Negri bodies are seen in
Correct Answer: Rabies
Description: Ans. b (Rabies). (Ref Robbin, Pathology, 7th ed., 137)PATHOGENESIS OF RABIES# The first event in rabies is the inoculation of virus through the skin, usually through a bite that delivers virus-laden saliva.# Initial viral replication appears to occur within striated muscle cells at the site of inoculation.# The peripheral nervous system is exposed at the neuromuscular and/or neurotendinous spindles of unmyelinated sensory nerve cell endings, with neurotransmitter receptors such as acetylcholine implicated in viral attachment and internalization.# The virus then spreads centripetally up the nerve to the CNS, probably via peripheral nerve axoplasm, at a rate of 3 mm/ h.# Once the virus reaches the CNS, it replicates almost exclusively within the gray matter and then passes centrifugally alone autonomic nerves to other tissues--- The salivary glands,Adrenal medulla,Kidneys,Lungs,- Liver,Skeletal muscles,Skin, andHeart.# The incubation period of rabies is exceedingly variable, from 7 days to 1 year (mean, 1 to 2 months)/# Rates of infection and mortality are highest from bites on the face, intermediate from bites on the hands and arms, and lowest from bites on the legs.# The neuropathology of rabies resembles that of other viral diseases of the CNS:- Hyperemia,- Varying degrees of chromatolysis,- Nuclear pyknosis, and- Neuronophagia of the nerve cells;- Infiltration by lymphocytes and plasma cells of the Virchow-Robin space;- Microglial infiltration; and- Parenchymal areas of nerve cell destruction.# The most characteristic pathologic finding of rabies is the eosinophilic cytoplasmic inclusions called Negri bodies within neurons. Each measures 10 nm and is made up of fibrillar matrix and virus particles.# Negri bodies are distributed throughout the brain, particularly in:- Ammon's horn,- Brainstem,- Hypothalamus, and- Purkinje cells of the cerebellumCerebellar,cerebral cortex,Dorsal spinal ganglia.# Negri bodies are not demonstrated in at least 20% of cases of rabies, and their absence from brain material does not rule out the diagnosis.RFFIT is valuable test to diagnose rabies.
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