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




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


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



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


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.

THANK YOU

Health & Medicine

Polio