Large-Strongyle Infestation

a disease caused by strongyles (palisade worms) that parasitize the intestine of horses and, less commonly, asses and mules.

Large-strongyle infestation is prevalent throughout the world. The causative agents develop without the participation of intermediate hosts. Most susceptible to infection are young animals in which the larvae complete their migration. Larvae of the species Strongylus equinus penetrate the pancreas, larvae of Alfortia edentatus settle under the serous membrane of the peritoneum, and larvae of Delafondia vulgaris enter the mesenteric artery. The larvae of some trichonematid species penetrate the intestinal wall. After further development the larvae emerge to the intestinal lumen, where they are transformed into mature worms and where the females deposit eggs. Invasive larvae develop from the eggs, which are passed in the feces, usually onto a pasture, where they are ingested by foraging animals.

The parasites inhibit the growth and development of foals. Symptoms include loss of appetite, digestive disorders, and emaciation. Infection by Delafondia vulgaris is characterized by attacks of intestinal colic that are often fatal. Large-strongyle infestation sometimes occurs without pronounced symptoms.

Systematic prophylaxis on infected farms involves the administration to susceptible animals of anthelmintics, such as pheno-thiazine and carbon tetrachloride. Pastures should be changed every five to seven days, and infected pastures should be left fallow for one year.