microbio 2125 unit 5 (part 23) - Lyme Disease

etiological agent

Borrelia burgdorferi

(& possibly Borrelia mayonii)

Distinguishing characteristics of etiological agent:

• Large, gram-negative spirochete with 3–10 irregular coils

• Transmitted by Ixodes ticks

• Complex 2-year cycle involving mice (larvae infection) and deer (adult stage)

Virulence Factor(s):

• Ability to persist and evade immune response

• Causes slow, progressive infection mimicking autoimmune disorders

Predisposing Factors:

Outdoor activities in endemic areas (exposure to ticks)

Transmission:

Tick bite (Ixodes ticks) after feeding on infected small animals (e.g., white-footed mice)

Syndrome (signs + symptoms): Early symptoms:

• Bull’s-eye rash (erythema migrans) in 50–70% of cases

• Fever, headache, stiff neck, dizziness

Syndrome (signs + symptoms): Late symptoms (if untreated):

• Cardiac and neurological symptoms

• Polyarthritis

Affected body region/system:

Skin, nervous system, joints, cardiovascular system

Treatment:

Tetracycline or amoxicillin during active infection

Prevention:

• Human vaccine discontinued

• Protective clothing outdoors

• Insect repellents with DEET

Other notes:

• Nonfatal but slowly progressive if untreated

• Early detection and treatment are critical to prevent serious complications

• Other species of Borrelia have recently been shown to also cause Lyme disease in some cases

life cycle of lyme disease 1

Newly hatched larvae become infected when they feed on small animals such as mice, which harbor the spirochete. The larvae continue development through this year. 

life cycle of lyme disease 2

In the second year the larvae molt into the nymph, an aggressive feeding stage. 

life cycle of lyme disease 3

The nymph takes blood from a number of hosts, including deer and humans. 

life cycle of lyme disease 4

On deer, the nymphs mature into adult male and female ticks, which mate. The female lays eggs in plant litter, where they hatch and once again begin the cycle.