A virus is turning animals into 'zombies'

According to recent news reports, a highly contagious virus known as canine distemper virus or Canine morbillivirus (CDV) has caused raccoons to behave like “zombies” throughout several parts of Canada.^[] 

A Toronto-based magazine, Streets of Toronto, notes that people have reported seeing raccoons “wandering close to humans, getting up on its hind legs or baring its teeth.”^[]

Veterinarian Dr. Marta Vidal-Abarca, BVSC GPCERT (OPHTHAL) MRCVS of Dogster.com, tells MDLinx symptoms generally include “strange behavior,” like circling, poor movement, lack of coordination, and loss of fear to humans. There may also be drooling, discharge of the eyes and nose, conjunctivitis, vomiting, diarrhea, skin pustules, or abnormalities of the pads. “The signs will depend on the animal type and their immune response,” she adds.

Streets of Toronto writes that Toronto Animal Services saw a massive spike in calls regarding sick or injured raccoons in 2024—with nearly 4,000 calls versus 719 in 2022. Toronto Public Health advised residents to avoid physical contact with infected animals.^[] 

The Ontario Wildlife Centre also says people sometimes think they’re reporting a raccoon with rabies; however, in many cases, the real issue is CDV. New York City also saw an outbreak of CDV in 2018.^[] 

According to a 2023 article published in Pathogens, the virus affects a wide range of hosts, including endangered species—and is still not entirely understood. It is thought CDV could have stemmed from a “measles virus in a species cross-over event, from humans to domesticated dogs (Canis lupus familiaris),” the authors write. “The clinical outcome associated with infection is variable and based on many factors, including the host species, the immune response of the individual animal to the infection, and variation in virus tropism and virulence,” the authors continue.^[]

Raccoons aren’t alone in CDV. Dr. Vidal-Abarca says that foxes, wolves, dogs, ferrets, and other animals have also been infected. “CDV is a type of virus, genus Morbillivirus, that is highly contagious. It causes life-threatening disease in many animal species. CDV cases affect approximately 90% of wild carnivores, but other types of animals can also be affected, and it is spread worldwide,” she says. 

The key issue is that “vaccination campaigns in wildlife are extremely challenging,” Dr. Vidal-Abarca says. There is currently a lack of a safe, effective vaccine for wildlife.^[] 

Dr. Vidal-Abarca notes that vaccination against CDV is available for dogs and that the vaccine is considered “core”—meaning it is highly recommended for all dogs, “regardless of their lifestyle or geographical location. The vaccine is highly effective,” she says. 

Research in Pathogens shows that vaccinating dogs “has contributed to a decrease in percentage of CDV-infected dogs in countries where high vaccine coverage exists, which now leaves wild carnivores such as raccoons (Procyon lotor) as the main reservoir.”^[]

Dr. Ashley Gray, medical director of Veterinary Emergency Group in Charlotte, NC, tells MDLinx that pet dogs may be at greater risk for CDV in spaces where there are other, “unvaccinated pet dogs, stray dogs, or wildlife (like foxes, coyotes, raccoons or wolves). This includes places like animal shelters, parks, pet stores, hunting or hiking trips, or even neighborhoods and backyards bordered by wooded areas,” she says.

Pet owners should know that CDV symptoms can be nonspecific and can result from many other diseases, “making it important to seek veterinary care promptly to determine if distemper is a concern. This disease is contagious to other pets, so seeing a veterinarian is important to ensure prompt diagnosis and treatment occurs,” Dr. Gray adds.

What this means for you and your patients 

While there’s no definitive evidence that CDV can cause disease in humans, it is known to affect some primate species, Dr. Vidal-Abarca explains. “Being such a dangerous and highly transmissible disease associated with high mortality rates, it is recommended to adopt safe habits and consider it a potential threat to humans,” she says. “People should never approach wildlife showing signs of distemper and must contact local authorities to deal with the potentially infected animal.”

There has been some research on CDV’s effect on humans. 

But that’s not all. Research published in Oncology Research and Treatment in 2024 indicates that CDV may play a therapeutic role in the fight against human ductal breast carcinoma cells: “[CDV] is known to induce apoptosis in tumor cells, thus serving as a potential candidate for oncolytic therapy. However, the mechanism of viral oncolytic activity is less studied and varies depending on the type of cancer and cell lines,” the researchers wrote. “CDV replication in the cells induced cytopathic effect and decreased in the cell proliferation rates compared to the uninfected control….The expression levels of the target genes suggest that CDV may be inducing the intrinsic apoptotic pathway in the cancer cell line.”^[]