A distinctive aphthous ileitis linked to Ancylostoma caninum

Ileal ulceration is diagnosed commonly at colonoscopy in northeastern Australia. This observation has occurred contemporaneously with the description of a painful enteritis caused through supposedly rare infections by Ancylostoma caninum, the cosmopolitan dog hookworm. In this study, we describe the morphology and prevalence of ileal ulcers and investigate their cause. There were 182 patients with a distinctive aphthous ileitis highlighted by haemorrhage into the tips of surrounding villi. The annual rate reached 4.7% of ileal examinations. Eosinophilic enteritis was the characteristic, but inconsistent, histological appearance. Ulceration was linked to infection by A. caninum through serological testing and, in three patients, by the retrieval of single hookworms. Affected patients were also more likely to own a dog (53%) than the total colonoscopic population (43%; P<0.02). The monthly rates of diagnosis were related to climate with fewest recordings during winter. Pain was the chief indication for colonoscopy (49%), proportionally higher than in controls (28%; P<0.0001). Patients with ulcers had increased blood eosinophil, immunoglobulin E and serological values. These results were higher still in the subset with pain compared with the rest. Most patients, however, had colonoscopy performed for unrelated reasons, such as bowel cancer surveillance, and were identified as having subclinical ulceration (rate 3.2%). The findings establish a distinctive aphthous ileitis characterized by tissue eosinophilia. The cause has been tentatively linked to canine hookworms. It is proposed that infection in this geographic region is common and only rarely does a painful enteritis develop as a consequence of hypersensitization.