EXPERIMENTAL DETECTION OF CANINE HEMOGLOBIN (OCCULT BLOOD) IN CANINE FECES BY REVERSED PASSIVE LATEX AGGLUTINATION

A reversed passive latex agglutination test (RPLA) using anti-canine h aemoglobin (Hb) antibody was developed for detecting bleeding in the l ower digestive organs in dogs, and its applicability as a simple test for faecal occult blood was assessed. In Ouchterlony's gel immunodiffu sion test, the anti-canine Hb antibody used to sensitize the latex rea cted with canine Hb but not with Hbs, plasmas or meat extracts from pi gs, goats, sheep, cattle, horses or chickens, or with fish extracts. U sing latex sensitized with 50 mu g/mg of anti-canine Hb IgG antibody, the lowest limit of detection for canine Hb was 21 mu g/ml, and the la tex reacted negatively with all test specimens other than canine Hb. I n an in vitro experiment with a mixture of canine faeces and erythrocy tes, the antigenicity of the Hb was found to undergo only very slight changes even when the specimens were allowed to stand for 12 h at room temperature. Hb could not be detected by RPLA in any of four successi ve faecal samples from three experimental dogs after infusion of autol ogous blood (5, 3 or 1 ml) into the stomach. In 3 other experimental d ogs given an infusion of autologous blood (5, 3 or 1 ml) into the asce nding colon, the presence of Hb was confirmed by RPLA in all four succ essive faecal samples obtained from those which received 5 or 3 ml of blood and in all except that obtained following the first defecation f rom the animal which had received 1 mi of blood.