Anopheles arabiensis

Anopheles gambiae is often referred to as the most important malaria vector in Africa. However, growingevidences indicate that A. arabiensis, the sister species of A. gambiae, is increasinglyresponsible for malaria transmission in Africa.  Reports indicate that in areas of high Insecticide Treated Net (ITN) coverage, A. arabiensis is replacingA. gambiae and is becoming thedominant vector species (Lindblade, et al. 2006, Bayoh et al. 2010).  If this phenomenon continues as large-scaleITN programs are rolled out across Africa, A. arabiensis may become the onlymedically relevant vector in many parts of the continent.  Consequently the ecology, vectorialcompetence and population genetics of this somewhat neglected vector merit urgentattention in preparation for future vector control scenarios.

Diversity in host preference and adult resting site behavior in A. arabiensis.

One of the primaryreasons why the global burden of malaria morbidity and mortality isparticularly high in sub-Saharan Africa is that, unlike in other continents,the principal vectors predominantly obtain blood from humans (anthrophilic). This behavior greatly increase contact rates between people andvectors and stabilize malaria transmission (Kiszewski, et al. 2004).  The magnitude ofanthrophily, however, variessubstantially between closely related species of African vectors.  For example, although A. gambiae s.s. and A.arabiensis are morphologically indistinguishable sister species, the former shows a high preference for feeding on humans (Chandler et al. 1976, Beier et al. 1990, Petrarca et al. 1991), whereas A. arabiensis usually prefers cows to people (White 1974, Githeko et al. 1994). Elucidating the existence and magnitude of suchvariation is a crucial first step for prediction of how vector behavior canimpact local malaria risk, and how ‘plastic’ these traits are in response toenvironmental change.

During the period of 2011-2013, we collected host choice data of 1772 A. arabiensis specimens from Tanzania.

 

Figure 1. Host choice of Anopheles arabiensis in Kilombero Valley, Tanzania