'One of the biggest surprises to come out of the genome sequencing projects is that these parasites -- despite major differences in how they are spread and how they cause disease -- nevertheless have a core of 6,200 genes in common.'

Their findings are published in this week's issue of Science.

Knowing the full genetic make-up of the three parasites --Trypanosoma brucei, Trypanosoma cruzi and Leishmania major -- could lead to better ways to treat or prevent the diseases they cause.

"Although relatively unfamiliar in the United States, the collective misery caused by these diseases throughout the world is considerable," says Anthony S. Fauci, MD, director of the National Institute of Allergy and Infectious Diseases (NIAID), which providing funding for the research.

"Having these genomes in hand will give us many new targets for drug and vaccine development," Dr. Fauci added.

Tsetse Fly, Sandfly, 'Kissing Bug'

All three diseases are spread by insects. T. brucei, which causes sleeping sickness, is spread by the tsetse fly and is found in sub-Saharan Africa. The World Health Organization estimates there may be as many as 500,000 cases of sleeping sickness each year. If left untreated, sleeping sickness is fatal.

Various forms of leishmaniasis are spread by the sandfly and are endemic in 88 countries on five continents. Visceral leishmaniasis, also known as kala azar, is the most severe form of the disease and causes high fever, a swollen spleen and severe weight loss before killing its victims.

Cutaneous leishmaniasis, also known as "Baghdad boil," produces numerous skin ulcers that can leave sufferers permanently scarred. Some 1,000 American service members have been diagnosed with cutaneous leishmaniasis according to testimony by Walter Reed Army Institute of Research's Alan Magill, MD, at an Institute of Medicine meeting in May 2005.

T. cruzi causes Chagas disease and is spread through the infected feces of an insect sometimes called the "kissing bug" for its habit of biting near a person's mouth.

Found throughout Central and South America, Chagas disease is particularly prevalent among the poor and claims 50,000 lives each year.

Core Genes in Common

"One of the biggest surprises to come out of the genome sequencing projects is that these parasites -- despite major differences in how they are spread and how they cause disease -- nevertheless have a core of 6,200 genes in common," says Martin John Rogers, PhD, of NIAID’s Parasitology and International Programs Branch.

The similarities among these parasites outweigh their differences, at a genetic level. The shared genes give scientists a vastly expanded array of targets for development of new drugs that conceivably could work against all three parasites, explains Dr. Rogers.

Conversely, analyzing the relatively smaller ways in which the organisms diverge genetically could help researchers design vaccines, drugs and improved diagnostics targeted to each of the three parasites, he adds.

NIAID supported the sequencing projects through grants to Kenneth Stuart, Ph.D., and Peter Myler, Ph.D., of Seattle Biomedical Research Institute (SBRI); to Najib El-Sayed, Ph.D., of The Institute for Genome Research (TIGR), Rockville, MD; and to Bjorn Andersson, Ph.D, of the Karolinska Institute in Stockholm, Sweden.

In addition to NIAID, The Wellcome Trust, London, supported the T. brucei and L. major genome sequencing projects.