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28 Cards in this Set

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What are the morphologically characteristics of strongyles?
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
What are the life cycle characteristics of strongyles?
1. Direct
2. Adults mainly parasites of host GI tract
3. Infection usually acquired by ingestion of L3
Primarily parasites of herbivores.
What kinds of equine strongyles are there?
1. Large strongyles: most pathogenic - larval migration pathways

2. Small strongyles: less pathogenic - larvae only migrate in gut mucosa
What is the morphology of large strongyles?
They have a well developed globoid buccal capsule and females are oviparous and produce typical strongyle type eggs.
What is the morphology of small strongyles?
They have a short buccal capsule that is more shallow and females are oviparous and produce typical strongyle type eggs.
Name the 3 large strongyles and morphology of each.
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.
How do large strongyles feed?
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.
What is the life cycle of Strongylus spp?
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.
What is the migration path of S. vulgaris larvae? (Prepatent period is 6 months)
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.
What is the pathology of S. vulgaris larvae?
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
What are clinical syndromes of S. vulgaris?
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)
What is the larval migration path of S. edentatus? (Prepatent period is 6-11 months)
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
What are the clinical signs for S. edentatus?
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
What is the larval migration path for S. equinus? (Prepatent period is 9 months)
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.
What are the clinical signs of S. equinus?
Signs can occur in heavy infection: liver hemorrhage, colic, anorexia, lethargy
What are equine small strongyles?
Cyathostomiasis

Dependent upon factors such as:
1. Age of horse
2. Nutrition
3. Anthelmintic usage
4. Level of exposure
5. Management system
What is the life cycle of small strongyles?
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.
What are some natural cyathostome infections?
Clinical disease associated with large populations of adult cyathostomes: crowding, poor nutrition, poor worming program, etc...

Adults: plug-feeders +/- suck blood
What are some clinical signs of natural cyathostome infections?
1. Weight loss or decreased rate of gain
2. Generalized debility
3. Retention of winter hair coat
4. May have diarrhea but not necessarily
What is larval cyathostomiasis?
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
What are clinical signs of larval cyathostomiasis?
1. Acute onset of fever
2. Persistent diarrhea
3. Hypoalbuminemia
4. Severe weight loss
What is the treatment for larval cyathostomiasis?
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
What is the epidemiology of small strongyles?
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
How should you manage equine strongyles?
1. Husbandry practices + strategic deworming
Name the arrows.
Tail end of male strongyle

Top left = Spicule
Top right = Bursal ray
Bottom = Copulatory Bursa
Name the letters.
A = S. edentatus
B = S. equinus
C = S. vulgaris
What is going on here?
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.
What is this?
Small strongyle larva encapsulated in the mucosa. Arrows are pointing to an eosinophilic infiltration.