Epidemiology
Etiology
- Pathogen
- Rabies is caused by several different members of the Rhabdoviridae family.
- Rhabdoviruses are rod or bullet shaped
- Genus: Lyssavirus
- ssRNA
- Transmission
- Most common animal reservoir worldwide: dogs
- Most common animal reservoirs in the US: bats, raccoons, skunks, and foxes
- Spread through saliva of rabid animal after bite injury
- Via aerosols (e.g., bat caves); rare
Pathophysiology
Rabies virus binds the ACh receptor of peripheral nerves in the bite wound → migrates retrogradely along the axonal microtubules (using motor protein dynein) → enters the CNS → infects the brain
Clinical features
Encephalitic rabies (most common type)
- Hydrophobia: Rabies patients experience involuntary, painful pharyngeal muscle spasms when trying to drink; later on in the disease, the sight of water alone may provoke nausea or vomiting.
- CNS symptoms
- Anxiety, agitation, and combativeness alternating with calm periods
- Confusion and hallucinations
- Photophobia
- Fasciculations
- Seizures
- ↑ Muscle tone and reflexes with nuchal rigidity
- Autonomic symptoms (e.g., hypersalivation, hyperhidrosis)
- Coma and death within days to weeks of the development of neurological symptoms
Paralytic rabies (< 20% of cases)
- Flaccid paralysis, gradually ascending and spreading from bite wound
- Paraplegia and loss of sphincter tone
- Respiratory failure and death
Diagnostics
- Postmortem brain tissue autopsy
- Histopathological findings: Negri bodies (eosinophilic cytoplasmic inclusion bodies typically found in the cerebellum and hippocampus)