Genes of Most Deadly Malaria Form Decoded

National Geographic News
October 2, 2002
Efforts to treat and prevent malaria, one of the world's most pressing health problems, just got a major boost. Two teams of scientists have decoded all the genes of the parasite and the mosquito associated with the most severe form of the disease.

The achievement gives researchers an important framework for exploring new ways of combating malaria by blocking transmission of the disease at the molecular and cellular levels.

A series of papers published this week in the journal Nature reveal the complete genome sequence of the single-celled malarial parasite Plasmodium falciparum.

At the same time, a team of 123 researchers from nearly a dozen countries has unraveled the genome of the mosquito Anopheles gambiae, the species most often responsible for transmitting malaria to people. Their results are reported this week in Science.

Understanding these two genomes and what functions their individual genes control could lead to the development of new drugs, insecticides, and possibly a vaccine against malaria.

Public Health Threat

The need is acute because of malaria's heavy toll and growing menace.

According to the World Heath Organization (WHO), at least a million people die of malaria each year, and millions more suffer its ill effects. The group most affected is young children in sub-Sahara Africa, where 90 percent of all malaria cases occur.

Public health initiatives years ago essentially wiped out malaria in more temperate regions of the world. The problem has been tougher to tackle in Africa and other tropical and sub-tropical regions, however, because of rapid population growth in the countries most affected and the mosquito's increased resistance to drugs (such as chloriquine) and insecticides (such as DDT) commonly used to fight the disease.

Nature and Science agreed to publish the genome-sequencing results simultaneously because together they represent a milestone in malaria research.

Both journals include additional research papers describing various aspects of the complex process whereby P. falciparum and A. gambiae act in concert to infect humans, with often deadly results [see sidebar].

Richard Holt of Celera Genomics, Inc., in Rockville, Maryland, the lead author of the main paper in Science, said the results of this combined research offer insight into "pathways that are likely to be useful in finding points of intervention for developing new insecticides and transmission-blocking vaccines."

Some of the possible approaches to tackling malaria suggested by the authors include:

• Altering genes to overcome the parasite's resistance to anti-malarial drugs and the mosquito's resistance to certain insecticides.

• Killing mosquitoes via new targets.

• Blocking the manufacture of certain proteins and lipids that the female mosquito needs to aid the development of her eggs.

• Producing vaccines that could block transmission of the disease between the malarial parasite and the mosquito, perhaps by promoting human antibodies that would circulate in the bloodstream and be passed along to a mosquito when it infects someone.

• Altering the chemo-sensory ability of mosquitoes to find human hosts.

• Altering genetic characteristics that make the mosquitoes prime vectors for the disease.

Roll Back Malaria

While advances in areas such as these are important, they alone aren't likely to combat malaria. Public health officials and policymakers say a broad arsenal of weapons—a combination of drug treatment, vaccines, and mosquito control—will be required to significantly reduce transmission.

In 1998, the WHO, the United Nations Development Program, UNICEF, the World Bank, and many government and non-governmental organizations around the world launched a collaborative program called "Roll Back Malaria" to combat the disease and reduce the toll in human lives.

The scientists who released the genomic data this week said they hoped the information could be used to improve control of malaria in the coming decades and possibly make inroads against other mosquito-borne diseases, such as yellow fever and West Nile virus.

"It is our hope that researchers will use the genome sequences to accelerate the search for solutions to diseases affecting the most vulnerable of the world's population," said Malcolm Gardner, a geneticist at the Institute for Genomic Research and lead author of the P. falciparum paper in Nature.

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