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Ask The Entomologist question about ticks and Lyme disease

Home / Expert Advice / Ask The Entomologist question about ticks and Lyme disease

Question:
Is it only the adult deer tick that can transmit Lyme disease or do we need to concern ourselves with the nymphs too?

Answer:
For some time, researchers believed that the primary host of Lyme disease was a wood tick identified as Ixodes dammini.  This tick was known as the “deer tick” in the Northeast and the “bear tick” in the Midwest.  Later, taxonomic work shows that this tick is, in fact, a northern variant of the black-legged tick Ixodes scapularis.  The primary reservoir of the disease is the white-footed mouse, and the disease organism (Borrelia burgdorferi) is transmitted from mouse to mouse and mouse to man by the larval and nymphal ticks, generally during late spring and early summer.  The black-legged tick has a two-year life cycle that begins in the spring when the female tick deposits her eggs.  The tiny, six-legged larvae are about the size of a pin head and obtain their first blood meal from rodents, in particular the white-footed mouse.  Larvae feeding on infected mice pick up the Lyme Borrelia spirochetes and after feeding, drop off to molt.  The following spring, the larval tick molts into an eight-legged nymph, finds a host (including deer, dogs, and humans), and takes another blood meal.  At this time, the spirochetes are transmitted to the new host.  After dropping off the host, the nymph molts into an adult.  Mating occurs in the fall and the female deposits her eggs the following spring.  The Virginia white-tailed deer is the most common overwintering host for the adult tick.  Because the overwintering adult tick does not ordinarily move from deer to man, however, the adult tick is not usually responsible for the transmission of the disease.