Tick-borne diseases

Last updated: November 23, 2023

CME information and disclosurestoggle arrow icon

To see contributor disclosures related to this article, hover over this reference: [1]

Physicians may earn CME/MOC credit by searching for an answer to a clinical question on our platform, reading content in this article that addresses that question, and completing an evaluation in which they report the question and the impact of what has been learned on clinical practice.

AMBOSS designates this Internet point-of-care activity for a maximum of 0.5 AMA PRA Category 1 Credit(s)™. Physicians should claim only credit commensurate with the extent of their participation in the activity.

For answers to questions about AMBOSS CME, including how to redeem CME/MOC credit, see "Tips and Links" at the bottom of this article.

Summarytoggle arrow icon

Tick-borne diseases are predominantly caused by pathogens that are transmitted by ticks (and sometimes other vectors), except tick paralysis, which is caused by a neurotoxin produced by the tick itself. Tick-borne diseases are typically associated with specific geographical regions. The most clinically significant tick-borne diseases in the US include Lyme disease, Rocky Mountain spotted fever (RMSF), babesiosis, ehrlichiosis, anaplasmosis, tularemia, Colorado tick fever, tick-borne relapsing fever, southern tick‑associated rash illness,tick paralysis, and the more recently recognized alpha-gal syndrome. While manifestations of these conditions vary, common symptoms include fever, flu-like symptoms, and skin rashes. Most tick-borne diseases are treated with antibiotics and patients usually respond well to treatment.

Lyme disease is covered in more detail in its own article.

Overviewtoggle arrow icon

Overview of tick-borne diseases [2]
Pathogen/cause US distribution

Clinical features

Diagnostics Treatment
Lyme disease
  • Upper midwestern and northeastern US
Rocky Mountain spotted fever (RMSF)
  • Midwestern, northeastern, and southern US
  • Midwestern (especially Minnesota and Wisconsin) and northeastern US
  • Mainly east of the Rocky Mountains
  • Some cases in the Southwest


  • Upper midwestern and northeastern US
  • Growing number of cases on the West Coast
Tularemia [3]
  • All states except Hawaii
Colorado tick fever (CTF) [4]
  • Western US
  • < 2 weeks after onset of symptoms: viral RNA detection by RT-PCR of blood sample
  • > 2 weeks after onset of symptoms: serum assay to detect CTFV-specific IgM antibodies
  • Supportive management only
Tick-borne relapsing fever [5]
  • Western US and Texas
  • Recurring episodes of high fever for 3 days and an afebrile period of 7 days
  • Arthralgia
  • Gastrointestinal symptoms
  • Macular rash or scattered petechiae
Southern tick‑associated rash illness (STARI)
  • Unknown
  • Southeastern and eastern US
Tick paralysis
  • Rocky Mountains and northwestern US
  • Remove the tick
  • Supportive therapy
Alpha-gal syndrome [6]
  • Midwest, southeastern and eastern US
  • Clinical diagnosis supported by
    • IgE against alpha-gal in serum
    • Clinical response to alpha-gal avoidance diet
  • Alpha-gal avoidance diet

Rocky Mountain spotted fever (RMSF)toggle arrow icon


Clinical features [8]

The rash may be less obvious in dark-skinned individuals; therefore, close inspection and a high degree of clinical suspicion are required. [9]

Diagnostics [9][10][11]

RMSF is a clinical diagnosis.

Do not delay treatment while waiting for confirmatory studies and do not discontinue treatment based solely on the results. [11]

RMSF is a nationally notifiable disease in the United States. Contact the state or local health department if a potential case is suspected. [9]

Differential diagnosis [11]


Initiate empiric antibiotic treatment immediately and consider consulting local infectious disease specialists. [11]

Treatment should be initiated as soon as RMSF is suspected, as it can be fatal if not treated early.

Disposition [11]

  • Consider hospitalization for patients who:
  • Escalate to critical care unit based on clinical condition.
  • In selected cases, consider discharge with oral antibiotics.

Prognosis [14]

  • If treated within the first 5 days, patients typically fully recover without hospitalization.
  • If treated after the first 5 days, symptoms are more severe and often require hospitalization. There is also a greater risk of long-term consequences of ischemia (e.g., amputations, paralysis, hearing loss, intellectual disability).
  • If not treated early enough, the disease can be fatal.

Babesiosistoggle arrow icon

Ehrlichiosistoggle arrow icon

Ehrlichiosis is a nationally notifiable disease in the United States. Contact the state or local health department if a potential case is suspected. [9]

Anaplasmosistoggle arrow icon

Anaplasmosis is a nationally notifiable disease in the United States. Contact the state or local health department if a potential case is suspected. [9]

Tularemiatoggle arrow icon

Colorado tick fever (CTF)toggle arrow icon

Tick-borne relapsing fevertoggle arrow icon

Southern tick‑associated rash illness (STARI)toggle arrow icon

Tick paralysistoggle arrow icon

References: [28]

Alpha-gal syndrometoggle arrow icon

  • Definition: an allergic reaction to the oligosaccharide galactose-alpha-1,3-galactose (alpha-gal) found on the cells of nonprimate mammals (e.g., cows, pigs, lambs) that is thought to occur after a parasitic infection or the bite of a tick [6]
  • Etiology [6]
  • Reservoir: deer (principal host)
  • Distribution [6]
    • US: Midwest, southeastern and eastern US
    • Worldwide: Western Europe, South Africa, Japan, Australia
  • Pathophysiology
    • Sensitization: Lone star tick bite or parasitic infection → production of IgE antibodies against alpha-gal
    • Type I hypersensitivity: consumption of mammalian-derived products in a sensitized individual → alpha-gal absorbed in GI tract enters the circulation → IgE against alpha-gal → mast-cell degranulation
  • Clinical features [6]
  • Diagnosis: primarily a clinical diagnosis, but may be supported by the following [6]
    • Positive clinical response after ≥ 1 month of alpha-gal avoidance
    • Serum: IgE against alpha-gal titers
  • Management: should be specialist-guided (e.g., gastroenterology, immunology) [6]
  • Prognosis: Sensitization to alpha-gal may fade or resolve over time. [6]
  • Prevention: tick bite prevention (further tick bites may worsen the allergy)

Alpha-gal does not cause anemia, GI bleeding, or weight loss. If these features are present consider alternative diagnoses. [6]

Referencestoggle arrow icon

  1. McGill SK, Hashash JG, Platts-Mills TA. AGA Clinical Practice Update on Alpha-Gal Syndrome for the GI Clinician: Commentary. Clin Gastroenterol Hepatol. 2023; 21 (4): p.891-896.doi: 10.1016/j.cgh.2022.12.035 . | Open in Read by QxMD
  2. Simon LV, West B, McKinney WP. Tick Paralysis. StatPearls. 2020.
  3. Rocky Mountain Spotted Fever (RMSF) - Epidemiology and Statistics. Updated: April 7, 2020. Accessed: January 27, 2021.
  4. Snowden J, Simonsen KA. Rickettsia Rickettsiae. StatPearls. 2020.
  5. Walls R, Hockberger R, Gausche-Hill M. Rosen's Emergency Medicine. Elsevier Health Sciences ; 2018
  6. Gottlieb M, Long B, Koyfman A. The Evaluation and Management of Rocky Mountain Spotted Fever in the Emergency Department: a Review of the Literature. J Emerg Med. 2018; 55 (1): p.42-50.doi: 10.1016/j.jemermed.2018.02.043 . | Open in Read by QxMD
  7. Biggs HM, Behravesh CB, Bradley KK, et al. Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis — United States. MMWR Recomm Rep. 2016; 65 (2): p.1-44.doi: 10.15585/mmwr.rr6502a1 . | Open in Read by QxMD
  8. Todd SR, Dahlgren FS, Traeger MS, et al. No Visible Dental Staining in Children Treated with Doxycycline for Suspected Rocky Mountain Spotted Fever. J Pediatr. 2015; 166 (5): p.1246-1251.doi: 10.1016/j.jpeds.2015.02.015 . | Open in Read by QxMD
  9. Blanton LS. The Rickettsioses: A Practical Update.. Infect Dis Clin North Am. 2019; 33 (1): p.213-229.doi: 10.1016/j.idc.2018.10.010 . | Open in Read by QxMD
  10. RMSF: deadly, but preventable. Updated: June 10, 2019. Accessed: January 27, 2021.
  11. Belongia EA. Epidemiology and impact of coinfections acquired from Ixodes ticks.. Vector Borne Zoonotic Dis. 2002; 2 (4): p.265-73.doi: 10.1089/153036602321653851 . | Open in Read by QxMD
  12. DPDx - Laboratory Identification of Parasites of Public Health Concern - Babesiosis. Updated: October 30, 2017. Accessed: January 28, 2021.
  13. Vannier E, Gewurz BE, Krause PJ. Human babesiosis.. Infect Dis Clin North Am. 2008; 22 (3): p.469-88, viii-ix.doi: 10.1016/j.idc.2008.03.010 . | Open in Read by QxMD
  14. CDC - Ehrlichiosis. Updated: October 1, 2020. Accessed: January 27, 2021.
  15. Bennett JE, Dolin R, Blaser MJ. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. Elsevier Saunders ; 2015
  16. Ismail N, Bloch KC, McBride JW. Human ehrlichiosis and anaplasmosis.. Clin Lab Med. 2010; 30 (1): p.261-92.doi: 10.1016/j.cll.2009.10.004 . | Open in Read by QxMD
  17. Guzman N, Yarrarapu SNS, Beidas SO. Anaplasma Phagocytophilum (Anaplasmosis). StatPearls. 2020.
  18. Tularemia. Updated: September 27, 2016. Accessed: December 11, 2017.
  19. $WHO Guidelines on Tularaemia.
  20. Colorado Tick Fever (CTF) - Symptoms & Treatment. Updated: December 3, 2018. Accessed: January 27, 2021.
  21. Tickborne Diseases of the United States - Colorado Tick Fever. Updated: January 10, 2019. Accessed: January 27, 2021.
  22. Snowden J, Yarrarapu SNS, Oliver TI. Relapsing Fever. StatPearls. 2020.
  23. Tick-borne Relapsing Fever (TBRF). Updated: January 8, 2016. Accessed: December 11, 2017.
  24. Southern Tick–Associated Rash Illness - STARI or Lyme?. Updated: November 19, 2018. Accessed: January 27, 2021.
  25. Southern Tick–Associated Rash Illness - Symptoms, Diagnosis and Treatment. Updated: November 19, 2018. Accessed: January 27, 2021.
  26. $Tickborne Diseases of the United States: A Reference Manual for Health Care Providers.
  27. Colorado Tick Fever. Updated: January 13, 2015. Accessed: December 11, 2017.
  28. $Contributor Disclosures - Tick-borne diseases. All of the relevant financial relationships listed for the following individuals have been mitigated: Alexandra Willis (copyeditor, is an independent contractor for OPEN Health Communications); Jan Schlebes (medical editor, is a shareholder in Fresenius SE & Co KGaA). None of the other individuals in control of the content for this article reported relevant financial relationships with ineligible companies. For details, please review our full conflict of interest (COI) policy:.

Icon of a lock3 free articles remaining

You have 3 free member-only articles left this month. Sign up and get unlimited access.
 Evidence-based content, created and peer-reviewed by physicians. Read the disclaimer