Small colon impaction outbreak and associated risk factors in horses at the Onderstepoort Veterinary Academic Hospital, South Africa in 2021

Abstract

Background During June-July 2021, the Onderstepoort Equine Clinic experienced an increase in diffuse faecal small colon impactions (SCI). Typically, SCI is diagnosed in 1.3–3% of horses admitted to referral centres for colic. Objectives This study aimed to describe the distribution, diagnosis, treatment, and outcomes of colic cases in 2021, focusing on SCI and to identify risk factors for SCI compared to large colon impactions (LCI). Method Medical records from the Onderstepoort Veterinary Teaching Hospital were reviewed to identify colic cases in 2021 and the population distribution, diagnosis, treatment, and outcome recorded. Cases of SCI were identified and compared to LCI. Owner questionnaires assessed potential SCI risk factors. Results Colic cases(182), comprised mainly LCI(26%), large colon displacements(20%), and SCI(13%). Treatments included medical(65%), surgical(32%), or euthanasia(3%). Most horses(85%) were discharged. SCI was diagnosed in 13% of cases, higher than previously reported rates. Immediate surgical treatment was performed in 30% of cases. In the remaining cases medical management was initiated although surgical intervention was later pursued in 43% of cases. Short-term survival was 87%, with surgical cases showing higher survival (94%) than medical (67%). Stallions were at risk to develop SCI compared to “all colic” diagnoses (OR 4.17). Friesians were more likely to develop SCI compared to “all colic” (OR 7.00). Draft breed horses were more likely to develop SCI compared to compared to “all colic” (OR 8.20) and compared to LCI (OR 32.7). The study identified a risk for horses to develop SCI in winter compared to “all colic” (OR 43.2) and compared to LCI (OR 124). Conclusion A SCI outbreak occurred in 2021, with increased risks in stallions, Friesians, and draft breeds, particularly in winter. Horse owners and veterinarians should be alerted to this, especially in at-risk groups during winter. Outcomes are favourable for SCI especially when treated surgically.