The risk of human infection with plague from domestic animals has been assessed: how to protect yourself

Officials in Deschutes County, Oregon, have announced that a local resident has been diagnosed with the plague – and that it was likely infected by a domestic cat.

“The cat that was symptomatic died from the infection, but the human patient is currently recovering,” said county public health program manager Emily Horton. No additional cases have been identified, officials said.

Although the plague is best known for killing tens of millions of people in medieval Europe, the bacterium that causes the disease still circulates. It is common in some wild rodent populations in the western United States.

“Many people don’t know that plague is endemic in parts of the United States,” explains Dr. Erin Phipps. “It’s not a disease of the past.”

Human cases are rare and treatable if detected early. But the Oregon case is a reminder that cat owners and veterinarians in plague-prone areas need to be alert to the risks of infection.

“If you have a domestic cat in the area that hunts outside, it should be on your radar,” says epidemiologist Sarah Lathrop.

Plague is caused by a bacterium called Yersinia pestis, which affects various populations of wild rodents. Fleas that feed on infected rodents can transmit plague to other animals, including humans. A person can also become infected through contact with a sick animal.

The disease manifests itself in several forms. With the so-called bubonic plague, people’s lymph nodes usually become enlarged. Fever, chills and headache are also common. The bacteria can also cause bloodstream infections, known as septicemic plague, or lung infections, known as pneumonic plague.

Although the disease can be fatal, it can be treated with antibiotics if detected early.

“There is sort of an emotional reaction to saying the word ‘plague’ and thinking about past pandemics,” Dr. Lathrop said. “It’s very treatable today.”

There are an average of seven human cases reported each year in the United States, according to the Centers for Disease Control and Prevention. More than 80 percent of these cases are the bubonic form of the disease.

The plague is most common in the rural West, especially in parts of Arizona, California, Colorado, Nevada, New Mexico and Oregon. In these areas, the bacteria can circulate among prairie dogs, gophers, chipmunks, tree rats and other animals.

According to the US Centers for Disease Control and Prevention, between a thousand and 2 thousand cases of the disease are reported annually worldwide.

Cats can become infected when they prey on infected rodents or are bitten by fleas associated with those rodents. Since 1977, 407 cats in New Mexico have been diagnosed with distemper, Dr. Phipps said.

“Pets that hunt are one of the highest risk groups,” added Sarah Lathrop. “Cats are very susceptible to distemper and it can be fatal to them.”

As with humans, infected cats can make a full recovery if the disease is caught early. But because the disease resembles symptoms of many other diseases, diagnosis can be difficult. Infected cats may develop a fever, become lethargic, and lose their appetite. Enlarged lymph nodes are also common, especially in the neck. Dogs can also be infected, but they generally do not get as sick as cats.

“The risk of you catching distemper from your cat is pretty minimal,” Lathrop reassures.

Cats and dogs can carry fleas containing the bacteria into the home, where they can infect pet owners. They can also transmit the bacteria to people through respiratory droplets or infected fluids.

Pet owners can minimize risks by keeping their pets indoors or on a leash, avoiding contact with dead or sick rodents and treating their pets with flea treatments, experts say. Keeping pet food in sealed, rodent-proof containers and removing rodent-hazardous debris such as woodpiles from the yard can also help reduce the risk of infestation.