<i>Parascaris</i> spp. induced surgical colic in juvenile horses—A Scandinavian perspective

BACKGROUND: Parascaris spp. commonly infects foals, and high burdens can cause fatal small intestinal impactions. Progressive anthelmintic resistance poses a risk for an increase of Parascaris spp. related disease in juvenile horses. OBJECTIVES: To investigate Parascaris-related surgical intestinal lesions, with special emphasis on ascarid impactions, in Scandinavia by exploring (1) disease occurrence and (2) short-term survival rates after laparotomy in affected foals and yearlings. STUDY DESIGN: Restrospective case series. METHODS: A retrospective clinical record search was conducted at six Scandinavian equine hospitals during a 7-15-year period. Horses older than 1 month but less than 2 years of age that had been surgically treated for colic were included. Age, breed, surgical diagnosis, presence of Parascaris spp. infection, immediate anthelmintic history and short-term survival, defined as survival to hospital discharge, were recorded. RESULTS: A total of 233 records were included and lesions involving the small intestine were observed in 52.8% (123/233). Fourteen foals were diagnosed with ascarid impaction at laparotomy, with an occurrence of 6.0% (14/233), encompassing 11.4% of surgical small intestinal lesions (14/123) and 9.7% of horses younger than 1 year of age (13/134). Six foals with ascarid impaction had been treated with an anthelmintic drug within 2 days of presentation. Four foals with ascarid impaction survived to discharge. Overall occurrence of Parascaris-associated intestinal lesions, including impactions, was 13.7% (32/233), encompassing 26.0% (32/123) of all small intestinal abnormalities, and with a short-term survival rate of 38% (12/32). MAIN LIMITATIONS: Retrospective study design, hospital-dependent variations could not be controlled. No previous data to compare disease occurrence. CONCLUSION: Parascaris spp. related disease in juvenile horses comprises a substantial portion of small intestinal surgical lesions with a poor prognosis for survival. With the appearance of multi-drug-resistant parasite populations, it is important to develop management practices to reduce parasite infection burdens.