Table 3.

Results of the mixed effects logistic regression model for equine coronavirus (ECoV) infection, including significant predictor variables and random effects parameters expressed as odds ratios (OR) and 95% confidence intervals (95% CI) for risk factors studied (region, age, breed, sex and use) in 5247 healthy US horses.

	ECoV positivea		ECoV negativeb		P
	OR	95% CI	OR	95% CI
Regionc
North-East	Ref	Ref	Ref	Ref
South	1.04	0.68–21.62	0.95	0.62–1.47	0.831
Mid-West	1.84	1.17–2.87	0.54	0.35–0.85	0.008
West	1.25	0.80–1.95	0.80	0.51–1.25	0.323
Age in years
1–5	Ref	Ref	Ref	Ref
5–10	1.12	0.82–1.53	0.89	0.65–1.21	0.472
11–15	1.13	0.82–1.58	0.88	0.64-1.22	0.437
16–20	1.18	0.82–1.70	0.85	0.59–1.21	0.375
>20	1.42	0.97–2.08	0.70	0.48–1.03	0.070
Breed
Quarter horse	Ref	Ref	Ref	Ref
Warmblood	0.98	0.65–1.46	1.02	0.68–1.52	0.924
Thoroughbred	0.48	0.32–0.74	2.07	1.36–3.15	0.001
Paint	0.99	0.65–1.50	1.01	0.67–1.53	0.957
Arabian	1.20	0.76–1.90	0.83	0.53–1.31	0.430
Draft horse	1.95	1.25–3.05	0.51	0.33-0.80	0.003
Pony/miniature	0.81	0.48–1.37	1.24	0.73–2.09	0.426
Other	1.04	0.78–1.40	0.96	0.71–1.30	0.790
Sexd
Female	Ref	Ref	Ref	Ref
Male	—	—	—	—	—
Use
Competition	Ref	Ref	Ref	Ref
Ranch/farm horse	1.32	1.02–1.72	0.76	0.58–0.98	0.034
Breeding	1.59	1.09–2.31	0.63	0.43–0.92	0.016
Other	0.79	0.07–8.71	1.26	0.11–13.9	0.848

Ref, parameter used as reference category.

^aRandom effects parameter: OR = 2.39; 95% CI (2.00–2.99); Likelihood ratio test vs. logistic regression: X²₍₁₎ = 40.42, P < 0.05.

^bRandom effects parameter: OR = 2.39; 95% CI (2.00–2.99); Likelihood ratio test vs. logistic regression: X²₍₁₎ = 40.42, P < 0.05.

^cNorth-East was considered reference for region; Quarter horse was considered reference for breed; Competition was considered reference for use; Female was considered reference for sex; 1–5 year old horses were considered reference for age.

^dSex was not included in multivariate model due to non-significance in univariate model.