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  1. 1. Poliomyelitis
  2. 2. Introduction  Greek poliós= "grey", myelós= marrow, and the suffix - itis= inflammation  First described by British physician Micheal Underwood in 1799 referring to it as "debility of the lower extremities.“  A viral infection most often recognized by acute onset of flaccid paralysis.  Primarily an infection of human alimentary tract, but may infect CNS in very small no. (i.e <1%)  Infection results in a spectrum of clinical manifestations……
  3. 3. Problem statement World  A worldwide problem in pre vaccination era  With the wide use of polio vaccine from 1954 disease being eliminated from most of the developed countries  In 1988 WHA resolved to eradicate the disease globally  Since than no. of endemic countries reduced from 125 in 1988 to 3 in 2012.  Reported cases worldwide decreased by 51% (1352 in 2010 to 650 in 2011)
  4. 4. Cont… India No reported cases since January 2011 (last case reported in 13th Jan 2011, Howrah, West Bengal) Considered polio-free since February 2012 Attained the status of eradication in 13th January 2014
  5. 5. Epidemiology
  6. 6. Agent factors Agent Poliovirus: belongs to “Picorna” viruses which are small RNA-containing viruses. Three serotypes- 1, 2 & 3 giving no cross immunity Long survival in environment….lives upto 4hours in water and 6 hours in faeces in cold enviornment. Readily destroyed by heat (e.g. pasteurization of milk, and chlorination of water).
  7. 7. Reservoir of infection  Man is the only reservoir of infection of poliomyelitis.  Man: cases and carriers  Cases: all clinical forms of disease  Most of the infections are subclinical- dominant role in spread of infection  Estimated subclinical infection ranges from 75 to 1000 per clinical case  No chronic cases or animal sources documented Foci of infection  Pharynx: the virus is found in the oropharyngeal secretions.  Small intestine: the virus finds exit in stools.
  8. 8. Modes of transmission Since foci of infection are the throat and small intestines, poliomyelitis spreads by two routes: Oral-oral infection: direct droplet infection Faeco-oral infection: – Through contaminated foods. Vehicles include milk, water, or any others that may be contaminated by handling, flies, dust…. – Hand to mouth infection. Polio virus has the ability to survive in cold environments. Overcrowding and poor sanitation provide opportunities for exposure to infection
  9. 9. Period of communicability  Estimated to about 2 weeks  Cases: 7 to 10 days before and after the onset of symptoms.  Virus is excreted commonly for 2 to 3 weeks, sometimes as long as 3 to 4 months in faeces.  In polio cases, infectivity in the pharyngeal foci is around one week, and in the intestinal foci 6-8 weeks. Incubation Period: 7-14 days
  10. 10. Host factors Age:  All age groups; children(6 MONTHS TO 3 YEARS most susceptible)  more than 95% reported in infancy and childhood with over 50% of them in infancy. Sex:  no sex ratio differences, but in some countries, males are infected more frequently than females in a ratio 3:1. Risk factors:  Fatigue, trauma,im injections, tonsillectomy, immunizing agents like alum containing DPT vaccine and excessive muscular exercise… Immunity:  Immunity by maternal antibodies till the age of 6months  Immunity conferred by natural infection fairly solid but doesn’t protects against the reinfection by other strains
  11. 11. Environmental factors Rainy season (june to september) Environmental sources- food, flies and water Overcrowding and poor sanitation- oppourtinities
  12. 12. Clinical spectrum
  13. 13. Inapparent infection  Occurs approximately in 91-96% of poliovirus infection.  Incidence is more than 75 to 1000 times the clinical cases.  No clinical manifestations, but infection is associated with acquired immunity.  Recognition only by virus isolation or rising antibody titre.
  14. 14. Clinical poliomyelitis Abortive polio (minor illness):  Occurs approximately in 4-8% of the infection.  Causes only a mild or self limiting illness due to viraemia.  Mild systemic manifestations for 1-2 days  Some abortive cases so mild to pass unnoticed.  Patient recovers quickly.  Manifestations:  Moderate fever  Upper respiratory manifestations: pharyngitis and sore throat  Gastrointestinal manifestations: vomiting, abdominal pain, and diarrhea.
  15. 15. Cont….. Involvement of the CNS (major illness):  Affects a small proportion of the clinical cases  Takes two forms: Non-paralytic and Paralytic polio. Non paralytic polio:  Occurs approximately in one per cent of all infections.  Presenting features are stiffness and pain in neck and back.  Disease lasts for 2-10 days.  Recovery is rapid.
  16. 16. Cont… Paralytic polio:  Occurs in less then one per cent of infections.  The virus enters the CNS and causes varying degree of disability with destruction of the motor nerve cells, but not the sensory nerve cells.  Forms: spinal, bulbar, and bulbospinal.  Paralysis usually appears within 4 days (around 7-10 days from onset of disease).  History of fever at the time of paralysis- suggestive of polio.  Progression of paralysis reaches maximum by 4th day (4-7 days)
  17. 17. Cont….  Other symptoms- malaise, anorexia, vommiting, headache, sore throat, constipation and headache.  Signs of meningeal irritation  Tripod sign may be present  Assymetrical, patchy flaccid paralysis, of descending type affecting the proximal group of muscle the most  Deep tendon reflexes (DTR) deminished before the the onset of paralysis.  Cranial nerve involvement seen in bulbar and bulbospinal paralytic poliomyelitis  Facial assymetry, difficulty in swallowing weakness of voice; respiratory insuffiency may lead to death
  18. 18. Spinal polio Different spinal nerves are involved Injury of the anterior horn cells of the spinal cord causing tenderness, weakness, and flaccid paralysis of the corresponding striated muscles. The lower limbs are the most commonly affected.
  19. 19. Bulbar polio Nuclei of the cranial nerves are involved, causing weakness of the supplied muscles, and maybe encephalitis. Bulbar manifestations include dysphagia, nasal voice, fluid regurgitation from the nose, difficult chewing, facial weakness and diplopia Paralysis of the muscles of respiration is the most serious life-threatening manifestation. Bulbospinal polio  Combination of both spinal and bulbar forms
  20. 20. Polio infection Polio infection Inapparent infection Clinical poliomyelitis Abortive polio (minor illness) Involvement of CNS (major illness) Paralytic polio Non-paralytic polio Spinal polio Bulbar polio Bulbospinal polio
  21. 21. Complications and case fatality  Respiratory complications: pneumonia, pulmonary edema  Cardiovascular complications: myocarditis, cor pulmonale.  Late complications: soft tissue and bone deformities, osteoporosis, and chronic distension of the colon.  Case fatality: varies from 1% to 10% according to the form of disease (higher in bulbar), complications and age ( fatality increases with age).
  22. 22. Diagnosis and laboratory testing Laboratory studies critical to rule out or confirm the diagnosis of paralytic poliomyelitis.  Virus isolation  The likelihood of poliovirus isolation is highest from stool specimens,  Intermediate from pharyngeal swabs, and very low from blood or spinal fluid.  Serologic testing A four-fold titer rise between the acute and convalescent specimens suggests poliovirus infection.
  23. 23. Prevention General prevention: Health promotion through environmental sanitation. Health education (modes of spread, protective value of vaccination).
  24. 24. Cont…. Seroprophylaxis by immunoglobulins: Not a practical way of giving protection because it must be given either or before or very shortly after exposure to infection. Dose-(0.25-0.3 ml/kg of body weight). Immunized status after a few weeks
  25. 25. Active immunization Inactivated (Salk) vaccine  Contains 3 serotypes of vaccine virus  Route of administration-intramuscular/ Subcutaneous.  Schedule  First dose given at the age of 6 weeks  Next 2 doses 1-2 months apart  4th dose after 6-12 month of 3rd dose  Additional doses prior to school entry  Repeated doses every 5 year after that till age of 18  Highly effective in producing immunity to poliovirus  >90% immune after 2 doses  >99% immune after 3 doses  Duration of immunity not known with certainty
  26. 26. Cont… Oral (Sabin) Polio Vaccine  Contains 3 serotypes of vaccine virus  Route of administration-intramuscular/ Subcutaneous.  Schedule  Zero dose vaccination recommended in hospital delivery  First dose given at the age of 6 weeks  Next 2 doses 1-2 months apart  One booster dose 12-18 months later recommended  Highly effective in producing immunity to poliovirus  50% immune after 1 dose  >95% immune after 3 doses  Immunity probably lifelong  Shed in stool for up to 6 weeks following vaccination
  27. 27. Salk versus Sabin vaccine IPV (Salk) OPV (Sabin) killed formolised virus Given SC or IM Induces circulating antibodies, but not local (intestinal immunity) Prevents paralysis but does not prevent reinfection Not useful in controlling epidemics More difficult to manufacture and is relatively costly Does not require stringent conditions during storage and transportation. Has a longer shelf life. live attenuated virus given orally immunity is both humoral and intestinal. induces antibody quickly Prevents paralysis and prevents reinfection Can be effectively used in controlling epidemics. Easy to manufacture and is cheaper Requires to be stored and transported at subzero temperatures, and is damaged easily.
  28. 28. Epidemiological Investigations Epidemic  Occurrence of 2 or more local cases caused by the same virus in any 4-weeks period  Sample of faeces to be collected from all the cases and suspected cases and subjected to lab testing  If possible, paired sera to be tested – First specimen at the clinical suspicion – Second at the period of convalescence  An increase in antibody titre provides confirmatory evidence  OPV should be provided to all persons over 6 weeks age who are not completely immunize de or immune status unknown in the epidemic area
  29. 29. Thank you