IMMUNOLOGICAL INCRIMINATION OF ANCYLOSTOMA-CANINUM AS A HUMAN ENTERICPATHOGEN

In northeastern Australia, the incidence of human eosinophilic enterit is (EE) and unexplained abdominal pain with peripheral blood eosinophi lia (PE) appear to be exceptionally high. Because adults of the common dog hookworm, Ancylostoma caninum, were found in situ in several case s, we compared specific antibody responses in patients with EE or PE w ith those of individuals from various control groups. Sera were obtain ed from three patients with confirmed dog hookworm infection, 25 patie nts with EE/PE, 42 with other diagnosed gastrointestinal disorders, ei ght with human hookworm infection, 27 with other diagnosed parasitic i nfections, and 100 blood donors from the State of Tasmania, where A. c aninum does not occur. They were analyzed by enzyme-linked immunosorbe nt assay (ELISA) and Western blot for IgG and IgE antibodies to excret ory-secretory (ES) antigens from adult A. caninum. In the ELISA, sera from 88% of EE/PE patients were positive for IgG and IgE antibodies td ES antigen. All eight patients infected with human hookworm (identifi ed as A. duodenale in three) were also seropositive, while most of tho se with other parasitic infections, as well the blood donors, those wi th diagnosed gastrointestinal diseases, and the control subjects, were seronegative. In Western blots, sera from 92% of EE/PE patients demon strated IgG and IgE antibodies to a component of ES antigen with a mol ecular weight of approximately 68 kD (Ac68), as did all sera from case s infected with human hookworms. Among the patients with other gastroi ntestinal disorders and parasitic infections, four of 42 (10%) and thr ee of 27 (11%), respectively, reacted positively. These findings sugge st that A. caninum is a major cause of EE and PE in northeastern Austr alia, and that the disease represents an allergic response to hookworm secretions. The putative allergen, Ac68, appears also to be a suitabl e antigen for use in the serodiagnosis of these conditions, which are likely to occur wherever people are exposed to infective larvae of A. caninum.