Eight desert sheep were each infected orally with 500 metacercariae of Fasciola gigantica and, after 4 weeks, four of the animals were given
niclofolan orally at the recommended therapeutic dose rate of 7 mg/kg, the other four remaining as controls. One week later, the animals were slaughtered and the fasciocidal effect of the
drug was evaluated on the basis of worm burden, haemogram, some plasma constituents, and gross and histopathological lesions of the liver, as indicators of efficacy. The treatment was found to be ineffective, the degree of
infection remaining the same as in the untreated control group. The experiment was repeated using eight infected sheep: four were given the
drug orally at a dose rate of 10.5 mg/kg, i.e., 1.5 times the recommended dose; and the same parameters were measured as described above. The
drug failed to cure the infected sheep, and caused depression,
anorexia and weakness. In a third experiment six sheep were infected as before and three were treated with
niclofolan by deep i.m. injection at the recommended therapeutic dose of 2 mg/kg. A week later the animals were killed and examined as before. The
drug was effective in treating the
infection and produced no untoward effects except for transient signs of
pain at the site of injection. It seems possible that the oral dose, unlike the i.m. dose, of
niclofolan is not absorbed and/or metabolized sufficiently to prevent elimination of the
infection.