Ascarid Impaction
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Signalment
Foals younger than 6 months on a poor worming schedule and with a heavy parasite burden. Recent history of being wormed with a product that causes sudden ascarid death.
Aetiology
Products that cause sudden death of ascarids, particularly Parascaris equorum within the small intestine. Adult ascarids are large and thus readily cause small intestinal impaction. Suspected products include(37):
- Organophosphates
- Ivermectin
- Pyrantel pamoate
Clinical Signs
- Acute onset colic after administration of anthelmintic (onset varies with degree of obstruction (37))
- Signs compatible with small intestinal obtruction
- Nasogastric reflux (occasionally dead parasites are seen in reflux)
Diagnosis
- History
- Clinical signs referable to small intestinal obstruction
- Abdominal imaging (radiography and ultrasonography) may demonstrate multiple loops of distended small intestine, but imaging is not required if the clinical presentation indicates immediate surgery.
Prognosis
Treatment
- Medical treatment: immediate treatment of hypovolaemic shock resulting from sequestration of fluid in small intestine
- Surgical treatment: enterotomy made over the intraluminal impaction and removal of ascarids
Prognosis
Fair in cases that are rapidly treated but poor in foals with evidence of hypovolaemia and septic shock. In a recent study, long term survival of 25 affected horses was 33%(37).