Climate &Mosquitoes &Vector Control Bill Brieger | 02 Dec 2023 06:29 pm
Changing Vector Behavior, one of the threats to malaria elimination
A new study from Kenya addresses one of the major challenges to malaria elimination. The authors note
changing vector behaviour towards early morning biting has been established. Children are observed to come to school early, as do mosquitoes that have “peak landing between 06:00 and 07:00.” They also found that mosquitoes continue their activity until 11:00. The An. funestus mosquitoes they collected “were either fed or gravid, potentially indicative of multiple bloodmeals within each gonotrophic cycle, and had a sporozoite rate of 2.05%.” this is of particular concern because school aged children are not always prioritized in various malaria control interventions.
In Cambodia researchers found that “20% of collected Anopheles were active during the day, with increased day biting during the dry season.” Ellie Sherrard-Smith and colleagues explain that bednets and indoor residual spray are intended to work best when people are indoors and sleeping. They caution that, “Mosquito bites taken outside of these times contribute to residual transmission which determines the maximum effectiveness of current malaria prevention.” Their review documented that on average 21% of mosquito bites in Africa take place outside bedtime.
A study in Tanzania by Nicodem J Govella et al. noted that the use of insecticide-treated nets for malaria control has been associated with shifts in mosquito vector feeding behaviour including earlier and outdoor biting on humans. They concluded that efforts highlighting the need for control methods that target early and outdoor biting mosquitoes are now required.
In short, various changing factors ranging from climate and mosquito genetics to even the existing interventions like bednets that we use to control the biting of malaria carrying mosquitoes, threaten our ability to eliminate malaria. New vector control measures are urgently needed as is expansion of other interventions like malaria vaccines.