Updated 08 October 2013

Malaria mosquitoes develop resistance to insecticides

Malaria deaths in Africa could increase as a result of mosquitoes' growing resistance to insecticides.


Malaria deaths in Africa could increase as a result of mosquitoes' growing resistance to insecticides, an expert said on Monday.

"Resistance is increasing all across the continent," Prof Hilary Ranson, of the Liverpool School of Tropical Medicine, said in Durban

Even with the use of mosquito nets and the range of insecticides available, malaria deaths were expected to increase from 639 000 to 644 000 a year.

Mosquitoes had developed resistance to insecticides in the past two decades.

Ranson was speaking at the Sixth Multilateral Initiative on Malaria Pan-African Conference.

She said no new insecticides had been developed since the late 1980s.

Had there been no resistance against the current range of insecticides, malaria-related deaths in Africa would have dropped to 385 000 a year.

The first instances of resistance were reported in 1993, in a few locations in West Africa.

Insecticide resistant

Mosquitoes are classified as insecticide-resistant when less than 90% die from exposure to an insecticide.

Ranson said it was difficult to determine precisely what affect this had on efforts to eliminate the disease because of a lack of data from the continent

She said the number of people in malaria-affected areas of Africa using mosquito nets had increased from 3% at the start of the century (2000) to about 50% in 2010.

This had helped to contain the epidemic.

The homes of about 10% of the population were being regularly sprayed for mosquitoes.

Ranson said that while there had been a growth in insecticides for agricultural purposes, little had been developed for public health purposes.

"We have very few insecticides classes available for public health.

"Pyrethroids were introduced in the late 1970s and 1980s. Since then we have no new classes of chemistry that are available for public health."

Mosquitoes were becoming resistant to the pyrethroid insecticides used on mosquito nets.

She said it would take at least another seven years before new insecticides would be available.

At the conference, it was announced that a consortium the Innovative Vector Control Consortium was developing a trio of new mosquito-fighting chemicals.


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