© 2004 Wadsworth – Thomson Learning Chapter 25 Infections of the Nervous System.

© 2004 Wadsworth – Thomson Learning

Chapter 25Chapter 25Infections of the Nervous Infections of the Nervous

SystemSystem

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The Nervous System

Figure 25.1

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Meningitis• Organisms

– Neisseria meningitidis• meningococcal

– Haemophilus influenzae– Streptococcus pneumoniae

• pneumococcal

– E. coli

• Pathogenesis– inflammation of the meninges membrane

• brain and spinal cord

– sudden fever, severe headache, neck rigidity– treatment--immediate antibiotics

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Meningitis• Aseptic meningitis

– viral origin

• Cryptococcal meningitis– Cryptococcus neoformans

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Tetanus• Organism

– Clostridium tetani– Spore former– Anaerobic growth

• deep wounds• decaying tissue

• Pathogenesis– tetanospasmin

• neurotoxin• ink dot enough for 30 deaths

– contraction of muscles• spastic paralysis• lockjaw• respiratory distress

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Tetanus• Treatment

– before clinical symptoms• antitoxin• blocks toxin

– after clinical symptoms• no treatment

• Prevention:– vaccine every 5-10 years– toxoid

• develop antibodies against toxin, not organism

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Botulism

• Organism– Clostridium botulinum

• spores many places• growth inhibited by low pH

• Pathogenesis– blocks release of acetylcholine– interferes with nerve impulse– paralysis of respiratory muscles– mortality 35%

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Botulism• Different types of toxin

– produced by different strains of C. botulinum– Type A

• most potent• west of Mississippi River

• Age associated– infant botulism

• differences in normal biota

– adult botulism• food poisoning• heat-labile toxin

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Rabies• bullet-shaped morphology• epidemiology

– reservoir: all mammals– humans: end of infectious cycle

• control– reduce exposure of virus in animals

• wild mammals--uncontrollable reservoir• bats--dormant for long periods• domestic--vaccine

• diagnosis: serology/brain tissue (negri body)• treatment: vaccine and immune globulin (RIG)

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Poliomyelitis• Pathogenesis

– alimentary phase--primary multiplication– lymphatic phase--tonsils, lymph nodes– viremic phase--spread in blood– neurological phase--CNS, extraneural tissue

• requires persistent viremia• low levels of antibodies prevent spread• >l% of infections lead to severe paralytic infection

– two vaccines• oral (OPV)--attenuated--Sabin• injected (IPV)--inactivated--Salk

– eradication schedule--2000

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Encephalitis• Arboviruses

• Eastern Equine Encephalitis (EEE)– severe

• Western Equine Encephalitis (WEE)• California Encephalitis (CE)• St. Louis Encephalitis (SLE)• Japanese B encephalitis

– endemic areas of Asia

• mosquito borne

• Other viruses• West Nile Virus

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Spongiform encephalopathy• Prions

– infectious proteins– Diseases:

• Creutzfeldt-Jakob disease (CJD)• Kuru• Scrapie (sheep)• Bovine spongiform encephalitis (mad cow)

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African Trypanosomiasis• Sleeping Sickness

– Trypanosoma brucei gamiense– Trypanosoma brucei rhodesiense– Protozoa– Transmitted by tsetse fly

• multiply in fly• tyrpanosome enters blood• spread to spleen, lymph nodes, liver• invade CNS• coma and death