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Researchers have long known that the Nile tilapia feeds on mosquito larvae, but the study was the first to test its potential to fight the disease in the field, said Francois Omlin, a researcher at the International Centre of Insect Physiology and Ecology in Nairobi.
"A fish in the field may act differently than a fish in an aquarium and it was important to test how effective it could be," said Omlin, who led the study.
"The tilapia species was never tested in the field for its ability to eat mosquito larvae."
Malaria primary killer in Africa
Malaria, caused by a parasite carried by mosquitoes, kills more than 1 million people a year worldwide and makes 300 million seriously ill. Ninety percent of deaths are in sub-Saharan Africa, and young children are mostly affected.
The disease has become resistant to some drugs and work on a vaccine has been slow. Bed nets, insecticides and anti-malarial drugs are effective ways to combat malaria and this study represented another potential protection, the researchers said.
The team, which published the findings in the BioMed Central journal on Thursday, chose the tilapia because it was native to Kenya and had a reputation as a mosquito eater, Omlin said.
Introduction of fish leads to less mosquitos
In the study, the team cleared three ponds of fish and vegetation in the highlands of Western Kenya and measured the mosquito population before introducing young tilapia.
Ten days later, no malaria mosquito larvae were recorded, compared with a similar pond with no tilapia, and 41 weeks after the fish were introduced, the number of mosquitoes fell by more than 94 percent, Omlin said.
The problem, however, was that many fish ponds in the country were poorly maintained or lacked fish, which made the stagnant pools of water prime breeding ground for mosquitoes and raised the risk of malaria, Omlin said. - (Michael Kahn, ReutersHealth, August 2007)
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