Outbreak of equine coronavirus infection among riding horses in Tokyo, Japan.

The research investigates an outbreak of equine coronavirus (ECoV) among 41 horses in a riding stable in Tokyo, Japan in 2020 and suggests that the virus variant causing the outbreak was different from previous ones. The study also highlights the role subclinical horses played in spreading the virus and points out possible variations in virus shedding periods among different horse breeds.

Investigation of the Equine Coronavirus Outbreak

• The researchers began by investigating an outbreak of ECoV in a riding stable in Tokyo comprising 16 Thoroughbreds and 25 horses of other breeds.
• Fifteen horses, or about 37% of them, exhibited mild symptoms like fever, lethargy, loss of appetite, and diarrhea. These horses recovered within three days of showing initial symptoms.
• Despite only 15 horses showing symptoms, a virus neutralization test revealed that all 41 horses got infected with ECoV. This finding unveiled that 26 horses, or 63%, were subclinical – they carried and possibly spread the virus without showing any symptoms.

Genome Sequence Analysis

• The researchers performed a genome sequence analysis on the virus. They found differences in gene lengths in the ECoV from this outbreak when compared with ECoV from previous outbreaks among draughthorses in Japan.
• This suggests that the virus causing this outbreak was a different variant from those that caused previous outbreaks.

Comparison of Virus Shedding Periods

• The team also analyzed virus shedding periods among the infected horses. This refers to the length of time a horse can excrete or “shed” the virus, potentially infecting other horses.
• The results indicated that non-Thoroughbred horses had significantly longer ECoV shedding periods than the Thoroughbreds.
• This finding might suggest a breed-specific predisposition to ECoV shedding and spread, which could prove significant for future ECoV management and control strategies among horses.