9 Most Common Internal Horse Parasites

It is important to realize that this worm has been quite good at developing resistance to deworming medications. To prevent a time when no medication effectively treats any horse with small strongyles work with your veterinarian to develop a deworming strategy that considers season and how many worm eggs your horse is shedding in its manure at any given time fecal egg count2  .
Large Strongyles
Large strongyles used to be a major

cause of colic and death in horses. Also known as the equine bloodworm these worms are ingested from pasture but migrate into the bloodstream of the large intestine as larvae before moving back into the large intestine as adults to release eggs. Arterial irritation by worm migration cause clots to form and migrate while blockage of vessels can lead to loss of oxygencarrying blood supply to part or all of the intestine causing damage that often cannot be repaired even surgically3.
Luckily this worm is still very sensitive to dewormers and effective against small strongyles so your deworming strategy against cyathostomins should also be effective against large strongyles.
Tapeworms
Tapeworms are the third most clinically significant internal parasite of the adult horse. They have worldwide distribution but are less common in arid