Gastrointestinal Nematode Parasites from Domestic Sheep, Ovis aries, in Nebraska

Abstract

Necropsies of 80 domestic lambs from Nebraska established the presence of the following 14 nematode parasites in that state: Haemonchus contortus, Ostertagia circumcincta, Trichostrongylus axei, Pseudostertagia bullosa, T. colubriformis, Strongyloides papillosus, Nematodirus spathiger, N. abnormalis, N. helvetianus, N. oiratianus, Cooperia curticei, C. oncophora, C. surnabada, and Trichuris spp. In general, small numbers of worms were recovered. This study confirms the presence in Nebraska of the common species of sheep nematodes and establishes new distribution records for P. bullosa, N. helvetianus, N. oiratianus, and C. surnabada. Little information is found in the literature concerning nematode parasites of sheep from Nebraska. Kelley (1955) made an oral report at the Conference on Parasites and Parasitic Diseases of Domestic Ruminants, which was later reproduced for limited distribution. In his report he listed nematodes recovered from cattle, and spoke of Haemonchus contortus, and Nematodirus spp. in sheep. The revised checklist of internal and external parasites of domestic animals in the United States and possessions and Canada (Becklund, 1964) states only that the geographical distribution of the common nematode species from sheep is generally in North America. Geographical distributions of the more uncommon species are recorded as specific areas where they have been recovered. Only one of these records includes Nebraska. Becklund and Walker (1967) reported Nematodirus spathiger and N. abnormalis in one lot of specimens collected from Nebraska sheep. With the opening of the U. S. Meat Animal Research Center, Clay Center, Nebraska, a comprehensive research program on sheep began. This program afforded the authors an opportunity to examine the viscera of some Nebraska lambs for gastrointestinal nematode parasites to establish further the presence of specific parasites in this state. The results of these examinations and information on the species recovered, including several new distribution records, are reported herein. MATERIALS AND METHODS Eighty lambs from the Meat Animal Research Center, Clay Center, Nebraska, were necropsied, 37 in January and 43 in July 1967. Suffolks, TarReceived for publication 24 February 1970. ghees, Corriedales, and various crossbred lambs were represented. All lambs were born at Clay Center, though their dams, except for the Corriedales, had been brought to Clay Center from Fort Wingate, New Mexico, in April 1966. The Corriedale ewes originated in Nebraska. The lambs which were killed and examined in January 1967 were born in May-June 1966; lambs killed in July 1967 were born in February-March 1967. Each group grazed the same permanent pastures but in different seasons in successive years. The lambs were killed at an abattoir, and the viscera were collected, frozen with dry ice, and taken to the Parasitological Laboratory at Beltsville, Maryland. There they were thawed and the procedures of Porter (1942) and Herlich (1956) were used to recover and enumerate the various nematode parasites. Representative specimens of most of the helminths recovered were deposited in the National Parasite Collection (Table I).