RABIES: WHAT YOU SHOULD KNOW
RABIES: WHAT YOU SHOULD KNOW
The following is a real life scenario I faced a number of years ago. It presented me with several tough decisions that were potentially matters of life or death. The story goes as follows:
A 23 year old young woman, who had been my patient her entire life, came into the office just a day or two after returning from her honeymoon. She and her husband had gone to someplace in Mexico for their first days of wedded bliss. One afternoon they decided to explore the local area and ended up on the outdoor patio of a raucous bar. While they were enjoying themselves, a large, uncollared, stray dog wandered into the area and bit the young lady on the leg for no obvious reason. The bite was deep and tore the skin. The dog immediately ran away never to be seen again. She sought care at a local clinic, but received nothing more than first aid. She returned home with a swollen leg and a lot of anxiety.
This is the kind of scenario family physicians occasionally face. We have a potentially serious situation with a young woman visiting a foreign country, being bitten by a stray dog, and worried sick about getting rabies. The dog ran away so there was no way to quarantine it to observe for signs of rabies. The young lady is not sick, but we know the incubation period for rabies can be weeks to months. So, what would you do?
Here’s what I did: I immediately called the Communicable (Infectious) Disease Department of the Indiana State Board of Health to ask for advice. Their response was to administer Postexposure Rabies Prophylaxis to the patient as soon as possible. We had an unprovoked attack by an unknown dog in a foreign country, and were unable to assess the animal for signs of illness. The circumstances necessitated postexposure prophylaxis (PEP). More specifics on PEP will follow later.
So this healthy young woman received human rabies immune globulin and rabies vaccine at the recommended dose and frequency and experienced no further ill effects from the dog bite. She is well to this day. She also had no adverse effects from the vaccines, as was not the case in years past. The antigenicity of today’s vaccine has been altered, and the number of shots to be given has been reduced so adverse effects (mainly pain at the injection site) are less common.
Rabies is a viral illness that attacks the brain and spinal cord, the central nervous system (CNS). It causes brain inflammation (encephalitis) in 80% of cases. The other 20% take on a paralytic form. Here, the bitten extremity develops ascending paralysis as the main manifestation. The arm or leg becomes paralyzed and unusable. Animals acquire rabies far more often than humans. Dogs, cats, raccoons, bats, foxes, and skunks are affected far more often then humans. The rabies virus is transmitted to a human in the saliva of a rabid animal through a bite. In Arizona, the most common animal vector is the bat, but skunks and foxes are a close second while the virus can “spillover” to bobcats, dogs, cats, coyotes, javelina, cows and horses. About 30 people are exposed to rabid animals in AZ every year. Any person exposed to a rabid animal must receive PEP to prevent infection, otherwise, once the virus enters the central nervous system, death is a certainty. The last documented rabies death in AZ was in 1981.
In Indiana, rabies is transmitted by bats, skunks, foxes, raccoons, and coyotes. Dogs and cats also transmit rabies, but rabid pets have not been found in Indiana for many years. In the U.S., most dogs are vaccinated against rabies so cases from domestic pets are virtually non-existent. The last case of rabies in a human in Indiana was in 1959. Out of 2151 animals tested for rabies in Indiana in 1996, only 9 were positive for rabies. Raccoons are the most aggressive of the rabies-carrying animals and represent 50% of the non-human cases of rabies in the U.S. So those cute little masked animals that peered through our family room windows at night were potentially lethal predators.
The most effective preventive measure for rabies is to leave wild animals alone and do nothing to provoke them. If, however, an individual is attacked by a rabid animal, PEP, postexposure prophylaxis is effective. “Hundreds of rabies post exposure prophylactic treatments are indicated annually in AZ to prevent rabies from developing after exposure.”
Worldwide, 55,000-59,000 persons die from rabies each year. A bite from a rabid animal is the source of most rabies, but the virus can enter a host through breaks in the skin, or mucous membranes in the eyes, nose, or mouth. Person-to-person transmission of rabies is rare. Persons who work in high exposure environments are urged to use extreme caution when handling potentially rabid animals.
The virus lies “dormant” in a human, or is incubating, until it travels to, and invades, the brain and/or spinal cord. How long that migration takes depends on how far the rabid bite is from the brain and spinal cord. It can take an average of 1-3 months. Once the CNS is affected, symptoms occur. Cerebral dysfunction, anxiety, confusion, autonomic instability, and agitation occur as well as hydrophobia (fear of water), delirium, hallucinations, abnormal behavior, and insomnia. Early on, a prodromal, flu-like period occurs as the first indication of disease—fever, headache, weakness, and discomfort. It can last up to 10 days. Once clinical signs of rabies occur, the disease is nearly always fatal.
That’s why Postexposure prophylaxis is so important. It involves not only the three-dose series of rabies vaccine, but also a single dose of rabies immune globulin. If I had not given my patient PEP, I was placing her in a precarious position had the dog been rabid. But we had no way to know. Giving her PEP was an expensive decision, but it was the right one. In this case, over-treating, or over-preventing was the best option. Any serious risk was eliminated by the series she received. PEP is nearly 100% effective.
Between 1980 and 1996 there were 32 cases of rabies in 20 states. Patients were predominantly male. 53% (17/32) were caused by bats, 38% (12/32) by domestic dogs while outside the U.S., 6% (2/32) by domestic dogs, and 1 (3%) by skunks. Fewer than 20 cases of human survival from clinical rabies have been documented. It is a fatal disease!
Dr. G’s Opinion: I’ve seen videos of patients infected with rabies. It’s horrible! Writhing, hallucinating, agitated, moving uncontrollably; it’s a miserable death. If you’re bitten by your dog or cat, or your neighbor’s pet, you’re safe because you know their rabies vaccination status, immediately. If you’re in the wild, and bitten by a raccoon, skunk, fox, bat or other, if you’re unable to capture the animal, you must begin postexposure prophylaxis as soon as possible—usually the same day. If by some miracle you can capture the animal, it should be tested for rabies immediately. That is unlikely so PEP should be started right away. Rabies PEP is not the major ordeal it was when I was a child, thus there is no reason to refuse the series. It will be lifesaving if it turns out your attacker was rabid. In this case, it is far better to err on the side of co-mission rather than omission.
References: Haviv J, Rishpon S, Gdalevich M, et al. Successful Postexposure Rabies Prophylaxis after Erroneous Starting Treatment Preventive Medicine 1999 July ;29(1):28-31.
https://www.azDHS.gov/preparedness/epidemiology-disease-control/rabies/index.php #about
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Noah DL, et al. Epidemiology of human rabies in the United States, 1980 to 1996. Ann Int Med 1998 June 1;128(11):922-930.
Nigg AJ, Walker PL. Overview, prevention, and treatment of rabies. Pharmacotherapy 2009 Oct;29(10):1182-1195.
JAMA PATIENT PAGE: Rabies JAMA 2023 January 24/32;329(4):350.
