encysted larval stage—the stage that causes the most damage - and resistance has been documented to one of these. Ask your veterinarian which products are currently most effective. Roundworms Roundworms, or ascarids, are most often a problem in young horses (especially foals, weanlings and yearlings). Adult roundworms are several inches long and almost the width of a pencil; in large numbers they can cause blockage (or impaction) of the intestine. In addition, roundworm larvae migrate through the internal organs until they reach the lungs. They are then coughed up and swallowed back into the digestive tract to complete their life cycle. Virtually all foals become infected with roundworms, and very few of them ever develop symptoms of disease. However, large infections can lead blockage of the small intestine of foals and young horses, leading to a painful and life-threatening colic. Roundworm infection in young horses can cause coughing, poor body condition and growth, rough coat, pot belly and colic. Colic is most likely in older foals (over 3 months of age) that are heavily parasitized with roundworms when dewormed for the first time. By this stage, the roundworms can have matured into adults that could cause an impaction. In this situation, it is a good idea to have your veterinarian deworm the foal or recommend a deworming plan for the foal. Resistance to many of the dewormers has become a big problem in controlling ascarid infections in foals. Tapeworms Like with the other parasites mentioned here, the large majority of horses harbor tapeworm infections without showing any signs of disease or discomfort. However, tapeworms can cause colic, ranging from mild cramping to severe colic that requires surgical treatment. The tapeworm life cycle involves a tiny pasture mite as an intermediate host, and horses are at a risk of developing tapeworm infection when they eat this mite in the grass. Praziquantel has been demonstrated to be highly effective against tapeworms and is available in several dewormer products. Pyrantel pamoate given in a double dose is effective as well. Most horses should be dewormed for tapeworms annually. Consult your veterinarian for advice on the best product to use for your situation. Other Internal Parasites
Large strongyles (bloodworms) have become extremely rare in managed horses because they are effectively controlled by most available dewormers. Infection with these parasites can cause unthriftiness, weight loss, poor growth in young horses, anemia (low numbers of red blood cells) and colic. In most cases, colic caused by these parasites is relatively mild, but severe infections can result in loss of blood supply to a portion of the intestine, leading to severe and potentially fatal colic. Pinworms lay their eggs on the skin around the horse's anus. The irritation they cause makes the horse repeatedly rub its tail.
You've reached the end of your free preview.
Want to read all 6 pages?
- Fall '15
- Parasitology, Tapeworm infection, Veterinarian, colic