Strongyles are species of most damaging internal parasites. Strongyles, are divided into two groups, called the large strongyles and the small strongyles. The harmful effects of large strongyles are much greater than of the small ones. The larvae of large strongyles damage blood vessels, while the larvae of small strongyles remains in the wall of the gut.
A horse gets infected by ingesting larvae present in grass and forage.
Large Strongyles (Bloodworms). One of the three species, Strongyle vulgaris, is the most harmful because its larvae enter the arteries, creates blood clots which block small vessels. This destroys part of the blood supply to bowels and other digestive organs.
The larvae live in the arteries for about 5 months, then return to the intestine and develop into adult worms, where they attach to the wall of the bowel. A heavy infection can cause severe anemia
Small Strongyles. Small strongyles are the most common internal parasites in adult horses and occur frequently in foals. Larvae produce colic, bleeding and anemia, protein loss, and intestinal malabsorption.
PREVENTION OF STRONGYLES.
Control of strongyles is most important in all deworming programs. Since the arterial worms are not killed by most dewormers(except for ivermectin), it is extremely important to eliminate the larvae at early stages. An occasional treatment does not offer protection and will not prevent the potentially devastating consequences of these parasites. Most veterinary experts recommend the inclusion of ivermectin in all deworming programs.