Microbes may hold key to malaria control

LAURI KUBUITSILE
Correspondent | Friday August 28, 2009 00:00

They say that when anopheles gambiae mosquitoes have bacteria in their intestines, an immune response is activated that stops them from being infected with plasmodium falciparum, the most deadly species of the micro-organisms that cause malaria. The scientists believe that their research may lead to new ways of controlling malaria that kills a child every 30 seconds.

On the Johns Hopkins' website a senior scientist in the study Professor George Dimopoulos said their research suggests that the microbial flora of mosquito is stimulating immune activity that protects the mosquito from plasmodium infection. 'The same immune factors that are needed to control the mosquitoes' infection from the microbes are also defending against the malaria parasite plasmodium,' he said.

Scientists found that mosquitoes in the wild have a variety of intestinal bacteria with wide ranges of infection.

In the Johns Hopkins study, scientists treated one group of mosquitoes with antibiotics to kill their intestinal bacteria and left the other group untreated. Then both groups were exposed to blood infected with plasmodium falciparum. They found that the group treated with antibiotics was more susceptible to infection with the malaria micro-organism.

It is hoped that if the specific bacterium that causes the immune response can be identified, it can be used to control the spread of malaria. This will be done by purposely infecting mosquitoes in the wild with the intestinal microbes and stopping the malaria cycles.

The Johns Hopkins scientists found during their study that mosquitoes with the intestinal bacteria have a shorter lifespan than those without the bacteria. Plasmodium must enter the mosquito and live for approximately two weeks before the micro-organism is ready to infect humans.  'The fact that these bacteria shorten the mosquito's life span is additional good news,' said Dimopoulos. If the mosquito dies before the plasmodium can develop enough to infect humans, then the malaria cycle would be broken. Malaria is endemic in 90 countries, including northern Botswana, with 300-500 million people contracting the disease annually. One million people die of malaria each year. The most common age of death is four-years-old.