Strongyle eggs are not found in the feces because the horses often have been dewormed, leading to removal of the adult worms. The disease, however, is caused by immature parasites that are not laying eggs. Because small strongyle infections are so common in horses and ponies, the potential for larval cyathostomosis to occur can be assumed to be quite high. The animal becomes weakened, but usually not depressed. A low-grade colic can occur that tends to be intermittent.
Death can occur in more severe cases.
Edema of the limbs and ventral abdomen might develop associated with lowered serum protein levels. With milder cases, the clinical manifestation can be an unexplained weight loss during the winter, with or without ventral edema. Tables 1-3 list the summary results of controlled efficacy studies. Table 1 is a summary of six published studies where ivermectin was evaluated for efficacy against the mucosal and lumenal stages of cyathostomes. While removal of larvae and adult cyathostomes in the intestinal lumen was mainly highly efficacious, the limited activity demonstrated against the mucosal larvae would not make ivermectin the drug of choice to prevent larval cyathostomosis in equines.