Multiple host feeding in field populations of Anopheles culicifacies and An. subpictus in Sri Lanka

A histological technique was used to detect the multiple blood-feeding of f emale mosquitoes, within the same gonotrophic cycle, in field populations o f the malaria vectors Anopheles culicifacies and An.subpictus (Diptera: Cul icidae) at a village in the low country of Sri Lanka, during 1994-96. Among 3306 An. culicifacies and 871 An.subpictus engorged females examined, resp ectively, 34.4% and 30.4% were multiple-fed. In these two species, double m eals accounted for 92.7% and 89.5%, and triple meals for 7.3% and 10.5% of multiple meals, respectively. More females of An. culicifacies (53.7%) than An. subpictus (44.5%) multiple-fed on different nights. Multiple feeding r ates in the two species were independent of sample size and field abundance . In An.culicifacies, but not An.subpictus, these rates were proportional t o ambient temperature but not to humidity. Bloodmeal ELISA showed that 8.3% of 242 An.culicifacies were human-fed and 80% of these (i.e. 6.6%) were co ncurrently bovid-fed. Combining the histological and ELISA data, it was est imated that multiple feeding involving a human host had occurred in 7.2% of the blood-feeding An.cullicifacies population at this study site. Only 1.2 % of 406 An. subpictus were human-fed and all of these were concurrently bo vid-fed. Multiple bloodfeeding within the same gonotrophic cycle was attrib uted to a local 'frequent feeding strategy' in these primarily zoophagic an d endophilic malaria vectors. Unfortunately this strategy enhances their hu man-biting rate and hence their vectorial capacity.