Lyme disease is a bacterial infection caused by the spirochete Borrelia burgdorferi, and it is the most frequently reported vector-borne illness in the United States. Public interest in the disease is high, particularly in areas like Colorado where the risk profile differs significantly from endemic regions like the Northeast and Upper Midwest. Understanding the specific ticks that transmit this pathogen is the first step in assessing local health risks. Focusing on the ecology of the bacteria and the ticks provides a clearer perspective on the actual threat level within the state.
The Primary Tick Responsible for Lyme Disease
Lyme disease transmission depends almost entirely on ticks belonging to the Ixodes genus, commonly known as Blacklegged or Deer ticks. In the eastern and central U.S., the primary vector is Ixodes scapularis, while Ixodes pacificus transmits the disease along the Pacific coast. These ticks have a complex two-year life cycle involving three blood meals: one each as a larva, nymph, and adult.
The nymphal stage is responsible for the majority of human infections because its tiny size often allows it to go unnoticed. A tick must remain attached for a significant period, generally between 36 and 48 hours, to successfully transmit the Borrelia bacteria to a host.
Lyme Disease Risk Assessment in Colorado
The risk of acquiring Lyme disease from a tick bite within Colorado is low because the state does not host established populations of the primary vector species (I. scapularis and I. pacificus). These Blacklegged ticks are not endemic to the high-altitude, arid environments that characterize much of the state. Consequently, the pathogen Borrelia burgdorferi is largely absent from Colorado’s native wildlife and tick populations.
When cases are reported in Colorado residents, almost all are classified as travel-associated, meaning the infection was acquired outside of the state in an endemic region. State health data reflects this low local risk, with only a handful of cases reported annually, none confirmed as originating from a tick bite within state borders.
While the traditional form of Lyme disease is rare, researchers have identified other Borrelia species, such as Borrelia bissettii, in local ticks like Ixodes spinipalpis and Ixodes angustus. These bacteria are known to cause Lyme-like illnesses in humans, contributing to the discussion about the full spectrum of local risk.
Other Tick-Borne Illnesses Prevalent in Colorado
Although Lyme disease is rare, residents must be aware of other tick-borne illnesses actively transmitted within the state.
Colorado Tick Fever (CTF) is the most common tick-borne infection, a viral illness transmitted primarily by the Rocky Mountain Wood Tick. Symptoms typically develop three to seven days after a bite and include flu-like signs such as fever, chills, and muscle aches, sometimes presenting in two separate cycles of fever.
Rocky Mountain Spotted Fever (RMSF), though rare in Colorado, is a potentially serious bacterial threat. Transmitted by the Rocky Mountain Wood Tick and the American Dog Tick, RMSF causes fever, headache, and often a rash. Early diagnosis and treatment are necessary for managing this infection.
Tick-borne Relapsing Fever (TBRF) is also a local concern, caused by soft ticks often encountered in rustic cabins where they live in rodent nests. This bacterial infection is characterized by high fevers that occur in cyclical episodes, relapsing every few days after a period of remission. Tularemia, a bacterial disease contracted from an infected tick bite, is another recognized risk in the state.
Effective Tick Prevention and Removal
Preventing tick bites is the most effective defense against all tick-borne illnesses. When spending time in grassy, brushy, or wooded areas, treat clothing and gear with products containing 0.5% Permethrin, an insecticide that kills ticks on contact. Applying an EPA-registered insect repellent containing ingredients like DEET or Picaridin to exposed skin provides another layer of protection.
Wearing long sleeves and pants, and tucking pant legs into socks, can block ticks from reaching the skin. Choosing light-colored clothing makes ticks easier to spot. Upon returning indoors, perform a thorough body check for ticks, paying close attention to hair, ears, armpits, and the groin area. Taking a shower within two hours of coming inside can also help wash away unattached ticks.
If a tick is found attached, it should be removed promptly using fine-tipped tweezers. Grasp the tick as close to the skin’s surface as possible and pull upward with steady, even pressure. After removal, clean the bite area and hands with soap and water or rubbing alcohol. If a rash or flu-like symptoms occur within several weeks of a tick bite, seek medical attention immediately.