Ask Dr. Richards: 05/07

What would you say is the chance of cats getting bubonic plague from fleas? And if a cat gets bubonic plague, can it be cured?

I can hear some of our readers saying, “Bubonic plague!? Youve got to be kidding me! I thought that disease disappeared hundreds of years ago.” The plague, or Black Death, did indeed peak in the mid-1300s in Europe and Asia, and ultimately killed millions of people. A more contained outbreak in London from 1664 to1665 claimed an estimated 100,000 people.

But the bacterium, Yersinia pestis, widely held to be the cause of the Black Death of antiquity is alive and well, causing roughly 1,000 to 2,000 human cases of plague every year, primarily in rural areas of developing countries. Requisites for the diseases persistence are the availability of rodent (or sometimes rabbit) “reservoirs” with the ability to reproduce to high numbers, the year-round feeding of appropriate flea “vectors” and the proper environmental conditions. In the United States, the majority of cases in reservoir rodents – usually rock squirrels, ground squirrels and prairie dogs – occurs in the Southwest, but infected animals may be seen anywhere west of the Rockies. During heavy outbreaks in these animals, cases have been detected as far east as Oklahoma, Kansas and Texas. Most human cases of plague in the U.S. arise from two areas: one in the region encompassing southern Colorado and northern New Mexico and Arizona, and the other encompassing western Nevada, California and southern Oregon.

Three forms of plague are recognized in cats and people: bubonic plague, septicemic plague and pneumonic plague. Bubonic plague is characterized by swollen, pus-filled lymph nodes (buboes); septicemic plague causes disease in multiple organs throughout the body; and pneumonic plague primarily affects the lungs. Spread of Y. pestis infection between reservoir rodents is usually via bites from fleas that have fed on other infected rodents. Cats, on the other hand, are most often infected after eating plague-infected rodents; flea-bite transmission appears to be much less common. A number of antibacterial medications are effective against Y. pestis, and with proper case management many cats, though certainly not all, can be cured of the disease.

Im unaware of the numbers of cases of plague in domestic cats, but there were 377 people in the U.S. diagnosed with the disease between 1970 and 2001. Not surprisingly, the vast majority were people residing in parts of the country with the highest numbers of infected rodents. How did these folks get plague? In one study, 82 percent of human cases resulted from flea bites, 15 percent from direct contact with infected wild animals, and three percent from exposure to infected cats. Cats with the pneumonic form of the disease are believed to be the most dangerous to people, because their coughing expels infected droplets that can infect a person if they are inhaled. Were not talking about huge numbers of cases, but this is a very serious disease: up to one in seven people with plague dies, most often because medical attention isnt sought quickly enough or because the disease is misdiagnosed in its early stages and treated inappropriately.

Prevention in cats and humans

The nature of Y. pestis, its reservoirs and its vectors make the prospect of eradicating plague from wild animal populations – and thus the human population – highly unlikely, even in developed countries. But in areas of the U.S. where plague exists in reservoir rodents (see above), the Centers for Disease Control and Prevention offer suggestions to minimize the chance that cats or humans will contract the disease. Quoting in part from the website,

u Do not pick up or touch dead animals.

u If plague has recently been found in your area, report any observations of sick or dead animals to the local health department or law enforcement officials.

u Eliminate sources of food and nesting places for rodents around homes, work places and recreation areas. Remove brush, rock piles, junk, cluttered firewood and potential food supplies, such as pet and wild-animal food. Make your home rodent-proof.

u If you anticipate being exposed to rodent fleas, apply insect repellents to clothing and skin, according to label instructions, to prevent flea bites. Wear gloves when handling potentially infected animals.

u If you live in areas where rodent plague occurs, treat pet dogs and cats for fleas regularly and do not allow these animals to roam freely. v