Infectious Diseases Affecting the Nervous System
Chapter 19
Infectious Diseases Affecting the Nervous System
Chapter Outline
19.1. The Nervous System and Its Defenses
A. The nervous system has two parts: the central nervous system (the brain and spinal cord), and the peripheral nervous system (spinal and cranial nerves)
B. Brain and spinal cord are enclosed within a tough encasing:
1. Three membranes called the meninges
a. Dura mater, arachnoid mater, and pia mater
b. Meninges is a common site of infection
C. Subarachnoid space is filled with cerebrospinal fluid (CSF):
1. Provides nutrition to CNS
2. Liquid cushion for brain, spinal cord
D. The blood-brain barrier
1. Prevents most microorganisms from penetrating into CNS
19.2. Normal Biota of the Nervous System
A. No normal biota
19.3. Nervous System Diseases Caused by Microorganisms
A. Meningitis
1. An inflammation of the meninges
a. Caused by bacteria, respiratory viruses, fungi
b. Lumbar puncture is performed to obtain CSF when meningitis is suspected
2. Signs and symptoms
a. Include headache, painful or stiff neck, and fever
b. Increased number of white blood cells in the CSF
3. Neisseria meningitidis
a. Gram-negative diplococcus
b. Pathogenesis and virulence factors
i. Petechiae
ii. Meningococcemia can become a fulminant disease with a high mortality rate
iii. Bacteria produce a protease that destroys IgA and a capsule which is antiphagocytic
c. Transmission and epidemiology
i. Attach to nasaopharynx using pili
ii. 3 to 30% of adults are carriers
iii. Highest risk groups are young children (6-36 months) and older children and young adults (10-20 years)
d. Culture and diagnosis
i. Identification is essential due to the disease causing rapid fatalities in some patients
ii. Detection in CSF via Gram stain
e. Prevention and treatment
i. Natural immunity due to opsonizing antibodies occurs in most people
ii. When disease occurs, penicillin G is effective when administered as soon as possible after presumptive diagnosis
4. Streptococcus pneumoniae
a. Gram-positive flattened coccus
b. Polysaccharide capsule that is antiphagocytic
c. Alpha hemolysin
d. Two vaccines
i. Prevnar (7 serotypes; childhood)
ii. Pneumovax (23 serotypes; adults)
e. Pneumococcal meningitis
5. Haemophilus influenzae
a. Gram-negative pleomorphic rod
b. Acute bacterial meningitis in humans
i. B serotype
c. Hib vaccine (contains capsular polysaccharide)
6. Listeria monocytogenes
a. Gram-positive coccobacilli
b. Listeriosis
i. Affects the brain and meninges
ii. Septicemia
iii. Contaminated dairy products, poultry, and meat
iv. Grows at refrigeration temperatures (cold enrichment)
7. Cryptococcus neoformans
a. Fungus
b. Chronic form of meningitis
i. Meningoencephalitis
c. Transmission and epidemiology
i. Bird droppings
ii. AIDS patients
d. Pathogenesis and virulence factors
e. Culture and/or diagnosis
f. Prevention and treatment
8. Coccidioides immitis
a. Fungal infection
i. Two shapes:
1. Hyphae at 25ºC
2. Spherule at 37ºC
b. Coccidioidomycosis of the meninges
c. Pathogenesis and virulence factors
i. Systemic fungal infection of high virulence
d. Transmission and epidemiology
i. Found in semiarid, relatively hot climate
ii. Outbreaks usually associated with farming, archeological digs, construction, and mining
iii. Southwestern United States, Mexico, and parts of Central and South America
e. Culture and diagnosis
f. Prevention and treatment
9. Viruses
a. Aseptic meningitis
b. Enteroviruses
c. Herpesviruses such as herpes simplex type 2, HHV-6 and HHV-7, HHV-3 (Varicella-zoster virus) and cytomegalovirus (CMV)
d. Arboviruses, arenaviruses, adenoviruses and HIV infection
B. Neonatal meningitis
1. Transmitted by the mother during passage through birth canal
2. Streptococcus agalactiae
a. Group B streptococci
b. Most frequent cause of neonatal meningitis
3. Escherichia coli
a. K1 strain
C. Meningoencephalitis
1. Two amoebas
a. Protozoan parasites
2. Naegleria fowleri
a. Primary amoebic meningoencephalitis (PAM)
3. Acanthamoeba
a. Granulomatous amoebic meningoencephalitis (GAM)
D. Acute encephalitis
1. Viral infection
2. Arboviruses
a. Pathogenesis and virulence factors
b. Culture and diagnosis
c. Prevention and treatment
d. Arboviral encephalitides:
i. Western Equine Encephalitis (WEE)
ii. Eastern Equine Encephalitis (EEE)
iii. California Encephalitis
iv. St. Louis Encephalitis (SLE)
v. West Nile Encephalitis
3. Herpes simplex virus
a. Type 1 and 2
4. JC virus
a. Progressive multifocal leukoencephalopathy (PML)
E. Subacute encephalitis
1. Toxoplasma gondii
a. Protozoan
b. Toxoplasmosis
c. Signs and symptoms
d. Pathogenesis and virulence factors
i. Obligate intracellular parasite
e. Transmission and epidemiology
i. Pregnant women
ii. Feline contact
f. Culture and diagnosis
g. Prevention and treatment
2. Measles virus
a. Subacute sclerosing panencephalitis (SSPE)
3. Prions
a. Proteinaceous infectious particles
b. Transmissible spongiform encephalopathies (TSEs)
i. Creutzfeldt-Jakob disease (CJD) in humans
ii. Scrapie in sheep and goats
iii. Bovine spongiform encephalopathy (BSE)
c. Signs and symptoms of CJD
d. Causative agent of CJD
e. Pathogenesis and virulence factors
f. Transmission and epidemiology
g. Culture and diagnosis
h. Prevention and/or treatment
F. Rabies
1. Zoonotic disease characterized by fatal encephalitis
2. Signs and symptoms
a. Hydrophobia
b. Coma phase (death from respiratory or cardiac arrest)
3. Causative agent
a. Rabies virus
b. Family Rhabdoviridiae, genus Lyssavirus
4. Pathogenesis and virulence factors
5. Transmission and epidemiology
a. The primary reservoirs of the virus are wild mammals
6. Culture and diagnosis
7. Prevention and treatment
a. Effective vaccine regimen is available
b. Human diploid cell vaccine
G. Poliomyelitis
1. Acute enterovirus infection of the spinal cord
2. Infantile paralysis.
3. Signs and symptoms
a. Neurotropic virus
b. Bulbar poliomyelitis
4. Causative agent
a. Poliovirus
b. Enterovirus in the family Picornaviridae
5. Pathogenesis and virulence factors
6. Transmission and epidemiology
7. Culture and diagnosis
8. Prevention and treatment
a. Inactivated Salk poliovirus vaccine (IPV)
b. Attenuated oral Sabin poliovirus vaccine (OPV)
H. Tetanus
1. Lockjaw
2. Caused by Clostridium tetani
3. Signs and symptoms
a. C. tetani releases tetanospasmin neurotoxin
b. Toxin blocks inhibition of muscle contractions
c. Muscles contract uncontrollably, resulting in spastic paralysis
4. Pathogenesis and virulence factors
a. Strict anaerobe that requires necrotic tissue that is pooly supplied with blood
b. Tetanospasmin toxin released as bacteria grow
5. Transmission and epidemiology
6. Prevention and treatment
a. Effective vaccine (tetanus toxoid)
b. Antitoxin therapy with human tetanus immune globulin (TIG)
I. Botulism
1. Intoxication
2. Signs and symptoms
a. Food-borne botulism (in children and adults)
b. Infant botulism
c. Wound botulism
3. Causative agent
a. Clostridium botulinum
4. Pathogenesis and virulence factors
a. Botulinum is a powerful exotoxin
5. Transmission and epidemiology of food-borne botulism in children and adults
6. Transmission and epidemiology of infant botulism
7. Transmission and epidemiology of wound botulism
8. Culture and diagnosis
9. Prevention and treatment
a. Antitoxin therapy
J. African sleeping sickness
1. Signs and symptoms
a. Sleeping sickness
2. Causative agent
a. Trypanosoma bruce.
b. Protozoan
3. Transmission and epidemiology
a. Tsetse fly
b. Sub-Saharan Africa
4. Pathogenesis and virulence factors
5. Culture and diagnosis
6. Prevention and treatment
1-1