Media outlets reporting numerous rabid animal attacks has led to increased caution and public education regarding rabies prevention and post-exposure prophylaxis. Recent reports include a rabid beaver attacking individuals in Pennsylvania and there have been 4 reports of rabid animal attacks in a 3-week period in Brunswick, Maine. These recent attacks highlight the importance of prevention and post-exposure prophylaxis.
In the United States, the CDC reports that wild animals account for 92% of cases of rabies, with bats being the most commonly infected. Domestic animals account for about 7.6% of cases of rabies, with humans accounting for <1% of all cases. Due to improved preventative measures beginning in the 1940’s with domestic animal vaccination, the number of human deaths from rabies has decreased from over 100 per year in the United States to 2-3 per year. However, worldwide rates of rabies fatalities in underserved areas are much higher, with an estimated 55,000 deaths per year.
The rabies virus infects the salivary glands of the host and is transmitted by direct contact with host saliva, typically in the form of a bite from an infected animal. The incubation period is up to 20-90 days, though may be as short as 4 days. The virus predominately attacks the central nervous system (CNS), replicating in the brain, spinal cord, and peripheral nervous system. Clinically, rabies infection results in encephalitis and demyelination of the gray matter in the CNS.
Rabies typically manifests with encephalitis in 80% of cases, but may present in a paralytic form in the remaining 20% of cases. The prodromal signs and symptoms of rabies infection are nonspecific and include limb weakness and pain of the affected extremity. Symptoms progress to include delirium, hallucinations, hypersalivation, hydrophobia (50%), hyperthermia, tachycardia, and hypertension. Active infection is almost universally fatal with the common causes of death including respiratory failure, seizures, cardiac dysrhythmias, or autonomic dysreflexia.
There is no known effective cure for rabies, heightening the importance of prevention. Individuals should take proper preventative measures and ensure to receive post-exposure prophylaxis when indicated, especially if bitten by a non-domesticated animal. Individuals that may have been exposed should immediately seek health care to be evaluated for post-exposure prophylaxis as the need for this is made on an individual basis.
Read more about rabies:
Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e: Chapter 157: Rabies
Harrison's Principles of Internal Medicine, 20e: Chapter 203: Rabies and Other Rhabdovirus Infections