POLIOMYELITIS

• Polio(grey)
• Myelon(marrow, indicating the spinal cord)
• First described by Michael Underwood in 1789.
• First outbreak described in us in 1843.
• Increased age of primary infection increased both the severity and deaths from polio.
• Incidence fell following introduction of effective vaccines.

POLIO VIRUS:

• Family picarnoviridae,Enterovirus(RNA)
• 3 serotypes:1,2,3
• Minimal heterotypic immunity between serotypes
• Rapidly in activated by heat, formaldehyde, chlorine, uvlight.

PATHOGENESIS:

·        Entry into  mouth

·        Primary multiplication occurs in pharynx,GIT,Local lymphatics

·        Rheumatologic spread to lymphatics ,CNS

·        Replication of virus in motor neurons of antr horn and brain stem results in all destruction.

CLINICAL FEATURES:

• Incubation  period 6 to 20 days
• Range: 3 to 35 days
• 95% are inapparent (or) asymptomatic
• 4 to 8% are minor, non specific illness without clinical (or) Lab evidence, known as abortive poliomyelitis, is characterized by complete recovery in a week.

Manifestations:

·        URI - sore throat, fever

·        GI disturbances –nausea, vomiting ,abd pain,diarrhoea (or) constipation

·        Influenza like illness.

·        Non paralytic aseptic meningitis (1 -2%) (Stiffness of back,neck,legs) Symptoms last for 2-10 days, followed by complete recovery.

·        Flaccid paralysis (< 1%) –sings and symptoms include loss of superficial reflexes, initially increased deep tendon reflexes, severe muscle aches and spasms in the limb and  back ,followed by flaccid paralysis with decreased deep tendon reflexes  ,usually asymmetrical ,without sensory involvement.

 ·        Three types of paralytic polio:

                  * Spinal polio (79%) – most common, most often involves legs.

                 * Bulbar polio (2%) –weakness of muscles inverted by cranial nerves.

                 * Bulbospinal (19%) –combination of bulbar and spinal paralysis.

LAB DIAGNOSIS:

(I)VIRUS ISOLATION:

        *      Polio virus recovered from stool (or) pharynx.

              *     Isolation from CSF is diagnostic.

                 *     Using oligonucleotide mapping (finger printing) (or) genomic sequencing

                         To determine if the virus is ‘wild type (or) vaccine virus’.

(II) SEROLOGY: 

          *      Neutralizing antibody appears early.

(III)CSF:

          *     Increased WBC (10 to 200 cells/ mm cube lymphocytes)

          *     Mildly elevated protein (40 -50 mg/100ml)

POLIOVIRUS EPIDEMIOLOGY:

         Reservoir                     -     Human

         Transmission               -     Fecal- oral

                                                     Oral- oral

         Communicability        -      7-10 days before onset

                                                 Virus present in stool for 3-6 weeks.

                                                        Seroconversion rates in susceptible household contacts                     

                                                        Of children -100% and adults -90%.

POLIOVIRUS VACCINE:

                  *       1955 –   Inactivated vaccine 

                  *       1961 --   Types 1 and 2 monovalent opv

                  *       1962   -   Type 3 monovalent opv

                  *       1963   -   Trivalent opv

                  *       1987   -   Enhanced IPV(IPV)

INACTIVATED POLIO VACCINE:

·        Contains  3 serotypes of vaccine virus

·        Grown on monkey kidney(Vero) cells

·        Inactivated with formaldehyde

·        Contains 2-phenoxy ethnol, neomycin, streptomycin, polymyxin B.

ORAL POLIO VIRUS VACCINE:

·        Contains 3 serotypes

·        Grown on monkey kidney(Vero) cells

·        Contains neomycin and streptomycin

·        Replicate in intestinal mucosa, lymphoid cells ,lymph nodes that drain the intestine

·        Maximum viral shedding occurs in first 1-2 weeks after vaccination.

IMMUNOGENICITY AND VACCINE EFFICACY:

 IPV:

• Highly effective in producing immunity to polio virus
• >90% immune after 2 doses
• >99% immune after 3 doses
• Duration of immunity not known

 OPV:

• High effective in producing immunity to polio virus
• 50% immune after 1 dose
• >95% immune after 3 doses
• Immunity probably life long
• Excelled intestinal immunity which helps prevent infection with wild virus

 Seroconversion following 3 doses of either IPV (or) OPV is 100% to all three vaccine virus.

VACCINATION SCHEDULE AND USE:

Recommendations (1996-1999)

·        Increased use of IPV recommended in 1996

·        Intended to reduce the risk of vaccine associated paralytic polio(VAPP)

·        Continued risk to contacts of  OPV recipients.

 POLIO VACCINATION RECOMMENDATIONS:

• Exclusive use of IPV recommended in 2000
• OPV no longer manufactured (or) routinely available in US.
• VAPP eliminated

POLIO VACCINATION SCHEDULE:

SCHEDULE THAT INCLUDE BOTH IPV AND OPV:

• Only IPV is available in US
• Schedule begun with OPV should be completed with IPV
• Any combination of 4 doses of IPV and OPV by 4-6 yrs constitutes a complete series.

 PAEDIARIX:

• Contains IPV,DTaP and hepatitis B vaccine
• Minimum age of 6 weeks ,maximum age 6 years
• Approved by FDA for first 3 doses of IPV  and  DTaP  series
• Not approved for booster doses.

 POLIO VACCINATION FOR ADULTS:

• Routine vaccination of US residents >\ 18 yrs of age not necessary (or) recommended.
• May consider vaccination of travelers to polio endemic countries and selected laboratory workers.

 POLIO VACCINATION OF UNVACCINATED ADULTS:

• IPV
• Use standard IPV schedule if possible (0,1-2 months,6-12 months)
• May separate doses by 4 weeks if accelerated schedule needed.

ADVERSE REACTIONS FOLLOWING VACCCINATION:

• Minor local reactions (pain, redness)[IPV]
• IPV contains trace amounts of streptomycin, polymyxin B, neomycin, allergic reactions may occur among persons sensitive to these antibiotics.

 VACCINE ASSOCIATED PARALYTIC POLIOMYELITIS (VAPP):

·        Rare adverse reaction following line OPV

·        Due to mutation (or) reversion of the vaccine virus to a more neutropic form. Mutated viruses are called revertants.

·        Increased risk in persons > 18 yrs

·        Increased risk in persons with immunodeficiencies particularly agammaglobulinenia, hypogammaglobulinemia which reduce the synthesis of immunoglobulin.

 CONTRAINDICATIONS AND PRECAUTIONS TO VACCINATION:

• Severe allergic reaction to a vaccine component (or) following a prior dose of vaccine
• Moderate (or) severe acute illness.

 STORAGE AND HANDLING:

• Maintained at 2- 8 c ,vaccine should be clear and colourless

 OUTBREAK INVESTIGATION AND CONTROL:

• Collect preliminary clinical and epidemiological information (vaccine history, contact  OPV)
• Notify the national immunization program, centers for disease control and prevention
• Collect appropriate specimen for rival isolates and serology.

 POLIO ERADICATION:

• Late case in united states in 1979
• Western hemisphere certified polio free in 1994
• Last isolate of type 2 virus in India in oct 1999
• Global eradication goal by 2005
• Strategy to achieve this goal by

                  1. Increasing vaccination coverage

                  2. Enhancing surveillance for suspected cases

                  3. Using supplemental immunization strategies such as national immunization  

                      Days, house to house vaccination, containment activities.

POST POLIO SYNDROME:

• After on interval of 30-40 yrs who had paralytic polio in childhood experience new muscle pain, exacerbation of existing weakness (or) develop new weakness (or) paralysis
• Risk factors includes increasing length of time since acute polio infection, presence of permanent residual impairment after recovery from the acute illness ,female gender
• Pathogenesis:

              Failure of oversized motor units created during the recovery            

              Process of paralytic polio.

• Not an infectious process
• Do not shed polio virus.