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Chapter 22, part B

Chapter 22, part B. Microbial Diseases of the Nervous System. Botulism. Clostridium botulinum Gram-positive, endospore-forming, obligate anaerobe Intoxication due to ingesting botulinal toxin Botulinal toxin blocks release of neurotransmitter causing flaccid paralysis Prevention:

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Chapter 22, part B

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  1. Chapter 22, part B Microbial Diseases of the Nervous System

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

  3. 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.

  4. Botulism • Type A • 60-70% fatality • Found in CA, WA, CO, OR, NM • Type B • 25% fatality • Europe and eastern U.S. • Type E • Found in marine and lake sediments • Pacific Northwest, Alaska, Great Lakes area

  5. Diagnosis Figure 22.7

  6. 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

  7. Leprosy Figure 22.8

  8. 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)

  9. Poliomyelitis Figure 22.10

  10. 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 + immune globulin

  11. Rabies virus (Rhabdovirus) Figure 22.11

  12. Rabies virus (Rhabdovirus) Figure 22.12

  13. Arboviral Encephalitis • Arboviruses are arthropod-borne viruses that belong to several families. • Prevention is by controlling mosquitoes

  14. Cryptococcus neoformans Meningitis (Cryptococcosis) • Soil fungus associated with pigeon and chicken dropping • Transmitted by the respiratory route; spreads through blood to the CNS • Mortality up to 30% • Treatment: amphotericin B and flucytosine

  15. Cryptococcus neoformans Meningitis (Cryptococcosis) Figure 22.14

  16. 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

  17. African Trypanosomiasis Figure 22.15

  18. Naegleria fowleri • Protozoan infects nasal mucosa from swimming water Figure 22.16

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

  20. Transmissible Spongiform Encephalopathies Figure 22.17a

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