Guideme4thesis (GM4T)

Poliomyelitis Lecture Notes for Medical Undergraduates

About the Disease

Discover – Poliomyelitis Lecture Notes for Medical Undergraduates – Poliomyelitis (polio) is a highly infectious viral disease that primarily affects children under 5 years of age. It is transmitted mainly through the faecal-oral route and multiplies in the intestine, from where it can invade the nervous system and cause paralysis. The deficit is purely motor, with sensation intact.

Poliomyelitis: Lecture Notes for Medical Undergraduates
Poliomyelitis Lecture Notes for Medical Undergraduates

Transmission

• Person-to-person spread via faecal-oral route.

• Contaminated water or food.

• Virus multiplies in the intestine and can lead to paralysis.

Mnemonic: F-W-C (Faecal-oral, Water, Contaminated food)

Epidemiology

Source: WHO. Endemic Countries: Pakistan and Afghanistan

About the Virus

• Three serotypes: Type 1, Type 2, Type 3.

• Immunity to one serotype does not confer immunity to the others.

• Type 2 eradicated in 2015, last seen in India in 1999.

• Type 3 eradicated in 2019, last seen in 2012.

• Only Type 1 still circulates today, primarily in two countries.

• Global polio incidence has decreased by 99%.

Vaccine-Associated Paralytic Poliomyelitis (VAPP)

• Caused by loss of viral attenuation in OPV.

• Extremely rare

• Linked to serotype 3, more common in immunodeficient patients.

Mnemonic: R-S-I (Rare, Serotype 3, Immunodeficient)

Circulating Vaccine-Derived Poliovirus (cVDPV)

• OPV virus can spread in areas with poor sanitation and offer passive immunization.

• In under-immunized populations, excreted virus can circulate for an extended time, undergo genetic changes, and mutate into a form that can cause paralysis.

• cVDPV takes at least 12 months to emerge in under-immunized populations.

• Low vaccination coverage is the main problem, not the vaccine itself.

• Solution: 2-3 rounds of high-quality immunization campaigns to stop the virus.

Mnemonic: I-P-G-M (Immunodeficient, Prolonged circulation, Genetic mutation, Mutated virus causing paralysis)

Diagnosis

• Tests include blood, cerebrospinal fluid (CSF), respiratory, and stool viral cultures, as well as PCR to detect poliovirus.

Mnemonic: B-C-R-S-P (Blood cultures, CSF, Respiratory cultures, Stool cultures, PCR)

Complications

• Major complications: Paralysis with bulbar involvement, fatal respiratory and cardiovascular collapse, and postpolio syndrome.

• Postpolio syndrome: New-onset or progressive muscle weakness in previously diagnosed polio patients.

Mnemonic: P-R-P (Paralysis, Respiratory collapse, Postpolio syndrome)

Prevention of Polio

  1. Routine Immunization
  2. Supplementary Immunization
  3. Surveillance
  4. Targeted “Mop-Up” Campaigns

AFP Surveillance: 4 steps

1. Finding and Reporting AFP cases: Detect at least 1 case of AFP per 100,000 children under 15 years of age.

2. Transporting Stool Samples: Samples should arrive at the lab within 72 hours, with two specimens collected 24 hours apart and arriving via reverse cold chain.

3. Isolating Poliovirus: Distinguish between wild and vaccine-related poliovirus.

4. Mapping the Virus: Map the genetic makeup and geographical areas of circulation.

• Note: 80% of AFP cases should have a follow-up examination at 60 days after onset of paralysis.

Mnemonic: F-T-I-M (Finding, Transporting, Isolating, Mapping)

Polio Eradication Strategy 2022–2026 strategic framework: Source WHO

Tip: Remember the vision and goals.

Current Challenges

• Afghanistan: Ban on house-to-house immunization has led to over 1 million children being missed, with 90% of WPV1 cases in inaccessible areas.

• Poor-quality campaigns due to insufficient planning, staffing issues, and lack of accountability.

• Pakistan: Progress stalled due to complacency, leadership transitions, vaccine hesitancy, and misinformation on social media.

• Marginalized Pashto-speaking communities disproportionately affected (81% of WPV cases).

Mnemonic: M-P-L-V (Missed children, Poor campaigns, Leadership issues, Vulnerable communities)

Sources:

  1. www.who.int
  2. www.polioeradication.org

Practice Questions

Multiple Choice Questions (MCQs)
  1. What is the primary mode of transmission for poliomyelitis?
    • a) Airborne droplets
    • b) Blood transfusion
    • c) Faecal-oral route
    • d) Skin contact
  2. Which serotype of poliovirus remains in circulation today?
    • a) Type 1
    • b) Type 2
    • c) Type 3
    • d) All three
  3. Vaccine-associated paralytic poliomyelitis (VAPP) is most commonly associated with which serotype?
    • a) Type 1
    • b) Type 2
    • c) Type 3
    • d) Type 4
  4. What is the characteristic feature of paralysis in poliomyelitis?
    • a) Sensory loss
    • b) Motor deficit with sensory intact
    • c) Complete paralysis of all limbs
    • d) Sensory and motor deficit
  5. Which diagnostic test is most specific for detecting poliovirus?
    • a) Blood viral culture
    • b) CSF viral culture
    • c) Stool viral culture
    • d) PCR
  6. Which year was Type 2 wild poliovirus declared eradicated?
    • a) 2012
    • b) 2015
    • c) 1999
    • d) 2019
  7. What is the minimum number of AFP cases per 100,000 children under 15 that a surveillance system should detect?
    • a) 1
    • b) 5
    • c) 10
    • d) 50
  8. What is the primary cause of circulating vaccine-derived poliovirus (cVDPV)?
    • a) Poor vaccine quality
    • b) Prolonged circulation of excreted vaccine virus in under-immunized populations
    • c) Lack of wild poliovirus
    • d) Transmission via mosquitoes
  9. Which of the following is NOT a complication of poliomyelitis?
    • a) Respiratory collapse
    • b) Paralysis with bulbar involvement
    • c) Myocarditis
    • d) Postpolio syndrome
  10. Which of the following factors does NOT contribute to vaccine hesitancy in Pakistan?
    • a) Misinformation on social media
    • b) Leadership transitions
    • c) Widespread knowledge about vaccines
    • d) Complacency after declining cases
  11. How many stool specimens are needed for adequate analysis in AFP surveillance?
    • a) 1
    • b) 2
    • c) 3
    • d) 5
  12. How long does it typically take for cVDPV to develop in an under-immunized population?
    • a) 1-6 months
    • b) 6-12 months
    • c) 12-18 months
    • d) 18-24 months
  13. Which of the following countries still has circulating wild poliovirus?
    • a) India
    • b) Afghanistan
    • c) Nigeria
    • d) Brazil
  14. Which of the following is the recommended method for stopping cVDPV outbreaks?
    • a) Two doses of inactivated polio vaccine (IPV)
    • b) 2-3 rounds of high-quality oral polio vaccine (OPV) immunization campaigns
    • c) Mass vaccination with measles vaccine
    • d) Isolation of infected individuals
  15. Which factor is the primary issue causing cVDPV outbreaks?
    • a) Faulty vaccines
    • b) Low vaccination coverage
    • c) Over-vaccination
    • d) Rapid spread of wild poliovirus
  16. What is the minimum follow-up period for AFP cases after onset of paralysis?
    • a) 15 days
    • b) 30 days
    • c) 45 days
    • d) 60 days
  17. Which season is poliovirus most commonly associated with?
    • a) Winter
    • b) Summer
    • c) Rainy season
    • d) Spring
  18. Which diagnostic tool is crucial to differentiate poliovirus from other viral causes of paralysis?
    • a) MRI
    • b) Blood viral cultures
    • c) PCR
    • d) CSF analysis
  19. Which of the following is NOT a recommended practice to improve immunization coverage in polio-endemic areas?
    • a) Using IPV instead of OPV
    • b) Removing Type 2 from OPV formulation
    • c) House-to-house immunization campaigns
    • d) Discontinuing OPV altogether
  20. Which polio strain was last detected in November 2012?
    • a) Type 1
    • b) Type 2
    • c) Type 3
    • d) Vaccine-derived strain
  21. Which complication is characterized by new muscle weakness after recovery from poliomyelitis?
    • a) Guillain-Barré syndrome
    • b) Postpolio syndrome
    • c) Transverse myelitis
    • d) Myasthenia gravis
  22. In which country was Type 2 wild poliovirus last detected?
    • a) Afghanistan
    • b) Pakistan
    • c) India
    • d) Nigeria
  23. Which population in Pakistan is disproportionately affected by wild poliovirus?
    • a) Urdu-speaking
    • b) Pashto-speaking
    • c) Bengali-speaking
    • d) English-speaking
  24. What is the ultimate solution to all polio outbreaks?
    • a) Enhanced sanitation measures
    • b) High-quality OPV immunization campaigns
    • c) Quarantine of affected individuals
    • d) Administration of antibiotics
  25. What is the recommended time frame for collecting stool samples after the onset of paralysis?
    • a) 7 days
    • b) 10 days
    • c) 14 days
    • d) 21 days

Answers to MCQs

  1. c) Faecal-oral route
  2. a) Type 1
  3. c) Type 3
  4. b) Motor deficit with sensory intact
  5. d) PCR
  6. b) 2015
  7. a) 1
  8. b) Prolonged circulation of excreted vaccine virus in under-immunized populations
  9. c) Myocarditis
  10. c) Widespread knowledge about vaccines
  11. b) 2
  12. c) 12-18 months
  13. b) Afghanistan
  14. b) 2-3 rounds of high-quality oral polio vaccine (OPV) immunization campaigns
  15. b) Low vaccination coverage
  16. d) 60 days
  17. c) Rainy season
  18. c) PCR
  19. d) Discontinuing OPV altogether
  20. c) Type 3
  21. b) Postpolio syndrome
  22. c) India
  23. b) Pashto-speaking
  24. b) High-quality OPV immunization campaigns
  25. c) 14 days

Subjective Practice Questions

  1. Explain the pathophysiology of poliomyelitis and how it leads to paralysis.
    • Hint: Discuss how the poliovirus infects the human body, multiplies in the intestines, invades the nervous system, and leads to motor paralysis. Mention pure motor deficit and the role of faecal-oral transmission.
    • Points to cover: Virus replication, invasion of the nervous system, motor deficit.
  2. Describe the development of circulating vaccine-derived poliovirus (cVDPV) and its contributing factors.
    • Hint: Cover how cVDPV develops due to low vaccination coverage, genetic mutations in the vaccine virus, and how it can cause paralysis like the wild virus.
    • Points to cover: Role of OPV, low vaccination coverage, genetic changes, prevention methods.
  3. Discuss the major challenges faced by Afghanistan and Pakistan in eradicating polio.
    • Hint: Mention issues like house-to-house immunization bans, poor-quality campaigns, vaccine hesitancy, and misinformation on social media.
    • Points to cover: Immunization bans, vaccine hesitancy, marginalized populations, and operational challenges.
  4. How is Acute Flaccid Paralysis (AFP) surveillance conducted, and why is it important for polio eradication?
    • Hint: Outline the four steps of AFP surveillance, including finding cases, stool sample collection, virus isolation, and virus mapping. Emphasize its role in monitoring poliovirus circulation.
    • Points to cover: AFP detection, sample transport, poliovirus isolation, and surveillance effectiveness.
  5. Compare and contrast Vaccine-Associated Paralytic Poliomyelitis (VAPP) and wild poliovirus infection in terms of pathogenesis and epidemiology.
    • Hint: Focus on the differences in origin (vaccine vs. wild), how VAPP is rare and more associated with serotype 3, while wild poliovirus affects unvaccinated populations.
    • Points to cover: Pathogenesis, serotypes involved, immunization coverage, and rarity of VAPP.

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