Rabies

Question 1

How is rabies transmitted?

Answer 1

Saliva contaminated bite
Orally
Droplet inhalation
Transplacentally

Question 2

How does the rabies virus enter and spread within the host?

Answer 2

1. Receptor mediated endocytosis via coated pits - enters host cells - pH dependent fusion of the viral envelope with the endosomal membrane occurs and the viral nucleocapsid is released into the cytoplasm
2. Myocytes at the inoculation site are infected and may remain undetectable for weeks before moving centrally
3. Progression along nerves occurs in tissue spaces of nerve fasciculus - progresses centripetally by axoplasmic flow and replicates in spinal and dorsal root ganglia
4. Virus reaches CNS - rapid spread and multiplication then reaches tissues outside the CNS via centrifugal movement along nerve axons

Question 3

What is the incubation period of rabies?

Answer 3

Usually 14-90 days

Question 4

What are the histopathological changes of rabies?

Answer 4

Negri bodies - intracytoplasmic eosinophilic inclusions in neurons and ganglion cells are pathognomonic
Mild non suppurative encephalomyelitis occurs - peri vascular cuffing, gliosis, glial nodules and neuronal degeneration