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Rabies

Background

Rabies is one of the world’s deadliest infections. The fatality rate is >99% 1 Worldwide, 99% of human rabies deaths are attributed to bites from infected dogs.1,2 In the US, the canine strain was eliminated in the 1960’s.1

Infectious Organism: Lyssavirus RNA virus Transmission: saliva of infected mammal1


Transmission

Transmitted by (US and Canada) :

  • Foxes
  • Coyotes
  • Skunks
  • Raccoons
  • Bats
  • Cats (wild, unvaccinated cats only)

Not transmitted by :

  • Squirrels
  • Chipmunks
  • Rats
  • Mice
  • Rabbits
  • Contact with intact skin (petting or handling an infected animal, unless it is a bat)
  • Contact with dry surfaces that might have had live virus on them. The virus is inactivated by sunlight and desiccation

Mode of transmission:

Exposure to saliva through broken skin, even small unnoticed wounds, exposure to mucus membranes, aerosolization (spelunking). Any exposure to bats is sufficient. From 1990-2015 only 17% of cases had a known bite from a bat, 41% had no history of bat exposure. 33% had a bat in the room while sleeping. 3,4


Travelers

If traveling outside the US and Canada, rabies is most commonly found in unvaccinated dogs. The CDC maintains a web page with rabies specific information and a tracker to search countries for levels of endemic rabies.

If a traveler had post exposure prophylaxis for rabies initiated outside the US, it is important to determine what products were given. Certain therapies are not used in the US due to lower efficacy, such as  purified vero cell rabies vaccine (Verorab ®, Imovax – Rabies vero ®, TRC Verorab ®), purified duck embryo vaccine (Lyssavac N ®), or different formulations of PCEC (Rabipur ®) or HDCV (Rabivac ®). The CDC maintains a webpage with instruction on how to proceed in these cases, inlcuding instrucitons for obtaining titers and consultation with state or local health departments. The page can be found here: What if I receive treatment outside the United States?


Disease Progression

There are 5 stages of infection3,4:

  1. Incubation
  2. Prodrome
    • Fever and vague symptoms
  3. Acute neurologic phase
    • Anxiety
    • Paresis, paralysis, and other signs of encephalitis
    • Hydrophobia – spasms of swallowing muscles stimulated by the sight, sound, or perception of water
    • Delirium
    • Convulsions
  4. Coma
  5. Death.

Most will develop symptoms within 1-3 months but can be as short as 5 days depending on amount of exposure. Once symptoms have started it is universally fatal. Therefore, urgent treatment after exposure is key.


Treatment

Unvaccinated3,4

  1. Wound cleansing
  2. Vaccine in unaffected limb, far from skin wound.
    • 1 ml IM on days 0, 3, 7, 14 with additional dose day 28 if immunosuppressed.
  3. Human rabies IG (HRIG)
    • 20 IU/kg infiltrated into wound, with any remaining give IM at site distant from vaccine on day 0.
    • Can administer up to 7 days after the first vaccine dose

Vaccinated3,4

  1. Wound cleansing
  2. Vaccine in unaffected limb, far from skin wound.
    • 1 ml IM on days 0 and 3
  3. No HRIG

References

  1. Pieracci EG, Pearson 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(23):524-528. Full Text
  2. Fooks AR, Cliquet F, Finke S, et al. Rabies. Nat Rev Dis Primers. 2017;3(1):17091. Full Text
  3. Storch B. Management of suspected rabies exposure in the emergency department. Emerg Med Pract. 2021 Apr;23(4):1-20. PMID: 33779128. Online
  4. CDC Yellow Book, 2020, Chapter 4 – Travel Related Infectious Diseases, Rabies; Wallace, R, et al. Full Text

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