Malaria fears up as mosquitoes show pesticide resistance

(CBS) Malaria experts are worried in the wake of an ominous new study from Senegal showing that the mosquitoes that spread the deadly disease can develop resistance to insecticide-treated nets.

Researchers studied malaria infections in a village in the West African nation and found that the disease may be rebounding because the insects are becoming resistant to the increasingly resistant to the insecticide deltamethrin.

Despite decades of efforts to beat malaria with insecticides, indoor spraying, bednets, and drugs, the disease kills nearly 800,000 people a year, Reuters reported. Most of the victims are babies and young children in sub-Saharan Africa.

In recent years, the nets have been widely distributed in Africa, and the World Health Organization says that when properly deployed they can cut malaria rates by half, the BBC reported. But will the nets lose their effectiveness if mosquitoes are resistant to the pesticide used to treat them?

To find out, researchers looked at malaria cases in the Senegalese village of Dielmo before and after the bednets were distributed there. During the two years from August 2008 to August 2010 after bednets were distributed, there was a sharp drop in malaria attacks, according to Reuters. But between September and December 2010 - 27 to 30 months after the nets had been given out - malaria attacks in adults and older children rose to even higher levels than before.

The rise in cases seemed to mirror the increasing proportions of malaria-carrying mosquitoes resistant to deltamethrin.

What does it all mean?

"Strategies to address the problem of insecticide resistance and to mitigate its effects must be urgently defined and implemented," concluded the authors of the study, which was published in The Lancet Infectious Diseases.

The CDC has more on malaria.