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Equine Parasite Definitions:
(Note diagnosing horses requires Veterinarian consultation - Click Here For A List of Florida Veterinarians)
Ascarids (Parascaris Equorum): Also known as Large Roundworms. These are the largest parasites reaching a length of up to 30cm long and about the thickness of a pencil. Their eggs, which contain the infective larvae, are well protected by a thick sticky outer coat that enables them to survive for years on pasture and in stables. Horses and foals become infected by swallowing the eggs picked up from the pasture or from cracks and crevices in contaminated stabling.
These can be present in the foal's small intestine from 12 weeks of age. Adult worms can stop weight gain and lead to the emaciation of the foal. Heavy burdens can block the gut causing digestive problems and in rare cases a fatal blockage or rupture of the gut.
The larvae migrate through the bloodstream to the liver and lungs before returning to the small Intestine to develop into adults again. Migrating larval stages can cause 'summer colds' with fever, coughing and loss of appetite as they migrate through the lungs. Foals develop their own immunity to these worms at about 18 months of age.
Ascarids Treatment: (Click Here To See A Treatment List)
Bot Fly (Gasterophilus spp): Commonly called Bots. Bots are insects not worms; they are the larvae of Bot Flies. They are the most common parasite of the stomach affecting horses of any age. Depending on the species, and there are several different types, the eggs are laid on the legs or around the muzzle of your horse. Female adult bot flies resemble bees and are often a considerable annoyance to the horse when laying eggs. After hatching, the larvae get into the horses mouth and burrow into the base of the tongue and below the gum line. After approximately a month in the mouth, during which they double in size, the bot larvae move on and attach themselves to the stomach lining where they develop into the full grown Bots.
Bots can cause ulcers in the stomach wall even penetrating the wall with fatal results. It has recently been discovered that they will also attach themselves in clumps to the first part of the intestines causing similar problems. This poses a special danger for small breeds and to young horses whose stomach and intestines are likely to be thinner and more easily damaged.
Bot Fly Life Cycle: Bots remain inside the horse until the spring when they pass out in the manure. They then pupate underground until the adult flies emerge in the summer months and begin to lay their eggs. The first hard frost kills off the adult flies so no re-infection will take place over the winter, resulting in targeted treatment following the first hard frost.
Bot Fly Treatment: (Click Here To See A Treatment List)
Lung Worm (Dictyocaulus arnfieldi): Larvae infest forage and are eaten by horses. They migrate through the blood stream to the main airways where they develop into adults. Eggs that are laid are coughed up or passed out in the feces. Lungworm causes respiratory problems and persistent coughing in adult horses. Symptoms are rarely seen in foals or donkeys, but they can act as carriers for the parasite.
Lung Worm Treatment: (Click Here To See A Treatment List)
Pinworms (Oxyuris equi): The pinworm; also known as threadworm or seat worm is a common intestinal parasite in humans and animals. The medical condition associated with pinworm infestation is known as enterobiasis, or sometimes oxyuriasis.
Pinworms can affect horses of any age; they are small, white round worms which live in the large intestine and around the anus. The females can be up to 10cm long and lay their yellow, sticky eggs on the skin around the outside of the anus. This causes intense irritation. Horses become infected by swallowing the eggs from multiple sources in the stable or onto paddock.
Pinworm Transmission: Horses acquire pinworms through contaminated food, water or bedding. Do not place your water buckets too close to hay or grain feeders. If you're finding a lot of excess hay or grain in the buckets, they're too close. Use elevated feeders when providing hay or grain---this prevents ground-dwelling parasites from contacting the feed. Keep stalls and pastures as tidy as possible; clean stalls daily and pick manure up regularly---at least twice a week.
Pinworm Symptoms: Pinworm Symptoms include rubbing and biting at the tail base. It is essential that separate sponges are used to clean the dock and head areas.
Pinworms Diagnosis: Pinworms are diagnosed by symptoms (tail rubbing and intense itching) and by the tape test; your veterinarian may use a piece of sticky tape to capture samples. Pinworms tend to travel by night, so perform this test as early as possible in the morning. Simply press a piece of sticky tape around your horse's anus. The results can be viewed under a microscope for accurate diagnosis.
Pinworm Treatment: (Click Here To See A Treatment List)
Natural Treatment of Pinworms
Oil Pinworm Treatment: Oils can suffocate pinworm larvae. Many horse owners have used mineral or baby oil to treat pinworms, but there are better choices. Consider olive oil as an alternative; as it is a safe, non-toxic oil that works well. Tea tree oil is an excellent antiviral and Neem oil has insecticidal qualities. Calendula oil is very soothing and can be used regularly. These oils can be mixed according to your preferences or used singly. Wipe the dock and tail area, coating thoroughly with oil. Repeat twice a day.
Diatomaceous Earth Pinworm Treatment: Diatomaceous earth, the powdered, fossilized shells of algae, is an excellent all-around insecticide. Shaken around the stall area, the microscopically sharp crystals lacerate and dehydrate eggs and worms. It can also be taken internally as a de-wormer. It works mechanically (by lacerating the worms) rather than chemically, so there is no risk of the drug resistance problems that are appearing in many chemical de-wormers.
Strongyloides is a genus of parasitic nematodes generally know as Roundworms.
Large Strongles (Strongylus vulgaris): Also known as Blood Worm is a large nematode (round worm) intestinal parasite of horses. Also known as blood worm, red worm, palisade worm, or just a large strongyles, it is one of the most dangerous horse parasites. An adult is actually quite small—only 14-24mm long. Like the hookworms of humans, it lives attached to the intestinal lining with a plug of intestinal tissue filling its mouth.
S. vulgaris adults live in the intestine. Larvae migrate in blood vessels. This is a deadly parasite of horses in temperate zones all over the world. S. vulgaris is found in temperate regions of the world (the zone between the tropics and the arctic) in grasslands wherever there are horses. Horses that graze together in areas where infected horses regularly graze are at greatest risk of infection. Early stages of larvae in the pasture—before they reach the infective stage—are quite susceptible to drying; therefore, a spell of hot dry weather, and breaking up of horse droppings, can greatly reduce the numbers of larvae.
S. vulgaris Life Cycle: The life cycle of S. vulgaris depends on horses grazing where droppings from infected horses contaminate the grass. Infective larvae present on vegetation in the pasture are swallowed by grazing horses. They travel to the small intestine where they shed their outer sheath, or skin. Larvae penetrate the intestinal lining of the horse and undergo a short period of development in the tissues there. Larvae migrate to arteries, particularly the mesenteric artery, where they remain, moving along the artery walls, for three to four months. They often lodge in the posterior aorta (the main vessel carrying oxygenated blood from the heart to the tissues). Larvae are pre-adult at about four months after infection. At this stage, they are found in nodules in the intestinal arteries. Pre-adults move into the intestine and attach themselves to the intestinal lining in the cecum (the first part of the large intestine after the small intestine). S. vulgaris worms mature in the intestine after six to eight weeks. They suck blood and produce eggs that are passed in the horse’s droppings. Eggs deposited outside in warm moist conditions soon hatch. Larvae develop to the infective stage in one to two weeks
S. vulgaris Treatment: (Click Here To See A Treatment List)
Small Strongles (Strongyles Trichonemaspp): Small Strongles are small nematodes (round worms) intestinal parasite of horses. Also know as Cyathostomes or Small Red worm.
S. Trichonemaspp is the most common parasite to effect your horse, with horses under 6 years of age being most at risk. The S. Trichonemaspp grows up to 2.5cm long, are thin and can range in color from white to red. S. Trichonemaspp larvae are picked up by horses while grazing. Historically the key period of risk was spring and summer, however recent climatic changes mean that Spring and Autumn have now become the periods of greatest risk. Worryingly recent studies involving monitoring pasture infectivity have shown high levels of infective larvae present on turnout paddocks even in January after snow, highlighting the importance of winter worming.
S. Trichonemaspp larvae can develop into adults within a period of five weeks; however in the autumn their development is prolonged remaining in cysts as tiny inhibited larvae within the gut wall, broadly termed encysted larvae. In the late winter or spring an unknown trigger causes these larvae to resume their development, simultaneous emergence of large numbers of 4th-stage larvae include colic, weight loss and diarrhea causing devastating damage to the large intestine with potentially fatal results. Even before emergence large numbers of encysted larvae can cause fatal illnesses accounting for over 90% of the total S. Trichonemaspp burden.
S. Trichonemaspp Life Cycle: The life cycle of the S. Trichonemaspp (cyathostomes) is very similar to large strongyles except the larvae do not migrate beyond the wall of the intestines. The larvae burrow in or encyst in the wall of the large colon. Horses with heavy infestations will show clinical signs of diarrhea and negative growth performance. These clinical signs usually occur when large numbers of the encysted cyathostomes emerge from the gut wall, resulting in inflammation. The severity of clinical signs is related to the degree of damage to the intestines, which varies with the level of infection. At present, it is unclear why the cyathostomes tend to emerge all at once. It is postulated that the occurrence of larval cyathostomosis may be associated with:
S. Trichonemaspp Treatment: (Click Here To See A Treatment List)
Tapeworms (Anoplocephala perfoliata): There are three species which infect horses and horses only:
As we learn more about tapeworms, our understanding grows that they are an important cause of both medical and surgical colic cases in equines. Tapeworms affect horses of any age. They were once considered a fairly benign parasite, unassociated with serious problems in equines. But recent studies show tapeworms are anything but harmless. Consider the statistics:
Tapeworm Life Cycle: The life cycle of the Tapeworm is around 3 months. The intermediate hosts are mites who eat the larvae and are then accidentally consumed by horses. When they mature, they are cream colored growing in segments up to 10cm long with the segments containing eggs. Tapeworm eggs are passed out in the manure and eaten by a microscopic mite called forage mites, which live on the pasture and completing the cycle. These mites containing tapeworm larvae can easily remain active in the winter by surviving in hay and bedding. Therefore re-infestation can take place throughout the year.
The adult worms attach themselves at the junction of the small and large intestine. In large numbers Tapeworms can cause local irritation and thickening at the site of attachment. Tapeworms are a recognized cause of certain types of colic in horses and can cause severe internal problems. Upon laboratory analysis if your horse were found to have a high tapeworm burden, an appropriate treatment may be a double dose of Tetrahydropirimidines- Pyrantel Embonate Based Wormers every six months (April & October).
Tapeworms Treatment: (Click Here To See A Treatment List)
Threadworms (Strongyloides Westeri): Also known as Intestinal Threadworms. Threadworms are long and hair like. Adults grow to be 8 to 9 mm in length (about 2/5 inch).
Threadworm life cycle: Larvae mature to adult worms in the small intestine. Infection can occur by eating infective larvae or by penetration through the skin. If the larvae enter the horse's system through its skin, they move to the lungs, then up the wind pipe where they are coughed up and swallowed. They mature in the small intestine, where adult females lay the eggs that are passed out in the manure. How the parasite enters the horse's system: The infective larvae of the threadworm can either be swallowed by the horse or the larvae can go through the horse's skin. Young foals can also be exposed to the worm by nursing from their infected mothers. Effects of parasite if left untreated: If the larvae enter through the skin the next stop is the lungs, where they can cause bleeding and respiratory problems. Inflammation and rashes can develop where the larvae penetrated the skin. The worst damage occurs in untreated foals. Infected through their mothers' milk, they can suffer diarrhea, weakness, weight loss and failure to thrive and grow at a normal rate. Veterinarians generally recommend de-worming your foal early in life and as often as every month until weaning. Diarrhea in 7-10 day old foals may be caused by intestinal threadworms. De-worming may be beneficial in these cases. Be very careful to read your de-wormer's label - some products cannot be used on foals this young
Threadworms Treatment: (Click Here To See A Treatment List)
