A systematic review and meta-analysis of the human blood index of the major African malaria vectors

BACKGROUND The proportion of mosquito blood-meals that are of human origin, referred to as the ‘human blood index’ or HBI, is a key determinant of malaria transmission. We conducted a systematic review of the HBI for the major African malaria vectors. RESULTS Evidence is presented for higher HBI among Anopheles gambiae (M/S forms and An. coluzzii / An. gambiae s.s. are not distinguished for most studies and therefore combined) as well as An. funestus when compared with An. arabiensis (prevalence odds ratio adjusted for collection location [i.e. indoor or outdoor]: 1.62; 95%CI 1.09-2.42; 1.84; 95%CI 1.35-2.52, respectively). This finding is keeping with the entomological literature which describes An. arabiensis to be more zoophagic than the other major African vectors. However, analysis also revealed that HBI was more associated with location of mosquito captures (R 2 =0.29) than with mosquito (sibling) species (R 2 =0.11). CONCLUSIONS Our findings call into question the appropriateness of current methods of assessing host preferences among disease vectors and have important implications for strategizing vector control.