What is the diagnostic algorithm and treatment for a patient with rising eosinophilia, who has a history of toxocarosis treated with albendazole (anti-parasitic medication) 2 years ago, and had a subsequent drop in eosinophil count at that time?

Diagnostic Algorithm and Treatment for Rising Eosinophilia After Previous Toxocariasis

Immediate Diagnostic Approach

Given the history of toxocariasis with initial response to albendazole followed by rising eosinophils 2 years later, you should first repeat Toxocara serology and consider reinfection or inadequate initial treatment, while simultaneously excluding other helminth infections through comprehensive stool microscopy and travel-related parasite screening. 1

Step 1: Confirm Toxocariasis Recurrence or Reinfection

• Repeat Toxocara serology (ELISA IgG) - A marked increase in titers compared to previous levels strongly suggests active infection 2
• Check total IgE levels - typically markedly elevated (>1,000 IU/mL) in active toxocariasis 2, 3
• Obtain complete blood count with differential to quantify absolute eosinophil count 4
• Assess for visceral involvement: chest X-ray and abdominal ultrasound or CT to evaluate for lung nodules, ground-glass opacities, or liver lesions 2

Step 2: Exclude Other Helminth Infections

• Perform comprehensive stool microscopy (minimum 3 samples on different days) to exclude Strongyloides, hookworm, Ascaris, and other intestinal helminths 1
• Obtain detailed travel and exposure history - specifically ask about travel to endemic areas for schistosomiasis, filariasis, or other tissue helminths 1
• Consider schistosomiasis serology if any freshwater exposure in endemic regions 1
• Screen for Strongyloides stercoralis through serology and stool examination, as this can persist for decades and cause hyperinfection 5

Step 3: Assess for Reinfection Risk Factors

• Investigate ongoing exposure sources: contact with dogs/cats, consumption of raw or undercooked meat (especially liver), soil exposure, occupational risks 2, 3
• Evaluate household members and pets for potential ongoing transmission 6

Treatment Algorithm

For Confirmed or Highly Suspected Toxocariasis Recurrence

Administer albendazole 400 mg orally twice daily for a minimum of 5 days, but consider extending treatment to 3-4 weeks for recurrent or severe disease, as standard 5-day courses may be insufficient. 1, 5, 3

Standard Treatment Protocol

• Albendazole 400 mg PO twice daily for 5 days is the first-line treatment for uncomplicated toxocariasis 5, 7, 8
• For recurrent disease: extend treatment to 3-4 weeks, as demonstrated in case reports of refractory toxocariasis 2, 3
• Add corticosteroids (prednisolone 0.5-1 mg/kg/day) if severe symptoms, marked eosinophilia (>5,000/mm³), or visceral involvement is present 5, 3, 8

Critical Treatment Considerations for Recurrent Cases

• Multiple treatment cycles may be necessary: one case required 6 cycles of 4 weeks each to achieve cure 3
• Another case required 3 separate courses of albendazole over several weeks before resolution 2
• Monitor for treatment failure: repeat eosinophil count 3-4 weeks post-treatment 6, 4
• If eosinophilia persists or recurs within 6 weeks, repeat albendazole for extended duration (3-4 weeks) 1, 2, 3

For Empirical Treatment When Diagnosis Uncertain

If comprehensive workup is negative but eosinophilia persists with appropriate exposure history:

• Consider empirical combination therapy: albendazole 400 mg single dose PLUS ivermectin 200 μg/kg single dose 5
• Critical safety warning: exclude Loa loa infection before administering ivermectin in patients with travel to Central/West Africa, as severe reactions can occur 5
• This empirical approach achieved 80% reduction in eosinophil counts in one study of unexplained eosinophilia 4

Follow-Up Strategy

Monitoring Protocol

• Repeat complete blood count with differential at 4 weeks post-treatment to confirm eosinophil normalization 6, 4
• Repeat at 6 and 12 months to monitor for relapse, as toxocariasis can recur 1, 2
• Repeat Toxocara serology at 3-6 months - titers should decline with successful treatment 2

Addressing Persistent or Recurrent Eosinophilia

• If eosinophils remain >1,000/mm³ after initial treatment, consider:
  • Extended albendazole course (3-4 weeks) 1, 3
  • Repeat cycles with 2-week drug-free intervals between courses 3
  • Specialist consultation for refractory cases requiring prolonged therapy 1, 5

Common Pitfalls to Avoid

• Do not assume single 5-day course is sufficient - recurrent toxocariasis often requires extended or repeated treatment 2, 3
• Do not overlook reinfection sources - ongoing exposure will lead to treatment failure 6, 2
• Do not miss Strongyloides co-infection - this requires different treatment (ivermectin) and can cause hyperinfection syndrome 5
• Do not use ivermectin without excluding Loa loa in patients with Central/West African travel history 5
• Do not delay corticosteroids in severe disease - marked eosinophilia with visceral involvement requires concurrent steroid therapy 5, 3, 8

Safety Monitoring for Extended Treatment

• No routine laboratory monitoring needed for standard 5-day course 6
• For treatment >14 days: monitor liver function tests and complete blood count, as albendazole can cause hepatotoxicity and bone marrow suppression 9
• Watch for neurological symptoms if CNS involvement suspected - may require corticosteroids to prevent inflammatory reactions 1, 5