Experimental inoculation of equine coronavirus into Japanese draft horses

Abstract

Recently, outbreaks associated with equine coronavirus (ECoV) have occurred in Japan and the United States. While ECoV is likely to be pathogenic to horses, it has not been shown that experimental inoculation of horses with ECoV produces clinical signs of disease. In this study, we inoculated three Japanese draft horses with an ECoV-positive diarrheic fecal sample to confirm infection after inoculation and to investigate the clinical course and virus shedding patterns of ECoV. Virus neutralization tests showed that all three horses became infected with ECoV. Two of the three horses developed clinical signs similar to those observed during ECoV outbreaks, including fever, anorexia, and gastrointestinal dysfunction. All horses excreted a large amount of virus into their feces for more than 9 days after inoculation regardless of the presence or absence of clinical signs, which suggests that feces are an important source of ECoV infection. ECoV was also detected in nasal swabs from all horses, suggesting that respiratory transmission of ECoV may occur. Both symptomatic horses developed viremia, while the asymptomatic horse did not. White blood cell counts and serum amyloid A concentrations changed relative to the clinical condition of the inoculated horses; these may be useful markers for monitoring the clinical status of horses infected with ECoV. This is the first report of induction of clinical signs of ECoV infection in horses by experimental inoculation. These clinical and virological findings should aid further investigation of the pathogenesis of ECoV.

Evolving views on enteric viral infections of equines: an appraisal of key pathogens

“…Though, nasal secretions came positive in PCR assay, experiments could not define whether this was due to nasal replication of the virus and subsequent shedding or due to environmental factors or both (Nemoto et al, 2014). Subsequently, in 2015 a study reported the whole genome sequencing of three earlier isolated ECoV strains from Japan Obihiri 12-1, Obihiri 12-2 and Tokachi09.…”

Rapid detection of equine coronavirus by reverse transcription loop-mediated isothermal amplification

“…ECoV was detected in patient fecal samples from the United States and Japan, and was also detected in a respiratory sample from Europe (Miszczak et al, 2014). An ECoV experimental challenge study showed that the virus could be detected in fecal samples and nasal swabs (Nemoto et al, 2014).…”

“…These racehorses were stabled at the Miho Training Center (Ibaraki Prefecture), where an ECoV has yet to be reported. Nasal swabs were suspended in a medium as described previously (Nemoto et al, 2014). Viral RNA and DNA were extracted from nasal swabs, and viruses isolated with a MagNA Pure LC Total Nucleic Acid Isolation Kit (Roche Diagnostics, Mannheim, Germany).…”

“…The analytical sensitivities of the RT-LAMP, RT-PCR, and qRT-PCR assays were evaluated using artificially synthesized ECoV RNA as a positive control. Artificial ECoV RNA was synthesized based on the sequence of the nucleocapsid gene from ECoV strain NC99 as described previously (Nemoto et al, 2014). NC99 was first isolated from a foal with diarrhea in the United States (Guy et al, 2000).…”

Prevalence of equine coronavirus in nasal secretions from horses with fever and upper respiratory tract infection

“…As with the closely related BCoV, ECoV has recently been detected in the nasal secretions of 1/200 foals and adult horses suffering from respiratory disease (Miszczak and others 2014) as well as the nasal secretions from three nine-month-old to 10-month-old Japanese draft foals experimentally infected with ECoV (Nemoto and others 2014). Despite a small number of ECoV qPCR-positive study horses, there was no difference in frequency of the predominant clinical signs between horses with monoinfection of ECoV and horses with coinfection of ECoV and common infectious respiratory pathogens.…”