Fleas in Arizona Test Positive for Plague

August 30, 2017
Kerry Lengyel

The plague has resurfaced, this time in two separate Arizona counties.

Two adjacent counties in Arizona have reported fleas carrying bubonic plague. Yes, that plague. The one responsible for the deaths of 75 million people in medieval Europe.

You may not hear the word “plague” much anymore, but the fact is the disease has never been eradicated and still occurs in humans and other animals. In fact, more than 1000 human cases of plague were reported in the United States between 1900 and 2012, and 80% of those were bubonic plague. According to the Centers for Disease Control and Prevention (CDC), an average of 7 human plague cases are still reported annually, primarily in the West. Four people died from the illness in 2015.

Fleas carrying the causative bacterium Yersinia pestis were detected earlier this month in Navajo and Coconino Counties in Arizona. Coconino County officials found plague-infected fleas on local prairie dogs. Residents have been warned to pay attention when hiking or camping in areas where dead animals or fleas may be present.


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In a statement, the Navajo County Health Department said it “is urging the public to take precautions to reduce their risk of exposure to this serious disease, which can be present in fleas, rodents, rabbits, and predators that feed upon these animals.”

Although rare, plague can be transmitted to humans and other animals in 3 ways: by the bite of an infected flea, by direct contact with an infected animal or its body fluid or tissue (including respiratory droplets), or by contact with a person with plague pneumonia.

The plague outbreak that occurred in the 14th century was also transmitted by fleas, but those fleas were transported by rats. Humans today don’t have quite as much contact with rodents, sanitation is much more advanced, and several antibiotics are available to treat plague effectively. If left untreated, though, the disease can spread throughout the body and ultimately result in death.

According to the CDC, the recurrence of plague is not completely unexpected. Outbreaks typically occur in southwestern states during the cooler months following wet winters.

Symptoms of plague in humans and pets typically appear within 2 to 6 days of exposure and include sudden onset of fever, headache, chills, inflammation, weakness, and one or more swollen, tender, and painful lymph nodes. If you think you may have come into contact with or been bitten by an infected flea in the Arizona area, contact your doctor immediately; also warn your clients to keep an eye out for any of these signs in their pets.