Giardia sp. in the Intestine of Nematodirus helvetianus (Nematoda: Trichostrongyloidea) Recovered at Necropsy from a Sheep (Ovis aries)

Abstract

Numerous trophozoites of a Giardia sp. were found in the intestinal tract of four female Nematodirus helvetianus recovered from a sheep at necropsy. Although no cysts or dividing trophozoites were seen in these worms, the number and viability of the trophozoites indicated colonization of the intestines of these nematodes. During an exercise on the post-mortem diagnosis of the parasites of the domestic sheep (Ovis aries Linnaeus, 1758), animals were euthanized and examined by groups of veterinary students. From one of these sheep, adult females of Nematodirus sp. were recovered, and each worm contained numerous specimens of Giardia within its intestinal lumen. Giardia has been reported previously in the intestinal tracts of trichostrongyloid nematodes (Dissanaike, 1954; Graham, 1935; Thomson, 1925), but such observations are of interest because of their infrequent occurrence. MATERIALS AND METHODS Fecal examinations were performed prior to necropsy using a zinc-sulfate flotation method. Four worms were collected from the intestinal tract of the sheep by repeated washing and sedimentation with tap water. All worms harbored trophozoites of Giardia sp. One worm was fixed in Karnovsky's fixative. Following fixation for 24 h, the worm was dehydrated, embedded in EponAraldite, sectioned, and examined using a Phillips 300 electron microscope. Two worms fixed in Bouin's fixative and the Epon-embedded specimen have been deposited with the USNM Helminthological Collection (81131).