The CDC’s Morbidity and Mortality Weekly Reports has a short report about two plague cases in the US. Plague, while often thought of as a historical disease (the Black Death), is alive and well in wild rodents in some areas of the world, including parts of North America, and human cases continue to occur.
Here are highlights of the CDC report (in italics) with some extra comments.
Plague, caused by Yersinia pestis, is enzootic (present in the population, typically at a low level) among rodents in the western United States. Humans can be infected through 1) the bite of an infected flea carried by a rodent or, rarely, other animals, 2) direct contact with contaminated tissues, or 3) in rare cases, inhalation of respiratory secretions from infected persons or animals. In September 2010, the Oregon Health Authority reported the first two cases of human plague in Oregon since 1995 and the only two U.S. cases in 2010.
Both illnesses began on August 21. The patients, aged 17 and 42 years, lived in the same household and might have been exposed to plague by infected fleas from one of their dogs; that dog was found to be seropositive for Y. pestis by the passive hemagglutination-inhibition assay (dilution of 1:64). One patient acknowledged sleeping in the same bed with the dog during the 2 weeks before illness onset. Both patients had high fever and multiple bilateral inguinal buboes; one patient had hypotension, tachycardia, and acute renal failure and was hospitalized. A gram-negative rod with bipolar staining was isolated from a specimen of that patient’s blood.
…25 days after specimen collection, the isolate was identified as Y. pestis… Both patients recovered uneventfully after empiric therapy with doxycycline and amoxicillin clavulanate potassium, respectively, although the latter is not considered effective in treating plague.
Plague is a Category A potential bioterrorism agent. Human infections are rare but can be life-threatening. The plague case-fatality rate depends on the clinical presentation (i.e., bubonic, septicemic, or pneumonic) and timing of antibiotic therapy initiation; if untreated, the case-fatality rate is >50% for bubonic plague and approaches 100% for pneumonic plague. Rapid laboratory identification can help guide therapy.
Sleeping in the same bed with dogs has been associated with plague in enzootic areas. Plague patients with no history of exposure to rodents can be infected by Y. pestis if their pets carry infected rodent fleas into the home. Veterinarians always should recommend flea control to dog and cat owners.
This is an example of a situation where pets can play a role in human infection while not being the direct source of infection. While direct pet-human transmission can occur, this typically involves situations where someone has close contact with a pet that is sick with the plague. Most often, this kind of transmission is associated with close contact with cats with pneumonic (respiratory) plague.
Key aspects of reducing the risk of pet-associated plague in areas where plague is, or may be, present, are:
- Preventing contact of pets with wildlife, living or dead.
- Preventing roaming of pets in the wild.
- Discouraging wildlife from living in or around homes.
- Keeping cats indoors.
- Routine flea control.
More information on plague and pets is available in our archives.