Lecture on Infectious Diseases of the Nervous System

Introduction

• The central nervous system (CNS) is sterile (no microbiota should be present).
• Pathogens can enter CNS through:
  • Physical trauma or breaks in membranes (meninges).
  • Medical procedures.
  • Traveling via peripheral neurons (e.g., rabies).

Infectious Diseases Affecting the CNS

1. Direct infection of CNS cells or neurons:

   • Meningitis (bacterial and viral).
   • Hansen’s disease (leprosy).

2. Production of toxins affecting CNS:

   • Botulism.
   • Tetanus.

Bacterial Meningitis

• Most common and dangerous form of meningitis.
• Symptoms: Sudden high fever, inflammation of the meninges, possible progression to encephalitis, coma, or death.
• Five Main Bacterial Causes:
  1. Streptococcus agalactiae (Group B Strep):
     • Causes meningitis in newborns.
     • Transmitted from mother during birth.
  2. Listeria monocytogenes:
     • Foodborne; can grow in refrigerators.
     • Risk groups: elderly, immunocompromised, pregnant women.
     • Intracellular infection mechanism.
  3. Streptococcus pneumoniae:
     • Present in throat; can penetrate the CNS.
  4. Neisseria meningitidis (Meningococcal meningitis):
     • Epidemic spread; vaccines available.
  5. Haemophilus influenzae type b (Hib):
     • Intracellular; vaccine available.

Hansen’s Disease (Leprosy)

• Caused by Mycobacterium leprae.
• Two forms:
  • Tuberculoid: Non-progressive, skin plaques.
  • Lepromatous: Progressive, tissue destruction.
• Transmission: Person-to-person, respiratory droplets.
• Treatment: Long-term antimicrobials, BCG vaccine available (not 100% effective).

Diseases Caused by Toxins

Botulism

• Caused by Clostridium botulinum.
• Forms:
  1. Foodborne Botulism:
     • Ingesting contaminated food.
  2. Infant Botulism:
     • Infants ingest spores; lack microbiome to prevent colonization.
  3. Wound Botulism:
     • Toxin produced in anaerobic wounds.
• Toxin causes muscle paralysis (flaccid paralysis).
• Prevention: Avoid feeding honey to infants under 1 year.

Tetanus

• Caused by Clostridium tetani.
• Toxin: Tetanospasmin, causes permanent muscle contraction (lockjaw).
• High mortality rate without treatment.
• Vaccine available (part of DPT/TDap).

Conclusion

• Understanding the differences in disease mechanisms helps in prevention and treatment strategies.
• Importance of vaccines and proper food handling to prevent these diseases.