Parasitic infections, diagnosed before cataract surgery: Strongyloides

 

An excellent Internal Medicine physician just called me about a patient scheduled for cataract surgery next week. She mentioned the patient had been experiencing mild difficulty breathing, so she ordered a chest X-ray — which revealed pulmonary nodules. She then ordered a serology test (Strongyloides IgG ELISA antibody titer) along with a stool ova and parasite exam (O&P) with stool culture for Strongyloides larvae. The results came back positive. The diagnosis: Strongyloides stercoralis infection. She called me because the patient is about to need corticosteroid eye drops after cataract surgery — and that changes everything.

Strongyloides stercoralis filariform (L3) larva — the infective stage that penetrates skin. Image: CDC/DPDx

Strongyloides & Cataract Surgery:
What Every Surgeon Must Know Before Reaching for Steroids

By Sandra Lora Cremers, MD, FACS  |  EyeDoc2020  |  Visionary Eye Doctors, Rockville, MD

What Is Strongyloides?

Strongyloides is a parasitic infection caused by a tiny roundworm called Strongyloides stercoralis. This parasite is found in tropical and subtropical regions worldwide, affecting an estimated 300–600 million people globally. The infection occurs when microscopic larvae from contaminated soil penetrate the skin — typically through bare feet.

Rhabditiform (L1) larva of S. stercoralis found in a stool sample. Image: CDC/DPDx

How Does the Infection Work?

Once the larvae enter the body, they travel through the bloodstream to the lungs and eventually to the small intestine, where adult female worms live and reproduce. What makes Strongyloides uniquely dangerous is its ability to complete its entire life cycle within the human body through a process called "autoinfection." This means the infection can persist for decades without treatment — even if the person left the endemic area years ago.

What Are the Symptoms?

Many people with Strongyloides have no symptoms at all. When symptoms do occur, they can include:

• Diarrhea and abdominal pain
• Skin rashes or itching — especially a distinctive rash called "larva currens"
• Cough and breathing problems
• Weight loss
• Anemia (low blood count)

"Larva currens" — the rapidly migrating, serpiginous skin rash characteristic of Strongyloides autoinfection.

⚠️ The Serious Risk: Hyperinfection Syndrome

The most dangerous complication occurs in people with weakened immune systems. If someone with Strongyloides takes medications that suppress the immune system — especially corticosteroids — the parasite can multiply rapidly and spread throughout the body. This condition, called hyperinfection syndrome, can be fatal in over 60% of cases if not treated promptly.

Strongyloides and Cataract Surgery

Important consideration: While Strongyloides infection itself is not a direct contraindication to cataract surgery, there is a critical concern. Cataract surgery routinely requires corticosteroid eye drops — and sometimes oral steroids — to reduce postoperative inflammation. In patients with undiagnosed or untreated Strongyloides, these steroids could trigger hyperinfection syndrome.

What this means for your practice: If your patient has lived in or traveled to areas where Strongyloides is common (tropical/subtropical regions, rural areas with poor sanitation), screen and treat for Strongyloides before surgery — especially if steroids will be used.

Treatment Options

✅ First-Line: Ivermectin

Ivermectin is the best and most effective treatment for Strongyloides. It is given as a single oral dose based on body weight (200 micrograms per kilogram). The cure rate is approximately 88–95% with a single dose.

Common side effects of ivermectin (usually mild and temporary):

• Dizziness (3%)
• Nausea or diarrhea (2%)
• Fatigue, headache, mild itching or rash

Serious side effects are rare. Ivermectin is generally very well tolerated.

Alternative: Albendazole

Albendazole is a second-choice medication used when ivermectin is not available. It is less effective, requiring a longer treatment course (400 mg twice daily for 7 days).

Common side effects of albendazole:

• Headache (11%)
• Nausea and dizziness (8%)
• Loose stools (10%)

Serious side effects (rare): liver enzyme elevation, blood cell abnormalities (leukopenia, anemia), allergic reactions. Avoid in first trimester of pregnancy.

Special Considerations: Elderly Patient with Breathing Issues and Mild Anemia

For an elderly patient with respiratory symptoms and anemia, treatment requires careful consideration:

• Ivermectin remains preferred even in elderly patients — the single-dose regimen is convenient and well-tolerated.
• The breathing issues and anemia may actually be caused by the Strongyloides infection itself, as the parasite can affect the lungs and cause GI blood loss.
• If the patient is immunocompromised or severely symptomatic, multiple doses may be needed (days 1, 2, 15, and 16 — or continued until resolution).

Important monitoring after treatment:

• Follow-up stool tests 2–4 weeks post-treatment
• Blood tests to monitor anemia improvement
• Assessment of respiratory symptoms
• Report any worsening immediately

🔑 Key Takeaways for Ophthalmologists

1. Strongyloides can persist for life without treatment — patients may not even know they're infected.
2. The main danger: hyperinfection syndrome triggered by steroids.
3. Screen before starting steroids — including perioperative drops for cataract surgery.
4. Ivermectin is gold-standard treatment: 88–95% cure rate, single dose.
5. Albendazole is an effective alternative but requires a longer course.
6. Elderly patients can safely be treated — with careful monitoring.

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References

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© Sandra Lora Cremers, MD, FACS  |  EyeDoc2020.blogspot.com  |  Visionary Eye Doctors, Rockville MD