January 26, 2023


By David Miller

Tularemia is commonly called rabbit fever, which is a disease caused by the bacterium Francisella tularensis. Tularemia is typically found in animals, especially rodents and of importance to us trappers, it is most commonly found in beaver and muskrats here in the United States. It has been reported in all states except for Hawaii.

In the U.S. it was never particularly common, with the disease most frequently found with trappers, hunters, cooks and agriculture workers. The incident rate has dropped through the 20th century resulting in an occurrence rate of 1 in 1,000,000 between 1990 and 2000, meaning that the disease is fairly rare today. This is in part mostly due to less and less people processing and handling animals in todays society, resulting in most all reported cases being in rural areas.

Infection may be caused by bites of infected insects (most commonly deerflies & ticks), by handling infected sick or dead animals, by eating or drinking contaminated food or water, or by inhaling the air born bacteria. Trappers and hunters can most easily be infected through a break in the skin while handling an infected animal, and more rarely by eating the poorly cooked flesh of infected animals. Waterborne infections account for up to 10% of all reported cases. The tularemia organisms can live for several months in the carcass of dead animals, and the same period of time in mud and water. Evidence of tularemia in an animal is white spots on the liver. I would suggest any one eating beaver or muskrat, or feeding them uncooked to pets to check the liver prior to use.

The history of the disease is interesting in that it was first documented in ancient Canaan in about 1715 BC. Subsequently, wars spread the disease in ancient times (sparing Egypt in the 14th century BC due to a quarantine). During this period it was deliberately introduced into western Anatoia, constituting the first known record of biological warfare. Today it is considered a viable biological warfare agent by the Centers for Disease Control and Prevention. It has been included in the biological warfare programs in modern times by the United States, Soviet Union and Japan. It is of concern today, as it may be used in terrorist attacks as a bioweapon and would most likely be made airborne so that the bacteria would be inhaled. Those who inhaled the bacteria would experience severe respiratory illness, including life threatening pneumonia and systemic infection if not treated.

Various natural outbreaks have occurred in recent years around the world. Interestingly, in January of 2011 researchers searching for brucellosis in feral hogs in Texas discovered widespread infections or evidence of past infections in populations of the hogs in two counties, though Tularemia is not normally associated with hogs. The spreading of the disease over a large area is of particular concern, or even may be already present in a very wide geographical area. Precautions were recommended for those who hunt, dress, or prepare feral hogs.

The incubation for the disease is a period of normally 3 to 5 days after expose, but it can be as long as several weeks. The illness usually starts suddenly, and may continue for several weeks after exposure. Symptoms include chills, eye irritation (conjunctivitis – if infection began in the eye), fever, headache, joint stiffness, muscle pains, red spot on the skin (growing into a sore – ulcer), shortness of breath, sweating and weight loss.

Testing for the disease includes a blood culture for the tularemia bacteria, blood test measuring the body’s immune system to the infection, chest x-ray, and a test for PCR from an ulcer.

It is cured with antibiotics. The disease is fatal in about 5% of untreated cases, and less than 1% of treated cases. Complications can result in bone infections, infection of the sac around the heart, meningitis, and pneumonia. Call your doctor if symptoms develop after a rodent bite, tick bite, or exposure to the flesh of a wild animal. This gives new meaning to “wearing rubber gloves” while pelting and dressing animals, and especially beaver or muskrat. Normally we trappers think of donning rubber gloves while handling animals normally associated with rabies. Although Tularemia is fairly rare today in the general public, we trappers have a greatly increased chance of contracting the disease – as they say, An Ounce of Prevention Is worth a Pound of Cure.

Dave Miller
Lexington TWP.

Dave Miller is a Maine resident, an outdoor writer and a member of the Carrabassett Valley Trappers Association.