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prairie dog barking

Plague in Boulder County

Plague is a bacterial disease transmitted by the fleas of rodents and is widespread in the western United States. Plague commonly infects prairie dogs and squirrels that can be found in parks and residential areas within Boulder County. Household pets, such as dogs and especially cats, can either get plague or carry infected fleas home to their owners.


The bacteria is transmitted to people through a flea bite and direct contact with infected animals. Fleas generally do not infect other animals unless their natural host (animal) is no longer available. Domestic cats and dogs can contract plague by catching and eating infected rodents and rabbits or by being bitten by infected fleas. They can then carry infected fleas home to their owners or, especially with cats, serve as a direct source of infection.


Symptoms include:

  • Sudden onset of fever and chills
  • Severe headache
  • Muscle aches
  • Nausea
  • Vomiting
  • General feeling of systemic (whole body) illness
  • Extreme pain and swelling in the lymph node


Treatment with antibiotics is effective during the early stages of the disease. If diagnosis and appropriate treatment are delayed, life-threatening complications may follow. Consult your physician as soon as you experience symptoms.

Control & Prevention

Rodent control should be carried out by a licensed professional. Poisoning of colonies should be avoided because it releases fleas to the environment, causing additional risk to people. Infected colonies will be posted with warning signs, and access to pets should be restricted.

  • Do not feed or entice any rodent or rabbit.
  • Eliminate rodent harborage, such as piles of lumber, broken cement, and trash or weeds.
  • Keep foundations in good repair, and trim back overhanging trees from the roof and windows.
  • Keep away from rodent-infested areas when camping.
  • Avoid contact with all sick or dead rodents.
  • Report instances of sick or dead rodents in the county to Boulder County Public Health at 303-441-1564.
  • While hiking, treat pants, socks, shoe tops, and shirts with insect repellent.
  • Keep all dogs leashed, and restrict cats from roaming in rodent-infested areas.
    Report all bites from wild carnivores and cats to Public Health at 303-441-1564.
    If onset of illness occurs within 2-6 days after activities in the outdoors, report it to your physician.

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Vector Control Program

Main: 303-441-1564
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