Chapter 26 Flashcards
CNS
brain and spinal cord
PNS
peripheral nerves
Nervous System
Cells are called neurons, no normal flora
Natural Defenses of the Nervous System
• Skull and vertebrae
• Microglial cells and macrophages
• Restricted entry into brain (blood-brain barrier) for: microorganisms , medications (including most antibiotics), immune system
Both Bacteria and viruses and parasites can cause
Meningitis and encephalitis
Meningitis
inflammation of the meninges =
membranes surrounding the brain and spinal cord
Encephalitis
inflammation of the brain
Nervous System Diseases (Viruses)
Rabies and Poliomyelitis
Nervous System Diseases (Neurotoxins)
Tetanus
Bacterial Meningitis (Haemophilus influenzae type b)
Infants, newborn (also, E. coli, Streptococcus agalactiae = Group B Strep)
Bacterial Meningitis (Streptococcus pneumoniae)
Children 1 month - 4 years, Elderly
Bacterial Meningitis (Neisseria meningitidis)
College students
Streptococcal Meningitis (Caused by Streptococcus pneumoniae)
• Gram + diplococci
• Virulent strains are encapsulated
• Children age 1 month – 4
years
• Elderly
Meningococcal Meningitis in College Students (Neisseria 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 caused by Naegleria fowleri)
Small free-living amoeba found in fresh water, can be normal flora. Protozoan feeds on bacteria but if introduced into
the CNS can feed on human tissue.
Acquired from hot tubs, warm ponds and ground water at high temperature, initially infects the nasal mucosa
Naegleria meningoencephalitis
Naegleria meningoencephalitis Symptoms
•Abrupt onset of symptoms 3 to 10 days after exposure to water
•Severe headache, fever, stiff neck, dementia and coma
•Children and young adults
Naegleria meningoencephalitis (TERRIFYING FACTS?)
•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
•Mortality rate of >95%
Toxoplasmosis (caused by 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
Toxoplasmosis
Toxoplasmosis High Risk Factors
-Causes serious disease in developing fetus
• Liver damage
• Brain abnormalities
• Blindness
-Serious disease in people with AIDS
Toxoplasmosis Prevention
no raw meat, no contact with cat litter box
Hansen’s Disease (Leprosy)
•Disease of skin and nerves
•Change of pigmentation, loss of sensation
•Slow progressing
•Transmits poorly
•Droplet or skin contact?
Mycobacterium leprae (Hansen’s Disease)
•Acid fast bacterium
•Slow growth
•Strict parasite
•Multiplies in macrophages
•Prefers cool areas of body
•Long course, drug cocktail
Rabies
Viral infection from bite of a “furious” rabid animal (Animal rabies: Wandering, aggression, biting, salivating)
Rabies Infection
- Bite then 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
A fatal zoonotic disease with a variable latent period
Rabies
Human “dumb” rabies
fever, confusion, anxiety, encephalitis, death
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….)
Paralytic Poliomyelitis
Neurotropic viral infection acquired by ingestion (Paralytic spinal cord infection)
Paralytic Poliomyelitis vaccine
-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
Poliovirus, an “Enterovirus” has
an icosahedral capsid shell that
protects it from digestion.
Clostridium tetani
soil organism and the causative
agent of tetanus (have a unique tennis racket morphology)
The Events in Tetanus
Bacterial invasion, release of bacterial toxin, and symptoms:
Rigid Paralysis
