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 Students Neisseria 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 Meningoencephalitis A 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 CNS Acute 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: Negri Bodies
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

42. 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

43. 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
 CNS Paralysis of motor neurons

44. 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.

45. 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