A Case Study of Human Infection with Necator americanus (Nematoda: Ancylostomatoidea) Found in Okayama Prefecture, Japan
A rare case of human necatoriasis found in Okayama Prefecture, Japan is reported. The patient was an 81-year-old woman residing in Soja City, Okayama Prefecture, Japan. She had repeatedly been admitted to Department of Medicine, Okayama Municipal Kibi Hospital and discharged from the hospital due to regurgitant esophagitis, cerebral infarction, superficial burn and provisional diagnosis of headache, constipation, thoracic discomfort, palpitation of the heart, and other complaints since 1991. On June 17th, 1996, adult worms of hookworm-like nematode were incidentally discovered on the mucous membrane of duodenal bulb of the patient by gastroenteroscopic examination when she readmitted to the hospital in order to take therapy for severe headache and palpitation. Two adult nematodes, one each of male and female were carefully removed from duodenal mucous membrane with a biopsy forceps. The removed nematodes were identified as adult worm of Necator americanus (Stiles, 1902) Stiles, 1906 based on morphological characteristics of cutting plates, male copulatory bursa and rays, and female caudal end. No characteristic symptom of the patient caused by adult N. americanus infection was recognized, and species specific eggs were not found in feces of the patient. The patient had a habit to eat fresh green vegetables, although a reliable route of infection was not clear. To our best knowledge, the present report deals with the first finding of human infection with N. americanus in Okayama Prefecture, Japan.