Intestinal Capillariasis

Intestinal capillariasis is a parasitic infection of the small intestine by Capillaria philippinensis, causing severe protein losing enteropathy, chronic diarrhoea and wasting. It is fatal without treatment.

It was first described in the Philippines in the 1960s and is endemic in the Philippines and Thailand, with cases in Japan, Taiwan, Egypt, Iran, India and travellers. It is acquired by eating raw or undercooked freshwater fish, and the worm multiplies within the host by autoinfection.

Pathophysiology.

Adult worms burrow in the mucosa of the jejunum and proximal ileum. Autoinfection increases the worm burden, causing villous damage, malabsorption of fat and protein, and loss of protein and electrolytes into the gut.

Chronic watery diarrhoea (5 to 10 stools daily), abdominal pain, borborygmi, anorexia, profound weight loss, oedema, hypokalaemia with weakness, hypoalbuminaemia, muscle wasting and, in untreated cases, death from cachexia, heart failure or sepsis in weeks to months.

Red flags.

• Severe hypokalaemia or arrhythmia.
• Anasarca or heart failure.
• Sepsis.
• Severe wasting.

Stool microscopy shows characteristic peanut shaped eggs with flattened bipolar plugs and striated shells, with larvae and adult worms in stool or intestinal biopsy. Eggs may be few, so repeat the test. Check potassium, albumin, calcium, magnesium and full blood count. Small bowel biopsy shows worms in the mucosa and villous atrophy. Eosinophilia is mild. Ask about fish consumption and travel.

Differential diagnosis.

• Strongyloidiasis.
• Giardiasis and other protozoal infections.
• Coeliac disease and tropical sprue.
• Whipple disease.
• Intestinal lymphoma.
• Other causes of protein losing enteropathy.

Give antiparasitic treatment for a long course to clear worms and prevent relapse from autoinfection, and replace fluid, electrolytes and protein.

• Albendazole: 400 mg orally once daily (or 200 mg twice daily) for 10 days; maximum 800 mg daily; monitor blood counts and liver tests; avoid in pregnancy and reduce in hepatic impairment.
• Mebendazole (alternative): 200 mg orally twice daily for 20 days; maximum 400 mg daily; monitor blood counts and liver tests; avoid in pregnancy.
• Potassium chloride: 20 to 40 mmol orally two to three times daily, with IV replacement when potassium is under 2.5 mmol/L; maximum 120 mmol daily orally; monitor potassium (aim 4.0 to 5.0 mmol/L), ECG and creatinine; reduce the dose in renal impairment.
• Albumin infusion (20%) for severe hypoalbuminaemia with oedema: 25 g IV once daily for 3 days; monitor for fluid overload; reduce in heart failure.

Replace magnesium (1.0 mmol/L or more), vitamins and trace elements, and give a high protein diet. Repeat stool examination at the end of treatment and 1 month later; treat again if eggs persist.

Monitoring. Daily electrolytes and weight in hospital; stool examination at end of treatment and at 1, 3 and 6 months.

Referral and escalation. Infectious disease and critical care for severe cases.

Special groups. Children need weight based dosing; albendazole 400 mg daily is used for children over 2 years.