Uganda (CU)_ Researchers have found that mosquitoes have become immune to certain chemicals that are used to kill them during an indoor residual spray exercise by the Ministry of Health in Northern Uganda. Scientists from Gulu University with assistance from Training Researchers into Vocational Excellence in East Africa (THRIVE) conducted this study. The disclosure was made during the dissemination of research results on the campus of Gulu University on Monday.
The researchers claim that mosquitoes in the Northern area have evolved specific adaptations over time to protect themselves from the impacts of the chemicals used to kill them. Dr Richard Echodu, one of the researchers, said, “We found that the effectiveness of chemical vector control measures using pyrethroid in the north is currently being challenged by the development of insecticide-resistance by all major malaria vector species. If left unchecked, it could lead to a substantial increase in malaria incidence and mortality.”
The study focused on finding anopheles sibling species and their vulnerability to carbamate (bendiocarb), pirimiphos-methyl and pyrethroid insecticides with samples gathered from the Gulu, Kitgum, Agago and Oyam districts and also Moroto and Abim districts of the Karamoja Sub-region where prevalence of malaria is high.
The results revealed that within 24 hours of post-exposure, the mortality rate of mosquito ranged from 98 to 100 percent for bendiocarb and 100 percent for pirimiphos-methyl insecticide. However, the mosquito samples exposed to pyrethroid insecticide had lower mortality rate. The study detected the adult anopheles mosquitoes morphologically and through Polymerase Chain Reaction (PCR) tests. During September and October 2019, to evaluate the susceptibility state of the adult anopheles mosquitos, the standard World Health Organization (WHO) tube test process was used.
The principal researcher, Prof Elizabeth Opiyo, during an interview said that a group of 500 adult female anopheles mosquitos aged between two-five days grown from larval/pupal collections of different breeding sites were subjected to tests to assess their susceptibility. Prof Opiyo said, “In areas where we have seen resistance, definitely we need to rotate and use other different classes of insecticides than the one in use now because the mosquitoes have developed resistance to pyrethroids, it can be bicarbonates or organophosphates.”
