Skip to main content

See also:

Rabbit fever seen in Colorado

The Weld County CO Department of Public Health announced on Aug. 12 that a Larimer County resident has been diagnosed with "rabbit fever" or tularemia after mowing on a property in Weld County. The bacterial illness is most common in small mammals. The Health Department believes this patient was exposed when he mowed over a dead rabbit in mid July.

Map illustrating U.S. counties reporting tularemeia for the period 2003 to 2012
CDC / public domain

On July 18, the Larimer County CO Department of Public Health announced a confirmed tularemia illness in a patient in that county. The department also reported the infection in four rabbits. Residents had noticed a die-off of rabbits and hares in the county for several weeks prior to the announcement.

Tularemia is the proper name for an illness called rabbit fever. Humans can contract the illness in several ways. It can be spread through the bites of ticks or deer flies. Skin contact with sick animals or drinking contaminated water can also be a source. And, as may have happened in Weld County, a patient can contract rabbit fever by inhaling contaminated dust or aerosols.

The signs and symptoms of tularemia are dependent upon how the patient was infected. A high fever, as high as 104 degrees, is common. If the patient was exposed through contact with an infected animal or through an insect bite, a skin ulcer will appear. If the patient inhaled the bacteria, he may develop pneumonia which can be serious or even fatal.

The illness responds to treatment with antibiotics. It may take up to 21 days of treatment to cure tularemia, and the symptoms may last for several weeks.

As of Aug. 2, there have been 58 human tularemia cases reported to the Centers for Disease Control in 2014. Case counts have been increasing, with 2009 seeing 93 cases in total and 2013 seeing 203. Those numbers are well down from the 1950s which saw between 500 and 900 cases per year. There was an uptick in rabbit fever cases between 1980 and 1985 but the highest year was just over 300 cases reported.

Tularemia is one of several bacterial illnesses that the U.S. government believes could be weaponized into a tool for bioterrorism. The bacteria which causes rabbit fever is Francisella tularensis, and it is highly infectious. Fewer than 50 organisms are necessary for a patient to contract the disease. The incubation period is three to five days but can range from one day to 12. The bacteria would most likely be made airborne for use as a bioweapon, since inhalation produces the most serious form of the disease.