Tiny Predator Has Big Role Curbing Dengue

It looks like no more than a flake of dandruff. But the small, white speck examined by health officials at the National Malaria Center last week could become Cambodia’s secret weapon to fight dengue fever.

Using high-powered microscopes, Kratie provincial health workers identified the white speck as the mesocyclops, a prawn-like predator of the mosquito larvae that carries potentially fatal dengue fever.

Health workers have been breeding the mesocyclops for use in water jars in Kratie province for the past year. Steered by Partners for Development and the Na­tional Center for Parasitology, En­tomology and Malaria Control, local health volunteers have successfully reduced the number of dengue-bearing mosquitoes with the voracious appetite of a one-eyed crustacean.

“Four generations of people have been drinking mesocyclops. When we patented this, people did not have a problem keeping what they had already,” said Dr Peter Ryan, a project technical adviser from Australia’s Queens­land Institute of Medical Re­search.

The program is already a proven success in parts of Viet­nam, which has one of the highest regional rates of dengue infection. In the late 1990s, Australian and Vietnamese scientists re­duced dengue-carrying mosquitoes by 96 percent in 45 villages in Hanoi, completely eliminating them in one, according to the Reu­ters news agency.

Now in Cambodia, the project could play a major role in preventing child deaths, said Dr Duong Socheat, National Malaria Center director. Dengue fever is one of the main killers of children in Cambodia, with 10,000 new child infections and 100 child deaths each year, he said.

Symptoms include a high fever which, in extreme cases, can lead to internal bleeding and rapid death.

Dengue epidemics are most common in urban areas, where a single mosquito can bite and infect a mass of people in a short time. But increased travel is spreading dengue to the prov­inces, raising the likelihood of countryside outbreaks, said Rick Jacobsen, Partners for Develop­ment’s dengue adviser.

In 2003, 11,821 dengue infections and 184 deaths were recorded nationwide, said Dr Ngan Chantha, the National Malaria Center’s National Dengue Pro­gram manager. Last year’s tally covers 51 weeks. In all of 2002, 12,441 cases and 195 deaths were recorded, he said.

A huge dengue outbreak in early 2003 prompted health officials to conduct massive preventative campaigns throughout the year, which could explain the de­cline from 2002, Ngan Chantha said. For the mesocyclops project to effectively reduce dengue, it demands not only the proliferation of the biological agent, but of public commitment as well.

“Without community participation, I don’t think our program can succeed,” Duong Socheat said.

Funded by the Australian gov­ern­­ment, village health volunteers are trained to identify and store mesocyclops in a water container for reproduction. Volun­teers then share the mesocyclops with neighbors, spreading the mosquito larvae-killers throughout the community.

So far, the results have been promising. Last February, a natural presence of mesocyclops was observed in 35 percent of main water containers in 100 households in Kanchor commune, Chhlong district.

After just seven months of the breeding project, mesocyclops were found in about 74 percent of the households’ containers, ac­cording to the project’s 2003 annual report.

In June 2003, 12,647 of the dengue-carrying mosquito larvae were identified in the containers. In September, just 5,379 larvae could be found.

Once the project is in full swing, Partners for De­velopment estimates that 1,300 households in the pilot area will be protected from dengue.

The task now is to convince village health volunteers to share their knowledge.

“Sometimes when we teach the mother, she doesn’t tell her daughter,” said Khieu Sopha, a Kratie provincial ma­laria control program staff. “So when we tell the mother not to clean the water, and she doesn’t tell the daughter, the water is emptied and the mesocyclops are lost.”

Khieu Sopha has worked on the mesocyclops program since its start, but he said he does not know how long Kratie can sustain the project.

“It depends mostly on volunteers, but they are poor,” he said. “So they are less effective be­cause they need some pay.”

 

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