Rabies is a rare but serious zoonotic infection caused by viruses in the Rhabdoviridae family. The virus is transmitted to humans through the saliva of an infected mammal – most commonly from bites or scratches from bats or dogs, but raccoons, skunks, and foxes are also vectors in North America. Although only a handful of human cases are reported in the United States each year, immediate action after exposure is vital to preventing infection and death.
What happens if someone exposed to rabies develops symptoms?
After exposure, the incubation period is usually one to three months but can range from a few days to years. Early symptoms (lasting days to weeks) include pain, pruritus, or paresthesia at the infection site and flu-like symptoms such as fever, headache, loss of appetite, and fatigue. As the virus gains access to the peripheral nerves and central nervous system, neurological symptoms develop followed by encephalopathy (in about 67%-80% of cases) or paralysis (in about 20%-33% of cases). Coma and death usually occur within one to two weeks of symptom onset. There is no known effective treatment for symptomatic rabies. For this reason, if a person is exposed to a potentially rabid animal or if exposure cannot be ruled out, prompt and accurate administration of postexposure prophylaxis (PEP) is recommended.
What is involved in a rabies assessment?
The initial assessment involves determining the type of exposure (e.g., bite, scratch, or saliva getting into the eyes, nose, mouth, or open wound), local patterns (e.g., whether rabies is endemic or non-endemic and the animals affected), circumstances of the exposure (e.g., animal behavior and potential signs of illness), and the availability of the animal for observation and/or analysis. For exposure involving dogs, cats, or ferrets, postexposure prophylaxis should only be immediately started if the animal is suspected to be rabid. If the animal is healthy and available, it can be confined for observation for 10 days. If no signs of rabies develop, rabies PEP is not needed. For any potential exposure involving bats in which a bite cannot be ruled out, PEP is typically recommended. For potential exposures from other animals such as skunks, raccoons, foxes, or other carnivores, consider immediate PEP unless the animal is proven negative by testing. Public health authorities can also be consulted to assess the risk from possible exposures.
What is involved in rabies postexposure prophylaxis (PEP)?
There are three strategies involved in rabies PEP: (1) wound care, (2) administration of human rabies immune globulin (HRIG), and (3) vaccination.
The first step of PEP for all patients is cleaning the wound with soapy water and a virucidal agent such as povidone-iodine. Wounds should be washed for at least 15 minutes. Additional wound care, such as debridement or antibiotic prophylaxis may be needed in some cases, but suturing of wounds should be avoided or postponed to prevent further viral contamination and to allow for sufficient infiltration of HRIG.
In patients without a previous rabies vaccination, HRIG should be administered for immediate passive immunity. The purpose is to provide a bridge until active immunity develops from the vaccine, which takes about seven days. The HRIG dose should be infiltrated directly into each wound site as much as possible. Any remaining dose can be administered intramuscularly at a site distant from the rabies vaccine administration. If direct access to the wound is not anatomically feasible, the entire dose may be administered intramuscularly.
Finally, all patients should receive a rabies vaccination. Patients who have not been previously vaccinated should receive a four-dose regimen administered intramuscularly on days zero (as soon as possible after exposure), three, seven, and 14 post-exposure. Patients who have received a previous vaccination should receive a two-dose regimen on days zero and three.
What are the potential barriers to effective rabies PEP?
Most failures of PEP are attributed to a lack of education on proper procedures and inadequate communication within healthcare teams. The emergency department is the most common setting for rabies PEP administration. Due to the rarity of the disease, however, these providers may be inexperienced in appropriate PEP protocols due to the infrequency of encounters with patients who have possible rabies exposures. Providers should familiarize themselves with current guidelines from professional organizations, including recommendations to start prophylaxis immediately, clean wounds thoroughly, and follow proper administration of HRIG to all wound sites.
Even with appropriate procedures in place, patient adherence to the vaccination schedule may be low due to the out-of-pocket costs and time required to return to the hospital several times for multiple doses. To optimize adherence, it may help to provide (and review with patients) a printed copy of the vaccine schedule with a list of locations to obtain follow-up vaccines. Ensure that patients are aware of the seriousness of the disease and stress the importance of adhering to the vaccination schedule. Suggesting convenient locations such as affiliated outpatient facilities or urgent care centers may boost adherence. Providers can also help alleviate concerns about the cost to uninsured or underinsured patients by providing information about patient assistance programs and facilitating the application process.
Rabies PEP after every potential bat exposure – is it worth it?
It is worth noting that, although the CDC recommends PEP for any potential exposure involving bats, the reported incidence of bat-variant rabies is very low. This is especially true when including situations where it is unclear whether contact with the bat actually occurred, such as finding a bat in the bedroom where a person was sleeping (a situation for which PEP is technically recommended). The reported incidence of rabies for this type of exposure was 0.6 cases per billion person-years between 1990-2007. This is problematic for two reasons. First, the cost of a full course of rabies PEP can be thousands of dollars, either directly to the patient or to taxpayers through various patient assistance programs. The CDC estimates that the societal cost of rabies PEP after a potential bat exposure could be up to $8.4 billion per life saved. Second, the rate of severe allergic reaction to the rabies vaccine is reported to be 11 per 10,000 doses given, which is much higher than the rate of rabies infection. This implies that over-administering the vaccine might be doing more harm than good on average.
Several publications have called for refining the definition of a potential exposure or developing a more nuanced risk assessment for determining which types of potential exposures necessitate immediate PEP (read more here, here, and here). However, current guidelines maintain that PEP should be undertaken in any situation where a bat bite cannot be ruled out, and there is no absolute contraindication to PEP.
