Tickborne Diseases of the U.S.

In the United States, some ticks carry pathogens that can cause human disease, including:

• Anaplasmosis is transmitted to humans by tick bites primarily from the blacklegged tick (Ixodes scapularis) in the northeastern and upper midwestern U.S. and the western blacklegged tick (Ixodes pacificus) along the Pacific coast.
• Babesiosis is caused by microscopic parasites that infect red blood cells. Most human cases of babesiosis in the United States are caused by Babesia microti. Babesia microti is transmitted by the blacklegged tick (Ixodes scapularis) and is found primarily in the Northeast and upper Midwest.
• Colorado Tick Fever Colorado tick fever is an acute viral infection spread by the bite of the Dermacentor andersoni wood tick.
• Ehrlichiosis is transmitted to humans by the lone star tick (Ambylomma americanum), found primarily in the southcentral and eastern U.S.
• Lyme disease is transmitted by the blacklegged tick (Ixodes scapularis) in the northeastern U.S. and upper Midwestern U.S. and the western blacklegged tick (Ixodes pacificus) along the Pacific coast.
• Powassan encephalitis Powassan (POW) virus is transmitted to humans by infected ticks.
• Rickettsia parkeri Rickettsiosis is transmitted to humans by the Gulf Coast tick (Amblyomma maculatum).
• Rocky Mountain Spotted Fever (RMSF) is transmitted by the American dog tick (Dermacentor variabilis), Rocky Mountain wood tick (Dermacentor andersoni), and the brown dog tick (Rhipicephalus sangunineus) in the U.S. The brown dog tick and other tick species are associated with RMSF in Central and South America.
• STARI (Southern Tick-Associated Rash Illness) is transmitted via bites from the lone star tick (Ambylomma americanum), found in the southeastern and eastern U.S.
• Tickborne relapsing fever (TBRF) is transmitted to humans through the bite of infected soft ticks. TBRF has been reported in 15 states: Arizona, California, Colorado, Idaho, Kansas, Montana, Nevada, New Mexico, Ohio, Oklahoma, Oregon, Texas, Utah, Washington, and Wyoming and is associated with sleeping in rustic cabins and vacation homes.
• Tularemia is transmitted to humans by the dog tick (Dermacentor variabilis), the wood tick (Dermacentor andersoni), and the lone star tick (Amblyomma americanum). Tularemia occurs throughout the U.S.
• 364D Rickettsiosis (Rickettsia phillipi, proposed) is transmitted to humans by the Pacific Coast tick (Dermacentor occidentalis ticks). This is a new disease that has been found in California.