Vampire Bats Are Moving into the US and Scientists Worry They Could Spread a Fatal Zombie Deer Disease to Humans

A blood-feeding bat's northward expansion meets a fatal brain disease.

In 2022, Peter Larsen awoke in the Guyanese rainforest with a strange sensation on his feet. Sleeping in an open-air house, the University of Minnesota researcher flicked on his headlamp and found a vampire bat—the exact animal he had traveled to South America to study—feeding on his blood.

The encounter was intriguing and also concerning. What if he’d get sick, Dr. Larsen thought? After all, bats are natural reservoirs for several high-consequence viruses and pathogens, including rabies, Ebola, Marburg, and SARS-like coronaviruses, largely due to their unique immune system.

The unsettling episode prompted Dr. Larsen to consider the unique pathogens these highly social mammals might carry—or acquire—as they adapt to a changing world. Driven by warming temperatures, common vampire bats (Desmodus rotundus) are gradually expanding their range northward from Latin America. Meanwhile, Chronic Wasting Disease (CWD), a fatal and incurable neurological condition affecting North American deer, is spreading south.

To a wildlife epidemiologist, these converging trajectories set the stage for a novel threat. CWD is driven by infectious, misfolded proteins called prions, which circulate freely in the blood of sick deer. Because vampire bats survive entirely by drinking the blood of large mammals, they are on a direct collision course with the pathogen.

If these bats begin feeding on infected deer, could they ingest those prions and act as airborne reservoirs, transmitting the disease’s corrupted proteins to new populations of wildlife, livestock, or humans?

The Nature of the Threat

CWD belongs to a family of transmissible spongiform encephalopathies, a group that includes “mad cow” disease in cattle and scrapie in sheep.

Unlike viruses or bacteria, the disease is not caused by a living microorganism. It is driven by prions: normal proteins that have misfolded into a corrupted shape. Once inside a host, prions force other healthy proteins to misfold in a cascading chain reaction, slowly degrading the nervous system and leaving the brain riddled with microscopic holes.

CWD is known to infect deer, elk, and moose, with grim consequences. After an incubation period spanning 16 to 36 months, the animals suffer emaciation, excessive thirst, and severe cognitive impairment. They develop a blank stare, take on wide stances, and lose their natural fear of humans, earning the condition the moniker “zombie deer disease.”

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For a vampire bat, a neurologically impaired deer is an ideal target. These fist-sized mammals survive solely on blood, typically seeking out large, easily accessible prey in the dark. Using razor-sharp teeth, they create a painless wound and secrete an anticoagulant to lap up the pooling blood.

Research has detected infectious prions circulating freely in the blood of CWD-positive animals throughout the disease’s long incubation period. The authors note that a single 20-milliliter blood meal from an infected deer could harbor numerous infectious doses.

The bats’ highly prosocial nature acts as a potential amplifier for the disease. If a bat fails to find food, roost-mates will regurgitate their own blood meals to share with the hungry individual. They also groom each other communally. From an epidemiological perspective, this behavior could effectively spread prion-infected blood meals to other bats, escalating exposure across entire colonies of up to thousands of individuals.

The Nightmare Scenario

The geographic overlap of these two species is no longer a distant concern. Predictive models suggest climate change will drive vampire bats into Texas, New Mexico, and Arizona within the next few decades.

Worse, the disease may have already beaten the bats to the border. The new paper notes that between 2021 and 2025, Texas ranches unknowingly exported hundreds of live white-tailed deer into Mexico. Authorities later confirmed that these Texas facilities housed CWD-positive animals.

Because prions can persist in the soil for years and the disease has a long incubation period, the pathogen has ample opportunity to establish itself in new environments. Dr. Larsen, co-director of the Minnesota Center for Prion Research and Outreach, suspects the overlap is already happening.

“If I had to guess, I would say it’s 70% possible that there are already vampire bats feeding on [CWD-] positive animals in Mexico,” Dr. Larsen said.

The central fear is that bats’ bodies might alter the prions in dangerous ways. When prions pass through the digestive tract of a new species, their molecular structure can shift, potentially changing which animals they can infect.

“The prion doesn’t really mutate like a virus or bacteria that can change their genome,” said Brent Race, DVM, a scientist at the National Institutes of Health’s Rocky Mountain Laboratories. “It is possible that if bats were susceptible to CWD, the resulting prion may be folded differently than typical CWD and potentially have an enhanced ability to infect other species, including humans and livestock. This is, of course, very speculative.”

A Call for Caution and Surveillance

Some experts advise caution before sounding the alarm. Rodrigo Morales, PhD, of the University of Texas Medical School at Houston, noted that while the new study is important, the threat remains hypothetical without definitive animal models.

“This is something still hypothetical because there isn’t a very clear or frequent interaction between the infected animals [deer] and the vampire bats they are referring to,” Dr. Morales said. “Unfortunately, there are no models yet suggesting that this could happen. For that reason, interpretations need to be weighed with caution.”

He pointed out that a bat’s specialized gastrointestinal tract might naturally destroy the prions. “If we take an infected animal and collect the blood, we may detect it, but that doesn’t mean that the amount of prions present in blood will be enough to transmit the disease,” he added.

Still, the potential economic and public health fallout is too massive to ignore. The study’s authors are calling for sweeping ecological risk assessments and cross-border surveillance. Testing large animals is difficult, but monitoring at-risk populations is vital.

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The study was published in the Journal of Mammology.