Signs and Symptoms

  • Anaplasmosis typically causes an acute febrile illness.
  • Signs and symptoms vary greatly from person to person.
  • Most people will have mild or moderate illness, though severe illness and death are possible.
  • Signs and symptoms typically begin within 5–14 days after the bite of an infected tick. However, because tick bites are not painful, many people will not remember a tick bite.
  • Healthcare providers should consider anaplasmosis or other tickborne infections in the differential diagnosis for patients with a non-specific febrile illness of unknown origin, particularly during spring and summer months when ticks are most active.

Early Illness

The following is a list of signs and symptoms commonly seen in the first few days of illness (days 1-5):

  • Fever, chills, rigors
  • Severe headache
  • Malaise
  • Myalgia
  • Gastrointestinal symptoms (nausea, vomiting, diarrhea, anorexia) in about 20% of cases

 Rarely reported

  • Rash (<10% of cases) in patients with anaplasmosis. The presence of a rash might indicate a coinfection with Lyme disease, or another tickborne disease.
  • Nervous system involvement (e.g., meningoencephalitis, focal paralysis, etc.)

Late Illness

If treatment is delayed and anaplasmosis is allowed to continue, disease may become severe. Severe illness is rare, but may involve:

  • Renal or respiratory failure
  • Peripheral neuropathies
  • Disseminated intravascular coagulation (DIC)-like coagulopathies
  • Rhabdomyolysis
  • Hemorrhage

Risk factors for severe disease

  • Delayed treatment
  • Older age
  • Immune compromising conditions, e.g., advanced HIV, persons receiving chemotherapy, or other immune suppressing medications


Healthcare providers should also look at routine blood tests, such as a complete blood cell count and a chemistry panel when making the diagnosis.

  • General laboratory findings can include mild anemia, thrombocytopenia, leukopenia (characterized by relative and absolute lymphopenia and a left shift) and mild to moderate elevations in hepatic transaminases.
  • Abnormal laboratory findings can appear in the first week of illness; however, normal laboratory findings do not rule out possible infection.

Clinical Course

Progression of disease varies greatly from person to person and may depend on patient age, co-morbid conditions, immune status and time of treatment. Patients who are treated early may recover quickly with outpatient treatment with oral antibiotics, while those who experience a more severe course might require intravenous antibiotics, prolonged hospitalization or intensive care.

For more in-depth information about signs and symptoms of anaplasmosis, see: Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis — United States: A Practical Guide for Health Care and Public Health Professionals (2016) pdf icon[PDF – 48 pages]