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United States Department of Agriculture

Agricultural Research Service

Title: Ovejector Structure in the Haemonchinae of Ruminants (Nematoda: Trichostrongyloidea)

Authors
item Lichtenfels, James
item Pilitt, Patricia
item Gibbons, Lynda - UNIV OF LONDON

Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 19, 2003
Publication Date: October 15, 2003
Citation: LICHTENFELS, J.R., PILITT, P.A., GIBBONS, L.M. OVEJECTOR STRUCTURE IN THE HAEMONCHINAE OF RUMINANTS (NEMATODA: TRICHOSTRONGYLOIDEA). JOURNAL OF PARASITOLOGY. 89: 984-993. 2003.

Interpretive Summary: Species of the genera Haemonchus, Ashworthius and Mecistocirrus are pathogens of cattle, sheep, and goats, causing significant roduction losses due to morbidity, mortality, cost of treatment and suboptimal use of contaminated pastures. The identification and classification of these large stomach worms of ruminants is hampered by a lack of characters for studies of relatedness among the 21 species. The ovejectors of the nematodes are described and a revised terminology is recommended to provide additional characters for such studies. The information will improve the ability to identify endemic and exotic species that threaten economically important hosts, to evaluate biological and chemical treatment and control agents, determine the importance of reservoir hosts such as wildlife, evaluate emerging or imported pathogens and to prevent the importation of others.

Technical Abstract: Species of the subfamily Haemonchinae include some of the most important nematode parasites of domestic and wild ruminants. The use of ovejector structure in the phylogeny of these important parasites is hampered by differences among nematologists in the application of terminology and the recognition of homologous parts. Some workers recognize a sphincter with 2 parts, but others recognize only the proximal, rounded part of the sphincter and include the distal cylindrical part of the sphincter with the vestibule. The results of this study demonstrate that all sphincters of Haemonchinae of ruminants have 2-parts, although distinguishing the junction of part 2 of the sphincter and the vestibule is difficult in 1 of the 4 species of the genus Ashworthius that were studied, the sphincter of that species (A. patriciapilittae) clearly includes both a rounded sphincter-like part 1 and a cylindrical part 2. In an effort to encourage the application of a uniform terminology to homologous parts of the ovejector, we propose the use of the terms sphincter 1 for the rounded part and sphincter 2 for the cylindrical part. It is hoped that clarification of the terminology for ovejectors of the Haemonchinae will provide a model for ovejectors of the rest of the Trichostrongyloidea.

Last Modified: 10/23/2014
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