Polio
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Transcript of Polio
POLIO
-by Dr. Sudhir
History
Sir Walter Scott(1771–1832) may have had the
earliest recorded case of polio.
First described by Michael Underwood in 1789
Initially thought to be due to trauma
Became known as the Heine-Medin disease due to
the work of Dr. Jakob Heine and Dr. Karl Oskar
Medin.
Later called infantile paralysis, based on its
propensity to affect children.
3rd human disease targeted for eradication
Poliovirus
Enterovirus
Spherical virion with a single strand
RNA
Three serotypes: 1, 2, 3
Burnhilde & Mahoney strains→ type1
Lansing & MEF-1 → type
2
Leon & Saukett →type 3
1 & 3 – epidemic 2 – endemicMinimal heterotypic immunity between serotypes
ANTIGENS
D or Native or N antigen- whole virion & is type specific- Anti-D antibody is protective and its conc in IPV denotes the potency of vaccine
C or Heated or H antigen- empty non-infectious virus & is less specific- anti-C antibody does not neutralise infectivity
Heated at 56º C - D →→→ C
Resistance
Resistant to ether, chloroform, bile, intestinal proteolytic enzymes & detergents
Stable at pH of 3
Can survive at -20ºC for yrs, 4ºC for months & at room temp for 1 day to several weeks
Inactivated by heat(55ºC for 30 min), formaldehyde, ultraviolet light & chlorination
Organic matter in water delays the activation by chlorination
Pathogenesis
Entry by feco-oral route through ingestion
Droplets from Patients with early disease
can enter through inhalation or through
conjunctiva
Replication in the epithelial cells of GI tract
& the local lymphatics
Local lymhatics of GIT ↓
Circulatory system (minor or primary viremia)↓
Reticuloendothelial system↓
Circulatory system (major or secondary viremia)↓
Spinal cord & Brain
NERVOUS SYSTEM
CNS – Multiplies in Neurons & destroys them Earliest change – Degeneration of Nissl bodiesFollowed by Nuclear changes & finally neuronal
deathSpinal cord – Lesions are mostly in the ant. Horns
causing flaccid paralysisPost. Horn & intermediate column may also be
involved
0 20 40 60 80 100
Percent
Asymptomatic Minor non-CNS illness
Aseptic menigitis Paralytic
90 to 95% polio virus infections are asymptomatic
Outcomes of Poliovirus Infection
Poliovirus Epidemiology
Reservoir Human
Transmission Fecal-oral Oral-oral possible
Communicability 7-10 days before or after onset .
Virus present in stool 3-6 weeks
Types
• Asymptomatic Polio
• Non-paralytic
• Paralytic
– Spinal
– Bulbar
– Bulbospinal
Asymptomatic Polio
• Accounts for approximately 95% of cases
• Virus stays in intestinal tract and does not attack the nerves
• Virus is shed in the stool so infected individual is still able to infect others
Non-paralytic Polio
•Abortive poliomyelitis
•Does not lead to paralysis
•Mild symptoms seen such as sore throat, fever, n/v, diarrhea, constipation ( Minor illness)
•Most recover in <1 week
•Non-paralytic aseptic meningitis ( Major illness)
– Occurs in 1-2% of polio infections
– Symptoms are stiffness in the neck, back, and/or legs
– Increased or abnormal sensations can occur
– Complete recovery after 2-10 days of symptoms
Paralytic Polio
Fewer than 1% of those infected develop this type
Acute flaccid paralysis seen. Initially focal but spreads over 3 – 4 days
Headache, neck/back stiffness, unusual sensations, increased sensitivity to touch
Tripod sign +
Descending paralysis
Asymmetrical patchy paralysis
Deep tendon reflex lost before onset of paralysis
Spinal Polio
–Most common form of paralytic; 79%
–Attacks motor neurons and causes paralysis of muscles of respiration and muscles of extremities
–Children <5 years most likely to become paralyzed in one leg
–Adults are most commonly paralyzed in both arms and legs
–Those affected still retain sensation in extremities
Bulbar Polio
• Accounts for 2% of paralytic polio
• Virus attacks motor neurons in brainstem
•Affects cranial nerve function
•Primarily inhibits ability to breathe, speak, and swallow effectively
Facial asymmetry present
Bulbospinal Polio
• Accounts for 19% of paralytic cases
• Affects extremities and cranial nerves
• Leads to severe respiratory involvement
Paralytic Polio Risk Factors
• Compromised immune system
• Pregnancy
• Mouth or throat surgery
• Injury or strenuous physical exercise after exposure to virus
Encephalitic Polio
•Very rare
•Causes inflammation of gray matter of brain
•Signs/symptoms include agitation, confusion, stupor, and coma
•Autonomic dysfunction is common and it has a high mortality
Past Medical Treatment
•Iron Lung - a sealed chamber with an electrically driven bellows that regulates breathing. •Rigid Braces•Body Casts
Supportive Treatment
• Antibiotics for infection• Analgesics for pain • Portable Ventilators for breathing problem• Moderate Exercise • Nutritional Diet
Post-Polio syndrome (PPS)
25 % of individuals, decades after recovering from the acute infection
Features include muscle weakness, extreme fatigue, or paralysis.
Due to failure of the over-sized motor units created during recovery from paralytic disease
Factors that increase the risk of PPS include time since acute poliovirus infection,permanent residual impairment, and both overuse and disuse of neurons
PREVENTION
Global Polio Eradication Initiative launched in 1988Polio cases have decreased by over 99% since 1988, from an estimated 350 000 cases then, to 1604 reported cases in 2009.In 2010, only four countries in the world remain polio-endemic, down from more than 125 in 1988. The remaining countries are Afghanistan, India, Nigeria and Pakistan
Wild Poliovirus 1988
Wild Poliovirus 2002
Wild Poliovirus 2012
Wild Poliovirus 2014
1. High infant immunization coverage with four doses of oral poliovirus vaccine (OPV) in the first year of life
2. Supplementary doses of OPV to all children under five years of age during SIAs(PPI)
3.AFP surveillance among children under fifteen years of age;
4. Targeted “mop-up” campaigns once wild poliovirus transmission is limited to a specific focal area.
Core strategies of GPEI
Poliovirus Vaccine
1955 Inactivated vaccine
1961 Types 1 and 2 monovalent OPV
1962 Type 3 monovalent OPV
1963 Trivalent OPV
1987 Enhanced-potency IPV (IPV)
Inactivated Polio Vaccine
Developed in 1952 by Jonas Salk
Contains 3 serotypes of vaccine virus
40 units of 1(Mahoney), 8 units of 2(MEF-1) &
32 units of 3(Saukett)
Grown on monkey kidney (Vero) cells
Inactivated with formaldehyde
Contains trace 2-phenoxyethanol, neomycin,
streptomycin, polymyxin B
Safe in immunocompromised & in pregnancy
Inactivated Polio Vaccine
Heat stable at room temp but should be refrigerated to preserve potency
Highly effective in producing immunity to poliovirus
>90% immune after 2 doses
>99% immune after 3 doses
Humoral immunity and to some extend pharyngeal immunity
Duration of immunity not known with certainty
Oral Polio Vaccine
Discovered by Albert Sabin
Contains 3 serotypes of vaccine virus
3 lakh TCID 50 of type 1
1 lakh TCID 50 of type 2
3 lakh TCID 50 of type 3
Grown on monkey kidney (Vero) cells
Contains neomycin and streptomycin
Shed in stool for up to 6 weeks following vaccination
Oral Polio Vaccine
Produces both Humoral & local immunity
Contributes to herd immunity
50% immune after 1 dose
>95% immune after 3 doses
Immunity probably lifelong
Heat labile: -20ºC
Can be stabilised by adding MgCl
Should not be frozen & thawed repeatedly
Polio Vaccine Adverse Reactions
Rare local reactions (IPV)
No serious reactions to IPV have been
documented
Paralytic poliomyelitis (OPV)
Polio Vaccine
Contraindications and Precautions
Severe allergic reaction to a vaccine
component or following a prior dose of
vaccine
Moderate or severe acute illness
Vaccine-Associated Paralytic Polio
Mutation of the vaccine inside the body may case lose of attenuation(itself brought on by reversion) leads to paralytic polio
Increased risk in persons >18 years & those with immunodeficiency ( B cell)
No procedure available for identifying persons at risk of paralytic disease
5-10 cases per year with exclusive use of OPV
2005 in India: Wild case: 66; VAPP 180
Many countries switched to sequential IPV-OPV and then only IPV schedules once the number of VAPP cases exceeded wild polio cases.
Vaccine-Derived Paralytic Polio
virus
These viruses like those causing VAPP are neurovirulent but additionally are transmissible
and capable of causing outbreaks. They have been classified into three groups;
circulating VDPV (cVDPV), VDPV in the immuno-deficient (iVDPV) and VDPV of
ambiguous origin (aVDPV).Risk factors for outbreaks due to cVDPV include
dropping immunization coverage (both routine and SIA's), high population densities, tropical
conditions and previous eradication of wild virus
POLIO & ITS PREVENTION IN INDIA
India is one of the four countries with wild polio virus
Most cases are reported from Bihar & UPCases seen in various states of north india are
due to import from there 2 states2010 – 42 cases
Last case of type 2 in 1999Last WPV3 Oct 2010Last WPV1 Jan 2011
Polio free country – Jan 2014
Polio Vaccination under UIP
Vaccine
OPVº
OPV1
OPV2
OPV3
OPV4
Age
birth
6 wks
10 wks
14 wks
16-24 Months
Two drops of OPV is used
Nose should not be pinched
Instead apply pressure to both side of mouth
Breast feeding is not contraindicated
Hot liquids to be avoided for ½ hr after OPV
Pulse Polio Immunization (PPI)
The supplementary immunization activities (SIAs) in India launched in 1995
Irrespective of the immunisation status
Usually Dec & Jan – Peak transmission
Providing additional OPV doses to every child aged <5 years at intervals of 4-6 weeks during National Immunization Days (NIDs) & sub-National Immunization Days (SNID's)
It “Flood” the community with OPV within a very short period of time, thereby interrupting transmission of virus throughout the community.
Intensification - house-to-house “search and vaccinate” component.
The number of PPI rounds is determined by the extent of poliovirus transmission in the country.
Cold Chain
The system of transporting, storing and distributing vaccine in a potent state at recommended temperature till it is administered to an individual.
If cold chain is not maintained from the manufacturer to the place of vaccination, the vaccine efficacy greatly suffers
Most vaccines lose their potency by heat and sunlight and hence need protection from both(2).
The Cold Chain Equipment
(a) Walk in cold rooms: 3 months and serve districts.
(b) Deep freezers (300 ltr) and Ice lined Refrigerators: Deep freezers are used for making ice packs and to store OPV and measles vaccines.
(c) Small deep freezers and ILR (140 ltr)
(d) Cold boxes: peripheral centers.mainly for transportation.
(e) Vaccine carriers:Used to carry small quantities of vaccines (16-20 vials) for the out of reach sessions.
(f) Ice packs
Vaccine Vial Monitoring
The vaccine vial monitor is a small thermochromic sticker on the vaccine vial and changes color as the vaccine is exposed to heat.
The color of the sticker tells whether the vaccine must be discarded due to excessive heat exposure.
It reduces uncertainty and waste.
AFP Survillance
Acute flaccid paralysis is defined as:
Any case of AFP in a child aged <15 years, or any case of paralytic illness in a person of any age when polio is suspected.
All health facilities, clinicians and other practitioners are required to notify AFP cases immediately to the DIO, by the fastest means available
Sample Collection
Two stool specimens are collected as soon as possible after the onset of paralysis in the child – ideally within 14 days of onset of paralysis and at least 24 hours apart. Specimens collected within 14 days are much more likely to yield the virus.
Each specimen should be 8 grams – each about the size of one adult thumb – collected in a clean, dry, screw-capped container. The container need not be sterile and no preservative/transport media should be used.
Reverse Cold Chain
The specimens are transported in the “cold chain” – on frozen ice packs or ice, in a stool specimen carrier or a vaccine carrier specifically designated for this purpose – to one of India’s eight WHO-accredited polio laboratories.
Indicator of the quality of the “reverse cold chain”↓
% of Stool specimens from which a non-polio enterovirus is isolated→ ≥10
(i.e. that the specimen has been continuously maintained at temperatures <8° C during
transportation from the field to the laboratory)
60-day follow-up examination:
To confirm the presence or absence of residual weakness. A 60-day follow-up exam if 1) inadequate or no stool specimens
2) isolation of vaccine virus from the stool3) isolation of wild poliovirus from the stool
4) strongly suggestive of poliomyelitis on initial examination (“hot case”).
The child is assessed for weakness, asymmetrical skin folds, and difference in left/right mid-arm/mid-thigh
circumference. The child is considered to have residual weakness if any of the above is present, even if
minimal. The finding of residual weakness taken into account during final case classification
Classification
Outbreak response immunization (ORI)
House-to-house immunization following the AFP case investigation and stool specimen collection
Children aged 0-59 months are given one dose of oral poliovirus vaccine (OPV) regardless of the number of doses received previously. The recipients include children of the target age group in the village/locality of the AFP case.
The investigation team searches for additional AFP cases in the community, which – if present – could signal the possibility of a polio outbreak.
Active case search
Where an AFP case resides – or where an AFP case has visited during the incubation period for polio (4-25 days before paralysis onset)
Carried out immediately along with ORI.
A search is conducted for any children aged <15 years who have had the onset of flaccid paralysis within the preceding 60 days. All cases that are found are investigated immediately, with collection of two stool specimens before administration of OPV.
“Mopping-up” immunization
Started when poliovirus transmission has been reduced to well-defined and focal geographic areas.
Intensive house-to-house, child-to-child immunization campaigns are conducted over a period of days to break the final chains of virus transmission.
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