Taking a bite out of malaria: efforts in Mexico and Central America are demonstrating how to fight this debilitating tropical disease without using toxic insecticides.

• Author: Chelala, Cesar

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Malaria is one of the world's most serious diseases in terms of its impact on human health. Although it claims more than a million lives a year--most victims are children--vaccines developed thus far have proven to be ineffective. But a new approach to fighting malaria shows that it can be controlled effectively without using toxic substances. How to treat malaria and how to reduce the number of new cases present two major challenges for public health in the Americas.

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It is not known for certain whether the origins of malaria treatments can be traced to history or legend; both are equally fascinating when it comes to this disease. It is said that in 1638, Francesca de Ribera, the second wife of the viceroy of Peru, came down with malaria in Lima. Her doctor, desperate to cure her, learned that in the city of Canizares, in Ecuador, people native to the area used the bark of a tree they claimed could cure the disease. A packet of the bark was sent to Lima and used to prepare a treatment for the ailing countess, who was cured.

It is also said that Jesuit missionaries in South America who knew about these healing properties had already sent some of the bark to Europe in 1630. What is known for certain is that by 1800, there was a thriving trade in this bark between South America and Europe, where the substance was known as "Jesuits' powder." It was found that different species produced different effects, until an Englishman named Charles Ledger identified a tree of the genus Cinchona as having the highest concentration of quinine. This natural alkaloid was used extensively in Europe to treat malaria until the development, many years later, of a synthetic drug called chloroquine. For centuries, quinine and its derivatives would prove to be one of the most powerful weapons available to fight this terrible disease.

The word malaria comes from medieval Italian: mala aria, or "bad air"--most likely an allusion to the swampy areas that are generally home to carrier mosquitoes. Ancient texts already refer to malaria and its effects. In the fifteenth century, the great Greek physician Hippocrates, known as the Father of Medicine, was among the first to draw a link between the disease and the environment when he noted that many cases of malaria occurred in places with swampy terrain.

In 1880, the French pathologist and parasitologist Charles Louis Alphonse Laveran--who would win the Nobel Prize in Medicine in 1907--became the first to observe malaria parasites in the red blood cells of people who had the disease. The parasite that causes malaria, called Plasmodium, is transmitted through the bite of the female Anopheles mosquito. When a person is bitten, the parasite enters the bloodstream and is lodged in the liver, where it divides rapidly. The parasites begin to attack and feed on red blood cells and multiply quickly, producing new parasites and invading new cells.

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The parasite's life inside the mosquito is a race against time, because the span required for the parasite to...