The Black Plague Still Exists — And Cats Can Get It

Cats become infected with plague through contact with rats and fleas, but it is also possible for cats to infect people.

Cats can pick up the bacterium causing plague via infected rats and fleas. By: andreeailin

Sounds alarming, doesn’t it?

These days, though, the incidence of plague is very low, unlike in medieval times, when what was called the “Black Death” wiped out nearly half the population of England. In modern America, this condition is mainly associated with rural U.S. areas and especially with rodents and rat fleas.

The plague is caused by a bacterium called Yersinia pestis (named after a Swiss-born scientist, a Mr. Yersin, who isolated the bug; “pestis” means plague or contagious disease).

Cats become infected through contact with rats and fleas. It is possible for cats to infect people, hence the need to be alert for symptoms in your cat. However, this condition is mercifully rare in modern America, so don’t lose too much sleep over it.


The plague has an incubation time of 1 to 2 days. After symptoms start, unless treatment is given promptly, the cat is likely to die within 4 to 6 days.

The plague takes 2 forms: the most common (around 80% of cases) is the bubonic form that affects the lymph systems, while the pneumonic form affects the lungs. Some unlucky animals can get both.

Infection circulates in the lymph system and lodges in the lymph nodes, causing them to swell. The bacteria reproduce in the lymph nodes, liver, lung and spleen, and bacterial toxins cause cell death and septicemia in the host. The cat will be feverish and have painful, enlarged lymph nodes.


A cat can become infected in 2 ways:

  1. Being bitten by a flea containing Yersinia
  2. Or eating infected rats

Yersinia breeds in the guts of fleas, so when the flea bites the cat, it transfers infection into the cat’s bloodstream. Likewise, fleas can also infect rats, and then the cat eats that rat.

For a human to acquire infection requires an infected cat flea to bite, which underlines just how important regular flea control is for all pets and in the home.

Hunting cats are generally at a higher risk of catching the infection. By: sonstroem


Diagnosis is made by harvesting samples from infected sites (such as a lymph node, liver, blood or spleen) and submitting them to a lab to look for the Yersinia bacterium.

This includes staining a smear and looking for the bacterium under the microscope or trying to grow it on a culture plate.

Anyone handling these samples must be extremely careful as there is a risk of humans catching the infection.


There is a high mortality rate among infected cats, and it is essential that treatment is given early for the patient to have a fighting chance.

Treatment is supportive care in the form of intravenous fluid therapy and antibiotics from the tetracycline family. It is essential to isolate the cat to decrease the risk of cross-infection.


The plague bacterium is carried by rodents and their fleas. So controlling the rodent population and regular flea control of pets goes a long way in reducing the risk of infected wildlife transmitting this disease to your cat — and possibly even to you.

Hunting cats are at greatest risk, and although neutering does not necessarily reduce a cat’s hunting instinct, it should make your cat more of a homebody and therefore less likely to be exposed to fleas carrying Yersinia.


  • “Clinical, clinicopathologic, and pathological features of plague in cats.” Eidson, Thilsted & Rollag. JAVMA, 199: 1191–1197.
  • “Public health implications of plague in domestic cats.” Kaufman. JAVMA, 179: 879–878.


This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed Oct. 13, 2018.

Dr. Pippa Elliott, BVMS, MRCVS

View posts by Dr. Pippa Elliott, BVMS, MRCVS
Dr. Pippa Elliott, BVMS, MRCVS, is a veterinarian with nearly 30 years of experience in companion animal practice. Dr. Elliott earned her Bachelor of Veterinary Medicine and Surgery from the University of Glasgow. She was also designated a Member of the Royal College of Veterinary Surgeons. Married with 2 grown-up kids, Dr. Elliott has a naughty puggle called Poggle, 3 cats and a bearded dragon.

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