Unexpected anthropophagic behaviour in Anopheles quadriannulatus

The strongly anthropophilic behaviour of Anopheles gambiae Giles sensu stricto (Diptera: Culicidae), the most important malaria vector in Africa, has been demonstrated by field and laboratory studies. Other members of the An. gambiae complex express varied degrees of anthropophily. Anopheles quadriannulatus (Theobald) species A and B are more zoophilic members of the complex and hence are considered to be of no medical importance. Olfactometer experiments with An. quadriannulatus species A have demonstrated attraction to both human and cow odour. To extend these olfactometer observations a choice experiment was conducted in an outdoor cage with a human and a calf as baits, using laboratory-reared mosquitoes. Anopheles gambiae s.s. (from Liberia) and two strains of An. quadriannulatus species A (SKUQUA from South Africa, SANGQUA from Zimbabwe), marked with different coloured fluorescent powders for identification purposes, were released simultaneously and given an equal opportunity to feed on either host. The experiment was repeated six times. Bloodmeals were identified using the precipitin technique. Anopheles gambiae s.s. showed highly anthropophagic behaviour, taking 88% of bloodmeals from the human host. In contrast, both strains of An. quadriannulatus fed with equal frequency on the human or the calf; the response to either host was not significantly different. These results confirm the olfactometer findings and demonstrate anthropophagic behaviour not previously recorded in this species. This finding has implications for prospective manipulation of host preference for genetic control purposes.