Atlas of livestock parasites
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Atlas of Parasites Contents Information sources Glossary Administration

Strongylidosis

Category:


Species:
Endoparasite


Description:
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Strongylidosis
Strongyle infection of horses and donkeys, Strongylosis, Cyathostomosis Cyathostominosis.


Geographical Distribution:
Worldwide, most common worms in grazing equids.

Significance:
Usually moderate, may be high.
1. First year grazing foals are the age group at risk of acute or severe chronic strongylidosis (or strongylosis) although disease may occur also in equids of any age.
2. Adult horses (mares) may carry substantial worm burdens, and their faecal egg output is responsible for spring contamination of pastures (there is a spring rise of FEC); cyathostomes commonly account for 95-100% of the strongyle egg output.
Pasture larval levels increase during the summer months, damp areas favour L3 accumulation; peak egg counts in July-September; in temperate northern latitudes, massive infections may occur in the second half of the grazing period.
Sheathed L3 are resistant to dryness; overwintering of eggs is more important than that of the infective stage as the surviving larvae show decreased infective potential in the spring.
Stable-infection is also possible with contaminated hay or bedding.

Effect on host

Chronic infection with adult forms of „large and small strongyles“ is usually regarded to be of little pathogenic significance, course of infection is often inapparent; chronic mixed infections with large numbers of adult strongyles may cause diarrhoea, unthriftiness, anaemia, impaired performance, dull haircoat, etc.
Migrating larvae of large strongyles may cause, though not very commonly, severe altera-tions, verminous arteritis and clinical manifestations mainly in young foals or yearlings.
Migrating larvae of S. vulgaris are the most pathogenic and may cause:
Thrombosis obturans of intestinal arterioles by mass penetration of L3 into the wall of gut leading to ulceration and necrosis, peritonitis; clinics: fever, inappetence, dullness, diarrhoea, colic, death.
In the trunk of the cranial mesenteric artery and in its main branches - larvae cause inflammation of the arterial wall, formation of cauliflowerlike thrombuses, thickening and dilatation of the wall of arteries, aneurysms, abscesses; clinics: asymptomatic or abdominal distress and transient colic; thrombuses of the ileal and femoral arteries may cause intermittent or permanent lameness.
Thromboembolism due to detached fragments of thrombuses lodged in smaller vessels of the wall of caecum, colon and elsewhere resulting in ischaemic or hemorrhagic infarction of the intestinal wall, peritonitis, ileus; clinics: colics of varying severity, increased pulse rate, fever, flatulence, haemorrhagic exudates in the peritoneal cavity, death.
Migrating larvae of S. equinus and S. edentatus may cause hemorrhagic tracks in the liver, formation of grey nodules on the peritoneum, rarely hepatitis, pancreatitis; S. edentatus larvae may also elicit smal1 subperitoneal haematomas, haemorrhages, peritonitis; clinical signs are uncommon.
Acute larval cyathostomosis is a common and important clinical entity; the synchronous emergence of many thousands of hypobiotic cyathostome L4 from mucosal nodules into the gut lumen may instigate catarrhal or haemorrhagic enteritis, hypoalbuminaemia (pathogenesis resembling that of type II bovine ostertagiosis); clinics: diarrhoea, discharge of large numbers of bright red larvae with the faeces, marked and rapid weight loss, emaciation, death.

Diagnostic information:
Based on grazing history, clinical signs, FEC; note that due to the „long prepatent period“ of large strongyles (6-11 months), possible hypobiotic development and low worm fecundity, clinically apparent strongylosis or strongylidosis may be associated with no or low FEC values; therefore, the parasitic o


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