Lyme disease is caused by the bacterium Borrelia burgdorferi, transmitted to humans through the bite of an infected Ixodes tick. While the disease is a major concern in the Northeastern and upper Midwestern United States, its status in Arizona is distinctly different. Arizona is not considered an endemic state, meaning the risk of acquiring the infection from a tick bite within the state borders is extremely low. However, Arizona residents have been diagnosed with Lyme disease after traveling to areas where the disease is widespread.
Lyme Disease Status and Surveillance in Arizona
Lyme disease is a reportable condition in Arizona, and surveillance data helps track its presence among the state’s population. The Arizona Department of Health Services (ADHS) and the Centers for Disease Control and Prevention (CDC) monitor all reported cases. While a small number of cases are reported each year, none have been confirmed as locally acquired from a tick bite in Arizona to date.
The vast majority of Lyme disease cases identified in Arizona residents are classified as travel-related exposures. This means the individual was likely bitten by an infected tick while visiting an endemic region, such as the Northeast or upper Midwest. This distinction confirms that the tick species responsible for transmission are not widely established in the state. Some patient advocacy groups suggest that official surveillance numbers may not reflect the total number of individuals treated for the infection in Arizona.
Why the Primary Lyme Vector is Absent
The absence of endemic Lyme disease in Arizona is directly linked to the ecological requirements of the primary tick vectors. Transmission relies almost entirely on the blacklegged tick (Ixodes scapularis) in the eastern US and the Western blacklegged tick (Ixodes pacificus) on the Pacific coast.
These Ixodes species require environments with high humidity to complete their life cycle and survive between blood meals. The arid and semi-arid conditions characterizing most of Arizona are unsuitable for sustaining these specific “deer ticks.” Consequently, the tick population that transmits the Borrelia burgdorferi bacterium has not established a self-sustaining presence across the state.
While Ixodes pacificus has been documented in the higher-elevation Hualapai Mountains in Mohave County, these isolated populations are limited. Furthermore, the few specimens collected have not shown evidence of carrying the Lyme bacterium. This lack of a widespread, infected vector population explains the rarity of locally acquired Lyme disease in Arizona.
Tick-Borne Illnesses Endemic to Arizona
Although Lyme disease is not a local threat, Arizona is home to over 25 tick species that transmit other significant illnesses. Rocky Mountain Spotted Fever (RMSF) is the most common tick-borne disease reported in the state, often accounting for more than half of all cases. The primary vector for RMSF in Arizona is the brown dog tick (Rhipicephalus sanguineus), which can infest homes and kennels.
RMSF is caused by the bacterium Rickettsia rickettsii and presents with initial symptoms like high fever, headache, and muscle aches, often followed by a characteristic rash. Another threat is Tick-Borne Relapsing Fever (TBRF), a rare disease transmitted by soft ticks of the genus Ornithodoros. These soft ticks are night feeders that remain attached for a short time, often biting people sleeping in rustic cabins or areas with rodent infestations.
Other pathogens causing Ehrlichiosis and Anaplasmosis are monitored in Arizona, though case numbers remain low. Rickettsia parkeri rickettsiosis is a concern similar to RMSF, identified in a few residents bitten by ticks in mountainous regions. The Rocky Mountain wood tick (Dermacentor andersoni) is present in the northern, brushy areas of the state and can transmit RMSF and Colorado tick fever.
Prevention Strategies for Local Ticks
Preventing tick bites in Arizona involves focusing on local habitats, including high-elevation forests, desert scrub, and areas where rodents are common. When venturing into tick-prone areas, wearing light-colored clothing makes it easier to spot ticks before they attach. Tucking pants into socks or boots creates a physical barrier preventing ticks from accessing the skin.
Using insect repellents containing DEET on exposed skin and treating clothing and gear with permethrin provides chemical protection. After spending time outdoors, performing a thorough tick check on yourself, children, and pets is important. Special attention should be paid to hidden areas, such as the scalp, underarms, and behind the knees.
If a tick is found attached, remove it promptly and carefully using fine-tipped tweezers. Grasp the tick as close to the skin’s surface as possible and pull upward with steady, even pressure. Do not twist or jerk the tick during removal. Afterward, the bite area and hands should be cleaned with soap and water or rubbing alcohol.