How should a patient presenting with fever and eosinophilia be evaluated and managed?

Evaluation and Management of Fever with Eosinophilia

In a patient presenting with fever and eosinophilia, immediately consider acute schistosomiasis (Katayama syndrome) if there is recent freshwater exposure in endemic areas (particularly Africa), and initiate empirical treatment with praziquantel while pursuing diagnostic confirmation. 1

Initial Clinical Assessment

Focus your history on these specific high-yield elements:

• Travel history: Freshwater swimming in Africa (2-8 weeks prior suggests Katayama syndrome), Southeast Asia (liver flukes, tropical pulmonary eosinophilia), or any endemic helminth regions 1
• Timing: Acute onset (2-8 weeks) versus chronic presentation
• Associated symptoms:
  • Urticarial rash + cough = strongly suggests Katayama syndrome 1
  • Dry cough + wheeze = consider tropical pulmonary eosinophilia or visceral larva migrans 1
  • Periorbital edema = trichinellosis 1
  • Abdominal pain = liver flukes (Opisthorchis/Clonorchis) 1
• Drug exposure: DRESS syndrome can present with fever, rash, and eosinophilia 2
• Food consumption: Raw/undercooked fish (liver flukes), raw meat/liver (Toxocara) 1

Diagnostic Approach

First-Line Testing

Order these tests immediately:

• Complete blood count with differential (quantify absolute eosinophil count - marked elevation >5 × 10⁹/L strongly suggests Katayama syndrome) 1
• Strongyloides serology - critical because of hyperinfection risk, especially before any steroid use 1
• Schistosomiasis serology - may be negative early but useful if positive 1
• Concentrated stool microscopy (3 samples) - though sensitivity is low for Strongyloides 1
• Faecal PCR if available (higher sensitivity) 1
• Chest radiograph - look for nodules, infiltrates, or pulmonary eosinophilia patterns 1
• HIV testing per BHIVA guidelines 1

Critical Pitfall

Never administer corticosteroids before excluding strongyloidiasis - this can precipitate fatal hyperinfection syndrome. Always obtain Strongyloides serology first. 1

Empirical Treatment Strategy

When to Treat Empirically

Treat immediately without waiting for confirmatory results if:

The combination of fever + eosinophilia + urticarial rash occurring 2-8 weeks after freshwater swimming in Africa makes Katayama syndrome highly likely and justifies empirical treatment 1

Treatment Regimens

For suspected Katayama syndrome:

• Praziquantel 25 mg/kg three times daily for 2-3 consecutive days 1
• Repeat treatment at 8 weeks (eggs and immature schistosomulae are relatively resistant; retreatment targets adult worms) 1
• Consider corticosteroids for severe symptoms (seek expert advice) 1

For undifferentiated fever with eosinophilia (no specific diagnosis):

• Albendazole 400 mg single dose PLUS ivermectin 200 μg/kg single dose 1
• Critical: Exclude Loa loa infection before ivermectin (check travel to Central/West Africa) - ivermectin can cause fatal encephalopathy in Loa loa 1
• Consider retreatment 1 month after symptom resolution 1

For tropical pulmonary eosinophilia (if suspected):

• Requires specialist consultation 1
• Diethylcarbamazine (DEC) is treatment of choice but requires careful monitoring 1

Specific Infectious Causes to Consider

Acute Presentations with Fever

1. Katayama syndrome (most important): Fever, cough, urticarial rash, diarrhea, headache; eosinophilia often >5 × 10⁹/L 1

2. Liver flukes (Opisthorchis spp.): Fever, abdominal pain, urticarial rash; treat with praziquantel 25 mg/kg three times daily for 2-3 days 1

3. Visceral larva migrans (Toxocara): Fever, eosinophilia, dyspnea, wheeze; more common in children but occurs in adults eating raw meat 1

4. Trichinellosis: Fever, periorbital edema, myocarditis risk 1

5. Tropical pulmonary eosinophilia: Fever, dry cough, wheeze; incubation up to one year 1

Non-Infectious Considerations

While helminth infections are the primary concern with fever and eosinophilia in travelers/migrants, also consider:

• DRESS syndrome: Drug exposure, rash, multiple organ dysfunction 2
• Fungal infections: Coccidioidomycosis, histoplasmosis, blastomycosis (specific geographic exposures) 1

When to Seek Specialist Input

Immediately consult tropical medicine/infectious disease if:

• Suspected strongyloidiasis with immunosuppression risk
• Loa loa possible (before any ivermectin use)
• Neurological symptoms (eosinophilic meningitis consideration) 1
• Severe systemic illness or organ dysfunction
• Diagnostic uncertainty after initial workup

Follow-Up Strategy

• Repeat eosinophil count 2-4 weeks after treatment
• Repeat schistosomiasis treatment at 8 weeks if initially treated 1
• Serology remains positive for years, so cannot assess treatment success 1
• Monitor for end-organ damage if eosinophilia persists