In 2015, after four days of flu-like symptoms, a 16-year-old star high school athlete died of plague, likely from contact with a flea-infested dead rodent on his family’s property near Fort Collins. His parents were so stunned, they took the exceptional student’s story public to raise awareness.
That same year, a 77-year-old Wyoming woman died of rabies six weeks after awakening to a bat on her neck. Seeing no bites, the woman’s husband captured and released the creature, dismissing the incident until perplexed hospital staff grilled him four weeks later in search of answers to severe symptoms that suddenly struck his wife.
The Colorado Department of Public Health and Environment (CDPHE) lists 10 animal-related diseases as Colorado threats along with data and resources for veterinarians.
Animal-related diseases, which range from rabies and plague to hantavirus and West Nile, are public health threats that rise with the animals’ activity in warmer months. The most recent human case of plague was reported in early July in Colorado’s Pueblo County. Knowing what to do after an encounter with potential carriers, from bats and ticks to rats and mosquitoes, can be life-saving.
Rabies grows rarer with public health efforts
Within the United States today, bats, raccoons, skunks and foxes are primary transmitters of rabies, a viral infection caused by the rabies lyssavirus, said Daniel Pastula, MD, MHS, professor of neurology, infectious diseases, and epidemiology at the University of Colorado School of Medicine and Colorado School of Public Health.
U.S. human rabies cases have grown increasingly rarer, thanks largely to the nation’s public health system and efficient use of prophylactic measures. From 2009 to 2018, 25 U.S. cases of human rabies were documented, seven of which were contracted outside of the country.
No longer endemic in U.S. dogs due to vaccination, rabies in canines remains a chief threat in countries without vaccine requirements.
“If you are in a different country, and there are roaming dogs around, realize that they might have rabies,” said Pastula, section chief of Neuro-Infectious Diseases and Global Neurology, who consults on suspected rabies cases region-wide. One of the most recent U.S. rabies deaths was of a Virginia woman who was bitten by a puppy while traveling in India in 2017.
Travelers to countries with high rabies rates should talk to their doctors about being vaccinated before their trips, Pastula said.
Severe neurological disease has no treatment
The rabies virus is transmitted via infected saliva of mammals through a bite or, more rarely, when saliva enters a person’s mouth, eyes or wound. The virus targets the central nervous system, with incubation periods lasting from weeks to months after a bite.
“It depends on where you get bitten and how much virus gets in you,” Pastula said. “The virus crawls up your nerves for several weeks, and then it gets into your brain and salivary glands and kills you. By the time you have symptoms, there is really no treatment.”
Four weeks after the bat incident with the Wyoming woman, her husband took her to the emergency room with severe weakness and loss of coordination, telling providers his wife had early dementia. After two weeks of multiple tests and hospital transfers, the woman had become quadriplegic and, eventually, comatose. She died two days after rabies was confirmed.
Whenever people have any contact with a bat or wild animal, they should seek immediate attention, whether they are sure of a bite or not, Pastula said. With bats, bites may not be visible.
Preventive treatment almost always saves lives
Rabies postexposure prophylaxis (PEP) consists of wound washing – which people also should do immediately after a bite – and a dose of human rabies immune globulin (HRIG) at the initial visit. The first of four vaccine doses is also given on the first day, followed by the other injections on days three, seven and 14.
PEP is highly effective if given early, with the only reported case of a rabies death following appropriate prophylaxis care in 2021 in an 84-year-old Minnesota man who had awoke to a bat biting his hand. An unknown immune deficiency was suspected to have contributed to the treatment’s failure.
Even though human rabies cases are rare, hundreds of thousands of animals are observed or tested for rabies each year, and 60,000 people require PEP – including many healthcare providers, according to the Centers for Disease Control and Prevention (CDC).
During the Wyoming woman’s two-week stay in two hospitals, it was determined she had contact with 100 providers before rabies was suspected. Nearly a quarter of them went through the expensive PEP treatment, along with her husband and other family members.
Western Colorado rodents prime plague carriers
Source: U.S. Centers for Disease Control and Prevention |
Plague, a bacterial infection that became known as the black plague after killing millions of Europeans in the 14th century, is believed to have traveled to the United States largely via infected rats and their fleas on cargo ships.
The disease’s bacteria, called Yersinia pestis, are found in wild rodents, such as wood rats, ground squirrels and prairie dogs, and are endemic to the western United States, Pastula said. Plague is caused by humans getting too close to live rodents, handling dead rodents without protective gear (gloves, masks) or getting bit by the fleas rodents carry, he said.
Between 1970 and 2020, there were nearly 500 cases of human plague reported in the U.S. – about seven cases on average each year, according to the CDC.
In Colorado, where both the bacteria and pet-lovers are endemic, extra care with cats and dogs is important, especially four-legged house members that wander rural properties and come in contact with rodents. Prevent roaming when possible, Pastula said, and treat pets as veterinarians advise for fleas and ticks (which also carry diseases of their own to humans), Pastula said.
Pets themselves or the fleas that ride in on them can transmit plague to humans. “If you have pets that roam outside, it’s probably best that they don’t sleep with you on the same bed, because the fleas and ticks can come off and bite you,” Pastula said.
Prompt antibiotic treatment can prevent death
Three types of plague exist, with bubonic plague the most common (about 80% of cases). Septicemic plague can occur on its own, as with the 16-year-old Fort Collins teen whose symptoms progressed so fast, he died before reaching the hospital. The bloodstream infection can also develop secondary to untreated bubonic plague. Pneumonic plague can occur when the bacteria are inhaled or as progression of untreated bubonic plague.
Antibiotics given early can prevent severe disease and death with all three plague types.
“All three of these types have a fairly high mortality rate if left untreated. Fortunately, we have antibiotics, and the sooner the person gets antibiotics, the better their outcome will be.”
In all animal-related diseases, awareness and prevention are the best option, Pastula said. “Let wildlife be wild. You can watch it from afar, but don’t get too close. And if you think you’ve been bitten, get treatment right away.”
