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Questions and Answers
What percentage of people infected with West Nile Virus exhibit flu-like symptoms?
What percentage of people infected with West Nile Virus exhibit flu-like symptoms?
What is the primary mode of transmission for West Nile Virus?
What is the primary mode of transmission for West Nile Virus?
What is the approximate incubation period for West Nile Virus?
What is the approximate incubation period for West Nile Virus?
What is the complication of polio that occurs 30-40 years after initial infection?
What is the complication of polio that occurs 30-40 years after initial infection?
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What is the primary reservoir for poliovirus?
What is the primary reservoir for poliovirus?
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What is the mode of transmission for poliovirus?
What is the mode of transmission for poliovirus?
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What is the estimated number of cases of polio in 1988?
What is the estimated number of cases of polio in 1988?
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What is the mortality rate for people who experience neuroinvasion due to West Nile Virus?
What is the mortality rate for people who experience neuroinvasion due to West Nile Virus?
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What is the percentage of people infected with West Nile Virus who do not exhibit any symptoms?
What is the percentage of people infected with West Nile Virus who do not exhibit any symptoms?
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What is the number of species that West Nile Virus can infect?
What is the number of species that West Nile Virus can infect?
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Study Notes
Bacterial Meningitis
- Inflammatory bacterial infection of the meninges, particularly the pia and arachnoid mater
- Causes meningial swelling, restricting CSF flow, and putting pressure on the organs, leading to nausea, pain, vomiting, and reduced brain function
- If the infection is in the spinal cord, muscles of the neck will become stiff, and motor control will be reduced
- If the infection is in the brain (encephalitis), sensory perceptions are decreased, behavioral changes occur, and coma or death may result
Testing for Bacterial Meningitis
- Cloudy CSF and positive meningitis test indicating bacterial infection
- Lumbar puncture (aka spinal tap) is used to collect CSF for testing
Many Bacteria Can Cause Bacterial Meningitis
- Opportunistic members of normal microbiota (e.g., Staphylococcus aureus, Streptococcus pyogenes, Klebsiella pneumoniae)
- Regular disease-causing bacteria (e.g., Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, Listeria monocytogenes)
Neisseria Meningitidis
- Causes meningococcal meningitis
- Virulence factors include fimbriae, polysaccharide capsules, lipooligosaccharide (with Lipid A/Endotoxin), and various factors to prevent digestion in phagocytes
Streptococcus Pneumoniae
- Leading cause of meningitis
- Virulence factors include capsule, secretory IgA protease, pneumolysin (inactivator of lysosomal enzymes)
- Primary virulence factor: phosphorylcholine (attachment to cells of lungs, meninges, blood vessels – and triggers endocytosis)
Listeria Monocytogenes
- Gram-positive coccobacillus found in soil, water, and many animals
- Obtained through contaminated food/drink
- Causes meningitis in immunocompromised individuals, but only mild flu in healthy adults
- Avoids immune system detection by dividing inside macrophages and epithelial cells
Pathogenesis of Bacterial Meningitis
- N. meningitidis, H. influenzae, S. pneumoniae – inhaled in respiratory droplets
- Listeria – through contaminated food/drink
- Bacteria usually spreads to meninges from infections of lungs, sinuses, or inner ear
- Head or neck trauma may expose meninges directly
- Bacteria ferment glucose in CSF for energy
Prevention
- Susceptible individuals should avoid undercooked veggies, unpasteurized milk, undercooked meat, and all soft cheese
- People living in dormitories should receive vaccinations
Hansen's Disease (Leprosy)
- Causative agent: Mycobacterium leprae
- Optimal growth – 30°C – so in the chilly parts of the body (peripheral nerve endings, earlobes, nose, tips of fingers and toes)
- Signs of disease may not be present for 10-30 years, but when the population becomes big enough, the immune system will aggressively attack them
Botulism
- Causative agent: Clostridium botulinum toxin (note: NOT an infection)
- 3 types of botulism: foodborne, infant, and wound
- Foodborne/Wound Botulism symptoms: paralysis of all voluntary muscles, blurred vision, nausea (death from respiratory paralysis)
- Infant botulism: not ingested, but C. botulinum can infect GI tract due to absence of microbiota
Tetanus
- Causative agent: Clostridium tetani
- Portal of entry: endospores enter through breaks in skin
- Signs/symptoms: tightening of jaw and neck muscles, difficulty swallowing, fever, spasms
- Treatment: aggressive treatment of wound, antibiotics
- Prevention: Vaccination
Tetanus Toxin (Tetanospasmin)
- Blocks release of inhibitory neurotransmitter, causing muscles to be fully contracted and unable to relax
West Nile Fever
- Absent from N. America until 1999
- New York isolate identical to Israeli goose
- Virus infects 100s of bird, 37 mosquito, 18 other vertebrate (including humans/horses) species
West Nile Virus Transmission Cycle
- Mosquito bite transmission
WNV - Pathogenesis
- Transmitted by mosquito bite
- Incubation period of 3-14 days
- 20-30% get flu-like illness called West Nile Fever
- 80% - NO symptoms
- 1/150 experience neuroinvasion
Epidemiology – US Cases
- Increased cases in the US since 1999
Epidemiology – Case Fatality Rate
- High case fatality rate
WNV Prevention
- Prevention measures to avoid mosquito bites
Poliomyelitis (Polio)
- Causative agent: Poliovirus
- Spread by fecal-oral transmission
- Peaks during warm months in temperate climates
- Complication: post-polio syndrome
Polio Epidemiology
- Decreased cases since the introduction of vaccination
- Americas/Europe: now "polio-free"
Emergence of Polio as an Epidemic in the 1900s
- Polio has only minor symptoms for infants and adults (seems like a mild cold)
- Early in the 1900s, white, wealthy children started getting paralytic polio
- Connection to modern plumbing, sewer systems, etc.
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Description
Learn about the inflammatory bacterial infection of the meninges, its causes, symptoms, and effects on the brain and spinal cord.
