Geographic distribution of ticks that bite humans

Of the many different tick species found throughout the world, only a select few bite and transmit disease to humans. These maps provide general insight into the expected distribution these human-biting ticks in the contiguous United States. Populations of ticks may be found outside noted areas. Naturally occurring populations of the ticks described below do not occur in Alaska; however, the brown dog tick is endemic in Hawaii.

Note that adult ticks are the easiest to identify and male and female ticks of the same species may look different. Nymphal and larval ticks are very small and may be difficult to identify.

American dog tick (Dermacentor variabilis) expanded

Where found: Widely distributed east of the Rocky Mountains. Also occurs in limited areas on the Pacific Coast.
Transmits: Tularemia and Rocky Mountain spotted fever .
Comments: The highest risk of being bitten occurs during spring and summer. Dog ticks are sometimes called wood ticks. Adult females are most likely to bite humans.

Approximate distribution of the American dog tick in the United States of America

About This Map

This map is not meant to represent risks for a specific tick-borne disease, because disease transmission is influenced by multiple factors beyond mere tick presence. This map has been designed to answer the question “What ticks should I be concerned about at a regional scale?” Please consult a local public health authority or USDA Agricultural Extension Office to determine more specific information at the state, county, or municipal level. Background data for this map is from the US National Atlas.

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