At a malaria seminar in Nairobi earlier this week, scientists at the World Health Organization said they believed two species of malaria-transmitting mosquitoes found in Kenya had developed resistance to popular synthetic insecticides, including Permethrin.

Permethrin belongs to a family of insecticides used to treat nets hanging over millions of beds in homes across Kenya.   

The head of malaria control at the Kenyan health ministry, Elizabeth Juma, says there is no evidence to suggest that insecticide-resistant mosquitoes are posing a danger to Kenyans, as suggested in the World Health Organization report.

"The Kenyan Medical Research Institute, which has been very active in western Kenya, has been doing resistance-monitoring on behalf of the ministry for many years.  And so far, they have not reported the mosquitoes, which are of interest to us, being resistant to any of the insecticides, which are used," she said.

Dr. Juma acknowledged that mosquitoes, carrying the genetic markers of being insecticide-resistant, are present in some parts of western Kenya.  But she says in her research, permethrin was just as effective in killing those mosquitoes as other species.

"The truth is, there is a big leap between having the genetic markers and actually showing evidence of resistance," she said.

Dr. Juma urged Kenyans to continue sleeping under treated bed nets, arguing it is still the most effective way to prevent malaria.   
The possible discovery of insecticide-resistant mosquitoes has raised concern among scientists because there are no other alternative insecticides available right now on the market.

The Kenyan government has downplayed the threat, choosing instead to focus on the progress it has made in fighting malaria.  The disease kills tens of thousands of people in Kenya every year and threatens as many as 28 million, or 70 percent of the total population, at any one time.  

Five years ago, the Kenyan government adopted a 10-year plan to reduce malarial infection rates in the country by focusing on improving access to treatment and on prevention.  

In 2005, government clinics began distributing insecticide-treated bed nets in malaria-infested coastal areas of Kenya.  The following year, free anti-malarial drugs were distributed in other parts of the country. They were given along with free bed nets for the two population groups most at risk of infection - pregnant women and children under the age of five.

Kenyan health officials have not released any concrete statistics.  But they say the government's anti-malarial efforts have led to a noticeable decline in hospital visits and deaths attributed to malaria.

But the disease remains one of the biggest killers in Kenya, responsible for as much as one-quarter of all deaths annually.