What is the recommended treatment for a patient suspected of having Anaplasmosis?

Treatment of Suspected Anaplasmosis

Doxycycline is the drug of choice for all patients with suspected anaplasmosis, including children of all ages, and treatment must be initiated immediately based on clinical suspicion without waiting for laboratory confirmation. 1

Immediate Empiric Treatment

Start doxycycline as soon as anaplasmosis is suspected based on clinical presentation, epidemiologic exposure, and compatible laboratory findings—do not delay for serologic confirmation. 1 Delay in treatment can lead to severe disease, organ failure, and death, particularly in older adults, immunocompromised patients, and those with comorbidities such as diabetes. 1

Dosing Regimen

Adults:

• Doxycycline 100 mg twice daily (oral or intravenous) 1

Children weighing <100 lbs (45 kg):

• Doxycycline 2.2 mg/kg body weight twice daily (oral or intravenous), maximum 100 mg per dose 1

Children weighing ≥100 lbs (45 kg):

• Use adult dosing: 100 mg twice daily 1

Route of Administration

• Oral therapy is appropriate for early-stage disease in patients who can be managed as outpatients and are not vomiting 1
• Intravenous therapy is indicated for hospitalized patients, particularly those who are vomiting, obtunded, or severely ill 1

Duration of Treatment

Treat for at least 3 days after fever subsides and until evidence of clinical improvement is noted, with a minimum total course of 5-7 days. 1 Severe or complicated disease may require longer treatment courses. 1

Critical exception: Extend treatment to 10 days if concurrent Lyme disease is suspected or cannot be excluded, as the tick vector Ixodes scapularis transmits both Anaplasma phagocytophilum and Borrelia burgdorferi. 1 Coinfection occurs in <10% of patients but must be considered in endemic areas. 1

Expected Clinical Response

Fever should subside within 24-48 hours after initiating doxycycline when treatment is started during the first 4-5 days of illness. 1

If no clinical improvement occurs within 48 hours of early treatment, consider:

• Alternative diagnoses 1
• Coinfection with Borrelia burgdorferi or Babesia microti 1
• Severe disease with multiple organ dysfunction (may require >48 hours for improvement) 1

Use of Doxycycline in Children

The concern about dental staining should never prevent the use of doxycycline in children with suspected anaplasmosis. 1 Limited courses of doxycycline during the first 6-7 years of life have negligible effect on permanent tooth color, and the life-threatening nature of untreated anaplasmosis far outweighs this minimal cosmetic risk. 1

Hospitalization Criteria

Hospitalize patients with:

• Evidence of organ dysfunction 1
• Severe thrombocytopenia 1
• Mental status changes 1
• Need for supportive therapy or intravenous medications 1
• Inability to take oral medications reliably 1

Approximately 7% of hospitalized anaplasmosis patients require intensive care unit admission. 1 Severe manifestations can include ARDS, renal failure, DIC-like coagulopathies, hemorrhagic manifestations, rhabdomyolysis, pancreatitis, and hemophagocytic syndromes. 1, 2

Critical Clinical Considerations

When meningococcal disease or bacterial sepsis cannot be excluded, administer appropriate antibacterial therapy (e.g., ceftriaxone) in addition to doxycycline while awaiting diagnostic clarification. 1 This dual approach ensures coverage for both rickettsial and bacterial pathogens.

Maintain close follow-up for all outpatients treated for anaplasmosis. 1 Emphasize to patients the need to return for reevaluation if substantial improvement is not observed within 24-48 hours of initiating treatment, as these diseases can rapidly progress. 1

Common Pitfalls to Avoid

• Never wait for serologic confirmation before starting treatment—patients typically do not have diagnostic antibody levels during the first week of illness 1
• Do not discontinue treatment prematurely—continue for at least 3 days after fever resolution with minimum 5-7 day total course 1
• Do not miss coinfection—leukopenia or thrombocytopenia in a patient with Lyme disease should raise suspicion for Anaplasma coinfection 1
• Do not overlook opportunistic infections—serious and fatal opportunistic viral and fungal infections have been described during anaplasmosis, particularly in immunocompromised patients 1, 3
• Calculate pediatric doses based on actual body weight, not age alone 4

Diagnostic Clues Supporting Empiric Treatment

Characteristic laboratory findings that support starting doxycycline empirically include:

• Thrombocytopenia 1
• Leukopenia 1, 5
• Elevated hepatic transaminase levels (typically 2-4 fold) 1, 5, 6
• Mild anemia 1
• Increased immature neutrophils 1
• Morulae within granulocytes on blood smear (seen in 20-80% of cases) 1, 6

Clinical presentation typically includes fever, headache, and myalgia; rash is rare in anaplasmosis (unlike Rocky Mountain spotted fever). 1 The case-fatality rate is <1%, but predictors of severe disease include advanced age, immunosuppression, comorbid conditions, and delayed treatment. 1