Peru trekker's mystery bug is new to science|Richard_F||06/11/07 at 13:15:01|richard_f|xx|0||SAN FRANCISCO
Peru trekker's mystery bug is new to science
UCSF researchers identify bacterium as cause of ailment
Sabin Russell, Chronicle Medical Writer

Thursday, June 7, 2007

UCSF researchers have identified a new species of bacteria, similar to the bug that caused trench fever in World War I, in an American tourist who was sickened after a spending three weeks trekking in Peru.

The culprit is a microscopic bacterium resembling a baked bean with a straggly beard. The university scientists have named it Bartonella rochalimae (ro-cha-li-ma-e), after a prominent Brazilian scientist, Henrique da Rocha-Lima, who decades ago identified the bacterium that causes typhus, and named the bacteria that caused trench fever, a painful scourge that immobilized tens of thousands of World War I soldiers.

A team led by Dr. Jane Koehler, an infectious disease specialist at UCSF Medical Center, tracked down the new organism after culturing a blood sample from a 43-year-old woman who came down with a chronic fever two weeks after returning from Peru, her legs covered with bug bites.

Their work is detailed in an article published in today's New England Journal of Medicine.

As unpleasant as the fever was -- a 102-degree fever and a swollen spleen that lasted eight days before she sought medical attention -- the illness responded to antibiotics and she completely recovered.

Researchers quickly zeroed in on a family of microbial pests called Bartonella, different species of which are responsible for a variety of diseases carried by fleas, sandflies or lice. The Peruvian trekker had traveled many places in the country during her 2003 visit, including a section where a bug called Bartonella bacilliformis is carried by sandflies and infects about 10 percent of the human population. It was often blamed for a disease called Oroya fever.

Sure enough, under powerful microscopes, the bearded bug cultured from the trekker looked a lot like it.

But Koehler -- an amiable microbiologist who already had a species of Bartonella named after her -- conducted genetic tests that showed this one to be an entirely different species, never before isolated. "Most doctors would have said, 'She went to Peru, it's bacilliformis.' But with my history of pursuing these things to the molecular level, I couldn't stop,'' she said.

Now, epidemiologists are confronted with the possibility that many cases of Oroya fever diagnosed in Peru had in fact contracted this bug, instead. And although there are no known cases of the new disease in the United States, Koehler's team discovered that the newly named bacteria can be carried by a common flea, raising the possibility that the disease could easily spread in North America.

Or it may already be here.

During the worst years of the AIDS epidemic in San Francisco, Koehler first encountered the Bartonella when HIV infected patients sought treatment for disfiguring purple lesions that doctors initially thought were Kaposi's sarcoma. But these tumors were actually different from that common opportunistic infection that felled thousands of AIDS patients in the early years of the epidemic.

Biopsies found the tumors were caused by rampant blood vessel growth surrounding colonies of two types of Bartonella -- one that was responsible for trench fever during World War I, and another traced to cats.

For nearly 80 years, scientists had been trying to discover the cause of "cat scratch fever," and the AIDS work by Koehler pinpointed it as Bartonella henslae. It causes skin sores, swollen glands and mild fever in most people. Those with compromised immune systems suffer the severe skin tumors.

"We found that the Bartonella cases among HIV patients were just the tip of the iceberg,'' Koehler said. Once thought rare, there are now 24,000 case of cat scratch fever diagnosed in the United States every year.

AIDS patients also were afflicted by Bartonella quintana, the trench fever bacteria carried by body lice. Although no soldiers died of the disease during World War I, it caused such excruciating pain in their legs that they had to be sent back from the front lines.

The bug responsible was originally named Rochalimae quintana -- the genus Rochalimae named after the same Brazilian scientist da Rocha-Lima. It was Koehler's research in the 1992 that led microbiologists to realize that the bug was actually misnamed -- it was from the Bartonella family. The long-dead da Rocha-Lima lost his genus.

So Koehler felt is was only right to name the newest member of the Bartonella family after da Rocha-Lima: poetic justice in the world of science.

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