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

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

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

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

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

32. THANK YOU