Don’t let blood-sucking ticks and dead beavers plague your Colorado hike |

Don’t let blood-sucking ticks and dead beavers plague your Colorado hike

Alli Langley
In 2014, mosquitoes infected 118 people in Colorado with West Nile virus, which arrived to the state in 2002. Four people died. The virus is rare in Summit County, but people should avoid mosquito bites when at lower elevations.
James Gathany / Centers for Disease Control and Prevention |

Long summer days mean getting outside, enjoying trails and, for some, cleaning out sheds and garages.

They also mean people in Summit County are more likely to be exposed to blood-sucking mosquitoes and ticks, rabid bats and skunks — and deadly viruses and bacteria left behind by mice, squirrels and other rodents.

The Colorado Department of Public Health and the Environment announced on July 8 the state’s first confirmed case of the mosquito-bourne West Nile virus with a man diagnosed with the illness in Mesa County.

The department also confirmed mosquitoes carrying the disease are present in Denver and Larimer counties, and officials expected to add more counties to the list throughout the summer. West Nile virus is by far the most prevalent of all the diseases transmitted to humans from animals — generally called zoonoses — diagnosed in Colorado, with 118 cases in 25 counties in 2014 and four deaths.

However, for Summit County environmental health manager Dan Hendershott, mosquitoes are low on the priority list.


His top two concerns are rabies and hantavirus, which are more difficult to treat because they are viral and are much more deadly.

Rabies has no cure and is nearly 100 percent fatal once symptoms appear, which include insomnia, anxiety, paralysis, hallucinations, increased saliva production, difficulty swallowing and fear of water. In Summit, the disease is carried and transmitted by some bats.

“We know it’s here,” Hendershott said. “If you get it, you’re going to die pretty much.”

Rabies has become more common in land animals in eastern Colorado in recent years, and, in 2014, 129 animals tested positive in the state, including 92 bats, 32 skunks and two cats.

He said besides avoiding any wild animals acting sick or strange, the best way to prevent rabies is to vaccinate pets.

Prevent bats from entering the home, and, if one is found, try to capture it and contact the county health department or animal control. Humans may not feel or be able to see a bat bite, and a post-exposure prophylaxis may be necessary.

The combination of vaccine and medication is given to anyone who may have been bitten by a rabid animal and can prevent the illness if given quickly. The prophylaxis is the reason why the last recorded human case of rabies in a Colorado resident was in 1931.

The most recent reported local encounter with a rabid bat was three years ago, when the animal attacked a family playing outside. The bat later tested positive for rabies, and the individuals were successfully treated.

Local Colorado Parks and Wildlife officer Elissa Knox said two people in Summit were bitten last year by foxes, which can carry rabies, and she emphasized the importance of not feeding wildlife.

Hantavirus, the other worrisome virus spread through animals, has been diagnosed in five people in Colorado so far in 2015, four of whom died. The five cases were found in Chaffee, Garfield, La Plata, Phillips and Weld counties and were all men with no underlying health conditions.

Since 1993, state health officials have documented more than 90 cases of hantavirus, and 40 percent of those infected died.

The virus is carried primarily by deer mice, and, when their droppings are stirred up, the virus contaminates the air and infects people who breathe it in.

Cases have been reported in recent years in Eagle, Park, Grand and Clear Creek counties, so the disease likely exists in Summit, Hendershott said. “The fatality rate of it is so high that we want people to be extra cautious with it.”

Activities such as cleaning rodent-infestations, working in enclosed spaces, moving woodpiles and clearing brush and junk piles are associated with the highest risk. People should use ventilation, gloves, face masks and disinfectant when removing, cleaning and disposing of droppings or dead mice.


Next, Hendershott warned of plague and tularemia, two bacterial diseases spread through small mammals and fleas.

Plague didn’t arrive in Colorado until about 1941 but is now firmly established throughout the state in rock squirrels, prairie dogs, wood rats and other species of ground squirrels and chipmunks. It is believed to be the same plague that caused the Black Death in Europe in the 14th century.

In 2014, a pet dog in Colorado that was exposed to plague through contact with wildlife habitat infected three of its owners, a veterinary tech and a cat before it died. In June, a 16-year-old in Larimer County died from plague.

Summit hasn’t seen any cases of plague, but Hendershott said they are possible, and people who visit the Front Range where infected prairie dogs are more common should be more careful.

“If you catch plague early, it’s very treatable,” he said. “We discourage people from sleeping with their pets, and we discourage people from letting their dogs roam off leash.”

Tularemia, also called rabbit fever, is widespread in Colorado and better known among hunters.

In 2014, tularemia-related animal die-offs were reported in at least 27 Colorado counties, including Summit. Sixteen human cases were reported — five times the state annual average and the second highest amount of recorded cases since 1955 behind a spike in 1983.

Knox said she was alerted of a die-off by a concerned fly-fisherman who found three or four dead beavers within a week around the Upper Blue River south of Breckenridge. The beavers tested positive.

2015 will be another spike year as 15 cases have already been reported in the state. Officials think wet weather has allowed the bacteria to spread, and increased rabbit populations may be a factor.

The bacteria typically infects people who breathe it in near where dead small mammals have been seen, but people can also become infected from direct exposure to infected animals, contaminated water and contaminated soil. Other small mammals, ticks, deer flies and infected pets can be carriers.

People can prevent tularemia by avoiding areas where dead animals have been seen, wearing closed-toe shoes, avoiding tick and deer fly bites and wearing gloves when handling sick or dead animals. Hendershott also discouraged people from trying to rehabilitate sick animals in their homes.

Both plague and tularemia can be successfully treated with antibiotics.


West Nile virus actually isn’t much of a concern for people bitten by mosquitoes in Summit County, Hendershott said.

The type of mosquito that carries the virus doesn’t easily survive through the winter, and temperatures never climb high enough to allow the virus to thrive. Here, mosquitoes are simply a nuisance, but people should try to avoid bites when traveling in other parts of the state.

“The best prevention for West Nile is don’t leave Summit County in July and August,” Hendershott said, smiling. “It’s the best months to be up here, so why would you want to leave anyway?”

Avoid mosquito bites by wearing loose long-sleeves and pants, staying indoors at dawn and dusk and using repellant, fans and screens on windows.

Ticks also feed on human blood, but tick-bourne diseases are rare in Summit. Rocky Mountain Spotted Fever is the most dangerous of the tick-bourne diseases in Colorado, and flu-like symptoms can progress to death if antibiotics aren’t used early.

Most animal-related diseases present with symptoms similar to common colds and fevers, Hendershott said. “Early detection is critical.”

Health care providers should be aware, and sick people should tell their doctors about possible exposures to hasten proper diagnosis and treatment.

For more information about animal-related diseases, call Summit County Public Health Department at 970-668-9161 or Environmental Health Department at 970 668-4070 or visit

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