Western Blacklegged Tick Surveillance

At a glance

  • The western blacklegged tick (Ixodes pacificus) is found along the Pacific coast of the United States, particularly northern California.
  • Larvae and nymphs often feed on lizards, birds, and rodents, and adults more commonly feed on deer.
  • Nymphs and adult females are more often reported on people, but larvae also bite people.
Closeup of a Ixodes pacificus tick.
Map of the United States highlighting projected suitable habitat for Ixodes pacificus ticks and counties where these ticks are established.

Map of the United States showing projected suitable habitat for Ixodes pacificus ticks and counties with established Ixodes pacificus populations through 2024.

A note about established status

An established county means six or more blacklegged ticks of a single life stage or more than one life stage of blacklegged tick was collected in a county within a 12-month period. A county that is not labeled as established does not mean ticks are absent. Once a tick species is recorded as established within a county, the status will remain "established" in subsequent years.

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Content Source:
National Center for Emerging and Zoonotic Infectious Diseases (NCEZID)