Equine coronavirus infection

Previous Authors: M B PENSAERT AND K VAN REETH

Current Authors:
L J SAIF - Professor, MS, PhD, Food Animal Health Research Program, CFAES and CVM, OARDC, Ohio State University, 1680 Madison Ave, Wooster, Ohio, OH 44691, USA 
M A ALHAMO - Researcher, DVM, MSc, OARDC Food Animal Health Research Program, Ohio State University, 1680 Madison Avenue, Wooster, Ohio, OH 44691, USA

GENERAL INTRODUCTION: CORONAVIRIDAE

Coronavirus-like particles have been sporadically observed by electron microscopy in the faeces of horses with enteric disease since 1975,^{1, 2, 6, 7, 14} but it was only in 2000 that the first isolation and identification of a coronavirus from a foal were made.⁴ While this virus was genetically distinct from other previously characterized coronaviruses, it showed close antigenic and genetic relationships to clade A betacoronaviruses, such as bovine coronavirus (BCV), porcine haemagglutinating encephalomyelitis virus and murine hepatitis virus. ‘Equine coronavirus’ (ECV) has therefore been classified as a betacoronavirus, clade A.⁴ Because of the close antigenic relationship with BCV, some immunological methods for BCV detection, such as an antigen capture enzyme-linked immunosorbent assay (ELISA) for demonstration of the virus in faeces, can also be used for diagnosis of ECV.^{2, 4}  However due to its rapidity and sensitivity, RT-PCR is now widely used to diagnose ECV infections.^{8, 10, 12}

Although most ECV infections appear to occur in neonatal foals, there are now multiple reports of  ECV enteric and respiratory infections in clinically affected adult horses in the USA and Japan^{6, 10, 12} and more recently from diseased foals and horses in Europe.⁸ Equine coronavirus  was also detected recently from about 2 per cent of rectal swabs obtained from healthy adult horses in the Middle East; however, horses with enteric or respiratory disease were not examined in this respect.⁵ During the latter study two further coronaviruses, closely related to dromedary camel strains in the BCV/HKU23 cluster of clade A betacoronaviruses, were also detected.

Coronavirus has been detected in young foals suffering from fatal enterocolitis.^{1, 2, 6} In naturally infected miniature horses, necrotizing enteritis and hyperammonaemic encephalopathy were reported.³ More recently, outbreaks in adult horses were reported that were characterized by anorexia, lethargy, colic lesions and haematological changes such as leukopenia.^{10, 12} In the 2011-2012 outbreaks in the USA, ECV was associated with diarrhoea in only about 20 per cent of affected horses.¹²

The pathogenicity of ECV and its aetiological role in enteric disease have been confirmed in a recent investigation. Draft horses inoculated with a Japanese ECV positive faecal sample  showed fever, anorexia and gastrointestinal disfunction with faecal shedding for  more than nine days and also nasal shedding.⁹ Others also reported nasal shedding of ECV in a low proportion of cases with fever and respiratory disease¹¹ and in clinically normal horses,^{5, 13} but usually at lower prevalence rates (7 per cent) than in sick animals (86 per cent).¹² Nevertheless, the prevalence of ECV infection and its importance as a cause of enteric/respiratory disease in horses  requires further investigation.

References

1. BASS, E.P. & SHARPEE, R.L., 1975. Coronavirus and gastroenteritis in foals. The Lancet, 2, 822.
2. DAVIS, E., RUSH, B.R., COX, J., DEBEY, B. & KAPIL, S., 2000. Neonatal enterocolitis associated with coronavirus infection in a foal: A case report. Journal of Veterinary Diagnostic Investigation, 12, 153–156.
3. GIANNITTI, F., DIAB, S., METE, A., STANTON, J.B., FIELDING, L., CROSSLEY, B., SVERLOW, K., FISH, S., MAPES, S., SCOTT, L. & PUSTERLA, N., 2015. Necrotizing Enteritis and Hyperammonemic Encephalopathy Associated With Equine Coronavirus Infection in Equids. Veterinary Pathology, 52, 1148-1156.
4. GUY, J.S., BRESLIN, J.J., BREUHAUS, B., VIVRETTE, S. & SMITH, L.G., 2000. Characterization of a coronavirus isolated from a diarrheic foal. Journal of Clinical Microbiology, 38, 4523–4526.
5. HEMIDA, M.G., CHU, D.K.W., PERERA, R., KO, R.L.W., SO, R.T.Y., NG, B.C.Y., CHAN, S.M.S., CHU, S., ALNAEEM, A.A., ALHAMMADI, M.A., WEBBY, R.J., POON, L.L.M., BALASURIYA, U.B.R. & PEIRIS, M., 2017. Coronavirus infections in horses in Saudi Arabia and Oman. Transboundary and Emerging Diseases, 64, 2093-2103.
6. HUANG, J.C.M., WRIGHT, S.L. & SHIPLEY, W.D., 1983. Isolation of coronavirus-like agent from horses suffering from acute equine diarrhoea syndrome. The Veterinary Record, 113, 262–263.
7. MAIR, T.S., TAYLOR, R.G.R., HARBOUR, D.A. & PEARSON, G.R., 1990. Concurrent cryptosporidium and coronavirus infections in an Arabian foal with combined immunodeficiency syndrome. The Veterinary Record, 127–130.
8. MISZCZAK, F., TESSON, V., KIN, N., DINA, J., BALASURIYA, U.B., PRONOST, S. & VABRET, A., 2014. First detection of equine coronavirus (ECoV) in Europe. Veterinary Microbiology, 171, 206-209.
9. NEMOTO, M., OUE, Y., MORITA, Y., KANNO, T., KINOSHITA, Y., NIWA, H., UENO, T., KATAYAMA, Y., BANNAI, H., TSUJIMURA, K., YAMANAKA, T. & KONDO, T., 2014. Experimental inoculation of equine coronavirus into Japanese draft horses. Archives of Virology, 159, 3329-3334.
10. OUE, Y., ISHIHARA, R., EDAMATSU, H., MORITA, Y., YOSHIDA, M., YOSHIMA, M., HATAMA, S., MURAKAMI, K. & KANNO, T., 2011. Isolation of an equine coronavirus from adult horses with pyrogenic and enteric...