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Chapter 23: Microbial diseases of the cardiovascular system

Bacillus anthracis (Anthrax)

  • Bacillus anthracis is a bacterium that produces endospores. These spores are extremely resistant and can survive for up to 60 years, remaining viable for about 60 years.
  • Transmission
    • Non-communicable disease; you must come into direct contact with endospores.
    • Typical exposure pathways include workers in tanneries and people handling animal hides from grazing animals that pick up endospores.
  • Three types of anthrax
    • Cutaneous anthrax
    • Most common and least severe form.
    • Early signs: an itchy, raised bump on the skin that develops into a blister within a couple of days.
    • The blister/ulcer then ruptures, leaving a swollen area with a center of black necrotic tissue (black eschar).
    • Fatality rate is 20\%, and mortality is typically due to secondary infections entering through the lesion rather than direct action of the bacteria.
    • Portal of entry is clearly visible as swelling and a vesicle with necrotic tissue.
    • Gastrointestinal anthrax
    • Acquired by ingesting contaminated meat from animals that carried endospores.
    • Symptoms are GI in nature and can lead to severe dehydration.
    • Death rate ranges from 0.25\% to 0.60\% (i.e., about 25\% to 60\%) when untreated, primarily due to fluid loss from nausea/vomiting.
    • Inhalation (pulmonary) anthrax
    • Least common but most severe form.
    • Early symptoms resemble a common cold, then progress rapidly and are typically fatal without effective treatment.
    • Anthrax is highly resistant; antibiotic treatment is necessary.
    • Treatment: Ciprofloxacin (Cipro) was used during the Boca Raton outbreak as a first-line agent.
    • Vaccine: Available but restricted to high-risk individuals (e.g., military personnel); the vaccine has been associated with some severe adverse reactions.
  • Key implications
    • Public health relevance includes bioterrorism risk due to spore stability.
    • Prevention focuses on avoiding exposure to endospores (protective equipment in at-risk occupations) and vaccination considerations for high-risk groups.

Borrelia burgdorferi (Lyme disease)

  • Causative agent of Lyme disease.
  • Vector and transmission
    • Transmitted by ticks, predominantly the deer tick, though other ticks can be carriers.
  • Bacterial morphology
    • Borrelia burgdorferi is a spirochete with a corkscrew-like shape.
  • Typical symptoms
    • Early symptoms include a characteristic rash, fever, chills, and body aches.
    • Outside of the rash, symptoms are nonspecific, making diagnosis challenging.
    • If untreated, progression can lead to chronic Lyme disease with arthritis, memory problems, and tingling in the arms and legs.
  • Rash considerations
    • The rash is not seen in many individuals; when present, it typically appears at the site of the bite but may go unnoticed if the bite is on the head.
    • Patients may have multiple rashes rather than a single lesion.
  • Diagnosis and treatment
    • Early-stage disease is easier to treat with oral antibiotics.
    • Late-stage disease requires IV antibiotics; Penicillin is commonly the antibiotic of choice.
  • Prevention
    • Prevention strategies focus on avoiding tick exposure in endemic areas:
    • Wear long pants and long-sleeved shirts, preferably in light colors to spot ticks easily.
    • Check yourself and pets (e.g., dogs) for ticks after outdoor activity.
  • Real-world relevance
    • Diagnosis can be difficult due to nonspecific early symptoms and variable rash presence, highlighting the need for awareness in endemic regions.

Helminthes: Schistosomiasis (Schistosoma sp.)

  • Epidemiology
    • A worm found primarily in tropical and developing regions.
  • Transmission and life cycle
    • Life cycle begins with fecally contaminated freshwater.
    • Freshwater snails serve as the vector; snails harbor the parasite during part of its life cycle.
    • The parasite develops within the snail and is released into the water; larvae are fragile and can survive briefly in the environment.
    • Larvae in water penetrate human skin and begin to grow.
    • Incubation period is approximately three weeks, during which most people show no symptoms.
    • As the worm matures, eggs are produced and migrate to the bladder and intestines; eggs are excreted back into water via urine and/or stool, completing the cycle.
  • Symptoms and progression
    • Early symptoms: rash, itchy skin, chills, muscle aches (nonspecific).
    • Later-stage complications can be severe and include paralysis, seizures, inflammation of the spinal cord, liver damage, intestinal damage, and lung damage.
    • A visible sign can be a distended abdomen due to organ involvement.
  • Prevention
    • Avoid exposure to fecally contaminated freshwater where snails are present.
    • In situations where water must be consumed, boiling the water is advised to kill larvae and eggs.
  • Treatment
    • Anti-helminthic therapy is short (approximately 1–2 days).
    • Praziquantel is most commonly used; other anti-helminthic drugs can also be effective.
    • In transcript, the drug Praziquantel is referred to as Praziquintel.
  • Practical considerations
    • Prevention and treatment require addressing environmental and water-use practices in endemic regions, which can be complex given multiple water uses.

Closing notes

  • Chapter 23 covered microbial diseases of the cardiovascular system, including bacterial pathogens (anthrax and Lyme disease) and a helminthic disease (schistosomiasis).
  • The material sets up transitions to Chapter 24, which will cover diseases of the respiratory system.