Poliomyelitis and rabies
- Lesion
Poliovirus kills motor neurons and leaves floppy paralysis; rabies travels up nerves to the brain and is almost always fatal.
What it is
Two classic neurotropic viruses show how tropism shapes disease. Poliovirus, an enterovirus spread by the faecal-oral route, infects lower motor neurons in the anterior horns of the spinal cord and brainstem, causing asymmetric flaccid paralysis. Rabies virus enters through a bite, travels inside peripheral nerves to the CNS and causes an encephalitis with little inflammation but characteristic cytoplasmic inclusions, the Negri bodies. Vaccination has nearly eliminated polio and prevents rabies after exposure.
Step by step
- Rabies virus multiplies in muscle at the bite site.
- It enters nerve endings and moves slowly up the axons to the spinal cord and brain.
- It spreads through the brain and then outward along nerves to the salivary glands.
- Neuron dysfunction causes agitation, hydrophobia and autonomic instability.
- Once symptoms start, the disease is nearly always fatal.
Poliomyelitis and rabies compared
| Feature | Poliomyelitis | Rabies |
|---|---|---|
| Virus family | Enterovirus (picornavirus) | Lyssavirus (rhabdovirus) |
| Entry | Faecal-oral, gut | Bite or scratch, saliva |
| Route to CNS | Blood (viremia) | Retrograde along peripheral nerves |
| Main target | Anterior horn motor neurons | Brainstem, limbic system, cerebellum |
| Histology | Neuronophagia, perivascular cuffs in anterior horns | Negri bodies, little inflammation |
| Prevention | Oral and inactivated vaccines | Animal vaccination; post-exposure vaccine and immunoglobulin |
Clinical notes
- Acute flaccid paralysis surveillance in Colombia and the Americas watches for any return of polio.
- Any bite by a possibly rabid animal needs wound washing and prompt assessment for post-exposure prophylaxis.
Test yourself
Think of the answer, then tap the question to see it.
Which neurons does poliovirus destroy?
Lower motor neurons in the anterior horns of the spinal cord and motor nuclei of the brainstem.
What is a Negri body?
An eosinophilic cytoplasmic inclusion of rabies virus, seen in hippocampal and Purkinje neurons.
How does rabies virus reach the brain?
By retrograde transport inside peripheral nerve axons from the site of the bite.
Elsewhere in DurgiPedia
Connections
Microorganisms2
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Poliomyelitis (World Health Organization, 2026); Rabies (World Health Organization, 2026).
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Representative model, for educational purposes only.