Lyme disease is a bacterial infection caused by Borrelia burgdorferi, transmitted to humans through the bite of an infected tick. This illness is the most commonly reported tick-borne disease throughout the mainland United States, particularly in the Northeast, upper Midwest, and along the Pacific coast. The infection can affect multiple body systems if not treated early. While cases are reported among residents, local acquisition is extremely rare or considered non-existent because the necessary biological vector is not established in the islands.
The Current Status of Lyme Disease in Hawaii
Understanding Lyme disease in Hawaii requires distinguishing between an imported case and an endemic one. An imported case means the infection was acquired while the patient was traveling outside of the state, typically on the mainland United States, and diagnosed after returning to Hawaii. Conversely, an endemic case signifies that the infection was acquired locally, meaning the entire transmission cycle, including the infected tick and host animals, exists within the state’s ecosystem.
The Hawaii State Department of Health (HDOH) confirms that Lyme disease is not considered an endemic illness. While healthcare providers diagnose and treat people with the infection, virtually all confirmed cases were contracted elsewhere. Public health surveillance data consistently reflects this pattern, showing the risk comes from travel history rather than local environmental exposure.
Lyme disease is a nationally notifiable condition, meaning every diagnosis must be reported to the Centers for Disease Control and Prevention (CDC). The consistent reporting of cases acquired outside of the islands confirms the disease is not established in the local environment. This provides reassurance that a tick bite received while hiking or spending time outdoors in Hawaii is unlikely to result in Lyme disease. Clinicians in Hawaii focus on the patient’s recent travel history when considering a Lyme disease diagnosis.
The Missing Link: Hawaii’s Tick Ecology
The reason Lyme disease is absent from Hawaii’s local transmission cycle is the lack of the specific tick species required to carry the Borrelia burgdorferi bacteria. On the U.S. mainland, the disease is transmitted primarily by the black-legged tick, Ixodes scapularis, in the eastern and midwestern regions, and the western black-legged tick, Ixodes pacificus, along the Pacific coast. These Ixodes species are suited to maintain the bacteria in a wildlife cycle involving small mammals like mice and squirrels.
The Ixodes tick species, often referred to as deer ticks, are not established in the Hawaiian Islands. This absence breaks the biological chain required for the disease to become endemic. Even if an infected animal or human were to arrive in Hawaii, there would be no competent tick vector to pick up the bacteria and transmit it to a new host, preventing local maintenance of the disease.
The tick species found in Hawaii are the brown dog tick (Rhipicephalus sanguineus) and the spinose ear tick (Otobius megnini). The brown dog tick is the most common species associated with humans and pets, but it is not a known carrier of Borrelia burgdorferi. The spinose ear tick primarily feeds on livestock and wildlife, attaching deep within the ear canal. While ticks exist in the environment, they do not possess the biological capability to sustain the Lyme disease cycle.
Other Tick-Borne Concerns in the Islands
While the risk of contracting Lyme disease in Hawaii is negligible, the presence of local tick populations means other tick-borne illnesses remain a health concern. The brown dog tick, Rhipicephalus sanguineus, is a known vector for other pathogens that can affect human health. This species is found across the islands and is the primary tick of concern.
The most notable non-Lyme disease transmitted by the brown dog tick in Hawaii is Rocky Mountain Spotted Fever (RMSF). RMSF is caused by the bacterium Rickettsia rickettsii and can be a serious illness if not treated quickly with antibiotics. Symptoms often begin with a fever, headache, and rash, making diagnosis sometimes challenging.
Other pathogens carried by ticks include Ehrlichia and Anaplasma species, which cause ehrlichiosis and anaplasmosis. While these diseases are commonly associated with the mainland, the potential for local transmission exists due to the established tick populations. Awareness should focus on preventing tick bites and monitoring for symptoms of any tick-borne illness, especially a persistent fever after an exposure.