RESISTANCE TO PYRETHROIDS IN MOSQUITOES IN ADO-ODO OTA, OGUN STATE.
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The spread of malaria can be controlled through long-lasting insecticidal nets (LLINs) and indoor
residual spraying (IRS) using pyrethroids. However, the increasing resistance to pyrethroids poses
a significant challenge to effective vector control in Africa. This study assessed mosquito species
composition in Ado Odo Ota, Ogun state, and evaluated the resistance levels to pyrethroids. A 6-
month longitudinal entomological survey was carried out using light trap and larval sampling.
Mosquitoes were collected from various selected towns in Ado Odo Ota, and Anopheles species
were identified through morphological and molecular analyses. The susceptibility status of
Anopheles gambiae sensu lato to permethrin (0.75%) and deltamethrin (0.05%) was assessed using
the World Health Organization insecticide susceptibility test. Additionally, the species were
screened for knockdown (kdr) target site resistance alleles. Five hundred seventy-nine (579) adult
mosquitoes were collected and morphologically identified using Coetzee’s taxonomic keys. Twothirds
(376/579) of the mosquitoes were identified as Culex spp., constituting the most abundant
species in Ado Ota local government. Molecular identification using intentional mismatch primers
confirmed Anopheles coluzzi's presence as the communities' main species. Thirty percent 30%
(22.5 – 37.5) of the Anopheles gambiae mosquitoes were susceptible to permethrin after 24 hours,
while 98% (95.7 -100) of the vectors were susceptible to deltamethrin. Sporozoite detection using
circumsporozoite ELISA showed none (0/40) of the tested blood-fed female Anopheles gambiae
were positive for sporozoites, and the West African and East African knockdown resistance genes
were detected in very high frequencies among the sampled population (L1014F – 64% [0.36 –
0.83], L1014S – 60% [0.30 – 0.77]. This study revealed that Anopheles coluzzi (99%) is the
predominant species in Ado Odo Ota local government area. Deltamethrin is still effective in
several communities; however, the high knockdown resistance of both the east and west alleles
calls for urgent implementation of integrated vector control in Ogun state.
Keywords
QH Natural history, QH301 Biology