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Title: PHYLOGENETIC ANALYSIS OF PARTIAL MITOCHONDRIAL CYTOCHROME OXIDASE C SUBUNITI & LARGE RIBOSOMAL RNA SEQUENCES & NUCLEAR INTERNAL TRANSCRIBED SPACER I SEQUENCES FROM SPECIES OF CYATHOSTOMINAE & STRONGYLINAE ... OF THE HORSE

Author
item MCDONNELL, A - UNIV GLASGOW, SCOTLAND
item LOVE, S - UNIV GLASGOW, SCOTLAND
item TAIT, A - UNIV GLASGOW, SCOTLAND
item Lichtenfels, James
item MATTHEWS, J - UNIV LIVERPOOL, UK

Submitted to: Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Strongyloid nematodes are a major cause of morbidity and mortality in equines in the United States. Resistance to antiparasitic drugs (currently the only means of controlling the nematodes) is common and alternative control methods for these parasites are needed. This research requires the identification and classification of more than 51 species of small strongyles parasitic in horses. Three nucleotide data sets, one nuclear (ITS-2) and two mitochondrial (COI and l- rRNA), were investigated in order to determine relationships among species of Strongylinae and Cyathostominae, intestinal parasites of the horse. The results supported the grouping of the Cyathostominea in a single tribe, grouped the genera Triodontophorus and Craterostomum separately from Strongylus but also separately from the the Cyathostominea, but failed to separate some closely related species within the Cyathostominea into genera defined morphologically. The results will be useful in developing predictive classifications to aid researchers worldwide working to control these economically important nematodes of horses, especially in the pharmaceutical industry, the Food and Drug Administration, and scientists evaluating biological control agents.

Technical Abstract: Three nucleotide data sets, one nuclear (ITS-2) and two mitochondrial (COI and 1-rRNA), have been investigated in order to determine relationships among species of Strongylinae and Cyathostominae, intestinal parasites of the horse. The data exhibited a strong mutational bias towards A and T and in the COI gene, silent sites appeared to saturate rapidly partly due to this substitution bias. Thus, the COI gene was found to be less phylogenetically informative than the 1-rRNA and ITS-2 genes. Combined analysis of the 1-rRNA and ITS-2 genes supported a monophyletic clade of the cyathostomes with Tridentoinfundibulum gobi, which has previously been classified as a nematode of "uncertain origin". The Strongylinae grouped consistently outside the clade containing the cyathostomes and T. gobi. Molecular analysis failed to provide strong evidence for the separation of cyathostomes into classical genera, previously defined by morphological classification.