THE MERCK VETERINARY MANUAL
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Trichostrongylus sp in Horses

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The small stomach worm (hairworm) of horses, Trichostrongylus axei, is also found in ruminants (see Trichostrongylussp in Horses) and, consequently, is generally a clinical problem only in horses commingled or rotated on pasture with ruminants. Adult T axei are slender and measure up to 8 mm long. Details of the life cycle in Equidae have not been carefully studied, but it is known that the larvae penetrate the mucosa. These worms produce a chronic catarrhal gastritis, which may result in weight loss. The lesions comprise nodular areas of thickened mucosa surrounded by a zone of congestion and covered with a variable amount of mucus. The lesions may be rather small and irregularly circumscribed, or they may coalesce and involve most or all of the glandular portion of the stomach, and erosions and ulcerations may be seen.

Definitive diagnosis based on fecal examination is difficult, because the eggs are similar to strongyle eggs. The feces can be cultured and, in ~7 days, the infective larvae identified. Some of the benzimidazoles and ivermectin are effective against T axei.

Last full review/revision October 2014 by Thomas R. Klei, PhD

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