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Infectious Diseases of the Nervous System

Infectious Diseases of the Nervous System. Nervous System. CNS : brain and spinal cord PNS : peripheral nerves Cells are called neurons No normal flora. Natural Defenses of the Nervous System. Skull and vertebrae Microglial cells and macrophages

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Infectious Diseases of the Nervous System

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  1. Infectious Diseases of the Nervous System

  2. Nervous System • CNS: brain and spinal cord • PNS: peripheral nerves • Cells are called neurons • No normal flora

  3. Natural Defenses of the Nervous System • Skull and vertebrae • Microglial cells and macrophages • Restricted entry into brain (blood-brain barrier) for: • microorganisms • medications, including antibiotics • immune system

  4. Nervous System Diseases • Meningitis: inflammation of the meninges = membranes surrounding the brain and spinal cord • Encephalitis: inflammation of the brain

  5. Bacterial infection

  6. Meningitis • Haemophilus influenzae type b • Infants, newborn • (also, E. coli, Streptococcus agalactiae) • Streptococcus pneumoniae • Children 1 month - 4 years • Elderly • Neisseria meningitidis • College students • Listeria monocytogenes

  7. Streptococcal Meningitis Streptococcus pneumoniae • Gram + diplococci • Virulent strains are encapsulated • Children age 1 month – 4 years • Elderly Subunit vaccine: induces opsonizing antibody to capsule

  8. Meningococcal Meningitis in College StudentsNeisseria meningitidis • Enters through nasal cavity (droplets) • Incidence = 2,500 Americans/year • 10-15% die, up to 20% long-term disabilities • Subunit vaccine: induces opsonizing antibody to capsule

  9. Neisseria meningitidis

  10. Naegleria MeningoencephalitisA rare infection • Naegleria fowleri • Small free-living amoebas • Found in soil, fresh water, and sewage • Can be normal flora • Protozoan feeds on bacteria but if introduced into the CNS can feed on human tissue

  11. Naegleria meningoencephalitis • Acquired from hot tubs, warm ponds and ground water at high temperature • Children and young adults • Initially infects the nasal mucosa • Abrupt onset of symptoms 3 to 10 days after exposure to water • Severe headache, fever, stiff neck and coma

  12. Naegleria meningoencephalitis • Destroys brain and spinal tissue • Death occurs within 10 days of the onset of clinical signs • No treatment • Chlorine kills the organism in spas and pools

  13. Protozoans infection

  14. Toxoplasmosis • Toxoplasma gondii • Flagellated protozoan parasite • Infects over 200 species of birds and animals • Primary reservoir is cats • Infection usually handled by immune system

  15. Toxoplasmosis • Acquired from contaminated meat or ingestion of oocysts in cat feces

  16. Toxoplasmosis • Causes serious disease in developing fetus • Liver damage • Brain abnormalities • Blindness • Serious disease in people with AIDS • Prevention: no raw meat, no contact with cat litter box

  17. Viral infection

  18. Viral Infections of the CNSAcute Viral Encephalitis • Arboviruses West Nile Virus Encephalitis Western or Eastern Equine Encephalitis California Encephalitis La Crosse Encephalitis • Herpes simplex 1 or 2 • Rabies

  19. Arboviral encephalitis…. … Results after the bite of a blood sucking insect, commonly mosquitoes The virus is inoculated directly into the blood stream and grows in monocytes and/or lymphocytes Virus is released into the blood and can enter the brain ….. infecting neurons.

  20. Arboviral encephalitis is prevalent worldwide … But each virus has its own locality, due to its host insect vector species (e.g. Culex species, WNV) … Most disease in the USA is mild with symptoms of fever and malaise, and only occasionally leads to infection of the brain … Most disease localities are known and controlled by via virus monitoring, disease monitoring and mosquito control

  21. Rabies • Viral infection from bite of a “furious” rabid animal: Animal rabies: Wandering, aggression, biting, salivating • Virus travels from the bite to the brain, via nerves • Thus, variable latent period • A fatal zoonotic disease Human “dumb” rabies: fever, confusion, anxiety, encephalitis, death

  22. Rabies Bite Virus grows in muscle Virus enters sensory nerve ending Virus travels to cord, brain Virus grows in brain, changes behavior Virus travels to salivary gland and is secreted

  23. Diagnosis of Rabies: • Performed via a Post-mortem autopsy on animals • Observing neuronal brain cells with intracytoplasmic inclusions (Negri bodies) • Identification of Rabies Strain • (Bat, Skunk, etc….) Negri Bodies Rabid brain stained with Fluorescent anti-rabies antibody Rabid brain stained with Hematoxylin and eosin

  24. Prevention of Rabies Pet Animal vaccines Wildlife edible bait vaccines Euthanize (kill) all rabid animals Quarantine biting, aggressive unvaccinated pets or pet animals bitten by wildlife

  25. West nile fever

  26. Caused by arbovirus • In the blood of imported birds • Main vector are about 46 types of mosquitoes • Starts from fever to neuroinvasive disease

  27. Other bacterial nerve disease

  28. Hansen’s disease • Also known as leprosy • Might also happen in skin and other area • To test, using the lepromin skin test which was similar to tubeculin test • Infecting immigrants

  29. Causes and symptoms • Cause by Mycobacterium leprae • Diagnosis similar to M. tuberculosis • Can also be identified using PCR and skin test • Progression from tuberculoid – lepromatous - lepromas

  30. Progression of leprosy Tuberculoid Lepromas

  31. Gram stain

  32. Treatment • Antibiotic such as rifampin, clofazimine and dapsone • Can reduce the nodules of lepromatous but not the lost tissue • Vaccine are NOT available, the discovery might take years to succeed

  33. tetanus

  34. Causes • Tetanus is often associated with rust, especially rusty nails, • The rough surface of rusty metal merely provides a prime habitat for a C. tetani endospore to reside, • An endospore is a non-metabolizing survival structure that begins to metabolize and cause infection once in an adequate environment. • Because C. tetani is an anaerobic bacterium, it and its endospores survive well in an environment that lacks oxygen.

  35. Symptoms • 4 – 10 days incubation • Muscle spasm • Lockjaw • Respiratory muscle paralyzed • Heart function disturb

  36. Types of tetanus • Neonatal tetanus • Local tetanus • Cephalic tetanus • Generalized tetanus

  37. Treatment and prevention • Tetanus toxoid vaccine • Antibiotic for injured pt • Antitoxin to reduce toxin inactivation • Tetanus neonatorum (from contaminated knife)

  38. botulism

  39. Botulism

  40. Paralytic Poliomyelitis • Neurotropic viral infection acquired by ingestion • Paralytic spinal cord infection • Effective vaccine (PV-1,2,3) • Unvaccinated children are at risk in parts of the world like India, Africa

  41. The unique stages of infection and pathogenesis of poliomyelitis. Poliovirus, an “Enterovirus” has an icosahedral capsid shell that protects it from digestion. GI Tract  Blood  Cord  CNSParalysis of motor neurons

  42. Virus travels through blood and the nerves … And each place in the cord that nerve cells are destroyed causes paralysis to that part of the body controlled by those motor neurons.

  43. Summer epidemics in the early 1900s in the USA caused panic Polio in the USA in spurred the first human vaccines: - Salk Killed Vaccine - Sabin Modified Live Vaccine

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