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Ixodes brunneus

Tick ID-Ixodes brunneus tick photo by Monica White

Ixodes brunneus

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Ixodes brunneus


I. brunneus is an ectoparasite of avians, migratory passerines in particular, and, because of this strong host association, it can be found in any of the United States. This tick’s known distribution in the US includes Alabama, Arkansas, California, Connecticut, Florida, Georgia, Indiana, Kansas, Massachusetts, Maryland, Missouri, Mississippi, North Carolina, New Jersey, New York, Ohio, Oklahoma, Oregon, Pennsylvania, South Carolina, Tennessee, Texas, Virginia, Wisconsin and Michigan; in Canada it occurs in Manitoba, New Brunswick, and Ontario.

We now add Colorado to the US distribution, based on a recent collection by our citizen science partners at Bird Conservancy of the Rockies. On May 17, 2018, one larval stage I. brunneus was collected from an American yellow warbler, Setophaga petechia, in Jefferson County. The specimen has been deposited in the CP Gillette Museum of Arthropod Diversity, Colorado State University, Fort Collins.


Passerine birds.

Vector Status

This tick is well known for causing paralysis, primarily in passerine birds, but it also has been associated with the agent of Rocky Mountain spotted fever, though its vector potential for this pathogen is unknown. Recently, Candidatus Rickettsia mendelii was detected in all active stages of I. brunneus collected in southeastern Virginia.


H Joel Hutcheson, James W Mertins, Boris C Kondratieff, Monica M White, Ticks and Tick-Borne Diseases of Colorado, Including New State Records for Argas radiatus (Ixodida: Argasidae) and Ixodes brunneus (Ixodida: Ixodidae)Journal of Medical Entomology, tjaa232,

First report of Candidatus Rickettsia mendelii in Ixodes brunneus from the United States

Ixodes brunneus

Tick ID-Ixodes brunneus tick photo by Monica White
Photo by Monica White. Ixodes brunneus larva collected by Meredith McBurney of Bird Observatory of the Rockies