OCCURRENCE OF LARVAL CYATHOSTOMIASIS IN H ORSES

In January 1995 and in January/February 1997 12 young horses with an a ge between 1 1/2 and 4 years and 5 three years old mares on a farm wit h 400 Haflinger horses had moderate or severe diarrhoea. Two horses di ed on the farm and two horses were destroyed after unsuccessful treatm ent. The clinical and pathological findings were severe weight loss, w atery diarrhoea and hypoalbuminemia. Based on the clinical signs, the parasitological results an the extremely hypoalbuminemia (10,0 g/l) th e diagnosis of the sick mare was larval cyathostomiasis. Encysted larv ae of Cyathostominae were detected microscopically in the caecum and l arge colon of rite stallion respectively in the Lamina propria mucosae and Tela submucosa. A piece of 100 cm(2) from the caecum was digested with pepsin and hydrochloric acid and 46250 larvae of small strongyle s (41150 third-stage larvae, 5100 fourth-stage larvae) were counted af ter sedimentation. In 1995 the sick horses on the farm were treated wi th 300 mu g ivermectin/kg b.w. orally every 3 weeks 2 to 4 times based on the severity of diarrhoea. Normal faeces were observed in horses w ith moderate diarrhoea after 3 weeks and in horses with watery diarrho ea 6 weeks after treatment. In 1997 the diseased horses were treated 3 times every 2 weeks with ivermectin. Prophylactical use of a broad sp ectrum anthelmintic (ivermectin) three times a year (at the beginning of the grazing season, July, November) and pasture hygiene (alternativ e grazing, pasture changing, collection of faeces) provide successful small strongyles control.