Secondary malaria vectors of Sub-saharan Africa: threat to malaria elimination on the continent

Secondary vectors of malaria include those anopheline species that are known to play
minor part in malaria transmission. Primary vectors of malaria in Africa are Anopheles
gambiae s.s, Anopheles coluzzii, Anopheles arabiensis, Anopheles funestus, Anopheles moucheti
and Anopheles nili, while Anopheles rivolorum, Anopheles pharoensis, Anopheles ziemanni,
among others are secondary vectors. They are recognized for their importance in
malaria transmission, as they may help to augment or extend the malaria transmission
period and potentially sustain malaria transmission after the main indoor resting and
indoor biting vectors have been reduced by vector control measures such as indoor
residual spraying or Long-lasting insecticidal nets (LLINs). Thus, the terminology
“secondary” versus “primary” vector is fluid and forged by ecological conditions and
malaria control strategies. Most secondary vectors are outdoor resting and outdoor
biting are thus, not taken care of in the current control methods. High use of insecticides
for vector control in Africa, climate change, unprecedented land use changes in Africa
are some of the factors that could influence the conversion of secondary vectors to
become main vectors in Africa. This chapter examines the role of secondary vectors in
malaria transmission and the possibility of them becoming main vectors in future.