A New York man contracted an extremely rare and fatal brain disorder after eating squirrel brains, according to a new report of the man's case. Doctors found the man developed a degenerative disease caused by the same infectious proteins that also result in the more infamous "mad cow disease."

An MRI of the man's head revealed that the scan was the same as those seen in people with variant Creutzfeldt-Jakob disease (vCJD), a fatal brain condition caused by infectious proteins called prions. According to reports, only a few hundred cases of vCJD have ever been reported. Most of these cases have been linked to consumption of contaminated beef in the United Kingdom in the 1980s and 1990s.

In the new case, the 61-year-old man was brought to a hospital in Rochester, New York, in 2015, after experiencing a decline in his thinking abilities. He was also unable to walk on his own. It is believed that the man's habit of eating squirrel brains may have raised his risk for vCJD.

According to the man's family, he liked to hunt and used to eat squirrel brains. Dr. Tara Chen, a medical resident at Rochester Regional Health and lead author of the report, said it's unclear if the man consumed the entire squirrel brain or just squirrel meat that was contaminated with parts of squirrel brain.

The case came to light when Chen was writing a report on suspected Creutzfeldt-Jakob disease cases seen at her hospital in the last five years, according to Live Science. 

Creutzfeldt-Jakob disease (CJD) is a progressive neurological disorder that affects only about 1 in a million people each year worldwide, according to the National Institutes of Health (NIH). There are about 350 cases in the U.S. per year.

There are three forms of CJD: one that is inherited, one that comes from exposure to infected tissue from the brain or nervous system, and one that is "sporadic" and does not appear to have a genetic or environmental cause. There is no treatment or cure and no known way to prevent sporadic CJD.

CJD has a long incubation period. Symptoms can take up to 40 years to appear. Initial signs and symptoms typically include personality changes, anxiety, depression, memory loss, impaired thinking, blurred vision or blindness, insomnia, difficulty in speaking, difficulty in swallowing and, sudden, jerky movements or seizures.

Because CJD is so rare, doctors at Rochester Regional Health were surprised when four suspected cases of the disease occurred at the hospital within a six-month period, from November of 2017 to April of 2018. This high number prompted Chen and colleagues to conduct a review of suspected CJD cases at the hospital from 2013 to 2018. That's when the doctors came across the case tied to squirrel brains.