From Success to Crisis

Why has dengue reappeared with such a vengeance? A prime factor is rapid, unorganized urbanization and the proliferation of slums throughout many Latin American cities, which has made it difficult for governments to provide adequate water and sanitation services. Stored water and discarded containers are ideal breeding grounds for Aedes aegypti.

Urbanization has also compounded the costs of traditional surveillance and vector control programs, which have been labor-intensive and heavily reliant on the application of chemicals.

"In the past, programs focused largely on the use of insecticides, and the government did just about everything," says Dr. Gary Clark, chief of the U.S. Centers for Disease Control and Prevention (CDC) Dengue Branch. Spearheaded by PAHO, those programs were so successful that more than 20 countries were certified free of Aedes aegypti.

Simple measures such as using mosquito netting can help reduce the incidence of dengue fever.

The resulting mosquito reinfestation has become so widespread, according to Dr. Clark, that it is now greater than it was in the 1930s. In response, during 1996 and 1997 combined, 25 countries with endemic dengue spent just over $1 billion total on Aedes aegypti programs. Yet in a study two years ago, PAHO estimated that to extend their programs to all affected areas, these countries would have to spend US$1.3 billion every year.

The nature of dengue, with its cyclical outbreaks every three to five years, leads government health officials faced with competing health and political demands to react with a crisis mentality to emergency epidemics, while in the long term carrying out sporadic, and generally ineffective, responses in non-outbreak years, sometimes even during non-dengue seasons.

"Interventions to control dengue with vertical [government-led] programs have failed," concludes Dr. Guillermo Gonzalvez, national director of the Dominican Republic's National Center for the Control of Tropical Diseases. Echoing the CDC, PAHO, and other dengue experts, Dr. Gonzalvez contends: "We have to rethink a strategy that hasn't worked. We need more cost-effective interventions that produce less harm to the environment and that can be sustainable by the people."

Dr. Arias agrees. "PAHO advocates social communication with community participation and behavioral changes," he says. "Not just with dengue, but also with tobacco and sexually transmitted diseases such as HIV/AIDS, man's behavior is conducive to the disease. The best way to avoid the disease is to change behavior."

Since mosquitoes breed near houses, says Dr. Arias, any intervention must begin at the household level, to eliminate larvae and eggs so they won't produce adults that can transmit the disease.

Yet shifting "ownership" of dengue control from governments to the people presents a serious challenge. "People still think vector control is the government's business," notes Dr. Gonzalvez.

Discarding empty soft-drink bottles is another way to combat the mosquito that transmits dengue fever.

"If you think you get it from other people, you don't care about the 55-gallon water drum in your backyard," says Dr. Linda Lloyd, a public health consultant who developed a pilot intervention project in Mérida in the mid-1990s with support from the Rockefeller Foundation. "They also didn't understand that the larvae in their water containers became adult mosquitoes, so they did nothing about them."

Dr. Lloyd and others say such experience indicates that the one-size-fits-all, top-down approach of governments must be replaced by lo-cally controlled programs that use knowledge of domestic arrangements for water and waste management to involve individuals, families, and communities in dengue control.

In the Dominican Republic, the challenge was how to make the ubiquitous 55-gallon drums used for water storage less hospitable breeding sites for mosquitoes. Dominican families typically have from three to 11 such drums on their property, and 45 percent of Dominican homes produce Aedes aegypti, primarily in the drums, according to Dr. Gonzalvez.

Following Hurricane Georges in 1998, Dr. Elli Leontsini of the Department of International Health at the Johns Hopkins School of Public Health, and Dr. Julia Rosenbaum, a medical anthropologist with the CHANGE project at the Academy for Educational Development, helped Dominican officials launch a dengue research and intervention program sponsored by the U.S. Agency for International Development, the CDC, and PAHO. Eliminating the drums, or hermetically sealing them, wasn't feasible because residents use water from them so frequently throughout the day: for cooking, washing, showers, and laundry.

Following extensive one-on-one interviewing of residents, "our recommendation ultimately was to improve the cleaning procedure that people were already following, because they are concerned about cleanliness in general, if not about mosquitoes," says Dr. Leontsini.

Because Dominicans were already using chlorine bleach to purify water stored in the drums, Dr. Leontsini and Dr. Rosenbaum recommended they use a sponge to dab the bleach-which kills mosquito eggs-on the walls of empty drums. They were then told to toss more chlorine in the bottom of the drums. If folks didn't feel like emptying each drum at least weekly, they could dab bleach on the walls of the drum just above the water line. "If they do that once a week, eventually all the eggs, new and old, will be killed before they have a chance to hatch," says Dr. Leontsini.

Dr. Lloyd, who has conducted and reviewed related research in Honduras and Mexico, says the evidence is clear that "a dengue program absolutely will not be successful unless you understand how the community views not just dengue, but its environment. It's really an environmental issue. Humans create the breeding sites, and the philosophy of behavioralists is that if we create them, we can control them."

The key is to develop locally appropriate solutions that are readily available and that people will embrace. In Honduras, a technique using a paste made of bleach and detergent was dubbed la untadita (the little dab), says Dr. Leontsini. In the limestone-rich Yucatán, notes Dr. Lloyd, two fistfuls of lime per month are now recommended to treat used tires, another potential breeding ground.

To avoid the old top-down syndrome, dengue programs in the Dominican Republic have tapped neighborhood associations such as sports clubs, religious organizations and housewives' groups to spread their message. Although these groups' primary objectives are not health related, they can still be effective, says Ms. Cheila Valera, a government social worker. "The families and women they visit have shown a lot of enthusiasm because they feel that somebody's truly interested in them and their families' health," says Ms. Valera. "The fact that they are visited by a community member, not someone from outside, has special positive significance for these families."

How volunteers present the message is also critical. Using a social communication strategy called Negotiation of Improved Practices, community volunteers begin each home visit by simply asking how the family takes care of its water drums. "There's no mention of dengue or the threat of disease," says Dr. Leontsini. "They talk about cleanliness in general and improvement of health by better cleaning of the most important resource, water."

Near the end of the visit, the volunteer suggests dabbing bleach as an additional practice. "Can you try complete dabbing? Can you try partial? Can you do it once a week?" the volunteer might ask. A week later, the volunteer makes a return visit to reinforce the behavior. "They give the family a chance to try this new behavior," says Dr. Gonzalvez, "and if they like it, if they think it's good, they'll do it."

In the few Santo Domingo neighborhoods where the program was launched last year, preliminary surveys indicate that the number of infested drums may have declined by 30 percent. As a result, the Dominican Republic intends to evaluate the community intervention program more formally and consider implementing it throughout the island nation.

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