Plague (aka the "black death") is a fascinating disease. It is one of the most important diseases in human history because it had a devastating impact of the human population during various outbreaks. Many people may not realize it, but plague is not just a historical problem – it is still alive and well in some areas of the world. Plague is caused by the bacterium Yersinia pestis, which tends to circulate in rodent populations and can be spread by fleas. In North America, plague is most common in some regions of the southwestern US, particularly New Mexico, Arizona and Colorado. We’re heading into the high-risk season for plague in those areas: March to October.
Plague can infect domestic pets, and pets can be a source of human infection. Cats are quite susceptible to plague, whereas dogs are quite resistant. Cats can transmit plague to people. Pneumonic plague (infection of the lungs with Y. pestis, not to be confused with bubonic plague which is primarily infection of the lymph nodes with Y. pestis (see picture left)) in cats is of particular concern, because in this form the bacterium can be spread through the air over short distances.
Prairie dogs (which some people keep as pets) are also very susceptible to plague.
A paper in Clinical Infectious Diseases a few years ago (Gage et al, 2000) described 23 cat-associated cases of plague in people, five of which were fatal. People were infected by face-to-face contact, bites, scratches or simply caring for an infected cat. Most affected people were cat owners, but some were veterinary clinic personnel. Plague is treatable with antibiotics, but the disease can progress rapidly, so it’s important to determine the diagnosis and start treatment as soon as possible.
Here are some things to consider if you live in an area where plague exists:
- Keep pets indoors as much as possible to help prevent exposure to infected wildlife.
- Use routine flea control measures as directed by your veterinarian.
- Consider any cat that develops a fever of unknown origin or enlarged lymph nodes a plague suspect.
- Don’t let cats and dogs hunt wild rodents, and don’t let them have access to rodent burrows.
- If your pet has been diagnosed with plague, you need to seek medical attention promptly in case you have been exposed. If a person in the household is diagnosed with plague, pets should be investigated as possible sources and should be treated prophylactically in case they have been exposed.
Lower photo: Bubo in the leg of a person infected with bubonic plague (source: Centers for Disease Control and Prevention)