Three Dangerous Parasites Share Genetic Core

Three single-cell parasites responsible for three diseases -- African trypanosomiasis or sleeping sickness, Chagas disease and leishmaniasis -- share a nearly identical genetic core, according to five related studies published Friday in the journal Science.

Investigators were surprised to find such overlap in the genetic maps of the organisms because they diverged from a common ancestor millions of years ago.

The parasites also produce dissimilar symptoms and are spread by different insects, said Najib El-Sayed, a researcher at the Institute for Genomic Research in Rockville, Md., and lead author of two of the studies.

The gene maps of the three parasites could help scientists pinpoint which of the roughly 6,200 shared genes the parasites need for survival.

The researchers linked dozens of the genes to the production of enzymes not normally found in people -- a key clue in developing drugs that could treat or prevent all three diseases.

Chagas disease, which is spread by “assassin bugs” that hide in the crevices of ramshackle housing, infects about 750,000 Latin Americans annually. It can cause deadly heart or brain damage.

Sleeping sickness, a sometimes-deadly condition named for its disruption of the sleep cycle, is spread by tsetse flies and afflicts 500,000 people in sub-Saharan Africa each year.

Leishmaniasis, which is particularly common in the Middle East, Brazil and Peru, is carried by sand flies. It leads to disfiguring skin sores in about 2 million people annually.

Pharmaceutical companies have not moved aggressively to create drugs for the illnesses, largely because profits tend to be low in developing nations, El-Sayed said.

“But if we can make it far more efficient for them -- one drug for all three -- it becomes far more attractive,” he said.