What are the next steps for an elderly patient who claims to have removed a worm from their tooth and has Blastocystis hominis in their stool test?

Management of Suspected Oral Worm and Blastocystis hominis in an Elderly Patient

The "Worm Around the Tooth" Issue

The patient's report of a worm wrapped around their tooth most likely represents pinworm infection (Enterobius vermicularis), and you should perform a cellophane tape test applied to the perianal area first thing in the morning before bathing to confirm the diagnosis. 1

Why Pinworms Are the Most Likely Culprit

• Pinworms are the only common helminth that would plausibly be found in or around the mouth, as gravid female worms migrate from the perianal region and can occasionally be transferred to the oral cavity via contaminated hands 1
• The patient's negative stool ova and parasite examination does not rule out pinworms, as stool examination is not recommended for pinworm diagnosis because eggs and adult worms are not typically passed in stool 1
• The cellophane tape test is the preferred diagnostic method due to its simplicity and effectiveness, specifically designed to capture eggs deposited on perianal skin overnight 1

Diagnostic Approach for the Oral Worm

• Perform the cellophane tape test on three consecutive mornings before bathing or defecation to maximize sensitivity 1
• Ask specifically about nocturnal perianal itching, which is the most common symptom of pinworm infection 1
• In elderly patients, also inquire about irritability, weight loss, diarrhea, or abdominal pain 1

Treatment if Pinworms Confirmed

• Administer albendazole 400 mg orally as a single dose 2
• Consider treating all household contacts simultaneously, as pinworm transmission is common in close living quarters 1

The Blastocystis hominis Issue

Blastocystis hominis should only be treated if the patient is symptomatic with gastrointestinal complaints, as its pathogenicity remains controversial and it may represent normal intestinal flora in asymptomatic individuals. 3, 4

When to Treat Blastocystis hominis

• Treat if the patient has abdominal pain (most common symptom, 76.9% of cases), diarrhea (50%), or abdominal distention (32.6%) 4
• Treatment is warranted when intestinal symptoms are present and other bacteriological and parasitological agents have been excluded 4
• In asymptomatic patients, treatment is debated and generally not recommended 3

Treatment Regimen if Symptomatic

• First-line: Metronidazole 250-750 mg three times daily for 10 days 5, 6, 3
• Be aware that metronidazole has variable efficacy—only 33% eradication rate in severe infections in one study 5
• Alternative: Trimethoprim/sulfamethoxazole (TMP/SMX) 1 tablet three times daily for 10 days, though this has even lower efficacy (22% eradication) 5
• Follow-up stool examination should be performed 2 weeks after treatment completion 4

Important Caveats About Blastocystis Treatment

• Metronidazole induces intolerable side effects in some patients and has teratogenic and carcinogenic potential 7
• Treatment failures are common, and the organism can persist for weeks to years even with appropriate therapy 3, 7
• The organism exists in multiple morphological forms (vacuolar, granular, ameboid, cyst, avacuolar, multivacuolar), and laboratories typically only identify the vacuolar form, potentially missing infections 3

Clinical Algorithm

1. Immediately perform cellophane tape test on three consecutive mornings to diagnose pinworms 1
2. Assess for GI symptoms (abdominal pain, diarrhea, distention) to determine if Blastocystis treatment is warranted 4
3. If tape test positive: Treat with albendazole 400 mg single dose 2
4. If symptomatic with Blastocystis: Treat with metronidazole 250-750 mg TID for 10 days 5, 6
5. If asymptomatic with Blastocystis: No treatment necessary 3
6. Follow-up stool examination 2 weeks post-treatment if Blastocystis was treated 4