Risk Factors Associated with an Equine Coronavirus Outbreak at a Saddlebred Farm in North Carolina

Abstract: Background- Equine coronavirus (ECoV) leads to outbreaks with variable morbidity and mortality. Few previous reports of risk factors for infection are available.

Objectives- To describe unique clinical findings and risk factors for infection and development of clinical disease with ECoV.

Animals- 135 horses from farm affected by ECoV outbreak.

Methods- Data obtained for each horse included age, breed, gender, activity level, housing, and feed at the onset of the outbreak. Factors were evaluated for assessment of risk of infection using simple logistic regression or Fisher’s exact test. Significance was set at p ≤ 0.05.

Results/Findings- Forty-three of 135 horses (31.8%) were positive on fecal PCR for ECoV, and 17 horses (12.6%) developed clinical signs. Colic occurred in 46.2% of affected animals. Three horses had small colon impactions, 2 of which required surgical intervention. Significant risk factors for having positive PCR results included presence of clinical signs (OR 56, 95% CI 8.298-594.6), being primarily stalled (OR 167.1, 95% CI 26.41-1719), housing next to a positive horse (OR 7.5, 95% CI 3.100-18.97), being in work (OR 26.9, 95% CI 4.573-281.9), being fed a ration of hay vs ad libitum (OR 418, 95% CI 36.83-4438), being fed alfalfa hay (OR 418, 95% CI 36.83-4438) and levothyroxine supplementation (OR 7, 95% CI 2.723-18.68).

Conclusions and Clinical Importance- This report describes risk factors for ECoV infection, including a series of factors associated with intensive management of show horses. Clinicians should be aware that clinical signs of ECoV vary and can include severe colic.