Surveillance and insecticide susceptibility status of Culicine mosquitoes in selected communities utilizing long-lasting insecticidal nets in Kwara state, Nigeria

Abstract

Vector control programs in Nigeria are mostly targeted towards reducing the burden of
malaria with less emphasis placed on other debilitating vector borne diseases such as
dengue, yellow fever and filariasis. This study assessed the indoor resting densities and
insecticide susceptibility status of Culex and Aedes mosquitoes in selected communities
utilizing long-lasting insecticidal nets (LLIN) in Kwara State, Nigeria. Pyrethrum spray
collections of indoor resting Aedes and Culex mosquitoes were conducted in three
communities while adults of both mosquito species reared from larval collections were
exposed to pyrethroid, organochlorine, and carbamate insecticides following WHO
procedure. Results showed that the higher indoor resting densities of Culex
quinquefasciatus (2.5 – 3.4) collected were not significantly (p>0.05) different from the
Aedes aegypti (0.3 – 1.3) in all the communities. Carbamate resistance (≤ 81 % post
exposure mortalities) was observed in both Culex (Ilota and Amoyo) and Aedes
populations (Gaa-Bolorunduro). Aedes in Gaa-Bolorunduro and Ilota were fully
susceptible (100 % mortality) to permethrin and DDT while the Culex population showed
differential susceptibility (64 – 100%) to pyrethroid and organochlorine insecticides
tested. These findings show focal insecticide resistance requiring specific intervention in
each community based on the evidence provided by this study. Pyrethroid resistance
status of the Culex quinquefasciatus in these areas may result in access of the vectors to
net occupants leading to lower LLIN utilization rates among users. Environmental
management strategy in addition to the use of effective insecticide will be most probable
for management of vector borne diseases in these localities.
Keywords: Insecticide resistance, Aedes aegypti, Culex quinquefasciatus, LLIN, Dengue, Lymphatic
Filariasis, Kwara State, Nigeria