Rabies
- Mary Malucci
- Mar 11, 2024
- 3 min read
Updated: Dec 24, 2024
A zoonosis [zo no sis] (plural zoonoses [zo no seas]) or zoonotic disease is an infectious disease of humans caused by a pathogen (an infectious agent, such as a bacterium, virus, parasite or prion) that can jump from a non-human (usually a vertebrate) to a human and vice versa.
One of the most lethal zoonoses in the world is Rabies, a viral zoonotic disease that causes progressive and fatal inflammation of the brain and spinal cord. Rabies virus is shed in the saliva and is most commonly transmitted through a bite from an infected mammal. Once the Rabies virus is introduced to a new host, it travels through the peripheral nerves, targeting the central nervous system (CNS) and causing encephalomyelitis. The rabies virus then travels away from the CNS back towards the peripheral nerves, especially to areas where the nerves are densely packed, like salivary glands. This causes hypersalivation and intense pharyngeal muscle spasms at the sight, taste or sound of water, which is called hydrophobia. Ultimately, the profound CNS inflammation causes complete failure of the entire nervous system and death.
After the initial bite wound inoculates the Rabies virus into a new host, the disease goes through 5 stages: incubation, prodrome, acute neurologic illness, coma and death.
Incubation is the period between the bite wound and the first onset of symptoms, ranging from days to years.
Prodrome is the stage in which vague non-specific symptoms appear, including GI signs, muscle aches and fever.
Neurologic symptoms characterize the third stage, which is categorized into three forms.
85% of Rabies patients will display the encephalitic, or furious, form. These patients may exhibit hydrophobia, agitation, aggression or other radical changes in mentation, progressing rapidly to hyperactivity. Neurologic signs may be accompanied by tachycardia, tachypnea and fever.
Less than 20% of rabies patients will exhibit the paralytic, or dumb, form which is characterized by profound weakness and sometimes accompanied by altered mentation, fever and bladder dysfunction.
The rarest form of Rabies is non-classic and generally associated with seizures and more profound motor and sensory symptoms.
Stage 4 is the coma stage and usually begins within 10 days of Stage 3.
Stage 5 is death and most patients succumb in 2-3 days. Once clinical signs are seen, Rabies is inevitably and universally Fatal! There is No effective treatment for Rabies!
If bitten by an animal that may possibly carry Rabies, first clean the wound thoroughly by scrubbing the wound and surrounding area with soap and water, ideally within 3 hours of being bitten. Flush deep puncture wounds with large amounts of saline. Apply antiviral solutions like povidone-iodine or benzalkonium chloride.
If the biting animal can be euthanized and tested, unnecessary post exposure treatments can be avoided. If the biting animal is a bat, skunk, raccoon or fox, start treatment immediately with Rabies vaccine and Rabies immune globulin. For all other bites, consult your local public health department. If the biting animal was an unvaccinated pet, local animal control authorities must be notified.
According to the World Health Organization, “Rabies is estimated to cause 59,000 human deaths annually in over 150 countries, with 95% of cases occurring in Africa and Asia. Due to underreporting and uncertain estimates, this number is likely a gross underestimate. The burden of disease is disproportionately borne by the rural poor populations, with approximately half of cases attributable to children under 15 years of age.”
99% of human deaths from Rabies begin with a bite from an infected dog. Thus, it becomes essential to keep our pets current with their Rabies vaccines to avoid exposure. In developed countries like the United States, where Rabies vaccines for pets and post-exposure treatments are readily available, human deaths from Rabies are very rare, about 2 per year for the past two decades. Even so, hundreds of thousands of animals are quarantined or tested for Rabies every year in the US and “between 30000 and 60000 people need to receive Rabies post exposure prophylaxis.”
For a number of reasons, including possible exposure to Rabies, wild animals should be safely observed from a distance. If you suspect a Rabid wild animal is on your property, contain your pets and call animal control. Do not attempt to catch the animal yourself. Dead or very sick animals should be handled with heavy gloves, if absolutely necessary.
Rabies - StatPearls - NCBI Bookshelf
World Health Organization - Rabies
Pan American Health Organization - Rabies
Center for Disease Control - Rabies
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