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Wednesday, February 20, 2013

Rabies virus

Properties of Rabies virus:

   1.            Rabies is a member of rhabdovirus family

   2.            Enveloped, RNA, single stranded virus

   3.            Bullet shaped, neurotropic virus

   4.            Attaches to the Ach receptor on the cell surface

   5.            Replicates in cytoplasm, killed by sunlight, heat or lipid solvent

   6.            If not treated, 100% mortality

   7.            Reservoir- Dogs, cats, bats, fox, raccoons, skunks, jackal, hyena, Mongoose

Structure of Rabies virus

Disease caused by Rabies virus:

Disease caused by Rabies virus is Rabies or Hydrophobia.

Structure and Characteristics of Polio virus:

   1.            Non-enveloped, RNA virus
   2.            Replicates in cytoplasm
   3.            Single, stranded, Icosahedral nucleocapsid
   4.            Acid and bile stable but no long term carrier state
   5.            Three serologic (antigenic) types  based on different antigenic determinants on the outer capsid protein
   6.            Release upon death of the cell
A child suffering from Poliomyelitis

Disease caused by Polio virus:

Disease cause by polio virus is poliomyelitis

Pathogenesis of Poliomyelitis:

          Transmission: faeco-oral route (by ingestion of contaminated food and drink)
          Host: Human
          Incubation period: 7-14 days
          Mechanism of pathogenesis:
                           1.            Polio virus enters into the body by faeco-oral route
                           2.            Replicate in the lymphoid tissue of the orophraynx and SI (Peyer’s patches)
                           3.            Spreads through blood stream to the CNS and also spreads retrograde along nerve axons
                           4.            Then replicates in the motor neurons located in the ant. Horn of the spinal cord
                           5.            Death of nerve cells
                           6.            Result: Paralysis of the muscle innervated by those neurons. Also affects the brain stem, leading to bulbar poliomyelitis (with respiratory paralysis) but rarely damage the cerebral cortex.