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28 Cards in this Set
- Front
- Back
What are the morphologically characteristics of strongyles?
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1. Well developed mouth and buccal cavity
2. Mouth OFTEN has a corona radiata 3. Teeth/cutting plates at BASE of buccal cavity 4. Males: have large bursa and spicules |
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What are the life cycle characteristics of strongyles?
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1. Direct
2. Adults mainly parasites of host GI tract 3. Infection usually acquired by ingestion of L3 Primarily parasites of herbivores. |
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What kinds of equine strongyles are there?
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1. Large strongyles: most pathogenic - larval migration pathways
2. Small strongyles: less pathogenic - larvae only migrate in gut mucosa |
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What is the morphology of large strongyles?
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They have a well developed globoid buccal capsule and females are oviparous and produce typical strongyle type eggs.
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What is the morphology of small strongyles?
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They have a short buccal capsule that is more shallow and females are oviparous and produce typical strongyle type eggs.
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Name the 3 large strongyles and morphology of each.
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1. Strongylus equinus: 3 teeth and adults are 2.5 to 4.7 cm long
2. Strongylus vulgaris: 2 teeth and adults are 1.5 to 2.5 cm long 3. Strongylus edentatus: no teeth and adults are 2.5 to 4.5 cm long. |
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How do large strongyles feed?
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Adults suck blood - common names are blood worms and red worms
Plug of gut mucosa sucked into buccal capsule and then teeth lacerate mucosal plug. |
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What is the life cycle of Strongylus spp?
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Direct life cycle: Adults lay eggs in cecum and/or colon. Strongylid eggs with morula end in feces.
In the environment: L1 develops in egg --> L1 hatches --> L2 --> infective sheathed L3 (resistant to drying/cold and can't feed). L3s are ingested on herbage. In new host: L3 ex-sheath and penetrate mucosa of intestinal tract. Molt to L4 in submucosa in 1 week and migrates to specific area of species. |
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What is the migration path of S. vulgaris larvae? (Prepatent period is 6 months)
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Penetrate small arterioles of GI tract and migrate within intima to larger artery branches
Reach cranial mesenteric artery in 2-3 weeks; most remain within arteries supplying gut but some continue to migrate to aorta, etc...Stay for 2-4 months Return to intestine and occlude blood flow to capillaries; L4 destroy capillaries and are released into gut wall where they develop into L5 then L5 rupture out of nodules into lumen of cecum or colon and mature to adults. |
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What is the pathology of S. vulgaris larvae?
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Results of larval migration within arterial intima of CMA and branches:
1. Arteritis, endarteritis and thrombosis 2. Potential for fatal infarction of gut wall 3. Aneurysms can develop 4. Altered intestinal motility, tone 5. Predispose to colic |
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What are clinical syndromes of S. vulgaris?
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1. Acute disease: foals/yearlings affected if large numbers of L3 ingested over short time (fever, depression, lethargy, abdominal distress, anorexia/weight loss, etc...)
2. Verminous colic: affect any age horse but more severe in young and more common than acute form (recurrent, intermittent coic, can be precipitated by exercise, often occurs in winter in upper MW) |
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What is the larval migration path of S. edentatus? (Prepatent period is 6-11 months)
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L3 --> gut mucosa --> hepatic portal veing --> liver
Develop to L4 in nodules and exit nodules; migrate free in liver for 2 months; leave liver and wander to cecum to emerge into cecal lumen as L5 then mature into adults |
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What are the clinical signs for S. edentatus?
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Disruption of liver tissue, migration in peritoneal cavity, inflammation of gut wall: acute septic or chronic hemorrhagic peritonitis and adhesions
Signs: fluctuating fever, anorexia, lethargy, abdominal pain, diarrhea/constipation, anemia |
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What is the larval migration path for S. equinus? (Prepatent period is 9 months)
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L3 --> L4 nodules in gut mucosa; L4 exits nodules --> liver via peritoneal cavity and migrate in liver (2 months) --> pancreas or peritoneal cavity --> L5 in gut wall --> emerge into gut lumen --> adults.
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What are the clinical signs of S. equinus?
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Signs can occur in heavy infection: liver hemorrhage, colic, anorexia, lethargy
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What are equine small strongyles?
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Cyathostomiasis
Dependent upon factors such as: 1. Age of horse 2. Nutrition 3. Anthelmintic usage 4. Level of exposure 5. Management system |
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What is the life cycle of small strongyles?
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Direct cycle similar to large strongyles
Larval migration pathway 1. Undergo mucosal migration in large intestine --> emerge into gut lumen as adults (prepatent period is 6-8 weeks). 2. L3 can become hypobiotic: persist in submucosal cysts in gut wall and emerge weeks to years later and complete life cycle. |
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What are some natural cyathostome infections?
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Clinical disease associated with large populations of adult cyathostomes: crowding, poor nutrition, poor worming program, etc...
Adults: plug-feeders +/- suck blood |
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What are some clinical signs of natural cyathostome infections?
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1. Weight loss or decreased rate of gain
2. Generalized debility 3. Retention of winter hair coat 4. May have diarrhea but not necessarily |
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What is larval cyathostomiasis?
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Clinical syndrome caused by mass larval emergence from mucosal cysts.
Factors affecting larval emergence from mucosal cysts: 1. of pasture contamination with L3 2. Season 3. Level of host resistance |
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What are clinical signs of larval cyathostomiasis?
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1. Acute onset of fever
2. Persistent diarrhea 3. Hypoalbuminemia 4. Severe weight loss |
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What is the treatment for larval cyathostomiasis?
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1. Anthelmintic with activity against larval stage may help: fenbendazole, oxibendazole or moxidectin
2. Supportive care: anti-diarrheal drugs and corticosteriods to reduce inflammation 3. "Refractory" to treatment |
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What is the epidemiology of small strongyles?
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Significance of strongyle eggs in foals varies with age:
1. < 6 weeks old: eggs probably ingested from mare feces; just passing through 2. > 6 weeks to < 6 months old: eggs likely result of infection with small strongyles 3. > 6 months both large and small strongyles |
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How should you manage equine strongyles?
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1. Husbandry practices + strategic deworming
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Name the arrows.
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Tail end of male strongyle
Top left = Spicule Top right = Bursal ray Bottom = Copulatory Bursa |
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Name the letters.
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A = S. edentatus
B = S. equinus C = S. vulgaris |
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What is going on here?
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Nodules resulting from passage of immature adults of S. vulgaris through cecal wall to reach the mucosal surface. Arrow points to a nodule starting to burst and release the migrating worm.
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What is this?
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Small strongyle larva encapsulated in the mucosa. Arrows are pointing to an eosinophilic infiltration.
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