*'''Aberrant migration of intestinal helminths''' may cause an obstruction if they enter the common bile duct. This has been reported with ''[[Ascaris suum]]'' in pigs and ''[[Parascaris equorum]]'' in horses and it may occur after these animals have been treated with an anthelmintic that causes spasticity of the parasite muscles. | *'''Aberrant migration of intestinal helminths''' may cause an obstruction if they enter the common bile duct. This has been reported with ''[[Ascaris suum]]'' in pigs and ''[[Parascaris equorum]]'' in horses and it may occur after these animals have been treated with an anthelmintic that causes spasticity of the parasite muscles. |