Plague concerns climb as more animals die
By Jeremy P. Meyer
Denver Post Staff Writer
Article Last Updated: 05/09/2007 12:09:47 AM MDT
Reports of dead squirrels continue to come into a hotline set up by the state health department to track what could be the first plague outbreak in Denver since 1968.
There have been positive plague tests on 15 squirrels and one rabbit in Denver, Jefferson and Arapahoe counties.
Thirteen of the animals were in Denver's City Park area, health officials said.
Between Friday and Monday, nearly 200 calls came into the hotline, reporting dead animals mostly in the City Park neighborhood, said John Pape, the state epidemiologist.
The city of Boulder this week closed Tom Watson Park to test a prairie dog town that has been unusually inactive.
"We're still trying to determine how widespread it is," Pape said.
"I wouldn't apply the term 'outbreak' to this," he said. "We normally see this kind of rodent die-off where plague is occurring, and it just happens to be occurring in Denver this year."
Colorado is one of the few states in the U.S. that harbor the disease, which wiped out an estimated 25 million people in Europe during the Middle Ages.
The plague bacterium is transmitted to people through flea bites and direct contact with infected animals.
It originally spread to the American West from an outbreak in San Francisco's Chinatown in 1900. In four years, plague killed 122 people in California.
In Colorado, the disease was first discovered in San Miguel County in 1941 and on the Front Range in 1943.
An urban plague outbreak among wildlife occurred in Denver in 1968. It was discovered after a 6-year-old girl was found to have caught the plague from squirrels.
The girl survived, and officials later found 47 plague-infected squirrels near her northeast Denver home.
Health officials set up 450 traps with peanut butter lures to catch squirrels and dose them with DDT to kill the fleas.
Every year, about 18 people in the United States die from the plague, according to the federal Center for Disease Control and Prevention.
Worldwide, about 1,000 to 2,000 fatal cases are recorded every year.
Most of the epidemic plague cases are associated with rats, the CDC said.
The last time a person in Colorado died of plague was 2004, when a 66-year-old Pueblo man hunting and skinning rabbits near the Tarryall Reservoir in Park County came down with flulike symptoms associated with the plague.
The man stayed in his trailer for four days before seeking medical attention. By then, it was too late.
Biologists are still confounded about why, where and when plague occurs, said Mike Antolin, a Colorado State University biology professor.
The outbreaks seem driven by the weather, he said.
"The plague is the Goldilocks of pathogenic bacteria," he said. "It doesn't like it too wet or too hot. It likes it right in the middle."
Plague stops at the 100th meridian. It's not found much east of the Kansas border, where rain patterns begin to change, he said.
During drought years in early 2000, plague seemed to have disappeared from Colorado.
It resurfaced again in 2004, when 92 animals in 24 counties tested positive for the disease, according to state records. Last year it was found in 25 Colorado counties.
"We are coming out of a hot, dry period," Antolin said. "It's taking off."
Urban squirrels are generally isolated from the plague because they don't have much interaction with wild animals carrying the disease, he said.
A fox or coyote - species that are generally immune - can carry plague into the city, he said.
Most cases of human infection come from a flea bite, but 20 percent of cases came from contact with an infected cat, according to a CDC study.
Last year, veterinarians diagnosed 23 plague-infected cats. Cats are highly susceptible to plague and are usually infected by eating rodents.
State health officials are warning people to not feed squirrels, not to let their pets catch or eat squirrels and to treat their pets for fleas if they have had contact with dead animals.
Denver Zoo officials say they are closely watching the animals for signs of sickness and are making sure the animals won't come in contact with dead squirrels.
Plague concerns climb as more animals die
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