Let me get the obvious out of the way – I’ve never seen a case of rabies. In fact, in the county in which I work there has not been a case of rabies in over 60 years. But, you will all see children bitten by some sort of creature. So, when should we worry about rabies? Which animals are high risk? How do I know what to give and when to give it? Read on and learn more!
What does rabies actually look like in a human?
Bad. It looks bad. And it’s almost uniformly fatal. Most patients die within 2 weeks after onset of coma. Here are some specifics:
Prodrome (up to one week)
Non-specific symptoms, including fever, chills, malaise, myalgia, nausea, vomiting, headache, photophobia and a lot more. Patients can have paresthesias radiating from the wound site as well as localized pain due to the wound response and local injury. These are somewhat specific for rabies actually.
Encephalitic rabies (80%)
“Furious” rabies presents with fever, hydrophobia (pathologic fear of drinking water!), pharyngeal spasms (triggered after a draft of air), facial grimace (opisthotonos) and hyperactivity later leading to paralysis, coma and death
Paralytic rabies (20%)
Ascending paralysis – kind of like Guillain-Barré syndrome. Initially patients develop flaccid paralysis most prominent in the bitten limb then it spreads. Patients have fasciculations and DTRs are lost.
How does one make the diagnosis?
It’s hard and you need a high index of suspicion, which is the most important thing in the ED really. techniques include immunofluorescent antibodies of skin samples, virus isolation from saliva or anti-rabies antibodies in the CSF.
How is it treated?
Since most of you will never see rabies I’ll keep this part brief – It’s hard and requires ICU level management with induction of coma and multiple parallel therapies. I’ve linked to an article below that describes the Milwaukee protocol. For the more “human” side of things you should listen to the RadioLab episode on this topic. it’s excellent!
OK, how about prophylaxis? That’s what I’ll do in the ED anyway.
Most of your patients have never been vaccinated against rabies, so this is the immediate Day Zero regimen.
Rabies Immune Globulin (RIG)
Dose 20 units/kg . As much of the full dose as feasible should be infiltrated around the wound(s). Give the remaining IM at a separate site.
Human diploid cell vaccine (HDCV) or purified chick embryo cell vaccine (PCECV) 1 mL, IM (deltoid) – on days 0, 3, 7 and 14. I like to remember these dates as first half score tallies from an American Football game.
Previously vaccinated patients shouldn’t get RIG, and then get the vaccine on days zero and 3. Patients with immune compromise get five doses of vaccine on days 0, 3, 7, 14, and 28. Also, check out this algorithm to help decide when to employ post-exposure prophylaxis.
Courtesy of Alfred DeMaria Jr, MD and the Massachusetts Department of Public Health
Which animals are highest risk for rabies?
A lot of this depends on where you live – so check out the following CDC figure.
Distribution of major rabies virus variants among mesocarnivores in the United States and Puerto Rico from 2008 to 2014.
Most cases of rabies are acquired through exposure to saliva from a bite. Per the CDC “Raccoons continued to be the most frequently reported rabid wildlife species (accounting for 30.2 percent of all animal cases during 2014), followed by bats (29.1 percent), skunks (26.3 percent), and foxes (4.1 percent).” Rarely persons are exposed to aerosolized virus in bat caves our labs (no, not where Batman works).
What about kids bitten by a stray dog?
Rabies cases among domestic animals is very rare in the US. Dogs are more likely to have it along the United States-Mexico border. Overall though more rabid cats than dogs are reported in the US – which is likely due to vaccination laws and a greater number of free-range cats. So, ultimately, the odds of getting rabies after being bitten by a dog in a public location are super low. Bacterial wound infections are far more likely. Animals uniformly get sick and die within 10 days (usually 5-7) once the rabies virus moves from the CNS to the salivary glands. If possible a healthy domestic dog, cat, or ferret that bites a patient should be confined for 10 days. Any sign of illness should be evaluated by a vet – and any ill animals should be euthanized. The head is then shipped under refrigeration to a lab certified to test for rabies. Conversely, if the animal survives for 10 days then it didn’t have rabies virus in it’s saliva when it bit the patient. So, in summary, if a child is bitten every effort should be made to locate, sequester and observe the animal for 10 days.
Obviously patients exposed to symptomatic animals should get post-exposure prophylaxis. Special care should be given if the exposure was to the head out neck, since it can worsen in 4-5 days (faster than other sites). You can always stop prophylaxis if the animal is negative. If the animal cannot be located you’ll have to have a risks and benefits discussion with the patient and family.
Since dogs, cats and ferrets are required to be vaccinated, inquiring as to whether or not the animal is vaccinated is a mandatory part of the history. Other important questions are whether the bite was provoked or not. Remember, most dog bites occur when the dog is approached by a child or with handling and feeding. Obviously, rabid animals are more likely to bite in an unprovoked fashion.
Human rabies: a disease of complex neuropathogenetic mechanisms and diagnostic challenges. Hemachudha et al. Lancet Neurol. 2002;1(2):101.
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