1. DISEASES OF THE NERVOUS SYSTEM

2. How Microbes Enter the Nervous System
Skull or backbone fractures
Medical procedures
Along peripheral nerves
Blood or lymph

3. The Nervous System
Figure 22.1

4. Microbial Diseases of the Nervous System
Bacteria can grow in the cerebrospinal fluid in the subarachnoid space of the CNS.
The blood brain barrier (capillaries) prevents passage of some materials (such as antimicrobial drugs) into the CNS.
Meningitis: Inflammation of meninges.
Encephalitis: Inflammation of the brain.

5. The Meninges and Cerebrospinal Fluid
Figure 22.2

6. Bacterial Meningitis Fever, headache, and stiff neck
Followed by nausea and vomiting
May progress to convulsions and coma
Diagnosis by Gram stain or latex agglutination of CSF
Treated with cephalosporins

7. Bacterial Meningitis
Figure 22.3

8. Haemophilus influenzae Meningitis
Occurs mostly in children (6 months to 4 years).
Gram-negative aerobic bacteria, normal throat microbiota
Capsule antigen type b
Prevented by Hib vaccine

9. Neisseria Meningitis, Meningococcal Meningitis
N. meningitidis
Gram-negative aerobic cocci, capsule
10% of people are healthy nasopharyngeal carriers
Begins as throat infection, rash
Serotype B is most common in the United States
Vaccination recommended for college students.

10. Neisseria Meningitis, Meningococcal Meningitis
Figure 22.4

11. Streptococcus pneumoniae Meningitis, Pneumococcal Meningitis
Gram-positive diplococci
70% of people are healthy nasopharyngeal carriers
Most common in children (1 month to 4 years)
Mortality: 30% in children, 80% in elderly
Prevented by vaccination

12. Listeriosis Listeria monocytogenes Gram-negative aerobic rod
Usually foodborne; it can be transmitted to fetus.
Reproduce in phagocytes.
Figure 22.5

13. Tetanus Clostridium tetani
Gram-positive, endospore-forming, obligate anaerobe
Grows in deep wounds.
Tetanospasmin released from dead cells blocks relaxation pathway in muscles.
Prevention by vaccination with tetanus toxoid (DTP) and booster (dT).
Treatment with tetanus immune globulin.

14. Tetanus
Figure 22.6

15. Botulism Clostridium botulinum
Gram-positive, endospore-forming, obligate anaerobe
Intoxication comes from ingesting botulinal toxin.
Botulinal toxin blocks release of neurotransmitter causing flaccid paralysis.
Prevention
Proper canning
Nitrites prevent endospore germination in sausages.

16. Botulism Treatment: Supportive care and antitoxin.
Infant botulism results from C. botulinum growing in intestines.
Wound botulism results from growth of C. botulinum in wounds.

17. Botulism Type A 60-70% fatality Found in CA, WA, CO, OR, NM. Type B
Europe and eastern United States
Type E
Found in marine and lake sediments
Pacific Northwest, Alaska, Great Lakes area

18. Leprosy Mycobacterium leprae Acid-fast rod that grows best at 30°C.
Grows in peripheral nerves and skin cells.
Transmission requires prolonged contact with an infected person.
Tuberculoid (neural) form: Loss of sensation in skin areas; positive lepromin test
Lepromatous (progressive) form: Disfiguring nodules over body; negative lepromin test

19. Leprosy
Figure 22.9

20. Poliomyelitis Poliovirus Transmitted by ingestion.
Initial symptoms: Sore throat and nausea
Viremia may occur; if persistent, virus can enter the CNS; destruction of motor cells and paralysis occurs in <1% of cases.
Prevention is by vaccination (enhanced-inactivated polio vaccine).

21. Poliomyelitis
FDR- Polio Pioneer

22. Poliomyelitis First vaccine made in Canada by Connaught Medical
Research Laboratories

23. Poliomyelitis
Figure 22.11

24. Rabies Virus (Rhabdovirus)
Transmitted by animal bite.
Virus multiplies in skeletal muscles, then brain cells causing encephalitis.
Initial symptoms may include muscle spasms of the mouth and pharynx and hydrophobia.
Furious rabies: Animals are restless then highly excitable.
Paralytic rabies: Animals seem unaware of surroundings.
Preexposure prophylaxis: Infection of human diploid cells vaccine.
Postexposure treatment: Vaccine plus immune globulin.

25. Rabies Virus (Rhabdovirus)
Figure 22.12

26. Rabies Virus (Rhabdovirus)
Figure 22.12

27. Rabies Virus (Rhabdovirus)
Figure 22.12

28. Rabies Virus (Rhabdovirus)
Figure 22.12

29. Rabies Virus (Rhabdovirus)
Figure 22.12

30. Rabies Virus (Rhabdovirus)
Figure 22.12

31. Rabies Virus (Rhabdovirus)
Negri Bodies in Neurons of Brain
Figure 22.12

32. Rabies Virus (Rhabdovirus)
Figure 22.13

33. Arboviral Encephalitis
Arboviruses are arthropod-borne viruses that belong to several families.
Prevention is by controlling mosquitoes.
Figure 22.14

34. Arboviral Encephalitis
Reservoir
Mosquito vector
U.S. distribution
Western equine
Birds, horses
Culex
Eastern equine
Aedes, Culiseta
St. Louis
Birds
California
Small mammals
Aedes
West Nile
Birds, mammals
Culex, Aedes

35. Cryptococcus Neoformans Meningitis (Cryptococcosis)
Figure 22.15

36. Cryptococcus Neoformans Meningitis (Cryptococcosis)
Soil fungus associated with pigeon and chicken droppings.
Transmitted by the respiratory route; spreads through blood to the CNS.
Mortality up to 30%.
Treatment: Amphotericin B and flucytosine.

37. African Trypanosomiasis
Trypanosoma brucei gambiense infection is chronic (2 to 4 years).
T. b. rhodesiense infection is more acute (few months).
Transmitted from animals to humans by tsetse fly.
Prevention: Elimination of the vector.
Treatment: Eflornithine blocks an enzyme necessary for the parasite.
Parasite evades the antibodies through antigenic variation.

38. African Trypanosomiasis
Figure 22.16

39. Naegleria fowleri Protozoan infects nasal mucosa from swimming water.
Figure 22.17

40. Transmissible Spongiform Encephalopathies
Caused by prions
Sheep scrapie
Creutzfeldt-Jakob disease
Kuru
Bovine spongiform encephalopathy
Transmitted by ingestion or transplant or inherited.
Chronic and fatal

41. Transmissible Spongiform Encephalopathies
Figure 22.18