Mosquitoes 'disappearing' in some parts of Africa
30th August 2011
Malaria carrying mosquitoes are disappearing from some parts of Africa, but scientists say it's too early to celebrate
Data from countries such as Tanzania, Eritrea, Rwanda, Kenya and Zambia indicate that the number of malaria cases is dropping fast.
Researchers have published a report in the Malaria Journal, saying that declining numbers are not just down to the use of mosquito nets and insecticides, as data has been taken from areas with few controls.
Professor Dan Meyrowitsch from the Department of Health Services Research at the University of Copenhagen said, “For more than ten years we have been collecting and counting the number of mosquitoes in Tanzanian villages. The number in our traps fell from 5,300 in 2004 to just 14 in 2009, and these were from villages without mosquito nets."
One possibility for the reduction in numbers is climate change. Researchers say that patterns of rainfall have been more chaotic in these regions of Tanzania and have often fallen outside the rainy season – disturbing the development of mosquitoes.
Meyrowitsch aded, "It could be partly due to this chaotic rainfall, but personally I don't think it can explain such a dramatic decline in mosquitoes, to the extent we can say that the malaria mosquitoes are almost eradicated in these communities. What we should consider is that there may be a disease among the mosquitoes, a fungi or a virus.”
Without knowing the cause of the decline, scientists have said that it is impossible to tell if, and when, the mosquito population will rebound. There are fears of an epidemic as children no longer have a natural immunity through exposure.
“If the mosquito population starts coming up again, and my own assumption is that it will, it is most likely we will have an epidemic of malaria with a higher level of disease and mortality especially amongst these children who have not been exposed,” said Meyrowitsch.
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