Washington has relatively few tick-borne disease cases reported each year in comparison to some other areas of the United States. While these diseases are transmitted by a tick bite, only some ticks transmit disease and only some of these diseases can be transmitted by ticks in Washington.
The best way to protect yourself and others against tick-borne disease is by reducing your exposure to ticks and preventing ticks from biting. Learn about prevention on DOH’s Tick page.
Learn about Lyme disease on DOH’s Lyme disease – general information page.
Learn about tick-borne relapsing fever on our relapsing fever – general information page.
What are spotted fever rickettsioses?
Spotted fevers, or spotted fever group rickettsioses, are a group of diseases caused by bacteria from the Rickettsia genus. The most severe type of disease in this group is Rocky Mountain spotted fever (RMSF). Rickettsia bacteria are most commonly transmitted by ticks, but mouse mites can carry a species that causes Rickettsialpox.How are spotted fever group rickettsioses spread and where are they found?
The Rickettsia genus bacteria that cause spotted fevers are usually transmitted by the bite of infected ticks. Different ticks carry different types of Rickettsia, which in turn cause different spotted fevers.
Rickettsia rickettsii, the bacteria that causes RMSF, is transmitted by the bite of infected American dog ticks, Rocky Mountain wood ticks, and brown dog ticks, found in regions throughout the United States and parts of Mexico. American dog and Rocky Mountain wood ticks are common in eastern Washington, although reported cases of RMSF in Washington are very rare.
Each year, 0-3 cases of RMSF are identified in Washington; most of these cases are infected in other states. RMSF cases in North Carolina, Tennessee, Missouri, Arkansas, and Oklahoma account for over 60% of cases reported in the US. Most spotted fevers, including RMSF, are reported between April and October (usually peaking in June and July), depending on the area of the country where the bite occurs.
What are the symptoms of spotted fever group rickettsioses?
Rash is a common sign in people who are sick with RMSF. For other spotted fevers, the appearance of a dark scab at the site of the bite, known as an eschar, is sometimes the first sign. Other symptoms range widely in severity and often include: fever, headache, rash, and muscle aches.
RMSF is the most severe type of spotted fever, and up to a quarter of persons with disease can die if untreated.
If you or your family member develops symptoms of spotted fever group rickettsioses and were recently bitten by a tick or were in brushy areas where ticks commonly live, immediately visit your healthcare provider or contact your local health department. If treatment is delayed, RMSF may progress to severe disease, possibly resulting in death, or, among those who recover, amputation of extremities, paralysis, or mental disability.
Tick paralysis is a rare disease thought to be caused by toxin in tick saliva. Symptoms of tick paralysis include progressive paralysis that begins after the tick has fed for 4-7 days. Paralysis usually starts in the legs, with muscle weakness, loss of coordination, numbness, and difficulty standing or walking; and progresses upwards to the abdomen, back, and chest. If the tick is not removed, paralysis of the chest muscles can lead to respiratory failure and death within 24 to 48 hours after symptoms begin. Prompt removal of the tick usually leads to complete recovery.
Tick paralysis is rare but found worldwide, with 0-2 cases reported each year in Washington State. Ticks associated with this illness include Ixodes, Dermacentor, and Amblyomma species that are widely distributed across the United States.
Learn about tularemia on DOH’s tularemia – general information page.
Anaplasmosis is caused by a bacterium called Anaplasma phagocytophilum, typically transmitted by the bite of an infected black-legged tick. Symptoms typically begin within 1-2 weeks (up to 3 weeks) after the bite, and can include chills, fever, severe headache, muscle aches, nausea, vomiting, and diarrhea. These early symptoms are usually mild to moderate but can progress to severe illness if treatment is delayed or the person has a weakened immune system.
The type of tick responsible for transmitting anaplasmosis in the western United States is the western black-legged tick (Ixodes pacificus), which lives in forested or brushy areas. Ixodes pacificus ticks infected with A. phagocytophilum have been found in Washington. Anaplasmosis has been diagnosed in numerous dogs in Washington State, and the first human case likely exposed in Washington was reported in 2022.
If you or your family member develops symptoms of anaplasmosis and were recently bitten by a tick or were in brushy areas where ticks commonly live, immediately visit your healthcare provider or contact your local health department. Many people may not recall having been bitten by a tick. If treatment is delayed, anaplasmosis may progress to severe disease, which can include respiratory failure, bleeding problems, organ failure, and, in less than one percent of cases, death.
Ehrlichiosis refers to diseases caused by bacteria in the genus Ehrlichia; the majority of reported cases are due to infection with E. chaffeensis. These bacteria are typically transmitted by the bite of infected lone star ticks (Amblyomma americanum) or black-legged ticks (Ixodes scapularis). Neither of these tick species are native to Washington and bacteria that can cause ehrlichiosis have not been detected in ticks collected in Washington.
Symptoms of ehrlichiosis typically begin within 1-2 weeks after the tick bite and can include fever, headaches, muscle aches, nausea and vomiting, diarrhea, confusion, and more commonly in children, rash. These early symptoms are usually mild to moderate, but can progress to severe illness if treatment is delayed or the person has a weakened immune system. No human cases of ehrlichiosis infected in Washington have been reported.
If you or your family member develops symptoms of ehrlichiosis and were recently bitten by a tick or were in brushy areas where ticks commonly live, immediately visit your healthcare provider or contact your local health department. Many people may not recall having been bitten by a tick. If treatment is delayed, ehrlichiosis may progress to severe disease, which can include brain and nervous system damage, respiratory failure, uncontrolled bleeding, organ failure, and, in less than 2% of cases, death.
Babesiosis is a disease caused by microscopic parasites of the Babesia genus, which are primarily transmitted by infected ticks. Many people who are infected do not experience any symptoms. Some people develop nonspecific, flu-like symptoms days to months after a tick bite; these may include fever, chills, sweats, headache, body aches, loss of appetite, or nausea. Among persons who do not have spleens, have weakened immune systems or serious health conditions, or are elderly, babesiosis can be life-threatening.
Black-legged Ixodes scapularis ticks are responsible for most infections, but babesiosis can also be transmitted from mother to infant during pregnancy or delivery and via blood or organ donation. Persons who have been diagnosed with babesiosis must defer from blood donation for life. In the United States, tick-borne transmission primarily occurs in the Northeast and upper Midwest. Babesia parasites have not been identified in ticks collected in Washington; however, a small number of babesiosis cases have reported infection in Washington.
If you or your family member develops symptoms of babesiosis and were recently bitten by a tick or were in brushy areas where ticks commonly live, visit your healthcare provider or contact your local health department. Many people may not recall having been bitten by a tick. Complications of babesiosis can include hemolytic anemia, low platelet count, blood clots and bleeding, organ malfunction, and death.
Species of ticks and the types of diseases they carry may vary by region. Below, is a chart of common tick-borne diseases and evidence for local transmission in Washington state.
|Disease||Identified in humans with WA-only exposure||Identified in ticks in WA|
|Rocky Mountain Spotted Fever||Yes||No|
|Tick-borne Relapsing Fever||Yes||Yes|