Microbial Diseases of the Nervous System

1. 22 Microbial Diseases of the Nervous System

2. How Microbes Enter the Nervous System • Skull or backbone fractures • Medical procedures • Along peripheral nerves • Blood or lymph • Some of the most devastating infectious diseases • Damage can lead to deafness, blindness, learning disabilities, paralysis, and death

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. • Meningoencephalitis- both

5. The Meninges and Cerebrospinal Fluid Figure 22.2

6. Bacterial diseases of the Nervous system • Infrequent, but serious

7. Bacterial Meningitis • Fever, headache, and stiff neck • Followed by nausea and vomiting • May progress to convulsions and coma • Spinal tap of CSF, look for WBC • Life threatening and develops rapidly

8. Bacterial Meningitis Figure 22.3

9. Haemophilus influenzae Meningitis • Heme (blood) philus (loving) • Occurs mostly in children (6 months to 4 years). • normal throat microbiota, occasionally enters the bloodstream and causes several invasive diseases • Hib vaccine • Name given b/c erroneously thought to be agent of 1889 and WW I influenza pandemic, does not cause the flu

10. Neisseria Meningitis, Meningococcal Meningitis • N. meningitidis • Symptoms caused by endotoxins rapidly produced • Rash does not fade when pressed • 10% of people are healthy nasopharyngeal carriers • Begins as throat infection, rash, bacteremia (sepsis) • 1992 Vaccine recommended for college students.

11. Streptococcus pneumoniae Meningitis, Pneumococcal Meningitis • Named pneumococcal b/c best known as a cause of pneumonia • 70% of people are healthy nasopharyngeal carriers • Most common in children (1 month to 4 years) • Mortality: 30% in children, 80% in elderly • Vaccine, recommended for infants under 2 • Side effect of vaccine is reduced otitis media

12. Listeriosis • Listeria monocytogenes • Usually foodborne widely distributed in soil and water • Adults- mild, but could invade CNS causing menigitis • Fetal/newborn- abortion or stillborn or newborn meningitis Figure 22.5

13. Tetanus • Clostridium tetani • Found in soil contaminated by animal fecal waste • Grows in deep wounds. • Tetanospasmin (neurotoxin) released from dead bacteria blocks relaxation pathway in muscles. • 1940 Vaccine:tetanus toxoid (DTP) and booster (dT) • Lockjaw, opisthotonos (head and heels bow backward)

14. Tetanus Figure 22.6

15. Botulism • Clostridium botulinum • Intoxication comes from ingesting botulinal toxin, botulus is Latin for sausage • Botulinal toxin blocks release of neurotransmitter causing flaccid paralysis could be fatal from respiratory or cardiac failure • Nausea, neurological symptoms • Prevention: Proper canning, Nitrites prevent endospore germination in sausages, acidic foods less than pH 4.7

16. Botulism • Infant botulism results from C. botulinum growing in intestines (b/c GI tract bacteria not fully developed) • Honey not recommend under age of 1 • Wound botulism results from growth of C. botulinumin wounds. • Cosmetically, Botox for “worry lines”, armpit sweating, strabismus (cross eyes), blepharospasm (inability to keep eyelids raised)

17. Botulism • Type A- most virulent • 60-70% fatality, can even be absorbed via skin • Foods might have spoiled odor • Type B • 25% fatality • Europe and eastern United States • Type E • Found in marine and lake sediments • Involve seafood

18. Leprosy/ Hansen’s disease • Mycobacterium leprae • Grows in peripheral nerves and skin cells. • Transmitted by prolonged contact with an infected person, possible from nasal or oozing lesions, not very contagious • Tuberculoid (neural) form: Loss of sensation in skin areas • Lepromatous (progressive) form: Disfiguring nodules over body, mucosa of nose (lion face)

19. Leprosy Figure 22.9

20. Viral Diseases of the Nervous System • Enter by circulation in the blood or lymph • Some can enter via peripheral nerve axons

21. Poliomyelitis • Poliovirus, initially multiplies in the tonsils • Transmitted: ingestion of contaminated water by feces • symptoms: fever, sore throat, nausea, headache • Viremia may occur; if persistent, virus can enter the CNS; destruction of motor cells and paralysis occurs in <1% of cases. Fatal if respiratory muscles • Vaccine: Enhanced-inactivated polio vaccine- E-IVP

22. Rabies Virus (Rhabdovirus) Latin=rage, madness • Transmitted by animal bite (zoonotic), scratches, and inhalation • wild populations of bats, skunks, raccoons, cats, and canines are primary reservoirs • Virus multiplies in skeletal muscles, then brain cells causing fatal encephalitis. • Symp: muscle spasms of the mouth and pharynx and hydrophobia, anxiety, agitation, muscle spasms, convulsions, paralysis • Furious rabies: Animals are restless then highly excitable. • Paralytic rabies: Animals seem unaware of surroundings. • Postexposure treatment: Vaccine plus immune globulin. • Pet vaccines & wild animal immunizations are being tried.

23. Rabies Virus (Rhabdovirus) Treatment of an animal bite for possible rabies includes debridement wash bite with soap detergent wound is infused with human rabies immune globulin (HRIG) postexposure vaccination with inactive vaccine Figure 22.12

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

25. Arboviral Encephalitis • Encephalitis caused by arboviruses • fever, headache, and rash • coma, convulsions, paralysis in severe cases • myalgia and orbital pain • muscle aches and joint stiffness

26. Fungal disease of the Nervous System • Seldom invaded by fungi • One is adapted to grow in CSF

27. 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% if progresses to chronic meningitis • common cause of meningitis in AIDS paitents

28. Protozoan Disease of the Nervous System • Rarely invades, but devastating effects

29. African Trypanosomiasis (Sleeping Sickness) • Trypanosoma brucei 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. • Few symptoms, eventually fever, headache

30. Meningoencephalitis • Primary amebic • Naegleria fowleri • infects nasal mucosa from swimming ponds/streams • 100% fatality • Granulomatous Amebic • Acanthamoeba • Lesions on brain, lungs Figure 22.17

31. Nervous system diseases caused by Prions • Several fatal diseases • Prions= abnormally folded proteins that can induce a change in the shape of a normal protein, causing proteins to clump • Diseases have long incubation periods, years • Insidious and slowly progressive

32. Transmissible Spongiform Encephalopathies • Porous, sponge like appearance in brain • Transmitted by eating brain material • Sheep scrapie- US 1947, animal scrapes raw spots • Creutzfeldt-Jakob disease-genetic, transplant • Gertsmann-Straussler-Scheinker syndrome • Kuru (native for shaking/trembling)- cannibalistic rituals • Bovine spongiform encephalopathy (mad cow)-feed from infected sheep matter, USDA banned animal protein, “downer” animals, certain portions of cows

33. Transmissible Spongiform Encephalopathies Figure 22.18

34. Disease of unknown agents • Chronic fatigue Syndrone (CFS)- persistent fatigue • Once thought to be psychiatric in nature, most experts believe some unidentified infectious agent • CFS appears after recovery from viral infections such as mononucleosis