Parascaris 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.