The malaria mosquito is disappearing -- but it is not just good news

The incidence of malaria in many African countries south of the Sahara is falling rapidly. A Danish-Tanzanian research group has discovered that the mosquito carrying the malaria parasite has practically disappeared from villages without organized mosquito control, and the researchers do not know why. There are several hypotheses but without proper data they cannot say whether malaria is being eradicated or whether it is just resting up before returning with renewed vigour.

"Many of our fellow malaria researchers think that the fall in countries such as Tanzania, Eritrea, Rwanda, Kenya and Zambia shows that all the control programmes are working, particularly the use of mosquito nets," says Associate Professor Dan Meyrowitsch from the Department of Health Services Research at the University of Copenhagen, and continues:

"That just isn't the whole story. For more than ten years we have been collecting and counting the number of in Tanzanian villages. The number in our traps fell from 5300 in 2004 to just 14 in 2009, and these were from villages without mosquito nets."

Dan Meyrowitsch explains that the 99 % fall in the malaria mosquito population during the end of the 1990s seems to be connected to a fall in precipitation. This may be due to global climate changes.

"From 2003 to 2009 the volume of precipitation was more stable, but the rain was more chaotic and fell outside the . And this may have disturbed the natural cycle of mosquito development," he says.

"Of course it is great that the number of malaria-related fatalities among children has fallen drastically in the last five or six years, but we need to know why!"

Since the researchers can discount , the question is whether the mosquitoes have succumbed to disease, or communities have been using pesticides, or whether the fall is due to the chaotic new precipitation patterns.

"Unless we find the answer we will not be able to predict when the will come back, and that could rapidly prove critical," Dan Meyrowitsch explains.

Many children and adults have not been exposed to malaria in the last five or six years, and so have lost or failed to develop immunity to the parasite.

When the mosquitoes suddenly come back this may mean dramatic malaria epidemics with many fatalities unless the population and the health authorities are ready for them.

More information: The study "Is the current decline in malaria burden in sub-Saharan Africa due to a decrease in vector population?" is published in Malaria Journal.

Related Stories

New insecticide created for mosquitoes

date Jul 18, 2007

French scientists have developed an effective insecticide-repellent compound that can be used against mosquitoes resistant to current chemicals.

Malaria top killer in Congo

date Apr 30, 2008

Health officials in the Democratic Republic of Congo say malaria is the primary cause of illness and death, despite prevention efforts.

Recommended for you

'Ebola will return', veteran scientist warns

date 1 hour ago

Congolese expert Jean-Jacques Muyembe may be little known to the public, but he has been one of the world's top Ebola investigators since the first epidemic erupted in central Africa in 1976.

Score IDs patients with upper extremity DVT at low risk

date 16 hours ago

(HealthDay)—For patients with upper-extremity deep vein thrombosis (DVT), six easily available factors can be used to create a score that identifies those at low risk of adverse events during the first ...

Combined drug treatment combats kidney disease

date May 29, 2015

A recent discovery by drug researchers whereby coupling specific cell membrane receptors has altered kidney cell function has triggered a re-think of how to treat chronic kidney disease (CKD) more effectively.

Active substance targeting dreaded hospital germs

date May 29, 2015

In the German Center for Infection Research (DZIF), scientists have conducted clinical studies on an active substance against the dreaded hospital pathogen Staphylococcus aureus: a highly effective protein from bacteriophages ...

User comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.