Serosurveillance of equine coronavirus infection among Thoroughbreds in Japan.
Authors: Kambayashi Yoshinori, Nemoto Manabu, Tsujimura Koji, Ohta Minoru, Bannai Hiroshi
Journal: Equine veterinary journal
Summary
# Equine Coronavirus Serosurveillance in Japanese Thoroughbreds Between 2017 and 2020, researchers used virus-neutralisation testing on serum samples from 161 yearlings and 181 active racehorses in Japan to map equine coronavirus (ECoV) prevalence and seasonality—a critical gap in understanding disease epidemiology within the Japanese racing industry. Notably, 44.1% of yearlings arrived at training facilities already seropositive, with infection rates peaking between August and December (60.9%), then dropping sharply to just 5.6% by the following spring; racehorses showed a distinct winter-spring outbreak pattern (November to May, 15.5% infection rate) with zero infections during summer months. The 39.2% morbidity rate in yearlings and 4% in racehorses during exposure periods translated to fever and gastrointestinal signs consistent with ECoV, yet no animals experienced severe clinical disease. For equine professionals managing Thoroughbreds in Japan, these findings suggest ECoV circulates predictably by season and age group, warranting targeted monitoring protocols during high-risk periods—particularly for newly arrived yearlings in late summer—though the mild clinical phenotype observed indicates the virus poses limited threat to herd health and performance.
Read the full abstract on PubMed
Practical Takeaways
- •Expect ECoV infections in newly arrived yearlings during late summer/autumn months in Japan; monitor for fever and lethargy during this high-risk period
- •ECoV prevalence is high in Thoroughbreds but typically causes mild disease with good prognosis, so management should focus on comfort care and preventing secondary complications rather than intensive intervention
- •Consider ECoV as a differential diagnosis for pyretic cases in yearlings during August-December; serology and virus neutralization testing can confirm infection
Key Findings
- •44.1% of yearlings were seropositive to ECoV upon arrival at the yearling farm in August, with infection rates rising to 60.9% between August-December
- •Infection rates differed significantly between yearlings (39.2% morbidity) and racehorses (4% morbidity) during estimated periods of viral exposure
- •ECoV infection showed clear seasonality with higher infection rates in yearlings from August-December and in racehorses from November-May
- •No horses in either population showed severe clinical signs despite substantial ECoV prevalence, indicating low risk to the Japanese horse industry