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| 1 |
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Description: Strongyles
Worms have different egg laying rates, some female worms like ascarids may lay 100,000 eggs per day, while others like strongyles, lay only a dozen or so. Ideally the worm eggs should be counted and differentiated as to type. |
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| 2 |
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| Description: It is impossible to differentiate eggs of large strongyles, from small strongyles, by microscope examination. |
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| 3 |
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| Description: Parasites are destructive in all horses regardless of age. The most serious damage occurs in young horses during their first two years of life. |
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| 4 |
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| Description: Nematodes, large strongyles. All strongyles complete their lifecycle in their definitive host. |
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| 5 |
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| Description: The adult large strongyles damage the mucosa of the cecum and the ventral colon while sucking blood. Large, strongyles are the most dangerous parasite infecting the horse. |
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| 6 |
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| Description: Infective larva can often survive a winter or a summer drought, because they are enclosed in a sheath that protects them from unfavorable, harsh environmental conditions. |
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| 7 |
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| Description: Strongylus vulgaris: The larva is particularly evident in the anterior mesenteric artery and its branches where they can cause thrombosis, aneurysms, and embolisms. |
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| 8 |
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| Description: Some enter the aorta and travel anterior to the heart and posterior to the renal and iliac arteries. |
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| 9 |
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| Description: The accumulated larvae tend to remain in the anterior mesenteric artery and may eventually develop into adults. |
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| 10 |
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| Description: Sexually mature S.vulgaris, worms finally develop after leaving their pea sized nodule incysted in the walls of the cecum and the large colon. The entire process of migration and development is completed about 6 months post infection. |
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| 11 |
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| Description: S.Vulgaris, is estimated to be the cause of 90% of colic in horses. Where effective parasitic control measures are not practiced. |
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| 12 |
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| Description: The adult strongyles are active blood feeders, causing anemia, weakness, emaciation and diarrhea. |
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| 13 |
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| Description: S.edentatus: the migratory path followed by S.edentatus larva is distinctly different from S.Vulgaris. The larva penetrate the intestinal mucosa principally in the cecum and travel through the portal vein to the liver where the primary damage is caused. |
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| 14 |
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| Description: Eventually the larvae reach the hepatic ligaments then proceed under the peritoneal lining of the abdominal cavity. |
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| 15 |
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| Description: Peritonitis may also be present. The sirosal surfaces of abdominal organs become roughened and inflamed with diffuse fibrin deposits. |
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| 16 |
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| Description: Further migration brings them to the gut wall where edematous lesions are found on the mucosal surfaces. The migration and development from infectious larva to egg laying adults occur in 11 months. |
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| 17 |
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| Description: Small strongyles are less harmful than large strongyles during their larval migration because the path of their migration is limited to the intestinal walls. Heavy worm burdens of small strongyles cause weight loss and symptoms of chronic parasitism. |
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| 18 |
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| Description: One family causes typical ulcers of the dorsal colon mucosa. |
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| 19 |
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Description: Ascarids:
Parascaris equorum; infections of this large roundworm are common. Especially in foals, sucklings, and weanlings and to a lesser extend in yearlings and 2-year-old horses. The infectious eggs are ingested in contaminated grass, feed and water. These eggs hold ascarid embryos. Migration and development require 10 weeks. And a complete cycle can take as little as 3 months.
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| 20 |
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| Description: Mature ascarids inhabit the anterior and mid portions of the small intestine. |
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| 21 |
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| Description: Eggs are passed to the outside in feces. |
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| 22 |
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| Description: The primary danger is the rupture of the small intestine caused by masses of worms resulting in fatal peritonitis. |
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| 23 |
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| Description: Intestinal rupture occurs along the line of mesenteric attachment. Blood vessels enter where the musculature is weakest. |
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| 24 |
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Description: Pinworms;
Oxyuris equi; Pinworm eggs adhere to stable structures such as fence posts, walls, bedding and so on. The development of infective larvae occurs in 3 to 5 days. The larvae become mixed with grass, water and feed where they are consumed.
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| 25 |
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| Description: The larvae develop in the colon in 3 to 10 days and are sexually mature in about 5 months. |
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| 26 |
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| Description: Adult pinworms are commonly found in foals but are rarely found in adult horses. |
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| 27 |
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| Description: The principle effect in pinworm infection is anal irritation caused by deposits of ruptured females. This results in loss of hair from the tail. |
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| 28 |
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Description: Stomach Worms:
Of the 3 species of stomach worms (spiurids) found in the equine stomach, Drachia megastoma produces the most severe lesions which may rupture and lead to a fatal peritonitis. The miniature stomach worm, Trichostrongylus axei, is usually found in sheep, cattle, and goats, but can infect horses. |
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| 29 |
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Description: Cestodes:
Tapeworms. Of the 2 species effecting horses, Anaplocephala perfoliata occurs more commonly than Anaplocephala magna. A.Magna is found in the distal half of the small intestine. A.perfoliata clusters around the ileo-cecal valve in the cecum. |
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| 30 |
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| Description: A.perfoliata result in severe ulcerations of the mucosa due to the clustering of the parasite. |
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| 31 |
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Description: Botts:
Embryonated eggs of Gastrophilius intestanilis do not hatch spontaneously, but must be stimulated by the moisture, warmth and action of the horse's lip. The eggs of G.nasalis hatch after 1 week of development when they first contain infective first instar larva. |
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| 32 |
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| Description: In either case, the first instar larvae invade the oral tissue and cause periodontal ulcers. |
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| 33 |
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| Description: After 3 weeks of growth and development, they proceed to the stomach and emerge into second instar larvae. |
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| 34 |
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| Description: Further growth and development to third instar larvae occurs in the stomach. This growth and development may take up to 10 months before they pass into the feces. |
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| 35 |
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| Description: Both species produce deep pits at the point of attachment and occasionally these perforate the wall and result in fatal peritonitis. However, normal infection of bott larvae is not as dangerous as that of S.Vulgaris. |
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| 36 |
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| Description: Oral ulcers from bott infection. |
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| 37 |
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| Description: Bott larvae inside the stomach. |
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| 38 |
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| Description: Bott larvae inside the stomach. |
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