Colorado - Prairie dogs found dead south of Briggsdale have tested positive for plague, the Weld County Department of Public Health and Environment confirmed.

The highly infectious bacterial disease is transmitted primarily by flea bites. Although human cases are rare, the illness can be life-threatening.

This year, 22 positive tests for plague have been confirmed in animals in the state.

"Plague is most commonly found in the prairie dog populations in the grassland areas of Weld County. People need to take precautions from being bitten by fleas when walking out in the grasslands by wearing insect repellent on lower legs and ankles," said Sara Evans, environmental health manager at the department.

Cats also can become infected and transmit the disease to humans.

Symptoms in humans include high fever, muscle pain, malaise, nausea and vomiting. Evans said individuals may develop swollen lymph nodes in the area of the bite, usually the groin or armpit.