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Infectious Diseases of the Nervous System. Nervous System. CNS : brain and spinal cord PNS : peripheral nerves Cells are called neurons No normal flora. Natural Defenses of the Nervous System. Skull and vertebrae Microglial cells and macrophages

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Infectious Diseases of the Nervous System

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Infectious diseases of the nervous system

Infectious Diseases of the Nervous System

Nervous system

Nervous System

  • CNS: brain and spinal cord

  • PNS: peripheral nerves

  • Cells are called neurons

  • No normal flora

Natural defenses of the nervous system

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

Nervous system diseases

Nervous System Diseases

  • Meningitis: inflammation of the meninges = membranes surrounding the brain and spinal cord

  • Encephalitis: inflammation of the brain

Bacterial infection

Bacterial infection



  • 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

Streptococcal meningitis

Streptococcal Meningitis

Streptococcus pneumoniae

  • Gram + diplococci

  • Virulent strains are encapsulated

  • Children age 1 month – 4 years

  • Elderly

Subunit vaccine: induces opsonizing antibody to capsule

Meningococcal meningitis in college students neisseria meningitidis

Meningococcal Meningitis in College StudentsNeisseria 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

Neisseria meningitidis

Neisseria meningitidis

Naegleria meningoencephalitis a rare infection

Naegleria MeningoencephalitisA 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

Naegleria meningoencephalitis

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

Naegleria meningoencephalitis1

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

Protozoans infection

Protozoans infection



  • Toxoplasma gondii

  • Flagellated protozoan parasite

  • Infects over 200 species of birds and animals

  • Primary reservoir is cats

  • Infection usually handled by immune system



  • Acquired from contaminated meat or ingestion of oocysts in cat feces



  • 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

Viral infection

Viral infection

Viral infections of the cns acute viral encephalitis

Viral Infections of the CNSAcute Viral Encephalitis

  • ArbovirusesWest Nile Virus Encephalitis

    Western or Eastern

    Equine Encephalitis

    California Encephalitis

    La Crosse Encephalitis

  • Herpes simplex 1 or 2

  • Rabies

Arboviral encephalitis

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.

Arboviral encephalitis is prevalent worldwide

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



  • 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



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

Infectious diseases of the nervous system

Diagnosis of Rabies:

  • 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

Prevention of rabies

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

West nile fever

West nile fever

Infectious diseases of the nervous system

  • Caused by arbovirus

  • In the blood of imported birds

  • Main vector are about 46 types of mosquitoes

  • Starts from fever to neuroinvasive disease

Other bacterial nerve disease

Other bacterial nerve disease

Hansen s disease

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

Causes and symptoms

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

Progression of leprosy

Progression of leprosy



Gram stain

Gram stain



  • 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





  • 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.



  • 4 – 10 days incubation

  • Muscle spasm

  • Lockjaw

  • Respiratory muscle paralyzed

  • Heart function disturb

Types of tetanus

Types of tetanus

  • Neonatal tetanus

  • Local tetanus

  • Cephalic tetanus

  • Generalized tetanus

Treatment and prevention

Treatment and prevention

  • Tetanus toxoid vaccine

  • Antibiotic for injured pt

  • Antitoxin to reduce toxin inactivation

  • Tetanus neonatorum (from contaminated knife)





Paralytic poliomyelitis

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

The unique stages of infection and pathogenesis of poliomyelitis

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

 CNSParalysis of motor neurons

Virus travels through blood and the nerves

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.

Infectious diseases of the nervous system

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


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