Sugar host preferences in adult Anopheles coluzzii : dry season plant selection in Burkina Faso

Abstract: Human plasmodian species, transmitted by mosquitoes of the genus Anopheles, are still one of the leading causes of human mortality in Sub-Saharan Africa. To supplement current vector control strategies, more knowledge about mosquito ecology is required. Central to studies is how malaria vectors relate to their blood hosts. Yet, while we know that sugar is fundamental to male survival and indirectly to female fitness, the relationship between sugar and the highly anthropophilic females of the principal vectors An. gambiae s.s. and An. coluzzii is debated. Sugar, acquired from floral nectaries and plant fluids, is important to replenish and maintain somatic energy reserves, is known to extend female longevity and is more readily available for flight. However, recent sugar meals inhibit attraction to blood, and sugar in the crop reduces the intake of blood and thus female fecundity. Nonetheless, studies on sugar source preferences on females of the principal malaria vectors have demonstrated the existence of sugar attraction and feeding. Females of An. gambiae s.l. appear to display polymorphism for blood host preference, which has led to the suggestion that their response to nectar stimuli is similarly genetically based. If so, they might display an intrinsic ranking of host plant based on the local composition of available plants. This study was aimed at testing the discriminative sugar source selection of males and females of An. coluzzii among plant species found during the dry season in South-western Burkina Faso. In the field, data was collected on visits to glue traps containing six common fruit- or flower bearing plant species of the area, by malaria vectors of locally present anopheline species as well as nonmalaria vectors of the Culex genus. The results from the field were used to select plants of two combinations for a four-choice bioassay with adult males and females of An. coluzzii in the laboratory. The results indicate that wild culicine and anopheline mosquitoes display discriminative sugar source preferences, differing between genera. The same preference ranking of sugar hosts was found among An. coluzzii mosquitoes in the laboratory regardless of sex, indicating a preference for Carica papaya and Delonix regia over Mangifera indica and Thevetia neriifolia. Fruit received the most feeding mosquitoes, while preferred plants generally attracted more resting and probing mosquitoes. The study was badly affected by climatic factors, which reduced mosquito activity. Nonetheless, it functioned as a pilot study on which further studies could be based, and was able to decisively demonstrate discriminative sugar source selection among female An. coluzzii in the laboratory.