sources of mosquito breeding. Fewer than 30% of households had and mosquito net, and people often sleep outside due to the hot climate.