Serial stool examinations should be obtained in the weeks and months after therapy to confirm eradication of the parasite. Infection is most common in Asia and is acquired by consuming food that harbors infectious larvae. Adult worms attach to the proximal small bowel and in most cases do not produce symptoms. The eggs of Trichostrongylus are somewhat larger and have less rounded ends than hookworm eggs. Most human infection with Capillaria is caused by C. philippinensis, which is found primarily in the northern Philippines and Thailand.
Humans acquire the infection by eating raw freshwater fish.
Symptomatic intestinal capillariasis is marked by diarrhea and abdominal pain. When infection is severe, edema, muscle wasting, fat and sugar malabsorption, and a protein-losing enteropathy may ensue. If left untreated, severe infection may result in death after several months. A. ceylonicum, a widely distributed canine and feline parasite of the tropics and subtropics, can cause intestinal infections in humans. Like human hookworm parasites, the sexually mature, egg-laying adult worms of this species can cause blood loss and consequent iron deficiency.