Lecture 3: Rabies

What are common clinical signs of rabies in domestic animals?

Signs are highly variable and may include inappetance, dysphagia, cranial nerve deficits, abnormal behavior, ataxia, paralysis, altered vocalization, and seizures. The terms "dumb" and "furious" rabies are considered outdated.

How is a case of rabies confirmed in animals?

Lab confirmation is required via: Positive direct fluorescent antibody (DFA) test, or Isolation of rabies virus (cell culture or lab animal bioassay)

What is the prognosis of rabies once clinical signs appear in animals?

Rabies progresses rapidly to death, and there are currently no effective antiviral treatments.

Describe the rabies presentation in a 41-year-old human patient.

Initial signs included shaking, speech difficulties, dysphagia, vomiting, and severe anxiety. The condition progressed to agitation and muscle tremors. The incubation period was ~4 months; clinical course lasted 11 days.

Describe the rabies presentation in a 4-year-old human patient.

Symptoms started as drowsiness, abdominal pain, anorexia, sore throat, and neck pain, followed by fever and behavioral changes. Incubation period was 18 days; clinical course lasted 9 days.

Has survival from rabies ever been documented in humans?

Yes, survival has been documented in at least 6 patients—at least 5 of whom received rabies vaccine (RV) before exposure or illness.

Are all mammals susceptible to rabies?

Yes, all mammals are believed to be susceptible to rabies infection.

In how many U.S. jurisdictions were rabid bats reported in 2021?

Rabid bats were reported in 50 jurisdictions, making bats a major rabies reservoir.

Which wild terrestrial carnivores are the most commonly infected with rabies in the U.S.?

Raccoons, skunks, and foxes are the most commonly infected wild terrestrial carnivores.

What should be assumed about bites from wild carnivores?

All bites should be considered potential rabies exposures unless the animal tests negative.

Are rodents and lagomorphs significant rabies reservoirs?

No. Rodents (e.g., squirrels, rats, mice) are not considered rabies reservoirs. Lagomorphs (e.g., rabbits, hares) are rarely infected and have not been known to transmit rabies to humans.

What is the rabies status of dogs, cats, and ferrets in the U.S.?

The U.S. is free of canine rabies virus variant transmission. More cats than dogs have been diagnosed with rabies since 2000.

What is the pre-exposure rabies vaccination regimen for veterinarians and staff?

Two doses of rabies vaccine (RV) on Day 0 and Day 7, followed by: Titer check every 1-3 years, or Booster dose after 3 years without titer testing

What are the NASPHV recommendations for rabies prevention in domestic animals? Vaccinate all dogs, cats, and ferrets, Remove strays/unwanted animals, Hold/impound for 3 days in case of ownership or exposure

Is rabies vaccination available for wild animals or wild hybrids?

No licensed parenteral rabies vaccines exist for wild animals or hybrids. Control is very difficult.

What regulations are encouraged for wildlife to prevent rabies?

States are encouraged to prohibit the importation, distribution, translocation, and private ownership of raccoons, skunks, coyotes, foxes, bats, and other wild species.

What is the post-exposure prophylaxis (PEP) protocol for unvaccinated individuals?

Immediate wound cleansing with soap and water, RIG (half at bite site, half IM), Four doses of RV on Days 0, 3, 7, and 14

What is the post-exposure rabies protocol for previously vaccinated individuals?

Wound cleansing, RV only on Days 0 and 3 (no RIG needed)

How should wild carnivores and bats be managed if unavailable for testing?

Considered rabid by default

What is the protocol for unvaccinated dogs, cats, or ferrets exposed to a rabid animal?

Euthanize immediately, or Vaccinate immediately + strict isolation 4 months for dogs/cats 6 months for ferrets

How should currently vaccinated dogs, cats, or ferrets be managed after rabies exposure?

Revaccinate immediately, Observe under owner control for 45 days

What if the exposed animal is overdue for a rabies booster, but has documentation?

Booster immediately, Observe under owner control for 45 days

What are the options for exposed animals overdue for vaccination without documentation?

Euthanize, or Vaccinate immediately + strict isolation (4-6 months)

What should be done if an exposed animal becomes ill or develops signs suggestive of rabies?

Immediately report to the health department, If rabies is suspected: Euthanize and test

How should unvaccinated livestock exposed to rabies be managed?

Euthanize immediately, or Confine and observe for 6 months (case-by-case)

What is the protocol for vaccinated livestock exposed to rabies?

Revaccinate immediately, Observe for 45 days

Can livestock exposed to rabies be slaughtered?

Custom slaughter allowed immediately, Commercial slaughter prohibited for 8 months

Does consuming meat or milk from a rabid animal constitute rabies exposure?

No. Proper cooking and pasteurization inactivate rabies virus, Consuming cooked meat or pasteurized milk does not pose a rabies risk

What has the CDC found in milk from rabid cows over the past 15 years?

No detectable antigen or nucleic acids—supporting extremely low risk of transmission via milk

How should other mammal species exposed to a rabid animal be managed?

Immediate euthanasia is recommended.

How long do dogs, cats, and ferrets shed rabies virus relative to clinical signs?

They shed the virus a few days prior to and during clinical signs.

What is the incubation period for rabies in domestic animals?

Usually 3-12 weeks, but it can range from a few days to 6 months.

What is the reported incubation period for rabies in humans?

Usually 1-3 months, but periods longer than 1 year have been reported.

What is the latent period in rabies?

Time from infection to onset of viral shedding; can be up to 6 months.

How does the incubation period compare to the latent period?

The incubation period (infection to clinical signs) is usually 5-10 days longer than the latent period.

What are the two main categories of animal-to-human rabies exposure?

Bite exposures (skin penetration by teeth), Non-bite exposures (e.g., corneal transplants, aerosol, open wounds contacting saliva)

What does not constitute rabies exposure in humans?

Petting or handling animals, Contact with blood, urine, feces, Contact of saliva with intact skin

Why do bat exposures require special attention?

Any direct contact, especially with children, may go unnoticed and still pose risk; testing or prophylaxis is often recommended.

What are the known cases of human-to-human rabies transmission?

Only through organ transplantation (16 total cases): 8 corneal transplants (5 in U.S.), 7 solid organs (3 in U.S.), 1 vascular graft

Is caring for a human rabies patient an exposure risk?

No, unless the caregiver is bitten or exposed to saliva through open wounds.

What two human rabies vaccines are licensed in the U.S.?

HDCV (Human Diploid Cell Vaccine), PCECV (Purified Chick Embryo Cell Vaccine)

How long does it take for rabies vaccines to stimulate an immune response?

7-10 days to develop neutralizing antibodies that can persist for several years.

What is the function of Rabies Immune Globulin (RIG)?

Provides rapid passive immunity for approximately 21 days until active immunity develops.

Are rabies vaccines available for wild or hybrid animals?

No licensed rabies vaccines exist for these species. Zoos may vaccinate, but this does not alter post-exposure guidelines.

What should be done if a person is exposed to vaccinia-vectored oral rabies vaccine?

Report to the health department, but it is not a rabies exposure.

When is a domestic animal considered immunized against rabies?

28 days after the initial vaccination, Immediately after a booster dose

What is the standard rabies vaccination schedule for dogs, cats, and ferrets?

Initial vaccine at 3 months, Booster 1 year later, Then every 3 years

What is the role of Oral Rabies Vaccines (ORVs) in wildlife control?

Used in select areas (e.g., Ohio-Pennsylvania border, Texas) for mass vaccination of raccoons and coyotes with government approval.

How significant are bats in human rabies cases in the U.S.?

Rabid bats are reported from all 48 contiguous states; have caused at least 43 human deaths in the U.S.

Why is bat population reduction not a viable rabies control strategy?

It is neither feasible nor ecologically desirable.

What is the observation protocol for dogs, cats, and ferrets that bite humans?

Confine and observe for 10 days (regardless of vaccine status), Do not vaccinate during observation, Euthanize and test if signs develop

What is the recommendation for strays or unwanted animals that bite humans?

Euthanize and test immediately.

How are other animal species managed after biting a human?

Evaluated case-by-case based on species, exposure details, local epidemiology, and animal's health history.

How should animals suspected of rabies be submitted for testing?

Submit head or brain (including brainstem)—refrigerated, not frozen or chemically fixed.

Are there USDA-licensed rapid test kits for antemortem rabies diagnosis?

No, there are no commercially available rapid tests for living animals.

Who regulates the importation of dogs and cats into the U.S.?

The CDC (Centers for Disease Control and Prevention).

What are requirements for interstate movement of pets in the U.S.?

Must be current on rabies vaccination, Must have a valid rabies certificate (NASPHV Form 51)