Ixodes scapularis

Ixodes scapularis

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Brief Summary

Ixodes scapularis, the Black-legged Tick (often known as the "Deer Tick"), is best known as an important vector in the eastern United States of Lyme borreliosis (Lyme Disease), the most prevalent tick-transmitted infection not only in this region but, more generally, in temperate areas of Europe, North America, and Asia. (In the western United States and Europe, the main Lyme disease vectors are the related ticks I. pacificus and I. ricinus, respectively.) This tick was formerly known as I. dammini, but in 1993 this name was shown to be a junior synonym of I. scapularis. Lyme disease occurs only sporadically in the southern United States. (Patnaude and Mather 2000 and references therein)

The distribution and abundance of I. scapularis is closely tied to that of its primary reproductive host, the White-tailed Deer (Odocoileus virginianus). As large-scale changes in the landscape of the eastern United States have led to large increases in deer populations, I. scapularis populations appear to have increased as well. (Patnaude and Mather 2000 and references therein)  A similar pattern seems to be evident for I. ricinus in western Europe as well (Jongejan and Uilenberg 2004).

Ixodes scapularis are small ticks, around 3 mm, and are dark brown to black in color. On females, the area behind the scutum is typically orange to red. This species is a three-host tick, i,e., the larva, nymph, and adult each feed on a different host. In June and July, eggs deposited earlier in the spring hatch into tiny six-legged larvae. Peak larval activity occurs in late summer, when larvae attach to and feed on a wide variety of mammals and birds, notably White-footed Mice (Peromyscus leucopus). After feeding for three to five days, engorged larvae drop from the host to the ground, where they overwinter. In late spring, larvae molt into nymphs, which feed on a variety of hosts for three to four days. Once engorged, a nymph detaches and drops to the forest floor where it molts into the adult stage, which becomes active in the late autumn. Adult female ticks feed for five to seven days, but males feed only sparingly, if at all. Adult ticks remain active through the winter on days when the ground and ambient temperatures are above freezing. (Patnaude and Mather 2000 and references therein)

Ixodes scapularis is an important vector of the Lyme disease spirochete Borrelia burgdorferi, the Babesia protozoans that cause human babesiosis, and Anaplasma phagocytophilum (formerly known a Ehrlichia phagocytophilum), the bacteria that cause human granulocytic anaplasmosis (formerly known as human granulocytic ehrlichiosis). (Patnaude and Mather 2000 and references therein)

United States Department of Agriculture researchers have developed a remarkably effective method for controlling populations of deer-dependent ticks, such as I. scapularis and Amblyomma americanum (Lone Star Tick). This device, known as a "4-Poster Deer Treatment Bait Station", rolls acaricide on a deer as it feeds from a feeding station (e.g., Pound et al. 2009).

(U.S. Centers for Disease Control and Prevention Ticks Website)

Author(s): Shapiro, Leo
Rights holder(s): Shapiro, Leo


JONGEJAN, F., & UILENBERG G. (2004).  The global importance of ticks. Parasitology. 129(07), S3.
Patnaude, M. R., & Mather T. N. (2000).  Blacklegged Tick or Deer Tick-Ixodes scapularis. Featured Creatures. accessed December 2011,
Pound, J M., Miller J A., George J. E., Fish D., Carroll J. F., Schulze T. L., et al. (2009).  The United States Department of Agriculture's Northeast Area-Wide Tick Control Project: Summary and Conclusions. Vector-Borne and Zoonotic Diseases. 9(4), 439 - 448.