Fighting Dengue Fever with Bats and Birds

St. Louis, Missouri

As summer approaches, US communities brace for another round of pesticide spraying. Though it is supposedly done to protect us from mosquitoes carrying West Nile Virus (WNV), the spraying actually seems more like military maneuvers designed to persuade the populace to accept chemical warfare as a part of everyday life.

Since the US relies heavily on pesticide poisons and explores genetic engineering to attack mosquitoes carrying WNV, it is fascinating to see a low-tech approach bring even greater success. A program in Vietnam shows that predators can offer an extremely effective technique of mosquito control.

There, researchers and community organizers are teaming up to fight dengue fever, which is carried by the mosquito Aedes aegypti. Globally, the dengue virus claims 50 million infections and over 12,000 deaths per year.

In the February 12, 2005 issue of the Lancet, Brian Kay and Vu Sin Nam describe their two-pronged mosquito control program: (1) distribution of a crustacean predator which feeds on mosquito larvae; and (2) community education and involvement in cleaning up containers of stagnant water.

As in most of the world’s poor communities, rural Vietnamese store water near their homes. This, along with various discarded containers, are favorite breeding spots for mosquitoes which carry dengue fever. The major part of the program was putting a tiny crustacean (the cyclopoid copepod Mesocyclops) into drinking water containers. As every student of Mesocyclops knows, these critters get the mosquito munchies when they spy larvae.

The other part of mosquito control was active involvement of the community. The researchers sought support from the chairperson of each participating commune. They then involved the women’s union, youth union, communal health personnel, teachers and school children. Health collaborators inspected 100 homes monthly for clean-up and distributed the mosquito predators.

The program succeeded in eliminating dengue fever in 32 of 37 communes and drastically reducing it in the other 5. This meant protection for 380,000 Vietnamese. Before the program, dengue fever had been as high as 146 cases per 100,000. Surrounding communes which had not been treated continued to have rates up to 112.8 per 100,000.

The cost of the program was $2 per person per year, including administrative and virological surveillance. But the post-program expansion was estimated to cost less than $0.20 per person.

This expense is small compared to the millions spent in the US to spray pesticides by truck and by air. It may be time for US cities to ask if mosquitoes can be controlled without chemicals. Crustaceans in drinking water may not be the best use of predators in the US; but there are several native species that gobble up mosquitoes.

Unfortunately, sprays kill insects, fish, birds and bats that eat mosquitoes at the same time they kill the mosquitoes themselves. Thus, there is no reason to believe that massive spraying actually reduces incidences of WNV.

It is probably no accident that pesticide spraying was not part of the Vietnamese program. Vietnamese still suffer catastrophic numbers of birth deformities and other illnesses from the defoliant Agent Orange sprayed by the US during its war against Southeast Asia. There is strong chemical similarity between herbicides such as Agent Orange and pesticides used for mosquito control.

In the same issue of the Lancet, Simon Hales and Wilbert von Panhuis comment that such programs may not work in western cultures because “community participation will be more difficult to establish and maintain in societies with a strong culture of individualism.”

This could be true. But since few have the opportunity to vote on spraying, we cannot know for sure. Americans just might prefer to have a bug or two on their greens and community health programs that peek into backyard stagnant water instead of running for asthma inhalers every time the pesticide truck goes by. If they were able to vote on spraying, Americans might well decide to take back their air.

DON FITZ is on the National Committee of the Green Party USA and is editor of Synthesis/Regeneration: A Magazine of Green Social Thought. He can be reached at:










Don Fitz  is on the Editorial Board of Green Social Thought where a version of this article first appeared. He was the 2016 candidate of the Missouri Green Party for Governor. He is author of Cuban Health Care: The Ongoing Revolution. He can be reached at: