When most families hear the word rabies, they envision a dog foaming at the mouth and think about receiving multiple painful, often intra-abdominal injections. However, the epidemiology of rabies has changed in the United States. Postexposure prophylaxis (PEP) may not always be indicated and for certain persons preexposure prophylaxis (PrEP) is available and recommended.
Rabies is a Lyssavirus that is transmitted through saliva most often from the bite or scratch of an infected animal. Sometimes it’s via direct contact with mucous membranes. Although rare, cases have been described in which an undiagnosed donor passed the virus via transplant to recipients and four cases of aerosolized transmission were documented in two spelunkers and two laboratory technicians working with the virus. Worldwide it’s estimated that rabies causes 59,000 deaths annually.
CDC
Fig 1. Line graph of species with rabies 1967-2017
Most cases (98%) are secondary to canine rabies. Prior to 1960, dogs were the major reservoir in the United States; however, after introduction of leash laws and animal vaccination in 1947, there was a drastic decline in cases caused by the canine rabies virus variant (CRVV). By 2004, CRVV was eliminated in the United States.
However, the proportion of strains associated with wildlife including raccoons, skunks, foxes, bats, coyotes, and mongoose now account for most of the cases in humans. Wildlife rabies is found in all states except Hawaii. Between 1960 and 2018, 89 cases were acquired in the United States and 62 (70%) were from bat exposure. Dog bites acquired during international travel were the cause of 36 cases.
Once signs and symptoms of disease develop there is no treatment. Regardless of the species variant, rabies virus infection is fatal in over 99% of cases. However, disease can be prevented with prompt initiation of PEP, which includes administration of rabies immune globulin (RIG) and rabies vaccine. Let’s look at a few different scenarios.
1. A delivery person is bitten by your neighbor’s dog while making a delivery. He was told to get rabies vaccine. What should we advise?
Canine rabies has been eliminated in the United States. However, unvaccinated canines can acquire rabies from wildlife. In this situation, you can determine the immunization status of the dog. Contact your local/state health department to assist with enforcement and management. Bites by cats and ferrets should be managed similarly.
Healthy dog:
1. Observe for 10 days.
2. PEP is not indicated unless the animal develops signs/symptoms of rabies. Then euthanize and begin PEP.
Dog appears rabid or suspected to be rabid:
1. Begin PEP.
2. Animal should be euthanized. If immunofluorescent test is negative discontinue PEP.
Dog unavailable:
Contact local/state health department. They are more familiar with rabies surveillance data.
2. Patient relocating to Malaysia for 3-4 years. Rabies PrEP was recommended but the family wants your opinion before receiving the vaccine. What would you advise?
Canine rabies is felt to be the primary cause of rabies outside of the United States. Canines are not routinely vaccinated in many foreign destinations, and the availability of RIG and rabies vaccine is not guaranteed in developing countries. As noted above, dog bites during international travel accounted for 28% of U.S. cases between 1960 and 2018.
Dr. Bonnie M. Word
In May 2022 recommendations for a modified two-dose PrEP schedule was published that identifies five risk groups and includes specific timing for checking rabies titers. The third rabies dose can now be administered up until year 3 (Morb Mortal Wkly Rep. 2022 May 6;71[18]:619-27). For individuals relocating to countries where CRVV is present, I prefer the traditional three-dose PrEP schedule administered between 21 and 28 days. However, we now have options. If exposure occurs any time after completion of a three-dose PrEP series or within 3 years after completion of a two-dose PrEP series, RIG would not be required. All patients would receive two doses of rabies vaccine (days 0, 3). If exposure occurs after 3 years in a person who received two doses of PrEP who did not have documentation of a protective rabies titer (> 5 IU/mL), treatment will include RIG plus four doses of vaccine (days 0, 3, 7, 14).
For this relocating patient, supporting PrEP would be strongly recommended.