THURSDAY, Aug. 22, 2002 (HealthDayNews) -- The Escherichia coli 0157:H7 that poisoned 51 people, mostly children, at a Pennsylvania petting zoo two years ago was likely caused by contact with calves and young cattle contaminated with the bacteria.
That's the conclusion of a new post-mortem of the outbreak, which helped spur the Centers for Disease Control and Prevention (CDC) to issue new guidelines for proper sanitation at petting farms.
Although no visitor who fell ill during the episode died, the newborn baby of the farm's owners died four days after birth from a mix of infections that included E. coli, officials said at the time. However, the subsequent investigation eliminated the 0157 strain as a culprit in the infant's death.
Petting zoos have long been known, among microbe hunters if not the public, to be infection risks. Children touch animals, pick up germs that live in their feces, and ingest those organisms by bringing their unclean hands to their mouths.
Incidents similar to that in Pennsylvania have been reported in England, Canada and other parts of the United States -- including one in 2000 in Washington that sickened five children, three of whom required hospitalization.
In response to the Pennsylvania and Washington outbreaks, the CDC issued voluntary guidelines for petting zoos. The agency called on farms to locate hand-washing stations close to animal pens, post signs stressing the importance of clean hands in preventing E. coli infection, and take other steps to reduce transmission of the bacteria.
"The single most important thing that people can do to avoid [E. coli] from farm animals is to wash their hands immediately after touching an animal," says Dr. John Crump, a CDC medical epidemiologist and lead author of the latest report.
"We have learned of some farms that have implemented changes," Crump adds, but he notes the agency has no enforcement powers. The analysis of the outbreak appears in tomorrow's issue of The New England Journal of Medicine.
The outbreak, at Merrymead Farms in Montgomery County, Pa., seems to have occurred between September and November. Of the 51 people sickened, 47, or 92 percent, were 10 years old or younger. Their symptoms included bloody diarrhea, fever, vomiting and other signs of gastric infection. None died, although 16 were hospitalized.
Thirty-three, or 15 percent, of the farm's 216 cows were found to be contaminated with E. coli0157:H7. However, none of the 43 other animals at the petting farm tested positive for the germs.
Of the 33 cows with the 0157 strain, 28, or 85 percent, had the same molecular profile as the bugs isolated from patients.
Not surprisingly, investigators learned, the petting zoo's youngest attractions were the source of the disease. "We know from the animal literature that it's the young animals that are most often colonized with E.coli. What we found with the herd at the farm was consistent with that," Crump says.
E. coli poisons roughly 73,000 Americans a year, killing 60. Most contract the infection through tainted food and water.
"You're more likely to come down with a diarrheal illness from a food product then you are from a petting zoo. But if you die from visiting a zoo, you're just as dead," says Philip Tierno Jr., a pathogen expert at New York University Medical Center in New York City.
"Of all of the things that expose children to pathogens, petting zoos are easiest to control," adds Tierno, author of The Secret Life of Germs.
What To Do
To learn more about E. coli, try the CDC or the U.S. Food and Drug Administration.
