Serving Colorado's Counties

Technical Update vol. 25 no. 32 - Fleas Plague Colorado

August 10, 2021

The Colorado Department of Public Health and Environment (CDPHE) has confirmed plague (Yersinia pestis) in animals and fleas from six counties after the death of a 10-year-old boy in LaPlata County. Plague is a zoonotic disease, which means it can pass from animals to humans. The Yersinia pestis bacteria is usually found in fleas and small mammals such as prairie dogs, squirrels, woodrats, and chipmunks. Pets can also carry plague-infested fleas.

Symptoms of Plague

Plague cases are rare in humans and can be treated if caught early, so it is vital to know the symptoms and seek treatment if plague is suspected. Plague symptoms depend on the clinical form: bubonic, pneumonic, or septicemic (

Bubonic – sudden fever, headache, chills, weakness, and swollen tender lymph nodes

Septicemic – fever, chills, extreme weakness, abdominal pain, shock, and possibly bleeding into the skin and other organs; skin and other tissues (e.g., fingers, toes, nose, etc.) may turn black and die

Pneumonic – fever, headache, weakness, and rapidly developing pneumonia with shortness of breath, chest pain, cough, and sometimes bloody or watery mucous

Control Exposure Risks

Animal-borne diseases can be contracted year-round but tend to increase in summer when people are more likely to come into contact with animals. The CDPHE recommends Coloradans take the following precautions (

  • Avoid fleas. Protect pets with a veterinary-approved flea treatment and keep them on a leash and out of wild rodent habitats.
  • Stay out of areas where wild rodents live. If you enter areas inhabited by wild rodents, wear insect repellent and tuck your pant cuffs into your socks to prevent flea bites.
  • Avoid all contact with wild rodents, including squirrels. Do not feed or handle them.
  • Do not touch sick or dead animals.
  • Prevent rodent infestations around your house by clearing plants and materials away from outside walls, reducing access to food items, and setting traps.
  • Consult with a professional pest control company to treat the area around your home for fleas.
  • Contact a veterinarian if your pet becomes ill with a high fever and/or an abscess (i.e., open sore) or swollen lymph nodes. Pets with plague can transmit the illness to humans.
  • Children should be aware of these precautions and know to tell an adult if they have had contact with a wild animal or were bitten by fleas.

What This Means for Counties

Coloradans should take steps to avoid coming in contact with fleas and small mammals that often carry Yersinia pestis. Know the symptoms of the plague and seek medical attention if they appear. For more information, consult the CDPHE or the CDC.

A PDF of this Techncial Update is available here.

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