Rabbit Fever on the Rise in the U.S.

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So far this year, 100 cases of rabbit fever have been reported in the U.S. These animals in the wild are known to carry the bacteria that causes the illness. REUTERS/Mark Blinch

Rabbits, even ones in the wild, are pretty cute. But a new report from federal health officials may make you reconsider your affinity for these fuzzy-tailed creatures. On Thursday, the U.S. Centers for Disease Control and Prevention (CDC) issued a report that finds rates of rabbit fever—a rare disease often transmitted by these animals in the wild—are on the rise.

A total of 100 people have been diagnosed with rabbit fever as of September 30, 2015, according to the study, published in the Morbidity and Mortality Weekly Report. The disease is also known as tularemia and is caused by the bacteria Francisella tularensis. These cases were diagnosed in Colorado (43), Nebraska (21), South Dakota (20) and Wyoming (16). U.S. health officials typically see a total of 125 cases of rabbit fever each year.

Health officials are unsure of why rates of the disease are rising, though they suggest that the increase in rainfall and growing rabbit and rodent populations may be contributing factors.In Colorado, for example, the weather has been extreme enough over the past few years to merit plenty of National Weather Service flash-flood warnings.

Francisella tularensis is transmitted to humans through direct contact with certain animals, including rabbits, cats and rodents. The bacteria is also sometimes found in soil and can contaminate food and water. A person can contract the disease through inhalation of the bacteria, which may happen as a result of all sorts of activities—even inadvertently running over an infected rodent while mowing a lawn. Deerflies and ticks may also carry the bacteria and transmit it through bites. The CDC says there are no records to date of human-to-human transmission.

A person who develops tularemia will experience a range of symptoms, including fever and chills, muscle and joint pain, respiratory problems, gastrointestinal illness, conjunctivitis, swollen glands and sometimes skin lesions. A patient will usually present with signs of the illness three to five days after initial infection, but the period may be as long as 14 days.

Approximately 2 to 24 percent of infected patients die—the dramatic range in the risk for death is because some strains of the bacteria are significantly more deadly than others. According to one study published in Clinical Infectious Diseases, the fatality rate from the A1b strain resulted in a mortality of 24 percent, while the A1a strain had a fatality rate of 4 percent and the type B strain had a 7 percent fatality rate. Thankfully, if caught early, rabbit fever is treatable with antibiotics including streptomycin, doxycycline, ciprofloxacin or gentamicin. Streptomycin is the first-line choice, but it can be difficult to obtain and the chemicals in the drug may be toxic to the ears and impact the eighth cranial nerve, also known as the auditory vestibular nerve, which is related to hearing and balance. To diagnose the disease, doctors typically analyze blood samples from a patient, though the bacteria can also be detected in spinal and respiratory fluids.

The CDC recommends people in affected states take certain safety precautions to prevent contracting the illness. These include wearing gloves when handling animals, using insect repellent and skipping yard work when there is a presence of dead animals that may be potential reservoirs for Francisella tularensis.