Just two weeks after a ground squirrel (whistle pig) found south of Boise has tested positive for Yersinia pestis, the bacterial agent of plague, Idaho health officials report that an Ada County dogs may be infected with the serious infection based on preliminary laboratory testing.

This image depicts a magnified view of an oriental rat flea, Xenopsylla cheopis. Image/CDC
This image depicts a magnified view of an oriental rat flea, Xenopsylla cheopis. Image/CDC

Confirmation is expected in about one week.

The dog, which had contact with ground squirrels within the area of impact (see map), south of Boise to the Snake River, and from Kuna to Mountain Home, became ill at the end of May. The owner took the dog to a veterinarian where a sample was taken and submitted to the State Public Health Laboratory for testing. The dog has since been treated and is recovering. Those who handled the dog while it was ill are being monitored and provided preventive medication if needed.

“This is a reminder that people who live and recreate in the area of impact need to take precautions to avoid contact with ground squirrels and their potentially infected fleas. Do not let your dog touch ground squirrels in the affected area. People can be exposed to plague when pets bring infected fleas back into the home, by caring for a sick pet without proper precautions, or by contact with rodents carrying fleas,” said Sarah Correll, epidemiologist for Central District Health Department.

Plague is a bacterial disease of rodents and is generally transmitted to humans through the bites of infected fleas. It can also be transmitted by direct contact with infected animals, including rodents, wildlife and pets.

Plague is a disease caused by the bacterium Yersinia pestis. The bacterium lives in several rodent species. When fleas feed on infected animals, the fleas become infected and spread the bacterium when they bite other animals and humans. When infected animals die, fleas will seek live animals, including humans, to feed on. With the current die-off of ground squirrels in the area, fleas from these animals will be hungry. Fleas can jump off of dead ground squirrels or from around abandoned burrows, and bite and potentially infect pets or people that get too close. Avoiding dead ground squirrels and their abandoned burrows is a good way to avoid exposure. Plague can also be transmitted when someone is exposed to tissue or body fluids of an infected animal. It also can be spread by droplets when an animal or person who has plague pneumonia coughs.

Bipolar staining of a plague smear prepared from lymph aspirated from an adenopathic lymph node, or bubo, of a plague patient./CDC
Bipolar staining of a plague smear prepared from lymph aspirated from an adenopathic lymph node, or bubo, of a plague patient./CDC

What are the symptoms of plague in people?

Plague is a life-threatening illness. It can cause three types of illness in people:

  1. Bubonic plague usually results from the bite of an infected flea. People ill with bubonic plague have sudden onset of fever, headache, chills, and weakness and one or more swollen, tender and painful lymph nodes (called buboes).
  2. Septicemic plague may result after handling an infected animal, the bite of an infected flea, or it may result from untreated bubonic plague. Infected people have fever, chills, extreme weakness, abdominal pain, shock, and possibly bleeding into the skin and other organs. Skin and other tissues may turn black and die, especially on fingers, toes, and the nose.
  3. Pneumonic plague occurs from septicemic plague or from inhaling infectious droplets from an animal or another person with pneumonic plague. Sick people have fever, headache, weakness, and a rapidly developing pneumonia with shortness of breath, chest pain, cough, and sometimes bloody or watery mucous.

What are the signs of plague in cats and dogs?

Plague can be life-threatening in pets. Cats generally get much sicker than dogs and are likely to die if they do not get veterinary care soon after they become ill. Cats can develop bubonic, septicemic, and pneumonic forms of plague, just like people. Cats can spread plague to people if they have the pneumonic form, by coughing.

Dogs usually have a mild illness, but they, too, can get seriously ill.

If your dog or cat has been to an area with dead ground squirrels and is not as active as usual, not eating, or has a fever, seek veterinary care for them immediately and tell the veterinarian that your pet was potentially exposed to plague.