Fun with Science Club®


			Can insecticide resistance lower the number of diseases? Carrie Straight 05.25.01 All over the world people use insecticides to kill mosquitoes. A common reason that people want to get rid of mosquitoes, other than that they are bothersome, is that they can carry diseases like malaria and filariasis. Lymphatic filariasis is a disease that affects over 120 million people worldwide, causing painful swelling of many body parts. One mosquito (Culex quinquefasciatus) is resistant to insecticides. Most people believe that once mosquitoes become resistant to insecticides they become a major problem, because the populations increase and more insects are able to spread diseases. But some researchers recently suggested that the chemicals that were originally sprayed to kill mosquitoes, but which they are now resistant to (meaning the insecticide no longer kills the mosquitoes) nevertheless may kill the parasites in the mosquitoes that cause filariasis. Scientists wanted to know more about the mosquitoes carrying the parasitic worm (Wuchereria bancrofti) that gives people filariasis. The researchers went to houses in Sri Lanka where people were diagnosed with filariasis. They captured female mosquitoes and froze them. They counted the number of parasitic worms in each female and measured the mosquito’s resistance to insecticides. As the mosquitoes became more resistant, the number of parasites in the mosquito dropped. So maybe insecticide resistant mosquitoes aren’t as bad as scientists first thought, because they might be more Wuchereria resistant too.


			McCarroll, L., M. G. Paton, S. H. P. P. Karunaratne, H. T. R. Jayasuryia, K. S. P. Kalpage, and J. Hemingway. 2000. Insecticides and mosquito-borne disease. Nature 407: 961-2.