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Scientists Crack Genetic Code of Exotic Disease

Posted on: Thursday, 24 April 2003, 06:00 CDT

By Randy Dotinga, HealthScoutNews Reporter

HealthScoutNews -- Chinese scientists say they've decoded the genetic makeup of the germ that causes leptospirosis, a pesky and potentially deadly disease that poses a threat to adventurous athletes and travelers.

Better understanding of the exotic disease could lead to more effective drugs and even a vaccine, says Dr. David Freedman, director of the Traveler's Health Clinic at the University of Alabama at Birmingham. Researchers "can also look at the variability between strains to see why some cause worse disease than others," he adds.

Leptospirosis, also known as swamp fever, is spread through bacteria that live in the urine of infected wild and domestic animals. Rats are an especially common carrier, Freedman says.

Humans become infected when they come in contact with the urine either directly or through contaminated water, such as a river or lake. Although most common in regions with poor sanitation, leptospirosis is "a very cosmopolitan bacteria," Freedman says. "It's a problem in just about every country of the world."

No one knows how many people are sickened by leptospirosis. Some researchers estimate the number at more than 100,000 cases annually, but the actual number could be 10 times that, says Ben Adler, a leptospirosis expert and professor of microbiology at Monash University in Victoria, Australia.

Symptoms of the disease, which begin days or weeks after infection, include fever, chills, headache, nausea and vomiting, jaundice, muscle aches and rash. Doctors generally treat the disease with antibiotics, but it can cause serious complications such as liver and kidney disease, meningitis and, occasionally, death, Freedman says.

The disease has made the news in recent years by striking athletes. Three years ago, about half of the 155 athletes in the Eco-Challenge 2000 Expedition Race were sickened during events in Borneo. And in 1998, dozens of athletes fell ill after competing in a triathlon in Illinois. They apparently became sick from swimming in a lake.

"It's increasingly a concern to travelers," Freedman says. "We're seeing more adventure travelers, and it does very well in water and puddles. People who are hiking, biking, trekking or canoeing may be exposed to leptospirosis."

Adding leptospirosis to the growing list of diseases whose genetic makeup is known, researchers at the Shanghai Institutes for Biological Sciences in China decoded the genome of the bacteria, which contains more than 4,500 genes.

They report their findings in the April 24 issue of Nature.

According to the researchers, the genome includes a group of proteins related to blood clotting, which may explain the bleeding problems encountered by some leptospirosis sufferers.

Adler says the new research could help scientists understand how the bacteria causes the disease, a topic that's now a complete mystery. "I hope that knowing all the genes of the bacterial genome will shed light on this," he says.

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On the Net:

CDC information

New York State Health Department

University of Alabama at Birmingham

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