Fears of Plague Are Raised After Mountain Lion Dies

Rangers in Cuyamaca Rancho State Park have posted warning signs near public campgrounds following the discovery that a mountain lion shot by a game warden last month was infected with bubonic plague.

Speculating that the infected lion was an isolated case, county health officials said Friday that wildlife observed and tested in the most heavily used areas of the park so far have shown no evidence of plague.

But Moise Mizrahi, chief of the county’s vector control division, said officials are keeping a close watch on the park and its inhabitants and are alerting hikers and campers to take precautions against possible exposure to the deadly disease.

“We suspect that the mountain lion may have picked this up in a remote wilderness area and we don’t think there is any cause for alarm,” Mizrahi said. “But we are stepping up our surveillance of the park to reassure ourselves and the public of that.”

The female lion was shot on Aug. 17 near the Hual-Cu-Cuish Boy Scout Camp by a game warden who had determined the animal was a threat to public safety. Mizrahi said the lion, estimated to be about two years old, had been “acting strangely,” roaming near camping areas during daylight hours.

Because the animal was emaciated and appeared diseased, the state Department of Fish and Game warden sent the carcass to pathologists at the San Diego Zoo for testing. On Aug. 24, results from those tests revealed that the lion had been infected by bubonic plague, a disease spread by fleas found on rodents.

Mizrahi said that because the mountain lion is a wide-ranging animal that may travel several miles in a given day, it is unclear just where it came into contact with the disease. Health officials said field surveys show that populations of ground squirrels--an easily observed indicator of the plague--are plentiful in areas near the Boy Scout Camp and in other park campgrounds.

Blood samples of squirrels and mice tested negative for the disease, Mizrahi said.

“We’ve examined the ground squirrels to see if there is anything out of the ordinary, like unused burrows or a low population level or something to indicate the possibility of disease,” Mizrahi said, “but we’ve found nothing unusual. It appears the lion was an isolated incident.”

Still, next week, observers from the county’s vector control division will expand their survey of squirrels and other rodents into more remote corners of the park, where lions are more commonly found.

Will Look for Signs

“We will try to hone in on an area that may have a problem but it’s likely that this lion may have been in a place that is totally inaccessible to humans,” Mizrahi said.

If an infected rodent population is found, officials likely would chemically dust burrows in an effort to kill the disease-carrying fleas. If the number of infected animals is high enough, elimination of the rodents themselves might be necessary, Mizrahi said.

“The key is breaking the transmission cycle, and doing away with the fleas is usually sufficient,” Mizrahi said.

Meanwhile, rangers have posted signs suggesting these precautionary measures:

- Avoid all contact with chipmunks, squirrels and other wildlife.

- Do not touch sick or dead animals; report them to the park ranger immediately.

- Do not camp, rest or sleep near animal burrows.

- While in park areas avoid fleas and protect your pets from fleas by treating them with powder or leaving them at home.

- See a physician if you become ill within a week of a park visit.

Mizrahi stressed that while the disease is spread by fleas, they are not the same sort of fleas commonly found in the home and on domestic pets.

The plague, which decimated European populations in the 14th Century and at other times in history, flares up periodically in the state’s rodent populations. It is sometimes spread to humans through fleas on infected animals, although human cases are rare, according the federal Centers for Disease Control.

Monitor Other Diseases

To detect an outbreak of the disease, a team from the county’s vector control division conducts ongoing surveys of wildlife in parks and other areas. Officials also monitor for encephalitis and malaria.

The last reported plague case documented in San Diego County was in 1982, when three dogs roaming near Cuyamaca tested positive for the disease. In 1979, seven dogs in backcountry areas showed evidence of infection and in 1977 there was a human case reported; that person, however, apparently contracted the disease outside of the region.

The last large outbreak was among squirrels in Julian, Lake Henshaw, Cuyamaca, Del Mar, Bonsall and Scripps Ranch.

“But,” Mizrahi stressed, “that was in the early 1940s.”

The plague can take two forms in humans--bubonic or pneumonic. Bubonic plague is characterized by swollen lymph nodes and a high fever. It develops slowly over a few days and is not very contagious. Both forms can be treated with antibiotics, but pneumonic plague, which attacks the lungs, progresses swiftly and can spread as easily as a cold.