Outbreak of larval cyathostomiasis among a group of yearling and two-year-old horses.

Larval cyathostomiasis was diagnosed as the cause of an outbreak of illness in a group of five young horses. One had the typical clinical signs of larval cyathostomiasis--sudden onset diarrhoea, weight loss, ventral abdominal oedema and pyrexia, but the other four suddenly started to lose weight rapidly and had limb and ventral abdominal oedema and pyrexia, in the absence of diarrhoea. Large numbers of cyathostome larvae were found in the faeces. Four of the five horses recovered after being treated with anthelmintics and steroids.