Initial Management of Fever and Eosinophilia

Immediate Clinical Assessment

The American College of Physicians recommends that all patients presenting with fever and eosinophilia should undergo concentrated stool microscopy on three separate samples and receive empirical treatment with albendazole 400 mg twice daily for 3 days when investigations are negative, while simultaneously pursuing a detailed travel and exposure history to guide targeted therapy 1, 2, 3
Documenting exact countries visited, duration of stay, and timing of symptom onset relative to travel is crucial, as incubation periods range from 1-2 weeks for Loeffler's syndrome to 2-9 weeks for Katayama syndrome 1, 3
Identifying specific high-risk exposures, such as freshwater swimming in African lakes/rivers 2-9 weeks prior, suggests acute schistosomiasis (Katayama syndrome) 1, 2, 4
Reviewing all medications started within the past 3 months, particularly NSAIDs, beta-lactam antibiotics, and nitrofurantoin, is necessary, as drug reactions are common causes of eosinophilia 3
Screening for organ involvement symptoms, such as dry cough, wheeze, urticarial rash, abdominal pain, diarrhea, or neurological symptoms, is essential, as these indicate specific syndromes requiring urgent treatment 1, 2, 5

Obtaining concentrated stool microscopy on three samples collected on separate days has high diagnostic yield for intestinal helminths 1, 2, 6, 3
Calculating absolute eosinophil count (AEC) from CBC with differential is necessary to determine severity: mild (500-1500/μL), moderate (1500-5000/μL), or severe (>5000/μL) 3
Ordering comprehensive metabolic panel with liver function tests, LDH, and uric acid is necessary to assess for organ damage 3
Performing peripheral blood smear review is necessary to evaluate for dysplasia, monocytosis, or circulating blasts that would suggest myeloproliferative disease 3

For patients with fever, eosinophilia >5000/μL, urticarial rash, and freshwater exposure in Africa 2-9 weeks prior, the Centers for Disease Control and Prevention recommends initiating empirical treatment with praziquantel 40 mg/kg as a single dose, repeated at 6-8 weeks, without waiting for confirmatory testing 1, 2, 4, 3
Adding prednisone 20 mg daily for 5 days is recommended, as case series evidence demonstrates steroids reduce symptom duration 1, 2, 4, 5
For patients with fever, urticaria, wheeze, dry cough, and pulmonary infiltrates on chest X-ray occurring 1-2 weeks after potential exposure, the American Thoracic Society recommends diagnosing clinically as symptoms occur during the prepatent period 1, 2, 5
Initiating empirical albendazole 400 mg twice daily for 3 days is recommended when investigations are negative, as this covers Ascaris, hookworm, and Strongyloides 1, 2, 5

Hypereosinophilia (AEC ≥1500/μL) is never explained by allergy alone and always requires further investigation to exclude secondary causes, including parasites, drugs, and myeloproliferative disorders, according to the American Academy of Allergy, Asthma, and Immunology 3
Measuring serum tryptase and vitamin B12 levels is necessary if hypereosinophilia is present, as elevated levels are characteristic of PDGFRA/PDGFRB rearrangements that show exquisite responsiveness to imatinib 3