High level of resistance in Anopheles arabiensis mosquito to pyrethroid insecticides from low malaria transmission zone of Moroto district, Karamoja region, Uganda: Implication for malaria vector control
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Date
2020
Journal Title
Journal ISSN
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Publisher
Research Square
Abstract
Karamoja region of Uganda previously classified as low malaria transmission zone is currently
experiencing significant upsurge of malaria incidences. Long lasting insecticidal nets (LLINs) impregnated
with pyrethroids constitute a major tool for malaria control in this region. Efficacy of this tool can be
hampered by resistance to the pyrethroids in the Anopheles mosquito vectors. Resistance status of these
mosquitoes in this region is poorly understood, effectively hampering better understanding of the impact of
LLINs in the malaria control initiative. Here, we assessed susceptibility of the Anopheles arabiensis from the
region to deltamethrin, permethrin (pyrethroids) and pirirmiphos-methyl (organophosphate) insecticides.
Method: We collected anopheline mosquito larvae from their natural habitats and reared them to adult
emergence in situ field insectary in Karamoja region. We then identified them morphological to species level
and exposed 513 emerge adult female An gambiae s.l., mosquitoes to diagnostic dosages of deltamethrin
(0.05%), permethrin (0.75%) and pirimiphos-methyl (0.25%) pyrethroids exposure using the standard WHO
insecticide susceptibility test assay. Synergic assays using piperonyl butoxide (PBO) were done to check for
the involvement of detoxification enzymes in pyrethroid resistant populations. We then screened for
knockdown resistance (KDR) and mosquito species diversity using Polymerase Chain Reaction (PCR).
Results: Majority (96%) of the mosquitoes we sampled were identified as An. arabiensis and 4% as An.
gambiae sensu stricto. We observed cross-resistance to both deltamethrin (11.9%) and permethrin (47%) but
susceptibility (100% mortality) to pirimiphos-methyl in An. arabiensis. The pre-exposure to PBO ameliorated
the resistance to both pyrethroids. We detected homozygous KDR -eastern variant in 1.8 and 50% of the An.
arabiensis and An. gambiae s.s. respectively.
Conclusion: Anopheles arabiensis and An. gambiae s.s. are the malaria vector in Karamoja region with An.
arabiensis predominating. Both species are susceptible to pirimiphos-methyl but resistant to both
deltamethrin and permethrin, through a metabolic process (phenotype). Mosquotoes with genetic (kdr)
mutations for resistance were minimal and hence have minimal contribution to the pyrethroid resistance
profile. An. arabiensis can thus be controled in Karamoja region using deltamethrin and/or permethrin
impregnated mosquito nets integrated with PBO and/or through indoor residual spraying of sprayable
human dwellings with pirimiphos-methyl.
Description
Keywords
Insecticide resistance, Deltamethrin, Permethrin, Pirimiphos-methyl, Low malaria transmission zone, Moroto, Karamoja, Uganda
Citation
Echodu, R., Anena, J., Iwiru, T., Mireji, P., Malinga, G. M., Opiyo, E. A., ... & David, O. (2020). High level of resistance in Anopheles arabiensis mosquito to pyrethroid insecticides from low malaria transmission zone of Moroto district, Karamoja region, Uganda: Implication for malaria vector control. https://doi.org/10.21203/rs.3.rs-16734/v2