Zoonotic diseases


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Zoonotic diseases

  1. 1.  ZOONOTIC DISEASES are diseases caused by infectious agents that can be transmitted between or are shared by animals and humans.  Example : Rabies
  2. 2. RABIES
  3. 3.  Acute, highly fatal viral disease of Central Nervous System.  Transmitted to man by either licks or bites of a rabid animal-mostly dogs.  Rabies infects both domestic and wild animals alike, and is then spread to people through close contact of the infected saliva of these animals , i.e., by bites or scratches.  This disease is present all over the world, but Asia and Africa has almost 95% human fatality .
  4. 4. Causative Organism: Rhabdoviruses are always associated with Rabies.
  5. 5. Rhabdoviruses • Bullet shaped virus. • Belongs to genus Lyssavirus. • 180*75nm length, with one end rounded conical and other end concave. • Has a lipoprotein envelope, that carries spikes. • Spikes consists of glycoprotein G; and are not present at planar end of the virus. • The genome of the virus is unsegmented linear –ve sense RNA.
  6. 6. COMMON FACTS ABOUT RABIES  The name ‘Rabies’ comes from: Latin : Rabidus – Mad Sanskrit : Rabhas - Frenzy.  The disease of rabies in human is called Hydrophobia, because the patient exhibits fear of water, being incapable of drinking though subject to intolerable thirst.  In 1881, Pasteur established that rabies virus was present in the brain of the infected animals.  In 1885, a 9 year old boy was bitten by a rabid dog, and was administered a course of 13 inoculations of the infected cord vaccine, i.e., injections of graded infectivity of the virus; The boy survived. This was a milestone in development of vaccines.
  7. 7. PATHOGENESIS :  Virus multiplies in the muscles, connective tissues or nerves at the site of bite for 48-72 hours.  It then penetrates the nerve endings and travels in the axoplasm towards the spinal cord and brain.  Virus moves in the axons at a speed of 3mm/hr.  Infection spreads centripetally from axon to neuronal bodies, and progressively up the spinal cord through synapses of neurons.  Virus ascends rapidly to brain, while multiplying & spreads long the nerve trunks to various parts of body, including salivary glands.
  8. 8. CONTD.  The virus then again starts multiplying in the salivary glands and is then shed in saliva.  When the virus ultimately reaches all the tissues in the body, it leads to fatality.  The virus may also be shed in milk and urine.  Though viremia is not clinically significant. Incubation Period : 1-3 months. could be as short as 7 days, could also extend up to 3 years. Incubation period is short in the persons bitten on faces and head, and longer in the persons bitten near legs.
  9. 9. STAGES OF RABIES ~ 4 STAGES  PRODROME : Fever, headache, malaise, fatigue & anorexia, apprehension, anxiety, irritability, insomnia, priapis m & excessive libido. Lasts for 2-3 days.  ACUTE ENCEPHALITIC : Hyperactivity, bouts of bizarre behaviour, agitation, seizures, Hydrophobia, only dry solids could be eaten, pharynx & larynx starts gagging and choking, patients even dread the sight of water, death occurs within a week due to respiratory convulsions, hallucinations.  PARALYSIS : some patients then go paralytic due to muscle spasms and seizures, while some slip into coma.  DEATH: After the stage of paralysis, patients die, due to respiratory arrest and other complications.
  10. 10. LABORATORY DIAGNOSIS :  Diagnosis may be made by postmortem by the demonstration of negri bodies in the brain.  Isolation of virus by intracerebral inoculation of mice can be attempted from the brain, CSF, saliva and urine.  If facilities are available , then detection of rabies virus RNA by reverse transcription PCR is a very sensitive method.
  11. 11. THANK YOU 