Center for Veteranary Public Health

Plague

Plague is a disease that has been around for a long time. In the 14th Century plague was responsible for the “Black Death” that killed 30 million people in Europe
Plague is caused by infection with the bacteria Yersinia pestis (see picture below)
Plague is a zoonotic, vector-borne disease spread primarily by fleas
In the US, plague is seen primarily in the “Four Corners” area out west where New Mexico, Colorado, Arizona, and Utah meet.

A magnified picture of Plague bacteria
(from the CDC’s Public Health Image Library)

blood ehgorged flea on human arm

Y. pestis is maintained in nature in a cycle involving rodents (frequently ground squirrels and mice) and fleas
Fleas from the rodents can bite humans; if a flea is infected with Y. pestis it can transmit the disease to people when it feeds
Humans can also become infected by having direct contact with a plague-infected rodent or other animal ·
Pets (primarily cats) may also become infected with plague and spread the disease to people
- When plague-infected rodents die, dogs and cats may eat the carcass and become infected
- Dogs and cats may also become infected by the fleas from the rodents
Once a human becomes infected, it is possible for direct person-to-person transmission to occur

There are three types of plague disease

Bubonic plague will develop close to the site where an infected flea has bitten a person. This typically occurs 2 to 8 days following the flea bite
Lymph nodes become swollen and are very tender and painful (“bubo”)
If bubonic plague is not treated, it can progress to septicemic plague
Bubonic plague is NOT transmitted person-to-person

Occurs when Y. pestis bacteria are in the blood
Symptoms include fever, chills, exhaustion and powerlessness, abdominal pain, shock, and bleeding through the skin and other organ
Septicemic plague is a very serious condition, and infection in the blood can quickly lead to pneumonic plague

Pneumonic plague:
- Occurs when the lungs become infected through the bloodstream or, rarely, by inhalation
- Symptoms include fever, chills, cough, coughing up blood, difficulty breathing, chest pain and rapid shock
- Death occurs if pneumonic plague is untreated or not treated early enough
- Pneumonic plague CAN be transmitted person-to-personWho is most at risk for plague disease?
- In the western United States, people who are exposed to rodent fleas, wild rodents, or other susceptible animals (such as prairie dogs and domestic cats)
- o During 1997 through 1998, 23 human cases of plague have been associated with exposures to infected cats
Plague has not occurred in rodents east of the Mississippi riverHow can plague be prevented?
Humans should avoid contact with wild rodents and their fleas
- Keep homes and property free of rodents
- Avoid wild rodents when camping, hiking, or other outdoor activities
- Apply appropriate flea-control products to dogs and cats to ensure that they do not bring fleas into the home. Ask your veterinarian for advice on these products.
A human vaccine is no longer availableAdditional information:
Plague is considered to be potential bioterrorism agent for the following reasons:
Yersinia pestis is a highly infectious agent
Yersinia pestis is found worldwide
Once a person is infected, person-to-person transmission can occur