A rare case of a disease called tularemia has surfaced in a dead rabbit in Larimer County in northern Colorado.

The bacterial infection, also called “rabbit fever,” can affect people in rare cases. So, public health officials and doctors are warning people to be careful about interactions with animals.

“In Colorado, tularemia has been reported in about 50 cases in the last ten years,” said Lauren Bryan, an infection prevention program manager at UCHealth Yampa Valley Medical Center. “Although the bacteria can be found throughout the state, cases are most frequently reported along the Front Range where the overlap of wildlife and people is the greatest.”

How do people get tularemia?

People can get tularemia in a handful of ways:

• Contact with an infected animal
• A bite from a vector, such as a tick or deer fly.

Tularemia is not spread through person-to-person contact, Bryan said.

According to medical experts at the U.S. Centers for Disease Control and Prevention (CDC), people can also get tularemia if they touch their eyes after contact with an infected animal. These infections can happen if people are working in labs or are butchering animals, and then rub their eyes. People also can get infected if they inhale contaminated agricultural or landscaping dust or drink contaminated water.

What are the symptoms of tularemia? 

Bryan notes that when people become infected with the tularemia bacteria through a tick or deer fly bite, an ulcerated sore with a red border develops, which will not heal on its own. This will lead to an infection that may enter the blood stream and develop into sepsis if the infected person doesn’t get help from a doctor.

Both forms of tularemia will be accompanied by a high fever.

“The most severe cases are aerosol infections, which usually occur after mowing over or handling an infected dead animal,” Bryan said. “When people inhale the bacteria, they can get respiratory issues that can lead to pneumonia and even death if not treated properly.”

Which animals can carry tularemia?

Colorado is home to a diverse population of small mammals, including cottontail rabbits, jackrabbits, prairie dogs and rodents, such as beavers and squirrels.

And all of these animals can carry tularemia or be infected, often with deadly consequences for the animal.

Just like people, it’s rare for animals to get tularemia. But the bacteria can cause a serious infection when not promptly treated. Tularemia naturally occurs in the environment. In Colorado, rabbits, hares and rodents are most susceptible to contracting the illness.

How common is tularemia in Colorado?

According to medical experts at the Colorado Department of Public Health and Environment, there were nine cases of tularemia in humans in Colorado in 2025. Each year, there are a handful of human cases in the state. The peak in human cases in recent years occurred in 2016, with 15 cases. Health officials also have confirmed a handful of cases each year in animals in Colorado.

The recent case of tularemia in a dead rabbit in northern Colorado has once again drawn attention to this bacterial infection.

In 2023, CDC officials reported 196 cases across the U.S., far fewer than the peak of 927 tularemia cases in 1950, when CDC officials began tracking the disease.

How do doctors help people if they get tularemia?

“Several antibiotic options are available to treat the infection, starting with oral options if the infection is in its early stages,” said Bryan. “For more advanced cases, IV therapies may be administered.”

Bryan says that there are many other possible diagnoses for rashes, sores, fevers and respiratory infections. Because tularemia is a rare occurrence, she stresses that it is important to let your primary care provider know if you have been bitten by a tick or deer fly or handled a dead animal. If possible, take a photo of the tick to share with your doctor for proper identification as not all ticks carry the tularemia bacteria.

“There are 100 things that can cause pulmonary symptoms,” Bryan said. “Help your doctor work through the differential diagnosis by letting them know if you have recently handled animals in a lab, been cut cleaning an animal during hunting season, been bitten by a deer fly, found a tick after a hike, or other potential scenarios to help narrow down a diagnosis.”

How can you prevent tularemia?

Be careful when you’re interacting with animals. The peak season for tularemia infections occurs from May through July when people are mowing lawns, hiking and enjoying the outdoors.

But Bryan warned that the tularemia bacteria is present in Colorado throughout the year.

The most important ways to avoid being infected with tularemia are:

• Avoid handling dead animals
• Wear gloves if an animal needs to be handled
• Prevent deer fly and tick bites.

When mowing or landscaping, check the area for dead animals, especially in tall grass or thick duff, before disturbing the area. Wearing a mask during any landscaping, mowing or agricultural work may also help prevent inhaling the bacteria.

During hunting or trapping season, especially for small game like rabbits, squirrels, hares and muskrats, use gloves when cleaning an animal. Make sure to cook the meat thoroughly before consumption.

Tick and deer fly bites can be prevented by spraying an insect repellent on skin and treating clothing and outdoor gear with a repellent designed for fabrics like permethrin. The EPA has a helpful search tool to help find the right product for individual needs.

Wear long pants and sleeves when outdoors, finding options that are moisture-wicking and have good airflow to prevent overheating in warmer temperatures. Tucking pants into long socks also prevents insects from attaching to legs.

If a tick is found on the skin, remove it promptly.

“Do a full-body check for ticks as soon as returning home after being outdoors, including along the hairline, under arms and all creases and folds,” Bryan said. “If possible, get a shower as soon as possible to stop ticks from getting embedded in the skin.”