POLIOMYELITIS.

Presentation on theme: "POLIOMYELITIS."— Presentation transcript:

1 POLIOMYELITIS

2 AGENT FACTORS: Agent: Poliovirus, - RNA virus, serotype –1,2,3 - Most outbreaks – type 1 -Survive for long periods in external environment in cold climate - Can live in water for 4 mnths & faeces for 6 mnths - hence faecal – oral route

3 Reservoir of infection:
Man is the only known reservoir Most are subclinical cases, no chronic carrier, no animal carriers Mild & subclinical cases plays an important role in spread of infection Submerged part in iceberg phenomenon For every clinical case children and 75 adult subclinical cases

4 Infectious material: Faeces and Oro-pharyngeal secretions of an infected person Period of communicability: Cases are most infectious 7 to 10 days before and after onset of symptoms In faeces the virus is excreted for 2 to 3 wks & can go on for as long as 3 – 4 mnth

5 HOST FACTORS: Age: occur in all age groups Children are more susceptible than adults Most vulnerable age is between 6 months to 3 years in India Sex: M:F, 3:1

6 Risk factors: Paralytic polio in an individual who have been already infected with polio virus, has been found to precipitated by factors like - fatigue, trauma, intra muscular injections, operative procedures esp. during epidemics of polio, immunizing agents particularly alum containing DPT

7 Immunity: Infection with one type does not offer complete protection against other two type of viruses Neutralizing Ab’s - index of immunity to polio after infection Environmental factors: More seen to occur in rainy season Sources are contaminated water, food, flies Overcrowding and poor sanitation provides opportunities for exposure to infection

8 Mode of transmission: Faecal-oral route – developing countries Droplet infection – developed countries, acute phase of disease Incubation period: 7-14 days(range days) Clinical spectrum: Inapparent (subclinical) infection Abortive polio or minor illness Non paralytic polio Paralytic polio

9 a) Inapparent (subclinical) infection:
Occurs in approx % infections No symptoms Recognized only by virus isolation or rising antibody titres b) Abortive polio or minor illness: Occurs in 4-8% of infections Causes only mild or self limiting illness Patient recovers quickly

10 c) Non paralytic polio:
Occurs in 1% of all cases s/o: stiffness and pain in neck and back Disease lasts 2 to 10 days Recovery is rapid It is synonymous to aseptic meningitis

11 d) Paralytic polio: Occurs in less than 1% cases Invades CNS & causes paralysis of varying degree Predominant sign – Asymmetrical flaccid paralysis (AFP) If fever at time of onset of paralysis – polio suspected Other symptoms - malaise, anorexia, nausea, vomiting, abdominal pain, sore throat, head ache and constipation

12 Signs: stiffness of neck & back muscles Tripod sign Descending paralysis – hip to downwards Asymmetrical patchy paralysis DTRs are diminished before onset of paralysis Progression of paralysis to reach its maximum in majority cases occurs in less than 4 days No sign of sensory loss

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15 Cranial nerve involvement seen in bulbar and bulbo spinal forms of paralytic polio
Facial asymmetry, difficulty in swallowing, weakness of voice Respiratory insufficiency can be life threatening & is usually cause of death Atrophy of muscles also seen Progressive paralysis, coma & convulsions indicate diagnosis other than polio Treatment: No specific treatment Physiotherapy and good nursing care from beginning can minimize/ prevent crippling

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18 Prevention: Immunization is the most effective method Two types of vaccine: Inactivated polio vaccine(IPV)/ Salk Oral polio vaccine(OPV)/ Sabin

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20 Inactivated polio vaccine(IPV)/ Salk:
Given i/m (preferred) or s/c injection Stable at ambient temperature, but should be refrigerated to ensure no loss of potency Freezing should be avoided Primary course of immunization consist of 4 inoculations Available as stand alone product or in combination form Induces humoral antibody and not intestinal/ local immunity

21 IPV protect individual from paralytic polio, but do not prevent re-infection of gut by wild polio viruses Hence it does not offer any benefit for the community as wild virus can multiply in gut and be a source of infection to others It is unsuitable during epidemic because: Immunity is not rapidly achieved, more than one dose required to induce immunity Injections are to be avoided during epidemics as they may precipitate paralysis

22 Advantages: Can be given in immuno compromised and pregnant women Associated risks: No serious ADRs except minor local erythema, induration and tenderness

23 Oral polio vaccine(OPV)/ Sabin:
Described by Albert Sabin in 1957 Contains live attenuated vaccine (type 1,2,3) National immunization schedule: Primary course of 3 doses at 1 month interval Starting at 6 wks and followed by 10 & 14 wks Zero dose is recommended at birth All infants should vaccination before 6 months of age as most polio cases occur between 6 months to 3 years period One booster dose of OPV is given at yrs

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25 Dose & mode: 2 drops, orally Development of immunity:
IgA produced in intestine prevent subsequent infection of alimentary canal with wild polio, thus preventing spread in community OPV induces both local & systemic immunity Vaccine progeny excreted in faeces 2* spread to household contact & susceptible host in community Herd immunity established This property eliminates wild polio from the community & replace it with attenuated strain

26 Advantages: Easy to administer Doesn't require highly trained personnel Induce both humoral and intestinal immunity Even single dose elicits substantial immunity Herd immunity Useful in controlling epidemics Relatively inexpensive

27 Complications: VAPP(vaccine associated paralytic poliomyelitis)----due to type 3 strain Containdications: All live vaccines are C/I in immuno compromised patients and pregnant women IPV given in immuno compromised if necessary

28 Storage: A) stabilized vaccine – recent vaccines are heat stabilized by adding magnesium chloride in it Can be kept for a year at 4* C & for a month at 25*C with out loosing potency B) Non stabilized vaccine – Vaccine sould be stored at -25*C in deep freezer Vaccine vial kept in ice at field level during administration to children

29 Sequential administration of IPV & OPV:
In some countries sequential schedule of 1 – 2 dose of IPV followed by > 2 doses of OPV has been adopted This approach reduce the event or even prevent VAPP, while giving both systemic and local immunity

30 Differences between IPV & OPV OPV(Sabin) IPV(Salk) Killed virus Live attenuated Given s/c or i/m Orally Only humoral immunity, no local immunity Both humoral & intestinal immunity More difficult to manufacture Easy to manufacture

31 IPV OPV Prevent paralysis and also intestinal re- infection
Prevent paralysis, but do not prevent re- infection with wild polio Not useful in epidemics Can be used in epidemics Virus content is 10,000 times more than OPV, Costlier Cheaper Doesn't require stringent condition during storage & transportation Required to be stored & transported in sub zero temperature

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