Diseases of the Nervous System

Question 1

Rabies

Answer 1

Rabies virus, enveloped RNA virus resulting in fatal encephalitis
Incubation period- virus first replicated in muscle cells at point of transmission –> Virus infects neuron and travels from site to brain –> Negri bodies are formed in brain –> Virus spreads to other parts of the body
Signs and symptoms: start with fever, head and muscle aches, sore throat, fatigue and nausea. Progression to agitation, confusion, hallucination, increases sensitivity to light sound and touch. Body temperature rise steeply, and increased salivation combined with difficulty swallowing result in frothing at the mouth. Hydrophobia, then coma and death results.
Transmission: from infection from saliva of infected animals. Inhalation of contaminated material from infected animals.
Treatment: wash bitten area thoroughly, apply antiseptic. Vaccine + Anti-rabies antibodies.

Question 2

Botulism

Answer 2

Clostridium botulinum- gram positive, endospore forming, obligate anaerobe, found in soil
Caused by A-B toxin
Bacteria cannot compete with established normal gut flora so no infection in adults
Infant botulism occurs when infants ingest endospores and normal flora isn’t present. Infection occurs and toxin is present.
Spore can survive boiling and cooking and bacteria grow in anaerobic conditions in food (canned food) and toxin is ingested *INTOXICATION
Toxin is not heat stable, although spore can survive boiling
Honey is a primary source for spores
Symptoms: progressive flaccid paralysis for 1-10 days + death may occur from respiratory and cardia failure
Antibiotics are useless because toxin is preformed

Question 3

Tetanus

Answer 3

Clostridium tetani- gram positive, endospore forming, obligate anaerobe
Spores are found in soil and are extremely long lives- can survive autoclaving for 10-15min
Infection usually comes from deep, penetrating wounds
Bacteria grow only as site of infection (bacteria don’t spread from the infection site, and no inflammation is caused
Toxemia disease due to production of potent neurotoxin tetanospasmin (A-B toxin)- symptoms are sustained, painful, and uncontrolled cramplike muscle spasms, which often begin with the jaw. Pain grows more severe as more muscles are involved and tense. Death is from spasms of respiratory muscles.
Vaccine is a toxoid- TDaP/DTaP
Neonatal tetanus due to treatment of umbilical cord (50% of cases in infants)

Question 4

Viral meningitis

Answer 4

Aseptic meningitis- more common than bacterial meningitis but has similar symptoms
Caused predominantly by enteroviruses spread fecally-orally
Mild, self-limiting disease that resolves in 7-10 days
Caused primarily by Enteroviruses that can exist for long periods of time in the environment

Question 5

Bacterial meningitis

Answer 5

For all causes, symptoms are largely the same, regardless of causative agent
Symptoms: severe headache, and stiff neck, followed by nausea and vomiting. May progress to convulsions and coma. Death occurs due to shock and inflammation.
A spinal tap and gram staining is necessary for identification and eventual treatment
When bacterial meningitis is suspected, broad spectrum antibiotics should be given immediately, without waiting for diagnostic test results

Question 6

Bacterial meningitis - Streptococcus pneumoniae

Answer 6

Streptococcus pneumoniae- gram positive diplococci, 90 different capsules, 25% of population are carriers of this organism
Primary virulence factor: capsule
May result as a sequelae of pneumonia, ear infections
High fatality rate, primarily strikes adults
Antibiotic resistance a factor
Vaccine can reduce incidence of disease, have both a polysaccharide and conjugated vaccine
Accounts for 30-50% of bacterial meningitis

Question 7

Bacterial meningitis - Neisseria meningitides

Answer 7

Neisseria meningitides- gram negative diplococci with capsule
Exist in the nasopharynx of 5% of the population and spread by respiratory droplets and close contact. Only a small fraction of carriers develop meningitis. Second most likely cause of meningitis.
Usually starts with a throat infection which leads to bacteremia and then meningitis.
Most symptoms are caused by endotoxin; specialized pili enable meningococci to bind to nasopharyngeal cells for transport across the mucosal barrier
Only meningitis in which a rash develops - DIC/petchiae
Only form of meningitis to cause large epidemics
Conjugated vaccine available

Question 8

Bacterial meningitis - Haemophilus influenzae

Answer 8

Haemophilus influenzae - normal throat flora, gram negative rod, has capsule
Used to be the primary cause of meningitis, but due to Hib vaccine, very few cases today. Targeted for elimination in US

Question 9

Bacterial meningitis - Streptococcus agalactiae

Answer 9

Streptococcus agalactiae: gram-postiive streptococci, group B strep, normal vaginal flora
Primarily causes meningitis in newborns
Antibiotics before delivery prevents transmission

Question 10

Listeriosis

Answer 10

Listeria monocytogenes- gram positive, motile rod, grows in macrophasges/phagocytes, (no capsule)
Only food borne cause of meningitis. Found in food that is not normally cooked prior to eating- slaw, sandwich meats, and dairy products (food borne outbreaks)
Capable of reproducing at refrigerator temperatures and can reproduce in monocytes, macrophages and spreads throughout body
Targets immunosuppressed, pregnant, or neonates
Symptoms: mild cases- symptomless disease in health adults who can be carriers, shed bacteria in feces. In older of immunocompromised individuals it causes meningitis as well as septicemia. In pregnant women it can cause spontaneous abortions, stillbirths, meningitis in infants.