Anti-Vax Spillover to Veterinary Medicine: Why Worry? RABIES

“Six deaths from rabies have been reported over the past 12 months in the U.S., the highest number in years."

Martina Kopf, Associate Producer, NBC News Health and Medical Unit

“If we continue to see plummeting vaccination rates or increasing vaccine hesitancy, are we going to see [rabies] in more pets, and not just wildlife? We’re kind of starting to sound the alarms.”

Gabriella Motta, DVM, Glenolden, PA

September 28^th is “World Rabies Day” (WRD); a day observed annually on September 28^th to raise awareness about the prevention and reduction in transmission of rabies in order to achieve the goal of eliminating dog-related rabies deaths by 2030. If you live in the U.S., it’s doubtful that WRD or even rabies is on your mind. But, the inadequate vaccination of dogs results in 59,000 canine-mediated rabies deaths in humans globally per year.

It now appears that many dog owners in the U.S. are hesitant about having their pets vaccinated for rabies. This has been dubbed the “spillover effect,” where a negative attitude toward human vaccines transfers to pet vaccinations. In this week’s post, I report not only on this disturbing development but also celebrate the legacy of Louis Pasteur who used his rabies vaccine some 140 years ago to save the life of a 9-year-old bitten by a rabid dog.

What is rabies (a recap)? Rabies tops the list of lethal and vicious zoonotic (animal-to-human) infections. It is present in animals in every state in the U.S. with the exception of Hawaii. And, it is one of a surprisingly small number of infectious agents that, if untreated, kills virtually all of its human victims. (The prion that causes Creutzfeldt Jacob Disease and untreated HIV are also on this shortlist.)

Rabies is an especially gruesome infection of the nervous system (brain and spinal cord) and has been known since around 2000 BCE. (See, “Rabies—Not In My Back Yard?,” Germ Gems, September 17, 2019). In Greek, the word rabies means “frenzy,” “rage,” or “madness.” The RNA virus of the genus Lyssavirus causes rabies. (Lyssa was the name of the minor Greek goddess of rage and fury in animals.) The virus is spread mainly through the saliva of infected animals.

The animal culprits. In the U.S., dog bites were the main source of infection in humans until 1960. Fortunately, rabies was effectively eliminated from the U.S. dog population by 2007 through widespread vaccination of owned and stray dogs—a remarkable achievement of veterinary medicine and the public health system. Nonetheless, dog bites continue to be the source of most rabies cases in Asia and Africa where dogs are not vaccinated.

Since about 1960, contact with the saliva of infected bats has led the list of animal exposures resulting in rabies cases in the U.S. Bites of other wildlife also pose a threat, including raccoons, skunks, and foxes. But small rodents, like squirrels, hamsters, guinea pigs, gerbils, chipmunks, rats, mice, and lagomorphs (rabbits and hares), are almost never infected with rabies virus and have not been known to transmit the virus to humans. 

In June, 2024, an outbreak of rabies occurred in seals in the Western Cape coast of South Africa. This was the first report of the virus within a marine mammal population. To date, seal-to-human rabies spread has not been seen.

Signs and symptoms of rabies. Symptoms of rabies include fever, headache, excess salivation, hydrophobia (fear of water), muscle spasms, paralysis, hallucinations, and confusion. They can appear anywhere from one day to one year after the bite of an infected animal. Once symptoms begin, the mortality rate is nearly 100%.

Treatment. Given its high mortality and the absence of a specific antiviral treatment of rabies, it is essential to confirm that the animal that did the biting had rabies before embarking on a series of vaccines to prevent rabies. Needless to say, once the diagnosis of rabies is confirmed highly expert medical care is critical.

Rabies is 100% preventable through timely administration of rabies vaccines called Rabies Post Exposure Treatment or PEP. Recently, a post-exposure prophylaxis regimen of rabies monoclonal antibody developed in India was described in The Lancet. (Kulkami, P., et al., “Post-exposure prophylaxis regimen  of rabies monoclonal antibody and vaccine in category 3 potential exposure patients: a  phases 4, open-label, randomized,  active controlled trial,” The Lancet, August 9, 2025). The results of this study are encouraging, but we must await data from randomized clinical trials. (Geurts van Kessel, C., Visser, L., “Efficacy and safety of monoclonal antibody PEP for rabies,” The Lancet, August 9, 2025).

Recent uptick in animal-to-human rabies cases in U.S. On September 17, 2025 the Centers for Disease Control and Prevention was tracking 14 potential rabies outbreaks in 20 states.  In the 12 months leading up to September, six people in the U.S. died of rabies, the highest number in years. An increase in wild animal rabies antedated the human rabies cases by several years but during the same period of time there was also an increase in canine vaccine hesitancy (CVH).

Decline in dog owner trust in vaccines. On August 31, 2023, the journal Vaccine published a study that showed a disturbing decline in dog owners’ trust in canine vaccines. (Motta, M., Motta, G., Stecula, D., “Sick as a Dog? The prevalence, politicization and health policy consequences of canine vaccine hesitancy [CVH],” Vaccine, September 22, 2023). This study found that nearly 40% of dog owners surveyed thought canine vaccines were unsafe, over 20% considered them ineffective, and 37% believed that vaccines could cause autism in dogs—even though autism is a human diagnosis and there is no scientific data that validates this for humans. (Query: How does one know that one’s dog has autism?)

The study was based on a survey of 2,200 U.S. adults which found that more than half of dog owners expressed some level of CVH. The research found a link between negative attitudes toward human vaccines, particularly COVID-19 shots, and skepticism about pet vaccines. The researchers suggested that concerns from the human vaccine debate have “spilled over” into veterinary medicine.

Bottom line on rabies vaccines. Louis Pasteur is credited with the discovery of the rabies virus and development of the first successful rabies vaccine in 1885. Through extensive research on rabbits, Pasteur developed a method to attenuate the virus by drying spinal cords and creating a less virulent form of the agent. He administered his vaccine for the first time to 9-year old Joseph Meister who had been bitten by a rabid dog and saved Joseph’s life.

It took until 1962 and the invention of the electron microscope for the rabies virus to be seen. Nonetheless, Pasteur’s work demonstrated that the virus was located in the brain and spinal cord of infected animals. His groundbreaking achievements ushered in the modern era of immunizations and established Pasteur as a pioneer in the field of immunology.

Since then vaccines have become the cornerstone of preventive health care for both humans and  pets saving human lives and also pets’ lives. The rabies vaccine is no exception.

Rabies is 100% fatal in dogs and it is a brutal death. The rabies vaccine is, however, 100% effective and it is safe. For those vaccine skeptics that are unfamiliar with what a “mad dog” –a dog in the furious form of rabies—looks like, I suggest watching the 1962 movie To Kill a Mockingbird to see the frightful behavior of a rabid dog before the poor animal is put out of its misery. After seeing that, wouldn’t you want to save your dog from this violent death by having your “best friend” vaccinated?

I am discouraged by what appears be a “spillover” into veterinary medicine of misinformation about the safety and efficacy of vaccines. As Matt Motta, one of the authors of the above-cited Vaccine article on CVH stated: “If non-vaccination were to become more common, our pets, vets, and even our friends and family risk coming into contact with vaccine-preventable diseases.”  We must all do more to restore trust in human (and veterinary) vaccine safety and efficacy before that happens. To quote the motto for the upcoming World Rabies Day: “Act now: you, me, communities.”