Infectious diseases of the nervous system
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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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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


  • 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

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


  • 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 infections of the cns acute viral encephalitis
Viral Infections of the CNSAcute Viral Encephalitis

  • Arboviruses West 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

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

  • Caused by arbovirus

  • In the blood of imported birds

  • Main vector are about 46 types of mosquitoes

  • Starts from fever to neuroinvasive 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




  • 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.

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