Plague and Related Diseases Quiz

Arthropod-Borne Infectious Diseases

• Learning Outcomes: Categorize arthropod-borne diseases and suggest appropriate control measures. Key topics covered are in chapters 22 and 23.

Arthropods That Transmit Disease

• Vectors include ticks, mosquitoes, fleas, and biting flies.
• Transmission is typically through biting.

Infections

• Viral (arboviruses):
  • West Nile virus
  • Encephalitic viruses (CNS)
• Bacterial:
  • Ricketsia rickettsii
  • Borrelia burgdorferi
  • Yersinia pestis (CVS)
• Parasites:
  • Malaria (CVS)

Arboviral Encephalitis

• Organism: Arbovirus
• Transmission: Mosquito-borne viruses
• Reservoir: Birds, horses, rodents, and mammals
• Seasonality: Summer months
• Symptoms: Fever, headache, and altered mental status (ranging from confusion to coma)
• Control: (Further details needed)
• Types of Arboviral encephalitis: (List of types needed)

Specific Diseases and Characteristics

• Western Equine Encephalitis (WEE): - Pathogen: WEE virus (Togavirus) - Mosquito Vector: Culex and Aedes - Reservoir: Birds, Horses - Epidemiology: Severe disease, frequent neurological damage, especially in infants - Mortality: 5%
• Eastern Equine Encephalitis (EEE):
  • Pathogen: EEE virus (Togavirus)
  • Mosquito Vector: Culiseta
  • Reservoir: Rodents
  • Epidemiology: More severe than WEE, effects mostly young children and younger adults
  • Mortality: >30%
• St. Louis Encephalitis (SLE):
  • Pathogen: SLE virus (Flavivirus)
  • Mosquito Vector: (Not specified)
  • Reservoir: Large mammals
  • Epidemiology: Mostly urban outbreaks, affects over 40, mainly adults
  • Mortality: 20%
• California Encephalitis (CE):
  • Pathogen: CE virus (Bunyavirus)
  • Mosquito Vector: (Not specified)
  • Reservoir: Large mammals
  • Epidemiology: Affects mostly 4-18 year olds in rural/suburban areas. ~10% have neurological damage
  • Mortality: 1%
• West Nile Encephalitis (WN):
  • Pathogen: WN virus (Flavivirus)
  • Mosquito Vector: (Not specified)
  • Reservoir: (Not specified)
  • Epidemiology: Most cases are asymptomatic. Symptoms can range from mild to severe
  • Mortality: 4-18%

Plague

• Organism: Yersinia pestis, gram-negative bacilli

• Transmission: Rat flea bite (Xenopsylla cheopis)

• Pathogenesis: (Further detail needed)

• Virulence factor: Resistance to phagocytosis

• Forms of Plague:

  • Bubonic: Enlargement of lymph nodes (groin, etc.), fever, malaise, headache. Most common form. Mortality rate: 50-75%
  • Septicemic: Bacterial endotoxins cause disseminated intravascular coagulation (DIC). Bleeding under skin, blackened skin (nose, fingers, toes), belly pain, diarrhea, vomiting, shock.
  • Pneumonic: Highly contagious, spread by airborne droplets. Cough (possibly with blood), shortness of breath. Mortality rate: 100% (unless detected within 12-15 hours of fever onset).

• Laboratory Diagnosis: Isolation of bacteria, direct detection of capsular antigen (within 15 minutes of blood or other body fluids)

• Treatment: Streptomycin and tetracycline

• Prophylaxis: Vaccine (details needed about target population)

Lyme Disease (Lyme Borreliosis)

• Causative organism: Borrelia burgdorferi

• Spirochete

• Obligate intracellular pathogen.

• Epidemiology

• First diagnosed as rheumatoid arthritis near Lyme, Connecticut

• Seasonal occurrence: Summer months

• Mode of transmission: Ixodes species ticks (deer ticks)

• Mammalian reservoir: Mice, deer

• Life Cycle:

  • Ticks feed three times: on field mice, field mice, and deer
  • Humans become infected by tick nymphs.
  • Ticks don't feed for 24 hrs, then 2-3 days before pathogen transmission.
  • Occurrence: 1% of tick bites are symptomatic.

• Stages of Lyme Disease (Symptoms):

  • First stage: Erythema migrans (bulls-eye rash), flu-like symptoms. Antibiotic treatment is highly effective in this stage.
  • Second stage: Dissemination – Bulls-eye rash spreads to other body sites. Heart palpitations, muscle/joint pain, headaches, neurological symptoms (facial paralysis, memory loss, meningitis, or encephalitis).
  • Third stage: Persistent infections lead to chronic arthritis, cognitive impairment, weakness, joint pain (especially in knees), fatigue. Can lead to permanent damage.

• Diagnosis: Clinical diagnosis (symptoms), laboratory tests (ELISA, IFA, confirmed by Western blot).

• Treatment: Streptomycin and tetracycline (treats all stages)

Typhus

• Causative organism: Rickettsias (gram-negative, pleomorphic bacteria – obligate intracellular parasites of eukaryotes)

  • Spread by arthropod vectors
  • Infect endothelial cells of vascular systems and multiply
  • Inflammation causes blockage and rupture of small blood vessels

• Types:

  • Epidemic typhus: R. prowazekii (Pediculus humanus)
  • Endemic typhus: R. typhi (Xenopsylla cheopis)
  • Rocky Mountain Spotted Fever: R. rickettsii (Tick-borne)

• Epidemiology (further details needed)

• Symptoms: High prolonged fever, small red spots (caused by subcutaneous hemorrhage)

• Mortality: High (if untreated)

• Treatment: Tetracycline, chloramphenicol

• Control: (details needed for each form)

• Additional characteristics