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Geographic Distribution

While adult ticks are the easiest to identify by species, immature stages of ticks may also transmit some pathogens. In addition, male and female ticks of the same species may look different.

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 of ticks that cause disease 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.

American dog tick

(Dermacentor variabilis)

American dog tick (Dermacentor variabilis)

American dog tick (Dermacentor variabilis) is the most commonly identified species responsible for transmitting Rickettsia rickettsii, which causes Rocky Mountain spotted fever in humans. The American dog tick can also transmit tularemia. This tick is widely distributed east of the Rocky Mountains and also occurs in limited areas on the Pacific Coast. D. variabilis larvae and nymphs feed on small rodents. Dogs and medium-sized mammals are the preferred hosts of adult D. variabilis, although it feeds readily on other large mammals, including humans.

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

Approximate distribution of the American Dog tick. (Click for larger image)

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Blacklegged tick

(Ixodes scapularis)

Blacklegged tick (Ixodes scapularis)

The blacklegged tick (Ixodes scapularis), commonly known as a "deer tick", can transmit the organisms responsible for anaplasmosis, babesiosis, and Lyme disease. This tick is widely distributed in the northeastern and upper midwestern United States. I. scapularis larvae and nymphs feed on small mammals and birds, while adults feed on larger mammals and will bite humans on occasion. It is important to note that the pathogen that causes Lyme disease is maintained by wild rodent and other small mammal reservoirs, and is not transmitted everywhere that the blacklegged tick lives. In some regions, particularly in the southern U.S., the tick has very different feeding habits that make it an unlikely vector in the spread of human disease.

Approximate distribution of the Blacklegged tick in the United States of America

Approximate distribution of the Blacklegged tick. (Click for larger image)

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Brown dog tick

(Rhipicephalus sanguineus)

Brown dog tick (Rhipicephalus sanguineus)

The brown dog tick (Rhipicephalus sanguineus) has recently been identified as a reservoir of R. rickettsii, causing Rocky Mountain spotted fever, in the southwestern U.S. and along the U.S-Mexico border. Brown dog ticks are found throughout the U.S. and the world. Dogs are the primary host for the brown dog tick for each of its life stages, although the tick may also bite humans or other mammals.

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

Approximate distribution of the Brown Dog tick. (Click for larger image)

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Gulf Coast tick

(Amblyomma maculatum)

Image for Gulf Coast tick (Amblyomma maculatum)

The Gulf Coast tick resides in coastal areas of the United States along the Atlantic coast and the Gulf of Mexico. The Gulf Coast tick can transmit Rickettsia parkeri rickettsiosis, a form of spotted fever. A. maculatum larvae and nymphs feed on birds and small rodents, while adult ticks feed on deer and other wildlife. Adult ticks have been associated with transmission of R. parkeri to humans.

Approximate distribution of the Gulf coast tick in the United States of America

Approximate distribution of the Gulf Coast tick. (Click for larger image)

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Lone star tick

(Amblyomma americanum)

Lone star tick (Amblyomma americanum)

The lone star tick (Amblyomma americanum) transmits Ehrlichia chaffeensis and Ehrlichia ewingii, causing human ehrlichiosis, tularemia, and STARI. The lone star tick is primarily found in the southeastern and eastern United States. White-tailed deer are a major host of lone star ticks and appear to represent one natural reservoir for E. chaffeensis. A. americanum larvae and nymphs feed on birds and deer. Both nymphal and adult ticks may be associated with the transmission of pathogens to humans.

Approximate distribution of the Lone star tick in the United States of America

Approximate distribution of the Lone Star tick. (Click for larger image)

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Rocky Mountain wood tick

(Dermacentor andersoni)

Rocky Mountain wood tick (Dermacentor andersoni)

Rocky Mountain wood tick (Dermacentor andersoni) can transmit Rocky Mountain spotted fever and tularemia to humans. This tick is found in the Rocky Mountain states. Adult ticks feed primarily on large mammals. Larvae and nymphs feed on small rodents. Adult ticks are primarily associated with pathogen transmission to humans.

Approximate distribution of the Rocky Mountain wood tick in the United States of America

Approximate distribution of the Rocky Mountain Wood tick. (Click for larger image)

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Western blacklegged tick

(Ixodes pacificus)

Western blacklegged tick (Ixodes pacificus)

The western blacklegged tick (Ixodes pacificus) can transmit the organisms responsible for causing anaplasmosis and Lyme disease in humans. Wild rodents and other mammals are likely reservoirs of these pathogens. This tick is distributed along the Pacific coast of the United States. Larvae and nymphs feed on birds and small rodents, while adult ticks feed on deer and other mammals. Both adult and nymphal ticks are known to transmit disease to humans.

Approximate distribution of the Western blacklegged tick in the United States of America

Approximate distribution of the Western Blacklegged tick. (Click for larger image)

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