Module 4: "The Exterminator" by Kirsten Weir

Few Americans ever give much thought to malaria. That wasn’t always so. Malaria once infected— and killed—many people in the United States.

Toward the end of the 19th century, scientists identified the true cause: a single-celled parasite they named Plasmodium.

About the same time, scientists also discovered that mosquitoes act as vectors for the parasite, passing it on when they bite people.

A vector is an organism that spreads disease-causing agents from host to host without harm to itself.

DDT is an insecticide, a chemical that kills insects.

At first, no one worried about the possible effects of the chemical on the environments.

Then in, 1962, an ecologist named Rachel Carson captured the country’s attention with her book, Silent Spring, which detailed the dangers of DDT.

The chemical first built up in the tissues of fish. It then accumulated inside eagles and other birds of prey that ate the fish.

Malaria begins with flulike symptoms: fever, sweating, chills, headaches, muscle aches, and nausea.

The parasites infect and destroy red blood cells, which can lead to severe anemia, a condition in which the concentration of red blood cells is too low to supply enough oxygen to the body’s tissues.

To be most effective, the drugs must be taken before the disease becomes severe.

Such prophylactic, or preventive, medications are also available.

Such prophylactic, or preventive, medications are also available.

Travelers can safely take time for a few weeks or months, but the pills are too toxic for people living in malaria-affected countries to tolerate for long periods of time.

Travelers can safely take time for a few weeks or months, but the pills are too toxic for people living in malaria-affected countries to tolerate for long periods of time.

The new insecticides were also widely used in farming, and the overexposed mosquitoes quickly became resistant to the chemicals.

Billions of Americans were exposed to high amounts of DDT when it was used in agriculture, Bate said, without any harm to human health.

KILLER GENES
Scientists have tried for decades to develop a vaccine to prevent malaria, without success.

Scientists have tried for decades to develop a vaccine to prevent malaria, without success.

Dozens of different species of mosquito carry the parasite inside them, infecting people with their blood-sucking bites.

Still, researchers haven’t given up. Many are looking for solutions in modern biotechnology.

In 2002, scientists sequenced the genomes of the most common malaria parasite, Plasmodium falciparum, and one of its most common carriers, the mosquito Anopheles gambiae.

A genome is the total genetic information in an organism.

Theoretically, scientists could use that genetic knowledge to tinker with the genome of the mosquito to make its immune system kill the parasite.

Theoretically, scientists could use that genetic knowledge to tinker with the genome of the mosquito to make its immune system kill the parasite.

Most scientists now think that eradicating malaria is impossible, given the complicated life cycle of the parasite.

Most scientists now think that eradicating malaria is impossible, given the complicated life cycle of the parasite.