Lyme disease Part I: Transmission, Pathophysiology andamp; Testing| VETgirl Veterinary CE Podcasts

In this VetGirl podcast, we discuss transmission, pathophysiology and testing for Lyme disease. Lyme disease is caused by the spirochete Borrelia burgdorferi (Bb). While Bb can be transmitted by urine, milk, and blood, the most common transmission is likely via tick infestation by hard-shell deer ticks (e.g., Ixodes scapularis or other related Ixodes species). Ixodes ticks have a 2-year life cycle and hatch in the spring (into larvae). A female tick lays approximately 2000 eggs. Larvae become infected with Bb when feeding on white-footed mice, which are persistently infected, but often remain unaffected or asymptomatic. The larvae molt into nymphs that feed on new hosts. While nymphs are less effective vectors than adult ticks, they can still infect their hosts within the four-day feeding period. Likewise, nymphs can become infected when feeding on an infected animal. In the fall, nymphs molt to adults, with 50% of adult ticks in the Northeast estimated to be carrying Bb. Once the tick attaches and feeds, the spirochetes (which live in the midgut of the tick) begin to migrate to the salivary gland and enter the host. Risk of infection is believed to be minimal during the first 12 hours of feeding. Typically, transmission of Bb occurs during prolonged feeding periods (typically > 48 hours).