Rat-borne illness found to be inner-city hazard Flulike disease had been considered solely a rural threat

February 01, 1997|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

A flulike illness, transmitted by animal urine and usually regarded as a rural threat, appears to be a common inner-city hazard, according to researchers at the Johns Hopkins School of Hygiene and Public Health.

Writing in the journal Annals of Internal Medicine, the scientists described three severe cases of leptospirosis in Baltimore and found strong evidence that the victims were infected through cuts suffered in rat-infested alleys.

A 1992 Baltimore study that revealed that many inner-city residents have developed antibodies from exposure to the bacteria.

"Leptospirosis may be the most common disease that rats carry and transmit to humans in the United States," the study said. "It's simply under-recognized."

Five cases have been reported in Maryland in the past eight years, said Dr. Diane M. Dwyer, state epidemiologist. Nationally, an average of about 60 cases a year were confirmed by the Centers for Disease Control and Prevention before 1995, when leptospirosis was dropped as a nationally reportable illness.

Leptospirosis typically causes aches, pains and fever that go away on their own. But one in 10 cases includes high fever, jaundice, meningitis (inflammation of the brain lining), acute kidney failure, internal bleeding and, occasionally, death. It is treatable with antibiotics.

Much as typhoid fever was a marker for poor sanitation in the 1920s, leptospirosis is "a marker of our social environment," said Dr. Joseph M. Vinetz, an author of the study. He is a fellow in infectious diseases at Hopkins and a fellow in parasitic diseases at the National Institutes of Health.

Vinetz thinks deteriorating economic conditions in many inner-city neighborhoods are exacerbating health risks.

Another rat-borne illness, caused by a hantavirus identified in Baltimore, is also being studied at Hopkins. Similar viruses in Korea and Finland have been linked to kidney failure in humans.

Dwyer said the Hopkins paper is evidence that "there are people who get exposed and infected who don't come to the attention of a doctor, or not so that they get diagnostic tests."

"I don't think we've got a huge leptospirosis problem," she said, but "clearly one of the things this makes us look at is, 'How good is our surveillance system?' "

Dr. Peter Beilenson, the city health commissioner, said the city might need to broaden its public school health curriculum to include warnings about infection risks. It already tries to teach children how to deprive rats in alleys of the trash they feed on.

"This rat stuff is pretty simple," Beilenson said: Don't put the trash out until just before pickup, use cans and keep them tightly lidded. But residents don't always comply, he said.

Robert E. Dengler, director of housing inspection, couldn't say whether rats have gotten more numerous. The city spends close to $800,000 annually to suppress them. Last year, $400,000 was added from a federal block grant to hire four private exterminators.

The city has ripped up ivy beds downtown that had become rat havens, and it tickets people who allow rats to flourish.

Leptospira interrogans lives and breeds in infected rats, dogs and livestock. The animals "shed" the bacteria in their urine. People get sick when the urine, or urine-contaminated water, reaches the nose, mouth, eyes or wounds.

Cases have been reported in which the was virus spread to people by unvaccinated dogs, Vinetz said. But genetic tests linked the Baltimore cases to rats.

In the tropics, the disease is endemic and kills about a third of victims. U.S. cases mostly involve farmers, veterinarians, and sanitation and sewer workers. Urine in fresh water has sickened campers and swimmers.

In the 1950s, Hopkins doctors traced leptospirosis cases to a Baltimore candy factory. They found that rats had urinated on candy-making tables at night.

But until the most recent study, "nobody was sure you could get it from doing normal stuff," Vinetz said.

There have been hints. A Detroit study 15 years ago found that a third of children tested for leptospirosis had antibodies. In 1992, investigators tested the blood of 1,150 patients at a Baltimore clinic and found the antibody in 185 of them, or 16 percent.

"That's a lot," Vinetz said. But "none of them were diagnosed."

To learn more about urban exposures, Vinetz teamed with Dr. Gregory E. Glass of the Hopkins public health school, Dr. Charles E. Flexner of the Hopkins School of Medicine, Dr. Paul Mueller of the Mayo Clinic and Dr. David C. Kaslow of the NIH.

They identified three people who had sought treatment at Hopkins from 1993 to 1995. The patients complained of severe leg pain and weakness but also had signs of meningitis, internal bleeding, jaundice and kidney failure.

The first was a woman, 23, whose doctors first thought her illness was linked to her drug use and the fact that she was a prostitute. They were "unaware that leptospirosis could develop in urban environments," the study said.

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