Kambayashi Yoshinori, Nemoto Manabu, Tsujimura Koji, Ohta Minoru, Bannai Hiroshi
Equine Research Institute, Japan Racing Association, Shimotsuke, Tochigi, Japan.
Equine Vet J. 2023 May;55(3):481-486. doi: 10.1111/evj.13857. Epub 2022 Aug 3.
Equine coronavirus (ECoV) causes fever, lethargy, anorexia and gastrointestinal signs in horses. There has been limited information about the prevalence and seasonality of ECoV among Thoroughbreds in Japan.
To understand the epidemiology and to evaluate the potential risk of ECoV infection to the horse industry in Japan.
Longitudinal.
The virus-neutralisation (VN) test was performed using sera collected three times a year at 4 months intervals from 161 yearlings and at 6-7 months intervals from 181 active racehorses in Japan in 2017-2018, 2018-2019 and 2019-2020. VN titre ≥1:8 was defined as seropositive, and ≥4-fold increase in titres between paired sera was regarded as indicative of infection.
The VN test showed that 44.1% (71/161) of yearlings were seropositive in August, when they first entered the yearling farm. The infection rate was significantly higher between August and December (60.9%, 98/161) than between December and the following April (5.6%, 9/161; p = 0.002). Among the racehorses, it was significantly higher between November and the following May (15.5%, 28/181) than between the preceding April/May and November (0%; p = 0.02). The morbidity rates during the estimated periods of viral exposure were 39.2% in the yearlings and 4% in the racehorses. No horses showed any severe clinical signs.
Clinical records did not cover the period during horses' absence from the training centre.
ECoV was substantially prevalent in Thoroughbred yearlings and racehorses in Japan, and there was a difference in epizootic pattern between these populations in terms of predominant periods of infection. ECoV infection was considered to be responsible for some of the pyretic cases in the yearlings. However, no diseased horses were severely affected in either population, suggesting that the potential risk of ECoV infection to the horse industry in Japan is low.
马冠状病毒（ECoV）可导致马匹发热、嗜睡、厌食和出现胃肠道症状。关于日本纯种马中ECoV的流行情况和季节性的信息有限。
了解日本ECoV的流行病学情况，并评估其对日本养马业的潜在感染风险。
纵向研究。
在2017 - 2018年、2018 - 2019年和2019 - 2020年期间，对日本的161匹一岁马每年采集三次血清，间隔4个月，对181匹现役赛马每隔6 - 7个月采集一次血清，采用病毒中和（VN）试验。VN滴度≥1:8定义为血清阳性，配对血清之间滴度增加≥4倍被视为感染指征。
VN试验显示，一岁马在首次进入一岁马场的8月时，44.1%（71/161）血清呈阳性。8月至12月期间的感染率（60.9%，98/161）显著高于12月至次年4月期间（5.6%，9/161；p = 0.002）。在赛马中，11月至次年5月期间的感染率（15.5%，28/181）显著高于前一年4月/5月至11月期间（0%；p = 0.02）。在估计的病毒暴露期间，一岁马的发病率为39.2%，赛马的发病率为4%。没有马匹出现任何严重的临床症状。
临床记录未涵盖马匹不在训练中心的时间段。
ECoV在日本纯种一岁马和赛马中普遍流行，且在这些群体之间，感染的主要时期在流行模式上存在差异。ECoV感染被认为是一岁马中一些发热病例的病因。然而，这两个群体中均没有患病马匹受到严重影响，这表明ECoV感染对日本养马业的潜在风险较低。
