Via Vanguard, an interview with Dr. Sam Awolola, head of the Department of Public Health in the Nigerian Institute of Medical Research: Malaria control under threat from insecticide resistance – Sam Awolola. Excerpt:
Awolola noted that their research in the last 10 years has shown clearly that there is a lot of resistance to public health insecticides used for malaria vector control in Nigeria. Due to continuous use of the four classes of chemical insecticides (pyrethroids, carbamates, organophosphates and organochlorines), the mosquitoes were subjected to a lot of pressure and over the years, they adapted to the environment so well that they have now become resistant to the insecticides.
“Mosquitoes react to an insecticide in two main ways: One is by trying to metabolise (decay) it using some chemical enzymes so that it becomes non-toxic. Another way is mutation. The mosquito gets in touch with the insecticide through its integument (legs, wings), it then changes the configuration of the gene that recognises the insecticide so that the site of recognition of the mosquito changes and the insecticide becomes ineffective.
"For the insecticide to be effective, the site of recognition with the mosquito must be identical. So immediately the mosquito changes the site of recognition, the whole system changes and the mosquito is able to survive. If that happens, the mosquito has mutated because genes are involved.
"The gene is a heritable material which means that the next generation of mosquitoes will be resistant to the insecticide because it has passed the gene to them and that gene will continue in that population. We, therefore, have an insecticide-resistant gene in the population and the next set of mosquitoes from that line, whether they have been exposed before or not, will be resistant to insecticides.
"You know that 350 mosquitoes can come out from one set of eggs. So if out of the 350, 100 survive and have a blood meal and are able to lay eggs, they will go on to produce another 350 mosquitoes each, and there will be an exponential increment in the number of mosquitoes that will be resistant in that population. That is how resistance spreads."
Way forward:
Dr. Awolola advised that all interventions must be evidence-based for them to be effective. “This means that before the intervention, you must have sufficient evidence to show that it will work. You must have collected some baseline information prior to the intervention, but unfortunately, that is not done inNigeria. But things have started changing at the national level because people have seen that you can spend millions of naira and it goes down the drain if you don’t do these things.
"We want to scale up our intervention, to have an ambitious coverage. So if you don’t get these fundamental bases of malaria control, then you are running your programme on a faulty start and you will end up having faulty results and faulty intervention and then malaria continues to stay with us.
“With insecticide resistance, we are in for it unless we put our house in order to ensure that our interventions are evidence-based.”
