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Ticks

Got a bug?  If you would like to have a tick (or other bug) identified, please fill out this form.

Ticks of Oregon that Transmit Diseases of Public Health Significance

Always consult your primary care provider when you are feeling ill and suspect you've contracted a tickborne disease. Some tickborne diseases, such as Rocky Mountain spotted fever, require immediate treatment. Always call 911 in an emergency.

Tickborne diseases acquired in Oregon are rare – about 1-2 people per million population per tickborne disease per year.

If you believe you got sick with a tickborne disease, it's important to tell your provider when you first started feeling sick and where in Oregon (or elsewhere) you think you were exposed. This will help your provider understand the kind of tickborne disease you might have.

Oregon is the home of “Borrelia" species, which are transmitted by two species of ticks that inhabit distinct geographic areas in Oregon separated by the Cascades Mountain range.

The Western black-legged tick (Ixodes pacificus) transmits Lyme disease (Borrelia burgdorferi) and hard tick relapsing fever (Borrelia miyamotoi) and generally inhabits wetter climates west of the Cascades, including Hood River County, which is just northeast of the Mount Hood.

A nesting “soft tick" (Ornithodoros hermsi) transmits soft tick relapsing fever (Borrelia hermsii) and is usually associated with high elevations (great than 1,500 feet elevation) east of the Cascades, such as Deschutes, Wallowa and Wasco counties.

Please look at the soft ticks on the video (below) of this web page; they were found in bed sheets within a cabin in Central Oregon.

Please review the maps and graphs of Oregon's four most common tickborne diseases (Colorado tick fever, Lyme disease, Rocky Mountain spotted fever, and soft tick relapsing fever) in the “Statistics" section associated with each tickborne disease on this page.

The Centers for Disease Control and Prevention (CDC) also has a wealth of resources about ticks and tickborne disease prevention. Please visit their site to learn more. 

For Clinicians:


All serologic tests for Borrelia species have the potential to cross-react. Commercial “tickborne disease" panels are typically geared toward diseases transmitted by Ixodes species – for example, anaplasmosis, babesiosis, and Lyme disease; and ehrlichiosis, which is transmitted by the lone star tick (Amblyomma americanum), which is not found in Oregon. Furthermore, the tickborne diseases encountered east of the Cascades, namely Colorado tick fever and soft tick relapsing fever are not typically included in “tickborne disease panels," which makes diagnosis via lab testing challenging.

Please call us at 971-673-1111 if you need assistance ordering tests for Colorado tick fever or soft tick relapsing fever, the two most common tickborne diseases found east of the Cascades.

TickTarget.PNG

Don't be a tick target - Spanish (pdf)



Soft Tick (Ornithodoros spp)

Region
Western half of the United States (including Texas)

Transmits
Soft tick relapsing fever

 

Soft ticks hide out in rodent nests at elevations over 1,500 feet, and can bite briefly and painlessly at night while you sleep. These ticks can transmit soft tick relapsing fever.

  • Avoid staying in cabins with rodent infestations (including chipmunks or squirrels nesting under the house or in the attic).
  • If you own a cabin with rodents, consult a pest control professional to safely remove nests and treat for ticks.
  • Wear an EPA-registered insect repellent.

Soft Tick Relapsing Fever (STRF)

(Borrelia hermsii)

The reservoir of soft tick relapsing fever is usually associated with small rodents, such as squirrels, chipmunks, and rats living near or in dwellings above 1,500 feet elevation.

CDC Information on soft tick relapsing fever.

​​​Soft tic​k relapsing fever is an illness caused by infection with some members of the genus Borrelia, the same genus of spiral-shaped bacteria that cause Lyme disease; however, it is transmitted by an entirely different tick – a “soft tick” of the genus Ornithodoros. In Oregon, Borrelia hermsii is transmitted by the soft tick, Ornithodoros hermsi​. The reservoir of soft tick relapsing fever is usually associated with small rodents, such as squirrels, chipmunks, and rats living near or in dwellings above 1,500 feet elevation. Most people will not know they were bitten by a soft tick, which generally does not attach for very long, sometimes minutes. The soft ticks can sometimes be found caught in bed sheets or sleeping bags.

​

​Approximately 7 days (range 4–21), with recurrent febrile episodes that last around 3 days and are separated by afebrile periods ​of approximately 7 days.

About 3-4 cases of soft tick relapsing fever are reported each year in Oregon among patients who were typically exposed on the east side of the Cascades, above 1,500 feet elevation​.

Soft tick relapsing fever statistics 



Illness is characterized by:

  • Periods of fever, often exceeding 38.8°C (102°F), lasting 2–7 days and alternating with afebrile periods of 4–14 days
  • Febrile periods are often accompanied by:
    • Shaking chills
    • Sweats
    • Headache
    • Muscle and joint pain
    • V​omiting, or nausea
    • STRF may be fatal in 5%–10% of untreated cases
    • STRF contracted during pregnancy can cause spontaneous abortion, premature birth, and neonatal death
  • Consult with your primary care provider if you have symptoms compatible with soft tick relapsing fever; please have them contact OHA 971-673-1111 for clinical consultation and testing.
    • ​​

​

​Soft tick relapsing fever is treated with antibiotics​.​​

While some commercial lab testing is ​available. If your health care provider suspects that you have soft tick relapsing fever, please have them contact the on-call epidemiologist OHA 971-673-1111 with regard to testing for soft tick relapsing fever.​

Western Black-legged Tick (Ixodes pacificus)

Region

Pacific coast states

Transmits

  • Lyme disease
  • Anaplasmosis
  • Hard tick relapsing fever
Image of Western Black-legged Tick overlayed on map 
 

Lyme disease

(Borrelia burgdorferi)

Most Lyme disease cases acquired Lyme disease outside Oregon in high-incidence states. Between 2022 and 2025, 12 cases of Lyme disease were reported among Oregon residents who had acquired Lyme disease in Oregon, which is a median of 2.5 cases per year (range 1-6). Annual incidence of Oregon-acquired Lyme disease is 0.7/million population/year.


  • The t​ick that gives Oregonians the most trouble is the Western Black-legged tick, Ixodes pacificus. The Western Black-legged tick’s counterpart, the Black-legged tick, Ixodes scapularis, is found on the midwestern and eastern half of the United States and just as troublesome. Black-legged ticks transmit a variety of diseases including Borrelia burgdorferi and B. mayonii (which cause Lyme disease), Anaplasma phagocytophilum (anaplasmosis), B. miyamotoi disease (a form of relapsing fever found on the west c​oast), and primarily on the east coast, Ehrlichia muris eauclairensis​ (ehrlichiosis), ​​Babesia ​(​babesiosis), and Powassan virus (Powassan virus disease).
  • ​​In most cases, the tick must be attached for 36–48 hours or more before the Lyme disease bacterium can be transmitted. Most humans are infected through the bites of immature ticks called nymphs. Nymphs are tiny (less than 2 mm) and difficult to see, which is why they may be attached for many hours without being detected. Nymphs feed during the spring and summer months. The incubation period for Lyme disease ranges from three to 30 days after tick exposure.
    However, the early stages of the illness may be asymptomatic, and the patient may later develop systemic symptoms and joint, neurologic or cardiac problems in varying combinations during a period of months to years. Infections are treated with antibiotics.
  • Currently, increasing recognition of the disease is redefining areas where ticks may carry B. burgdorferi; Lyme disease cases have been reported in 49 states, and in Ontario and British Columbia, Canada. Related borrelioses have been found in Europe, the former Soviet Union, China and Japan.
​
3-30 days​​​

Most Lyme disease cases acquired Lyme disease outside Oregon in high-incidence states. Between 2022 and 2025, 12 cases of Lyme disease were reported among Oregon residents who had acquired Lyme disease in Oregon, which is a median of 2.5 cases per year (range 1-6). Annual incidence of Oregon-acquired Lyme disease is 0.7/million population/year.

Lyme disease statistics​

​​

Clinical symptoms include:

  • Fever​
  • Chills
  • Headache
  • Fatigue
  • Muscle and joint aches
  • Swollen lymph nodes may occur in the absence of rash
  • About 60% of patients include a red spot or bump that expands slowly with clearing in the middle, forming a ring or “target,” or a bull’s eye sometimes with multiple similar lesions. This distinctive skin lesion is called “erythema migrans.” ​​

​
Infections are treated with antibiotics​.​

Laboratory testing by commercial labs is available.​​

Anaplasmosis

(Anaplasma phagocytophilum)

Anaplasmosis is an uncommon tickborne disease in Oregon with 1 or 2 cases per year; however, it is transmitted by the same tick, the Western black-legged tick (Ixodes pacificus), which also transmits Lyme disease and “hard tick relapsing fever”.

CDC Information on Anaplasmosis.

 

Anaplasmosis is transmitted by the same tick, the Western Black-legged tick (Ixodes pacificus)​, which also transmits Lyme disease and “hard tick relapsing fever”. The distribution of the Western Black-legged tick is found primarily west of the Cascades (includes Hood River county​), but the Western Black-legged tick might be found incidentally in other counties east of The Cascades. Anaplasmosis is also transmitted by the Lone Star Tick (Amblyomma americanum​​)​​, which is found in the midwestern and eastern States.

​
5-14 days​

Anaplasmosis is an uncommon tickborne disease in Oregon with 1-​2 cases per year, about half of Oregon’s cases acquired anaplasmosis in Iowa, Massachusetts, Minnesota, New York, and Wisconsin.

​​

Please note that few people develop all symptoms and the number and combination of symptoms varies from person to person:​

  • Clinical symptoms of anaplasmosis, caused by the bacterium Anaplasma phagocytophilum​
  • Fever, chills, rigors
  • Severe headache
  • Malaise
  • Muscle aches
  • Gastrointestinal symptoms (nausea, vomiting, diarrhea, anorexia)
  • Rash in <10% of cases
  • Fatality is rare, but illness can be more severe among the elderly and immunocompromised. Consult with your primary care physician if you are feeling symptoms compatible with anaplasmosis. Be sure to note any areas where you might have been exposed to ticks 7-14 days before your onset of disease, including exposures in other states, where anaplasmosis can be transmitted also be transmitted by the Black-legged tick (Ixodes scapularis)​ or if you have had a recent blood transfusion.

​​

​Infections are treated with antibiotics.​

Laboratory testing by commercial labs is available.

  • Some tests will require two tests:
    • ​The first sample should be taken within the first two weeks of illness
    • The second sample should be taken 2-4 weeks after the first sample
​ ​​​

​

Hard Tick Relapsing Fever (HTRF)

(Borrelia miyamotoi)

Hard tick relapsing fever is an uncommon emerging disease first identified in Japan in 1995. Less than five cases have been reported in Oregon.

CDC information on hard tick relapsing fever.


Hard tick relapsing fever is an uncommon emerging disease first identifie​d in Japan in 1995. It is caused by a spiral-shaped bacterium, Borrelia miyamotoi, which is closely related to the bacterium that causes soft tick relapsing fever (Borrelia hermsii); however, hard tick relapsing fever is transmitted by the same tick that transmits Lyme disease and anaplasmosis -- the Western Black-legged tick (Ixodes pacificus​). Like Lyme disease, the most likely area of transmission is west of the Cascades.​

​

3 days to 6 weeks, exact range unknown

​Less than five cases have been reported in Oregon; all were acquired west of the Cascades.​

​​​Clinical symptoms may include:

  • Fever​
  • Chills
  • Relapsing fever in 10-40% of patients
  • Fatigue
  • Muscle aches
  • Joint aches
  • Rash is uncommon

​

​Infections are treated with antibiotics.​

While some commercial lab testing if available. If your health care pro​vider suspects that you have hard tick relapsing fever, please have them call the on-call epidemiologist OHA 971-673-1111 with regard to testing for hard tick relapsing fever.

​
​

American Dog Tick (Dermacentor similis),  Brown Dog Tick (Rhipicephalus sanguineus) and Rocky Mountain Wood Tick (Dermacentor andersoni)

American Dog Tick
Region
West of the Rocky MountainsClose-up of an American Dog Tick
Transmits

  • Rocky Mountain spotted fever     
  • Tularemia        

Brown Dog Tick
Region
Worldwide
Close-up of Brown DogTick
Transmits

  • Rocky Mountain spotted fever   

Rocky Mountain Wood Tick
Region
Rocky Mountain states Rocky-Mountain-Wood-Tick.png
Transmits

  • Colorado tick fever    
  • Rocky Mountain tick fever  
  • Tularemia      

Rocky Mountain Spotted Fever

(Rickettsia rickettsii)

In addition to transmitting Colorado tick fever, the Rocky Mountain wood tick also can transmit Rocky Mountain spotted fever, tularemia, and Q fever.

CDC Information on Rocky Mountain spotted fever.

​In addition​ to transmitting Colorado tick fever, the Rocky Mountain wood tick (Dermacentor andersoni), also transmits Rocky Mountain spotted fever and a few other uncommon diseases such as Q fever and tularemia. The Rocky Mountain wood tick is usually found about 4,000 feet elevation west of the Cascades. However, the Brown Dog Tick (Rhipicephalus sanguineus) and American Dog Tick (Dermacentor similis)​ also transmit Rocky Mountain spotted fever, and they are found throughout Oregon, as well as throughout the United States. ​​

​

3-12 days

Only about 3-4 Oregon patients are reported with Rocky Mountain Spotted Fever (RMSF) each year, about two-thirds of whom acquired it outside Oregon. The rate of Oregon-acquired RMSF is about 0.2 per million population per year, or about one case patient per year.  A recent Oregon case of RMSF-like illness caused by Rickettsia lanei was discovered in 2025; the rabbit tick and Pacific Coast tick are supposed vectors.

https://wwwnc.cdc.gov/eid/article/32/4/25-1962_article
Rocky Mountain Spotted Fever Statistics ​

​ ​​

​​​Rocky Mountain Spotted Fever can be rapidly fatal if not treated within the first 5 days of symptoms. Before tetracycline antibiotics were available, case fatality rates ranged from 20–80%. Early symptoms (first 4 days) include

  • High fever​​
  • Severe headache
  • Malaise
  • Muscle aches
  • Edema around eyes and on the back of hands
  • Gastrointestinal symptoms (nausea, vomiting, anorexia)
  • Rash
  • Possible multi-organ failure.
  • Late symptoms (5 days and beyond) include
  • Altered mental status
  • Coma
  • Cerebral edema
  • Respiratory compromise
  • Necrosis, requiring amputation
  • Multiorgan system damage (for example, renal failure)
  • Early treatment (within 5 days of symptoms) is imperative
​​

Rocky Mountain Spotted Fever can be rapidly fatal if not treated within the first 5 days of symptoms. Before tetracyclin​​e antibiotics were available, case fatality rates ranged from 20–80%.
Early treatment (within 5 days of symptoms) is imperative.​

​

NOTE: Laboratory values are often within normal limits in early illness. ​LABORATORY DIAGNOSIS § Demonstration of a four-fold rise in IgG-specific antibody titer by indirect immunofluorescence antibody (IFA) assay in paired serum samples. The first sample should be taken within the first 2 weeks of illness and the second should be taken 2 to 4 weeks later. § Detection of DNA in a skin biopsy specimen of a rash lesion by PCR assay or in an acute phase whole blood specimen. Additionally, new pan-Rickettsia and R. rickettsii-specific PCR assays are available at some local and state health departments. § Immunohistochemical (IHC) staining of organism from skin or tissue biopsy specimen.

Colorado Tick Fever

(Colorado tick fever virus)

Colorado tick fever is an uncommon tick-borne disease in Oregon with a few Oregon patients per year. It is transmitted by the Rocky Mountain wood tick, which is generally found about 4,000 feet elevation on the east side of the Cascades.

CDC information on Colorado tick fever.

 

It is transmitted by the Rocky Mountain wood tick, which is generally found above 4,000 feet elevation on the east side of the Cascades.​

​

​1-14 days

Colorado tick fever (CTF) is a hard-to-diagnose but uncommon tickborne disease in Oregon with a median of 1 case per year (range 1-5). Most cases acquired Colorado tick fever between April and July in Deschutes County and other areas east of the Cascades above 4,000 feet.​

Colorado tick fever (CTF) Statistics

​

Symptoms of Colorado Tick Fever include:

  • Fever, chills, headache, myalgias, and lethargy
  • About half the patients have a biphasic illness with symptoms remitting after 2 to 4 days, but then recurring 1 to 3 days later
  • Conjunctival injection, pharyngeal erythema and lymphadenopathy may be present.
  • Maculopapular or petechial rash in <20% of patients
  • Prolonged convalescence characterized by weakness and fatigue is common in adults
  • Life-threatening complications and death are rare and usually associated with disseminated
    intravascular coagulation or meningoencephalitis in children.

​Symptomatic management with analgesics and antipyretics.

  • C​ommercial testing is available. Consult with your primary care physician if you are feeling symptoms compatible with Colorado tick fever virus, and please have them contact OHA 971-673-1111 for clinical consultation and testing.
  • If positive for Colorado tick fever, the patient’s subsequent blood donations should be deferred for at least six months.
    • ​​
​ ​​​

Tularemia

(F. tularensis)

Probably no bacterial agent has more diversified modes of transmission than Francisella tularensis, the infectious agent of tularemia. Infection can occur (i) by direct contact with infected animals, infectious animal tissues or fluids; (ii), by arthropod bite; (iii) by ingestion of contaminated water or food; or, (iv) by inhalation of infective aerosols. There is no human-to-human transmission. The portal of entry determines the form of illness.

CDC Information on Tularemia.

​​Tularemia is caused by the highly infectious F. tularensis​​ bacteria. It is spread through exposure to infected arthropods (including deer flies and several species of ticks, including the American dog tick and the Rocky Mountain wood tick), contact with infected carcasses or animals (such as rabbits, hares, and rodents), contaminated food or water, or inhalation of aerosols (such as by mowing over an infected rabbit carcass).

​3–5 days (range 1–21 days)​

3-4 cases per year in Oregon; most of which were not transmitted by ticks

​

The clinical presentation of tularemia depends on many factors, including the route of inoculation and subtype of F. tularensis​. Tularemia can be serious or fatal without adequate treatment. Unusual and severe clinical manifestations have been described in patients with immunocompromising conditions.

  • Fever, chills
  • Headache
  • Malaise, fatigue
  • Anorexia
  • Myalgia
  • Chest discomfort, cough
  • Sore throat
  • Vomiting, diarrhea
  • Abdominal pain

(Ulcero) Glandular

  • ​​​​​Localized lymphadenopathy
  • Cutaneous ulcer at infection site (not always present)

Oculandular

  • Photophobia
  • Vision impairment/loss
  • Conjunctivitis
  • Regional lymphadenopathy

OROPHARYNGEAL

  • Severe throat pain
  • Exudative pharyngitis or tonsillitis
  • Regional lymphadenopathy

PNEUMONIC

  • Non-productive cough
  • Substernal tightness
  • Pleuritic chest pain
  • Hilar adenopathy, infiltrate, or pleural effusion may be present on chest X-ray

TYPHOIDAL

  • Characterized by any combination of the general symptoms without the localizing symptoms of other syndromes
  • May have infiltrates in chest radiograph in the absence of respiratory symptoms has context menu​
​

Infections are treated with antibiotics​.​

​use commerical labs as in lyme​​​​