Hard Tick Relapsing Fever (HRTF) Information for Health Professionals

Hard Tick Relapsing Fever (HRTF) is a bacterial illness transmitted to humans by the blacklegged (deer) tick. The disease agent is closely related to the bacteria that cause soft tick relapsing fever and distantly related to the bacteria that causes Lyme disease. Human illness due to HRTF was first identified in 2011 with the first case in Minnesota reported in 2016. Since then, a low number of cases have been reported in Minnesota residents each year.

On this page:
Clinical presentation
Diagnostic tests
Treatment
Guidelines
Reporting

Clinical Presentation

While the spectrum of illness due to HRTF is still being described, common signs and symptoms that have been reported to date include fever, headache, myalgia, and fatigue. Some patients HRTF have described recurring symptoms prior to diagnosis and treatment, but evidence suggests that most patients (90%) with HTRF most commonly involves a single episode of fever. Severe illness, such as meningoencephalitis, has also been reported.

Diagnostic tests

Currently, confirmation of a diagnosis relies on the use of polymerase chain reaction (PCR) tests that detect DNA from the organism or antibody-based tests. Further research is needed to better understand how frequently cross-reactivity with similar Borrelia species may occur with serologic testing for B. miyamotoi. Serologic and PCR tests are not widely available but can be ordered from some commercial laboratories or through CDC.

Treatment

There are no randomized controlled trials that have evaluated treatment regimens do HTRF, but patients diagnosed with infection due to HTRF have been successfully treated with antibiotics that are effective for Lyme disease.

Guidelines

• CDC: Clinical Guidance for Hard Tick Relapsing Fever (HTRF)
• CDC: Tickborne Diseases of the United States
  CDC Handbook, designed as a way for health care providers to access information on tickborne diseases and tick identification.
• IDSA: Clinical Practice Guidelines: 2020 Guidelines for the Prevention, Diagnosis and Treatment of Lyme Disease
  Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA), American Academy of Neurology (AAN), and American College of Rheumatology (ACR).

Reporting

• Reporting Hard Tick Relapsing Fever (borrelia miyamotoi)
  Borrelia miyamotoi (Hard Tick Relapsing Fever) is reportable under the Minnesota Rules Governing Communicable Diseases and should be reported to MDH within one working day.
  • MDH staff also are available to provide clinical consultation regarding diagnosis and treatment of HTRF and other tick-borne diseases. Call 651-201-5414 for a clinical consultation.