Rabies, the epitome of One Health: A veterinarian’s role

Part of a veterinarian’s One Health duty includes ensuring preventative measures to protect our pets and pet parents, friends, family, and society from an easily preventable yet deadly disease: Rabies.

Zoonotic disease prevention: A veterinarian’s duty

Rabies vaccination administration and the successful eradication of the canine rabies virus variant (CRVV) in the United States provide a perfect example of how veterinarians play a pivotal role in public health.

Rabies prevention and education of clients epitomizes a veterinarian’s One Health role. Achieved by using a mixture of oral and injectable vaccines for domestic and wildlife species, The CRVV eradication effort remains one of the “most important public health successes of the 20^th century.” ¹

As a proponent of One Health, I would be remiss in not writing about rabies, a lethal yet preventable viral disease.

Why is rabies of such public health concern?^1–5

While we may see only 1-3 human rabies cases annually in the US, several factors help explain why it remains a global public health concern.

Worldwide, almost 60,000 human cases occur annually.

• Think about what that means. Every 9 minutes, a person dies from rabies. This seems an astoundingly large number given the effectiveness of the vaccines developed to date.
• Children make up 40% of these cases.
• Cases in the US most commonly involve wildlife reservoirs and rabies variants associated with bats, raccoons, skunks, and foxes.
• While the US eradicated the CRVV, 98% of the cases occurring outside the US are due to that specific strain.

Additionally:

• Antarctica remains the only continent without the disease.
• Australia doesn’t have the disease in terrestrial mammals but does have bat rabies.
• 2019 laboratory data confirmed rabies in almost 4700 individual animals in the US.
• Rabies remains one of the most fatal diseases known, with near 100% fatality rates.
• It can infect and cause clinical disease in any mammal.
• It is 100% preventable via vaccination strategies worldwide.
• There are two transmission cycles (sylvatic and non-sylvatic).
• We know global eradication of the CRVV is achievable. This could be accomplished if the worldwide community focused efforts and funding to support vaccination programs.
• There remains no specific treatment for the disease. However, prompt recognition of exposure and administration of post-exposure prophylaxis (PEP) saves lives. (PEP consists of a series of rabies vaccinations and immune-globulin therapy).

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Rabies in wildlife and domestic animals^1,6–8

All mammals are susceptible to rabies. However, the predominantly infected wildlife species in the US include feral cats, bats, raccoons, foxes, coyotes, and skunks.

Dominant variants

The two most common dominant variants in the US include raccoon and bat rabies, though others persist. See the National Park Service map depicting the distribution of the terrestrial animal virus variants throughout the United States.

The raccoon variant predominates on the East Coast, while skunk and fox are common in other parts of the country. Bat rabies prevails in areas on the map not covered by a terrestrial animal.

In several regions of the US, via oral rabies vaccine wrapped in flavored bait successfully curbed the westward expansion of the raccoon variant. Since the raccoon rabies variant affects up to 75% of non-bat rabies cases, these oral vaccines helped dramatically reduce the risk of disease.

Human exposures where bat and raccoon variants coexist within the animal reservoirs are 600% higher than in areas with only the bat variant. Not only does it provide a prime example of a successful vaccine campaign, but it demonstrates that through cooperative One Health efforts, positive change occurs.

Clinical signs

How disease manifests in animals, including humans, varies based on

• The location of the exposure relative to the brain,
• The infecting variant, and
• Any existing immunity (such as those vaccinated)

Rabid wildlife may demonstrate a wide array of behaviors, including what appears to be acute sudden death. Signs, likely missed in wildlife, may be vague initially and include vomiting, fever, decreased appetite, and listlessness. Within only a few days, progression to severe neurologic dysfunction will occur.

Signs may consist of ataxia, weakness, dyspnea, dysphagia, cerebral and cranial nerve dysfunction, ptyalism, aberrant behaviors, such as being active during times not normally active, aggressive behaviors, or self-harm.

Horses and livestock may demonstrate aggressive behavior and show similar signs to wildlife but have also exhibited photophobia, depression, and self-mutilation.

Generally speaking, significant behavioral changes and unexplainable paralysis are most commonly noted with rabies. However, consider an animal rabid until proven otherwise in any animal demonstrating clinical signs consistent with an unexplained neurological condition.

More from Dr. Tramuta-Drobnis: Taking time for self-care: One veterinarian’s journey to tai chi

Rabies in humans

Easily preventable, human rabies cases still occur worldwide. We need to ensure disruption of the transmission to truly prevent disease.

Dominant variants

The bat rabies variant accounts for the most human deaths within the US despite domestic animal exposures remaining the main reason for people getting PEP.

Bat bites and scratches often go unnoticed, but a bat in the home or caught by the family dog presents a concern for exposure.

Clinical signs

Initial findings in humans may include flu-like symptoms such as weakness, headache, or fever. Some people have reported a tingling or itching sensation at the bite site. This initial phase may last for a few days, eventually progressing to neurologic signs. These include hydrophobia, delirium, agitation, confusion, anxiety, and trouble sleeping.

The presentations vary, and any evidence of cerebral dysfunction with other neurological changes could represent rabies.

Signs typically last 2-10 days before being almost always fatal, with less than twenty human cases of survival ever documented, most with a history of either pre-or post-exposure prophylaxis.

Rabies transmission^9–11

Regardless of species, rabies transmission occurs via direct contact with saliva or tissue of the brain from an infected animal. Damaged areas in the skin or mucous membranes (nose, mouth, eyes) provide entry points for the Lyssavirus.

The most common rabies exposure in humans occurs via a rabid animal’s bite. Rarely, transmission can occur through scratches or open wounds exposed to infected material. Another source of potential non-bite exposure exists as well. This involves the inhalation of aerosolized virus primarily in laboratory workers.

One final exposure, close contact with bats, also must be considered. Often bat bites and scratches go unnoticed or recognized as they are tiny and may not be painful. As a result, bats in a home can constitute exposure even without confirmed direct contact.

We all know that exposure to urine, blood, feces, and other bodily fluids except saliva and nervous system tissue post no infection risk. Additionally, the virus easily inactivates when exposed to sunlight. Once the material with any infectious material like saliva dries, it is considered non-infectious.

More on One Health: One Health, Covid and veterinary profession implications

Rabies laws, vaccination, and control efforts^11,12

Rabies vaccination requirements and animal exposure quarantine laws vary from one state to another.

States provide guidelines for veterinarians on what species require vaccination legally, and the duration of that vaccine remains legal regardless of the vaccine’s licensure. Additionally, states set importation regulations and entry requirements for visiting animals.

Some have minimal requirements, while others, like Hawaii, the only US state free from rabies, remain stringent.

Various county, municipal, and state health departments undertake broad rabies control efforts. Preventative measures are the focus, including bite prevention, vaccinations for domestic animal campaigns, and more.

Finally, larger-scale efforts via oral vaccine programs remain aimed at wild carnivore species. These endeavors occur via the combined efforts of various state agencies, the Centers for Disease Control and Prevention, and the USDA’s Wildlife Services. The ultimate goal is to eliminate the raccoon virus variant in land-dwelling wildlife reservoirs.

Why do we bother with vaccines? ^1,8,9,13

In May 2022, this question seems to come up often. Vaccination for COVID-19 confuses many. Does it help prevent disease or only some variants of the virus? Does it still allow infection but minimize the risk of hospitalizations and deaths? The questions abound and continue to do so as we head into another surge of COVID-19.

However, rabies vaccination works! Rabies vaccination remains much more cut and dry than that of COVID-19. The virus itself remains stable, not readily mutating. Though new rabies variants infrequently are identified, such as a novel strain identified first in a capuchin monkey and recently in a wild kinkajou in Brazil, these variations haven’t been readily identified in common wildlife and domestic species to date.¹⁴

In the US, we successfully eradicated the CRVV simply by enacting leash laws and successful vaccination campaigns and legislation.

• The lack of the CRVV within the US borders recently made the news. In 2021, the importation of rabid dogs with the CRVV from other countries made rabies concerns all too real, with 36 animals and 19 people exposed. A re-evaluation of the country’s importation laws and rabies requirements resulted.
• Because of the successful vaccination programs in dogs, man’s best friend only represents 1% of the reported annual rabid animals in the United States.
• However, in over 150 countries that still have the CRVV, 99% of human cases occur due to exposure to a rabid dog.
• Pieracci et al.,¹ discuss the vaccine threshold needed to prevent disease. By maintaining at least a 70% rabies vaccination rate in dogs, we can ensure the CRVV never again takes hold within the US.

When is rabies vaccination warranted?

One a general practitioner, there wasn’t a day that went by without at least administering one rabies vaccination to a patient. However, as an emergency veterinarian, I don’t usually give vaccines, and my patients are often sick when they present.

Sure, I get the occasional kitten or puppy who jumped off the bed and broke a leg, so they are “healthy.” However, vaccinating them isn’t my place, especially if my practice doesn’t serve as the primary care veterinarian.

However, those that come in with bite wounds or wounds of unknown origin or known altercations with wildlife present a different scenario altogether.

Rabies vaccination timing

Generally speaking, rabies is given between 12-16 weeks of age, boostered one year after the first vaccine, and then every 1-3 years, depending on the veterinarian’s state of practice.

While the vaccine is licensed at 12 weeks and many states require it, many vets elect to wait until 16 weeks to vaccinate. Many vets have concerns that maternal antibodies may still be present at 12 weeks of age, and vaccinating at a younger age may interfere with vaccine efficacy.

All too often, rescues vaccinate pets too young, fearing that they won’t get the vaccine properly once they leave the shelter or foster home. Vaccinating too young isn’t a safety concern. However, the legality of the vaccine in most jurisdictions and the immune system’s ability to adequately respond to a single vaccine are highly questionable. In these cases, boosters may be warranted before one year of age.

The job of rescue personnel and veterinarians is to educate owners or potential adopters of the risks and importance of obtaining the vaccine at the proper age. Pet stores and other intermediaries need to be properly educated on rabies vaccination timing. They are responsible for informing owners if additional vaccination requirements exist for the newly adopted or purchased pet.

Rabies vaccination indications in domestic small animals

Given this information, veterinarians should vaccinate against rabies in various species according to state regulations and guidelines. Rabies vaccines should be given to dogs, cats, and ferrets

• As juveniles (12-16 weeks of age)
• 1 year after the first vaccine
• Every 1-3 years, as required by state law
• As post-exposure prophylaxis
  • Ideally, animals should be boostered for rabies at the time of exposure
    • Animals current on rabies vaccination with wounds of unknown origin
    • Animals current on vaccinations with known exposure to a wild animal where the wild animal cannot be tested
    • Animals with no history of vaccination or those with a lapsed vaccine should be vaccinated in accordance with state laws under the same exposure scenarios as those who are vaccinated
  • Quarantine regulations play a role in the above and vary from state to state.

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Client education^1,11

By educating clients about the disease, the means to protect their loved ones, and the true benefits of vaccination, we can ensure the protection of our domestic animals and pet parents. We need to educate each new pet owner. This instruction needs to include

For the pets:

• The benefits of pet vaccination
• The minimal risk of vaccine reaction compared to the numbers of patients receiving the vaccine
• The fact that they cannot get the disease in any way from the vaccine itself
• Ensuring pets are not allowed to roam free when feasible
• Ensure any wound of unknown origin gets immediate medical attention and explain why we will booster the vaccine in these cases
• Ensure clients understand the expected behavior of various species and when to be hypervigilant – Clients should know when raccoons and other potential sources of infection most commonly roam and may be seen out and about. They should understand that foxes and most species will not just come up to you. If they are aggressively seeking them out, this could be dangerous and signify concern.
• Clients should know to report to the proper authorities in their area any abnormal animal behavior
• Provide your clients with websites and resources from reputable sources that can provide further detailed information
• Inform them of species of concern and remember to include exposure to bats. A bat in the house could itself constitute an exposure and should be reported

For humans:

• Avoid contact with wildlife
• Seek medical attention if scratched or bitten by any animal – Not just for rabies prevention but also for wound evaluation and potential medical treatment as warranted
  • Ensure an understanding of the reasoning behind timely therapy is to ensure suitable administration of PEP and medical care
• Don’t reach under things when you cannot see to the other side – no reaching under hedges or bushes and if needed, wear protective clothing and gloves.
• Avoid nursing sick and abandoned animals. Take them to rescue groups trained to work with wildlife and monitor for rabies signs.
• Don’t pet, feed, or touch stray or wild animals
• If a bat is found in the home, try to capture it and have it tested. If positive, this will guide whether the family members will need PEP.
• Ensure children are taught not to play with animals they do not know

Rabies prevention and control epitomizes the essence of One Health

A one health outlook allows partners on all fronts to interact and achieve global impacts to minimize the adverse effects of human activity on climate change, land development, the environment, habitats, and more.

As veterinarians, we can play a pivotal role in educating clients on the risks of certain behaviors, exposures to wildlife, and what to do if they become exposed. We can help to protect our patients by ensuring the continued routine vaccinations against public health threats, such as rabies.

World Rabies Health Day, which started in 2007, continues annually every September 28. An entire day designated to the disease suggests worldwide the importance of remembering the disease and including it in our prevention strategies, from the local veterinarian to the public health gurus of the world.⁸

The fight against rabies must be worldwide and include professionals from all walks of life. More must be done to help minimize risk and decrease the death tolls from a deadly yet easily preventable disease. Zoonotic disease prevention and control constitutes a large portion of a veterinarian’s wheelhouse.

We veterinarians can do our part by continuing to ensure the CRVV remains extinct within the US. Continued vigilance and due diligence with our patients’ vaccinations and client education remain vital for preventative care.

Erica Tramuta-Drobnis, VMD, MPH, CPH is the Founder & CEO ELTD of One Health Consulting, LLC, as well as a freelance writer, consultant, researcher, public health professional and small animal veterinarian.

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References

Pieracci EG, Pierson CM, Wallace RM, et al. Vital Signs: Trends in Human Rabies Deaths and Exposures — United States, 1938–2018. MMWR Morb Mortal Wkly Rep. 2019;68. doi:10.15585/mmwr.mm6823e1

American Society for Microbiology. The One Health of Rabies: It’s Not Just for Animals. ASM.org – American Society for Microbiology. Published September 27, 2021. Accessed May 10, 2022. https://asm.org/Articles/2021/September/The-One-Health-of-Rabies-It-s-Not-Just-for-Animals

Acharya KP, Acharya N, Phuyal S, Upadhyaya M, Lasee S. One-health approach: A best possible way to control rabies. One Health. 2020;10:100161. doi:10.1016/j.onehlt.2020.100161

Global Alliance for Rabies Control. How big is the problem of rabies? Global Alliance for Rabies Control. Accessed May 10, 2022. https://rabiesalliance.org/about/about-rabies/how-big-problem-rabies

Centers for Disease Control & Prevention (CDC). Human Rabies – Rabies in the US. Centers for Disease Control and Prevention. Published September 22, 2021. Accessed May 13, 2022. https://www.cdc.gov/rabies/location/usa/surveillance/human_rabies.html

U.S. National Park Service. One Health and Disease: Rabies. National Park Service. Published March 27, 2018. Accessed May 10, 2022. https://www.nps.gov/articles/one-health-disease-rabies.htm

Centers for Disease Control & Prevention (CDC). Veterinarians: Clinical Signs of Rabies in Animals – Rabies. Centers for Disease Control and Prevention. Published February 22, 2019. Accessed May 13, 2022. https://www.cdc.gov/rabies/specific_groups/veterinarians/clinical_signs.html

The American Veterinary Medical Association (AVMA). Rabies and Your Pet. American Veterinary Medical Association. Accessed May 13, 2022. https://www.avma.org/resources/public-health/rabies-and-your-pet

Centers for Disease Control & Prevention (CDC). How is rabies transmitted? Centers for Disease Control and Prevention. Published June 11, 2019. Accessed May 13, 2022. https://www.cdc.gov/rabies/transmission/index.html

Centers for Disease Control & Prevention (CDC). What are the signs and symptoms of rabies? Centers for Disease Control and Prevention. Published February 16, 2022. Accessed May 13, 2022. https://www.cdc.gov/rabies/symptoms/index.html

Centers for Disease Control & Prevention (CDC). Avoid risk of rabies from bats. Centers for Disease Control and Prevention. Published March 9, 2022. Accessed May 13, 2022. https://www.cdc.gov/rabies/animals/bats/index.html

Ma X, Monroe BP, Cleaton JM, et al. Public Veterinary Medicine: Public Health: Rabies surveillance in the United States during 2018. Journal of the American Veterinary Medical Association. 2020;256(2):195-208. doi:10.2460/javma.256.2.195

The Centers for Disease Control and Prevention (CDC). CDC Responds to a Case of Rabies in an Imported Dog: World Rabies Day. Centers for Disease Control and Prevention. Published September 22, 2021. Accessed May 10, 2022. https://www.cdc.gov/worldrabiesday/disease-detectives/rabies-imported-dog.html

Dell’Armelina Rocha PR, Velasco-Villa A, de Lima EM, et al. Unexpected rabies variant identified in kinkajou (Potos flavus), Mato Grosso, Brazil. Emerging Microbes & Infections. 2020;9(1):851-854. doi:10.1080/22221751.2020.1759380