Infectious agents associated with diarrhoea in neonatal foals in central Kentucky: a comprehensive molecular study

Equine coronavirus: An emerging enteric virus of adult horses

Equine coronavirus (ECoV) is an emerging virus associated clinically and epidemiologically with fever, depression, anorexia and less frequently colic and diarrhoea in adult horses. Sporadic cases and outbreaks have been reported with increased frequency since 2010 from Japan, the USA and more recently from Europe. A faeco‐oral transmission route is suspected and clinical or asymptomatic infected horses appear to be responsible for direct and indirect transmission of ECoV. A presumptive clinical diagnosis of ECoV infection may be suggested by clinical presentation, haematological abnormalities such as leucopenia due to lymphopenia and/or neutropenia. Confirmation of ECoV infection is provided by specific ECoV nucleic acid detection in faeces by quantitative PCR (qPCR) or demonstration of coronavirus antigen by immunohistochemistry or electron microscopy in intestinal biopsy material obtained ante or post mortem. The disease is generally self‐limiting and horses typically recover with symptomatic supportive care. Complications associated with disruption of the gastrointestinal barrier have been reported in some infected horses and include endotoxaemia, septicaemia and hyperammonaemia‐associated encephalopathy. Although specific immunoprophylactic measures have been shown to be effective in disease prevention for closely‐related coronaviruses such as bovine coronavirus (BCoV), such strategies have yet not been investigated for horses and disease prevention is limited to basic biosecurity protocols. This article reviews current knowledge concerning the aetiology, epidemiology, clinical signs, diagnosis, pathology, treatment and prevention of ECoV infection in adult horses.

Low prevalence of equine coronavirus in foals in the largest thoroughbred horse breeding region of Japan, 2012-2014

Background

Equine coronavirus (ECoV) is considered to be a diarrheic pathogen in foals. In central Kentucky in the United States, it has been shown that approximately 30 % of thoroughbred foals are infected with ECoV and thus it is considered widely prevalent. In contrast, the epidemiology of ECoV and its relationship to diarrhea in foals are poorly understood in Japan. We investigated ECoV in rectal swabs collected from thoroughbred foals in Japan.

Results

We collected 337 rectal swabs from 307 diarrheic foals in the Hidaka district of Hokkaido, the largest thoroughbred horse breeding region in Japan, between 2012 and 2014. In addition, 120 rectal swabs were collected from 120 healthy foals in 2012. These samples were tested by reverse transcription loop-mediated isothermal amplification and a real-time reverse transcription-polymerase chain reaction. All samples collected from diarrheic foals were negative, and only three samples (2.5 %) collected from healthy foals were positive for ECoV. Compared with central Kentucky, ECoV is not prevalent among thoroughbred foals in the Hidaka district of Hokkaido.

Conclusion

ECoV is not prevalent and was not related to diarrhea in thoroughbred foals in the Hidaka district of Hokkaido between 2012 and 2014.

Comparison of two commercial kits and an in-house ELISA for the detection of equine rotavirus in foal feces

Group A rotaviruses (RVA) are important infectious agents associated with diarrhea in the young of several animal species including foals. Currently, a variety of diagnosis methods are commercially available, like ELISA, latex agglutination and immunochromatographic assays. These commercial tests are mainly designed for the detection of human RVA; its applicability in veterinary diagnosis has been poorly studied. The aim of this study was to compare the sensitivity and specificity of two commercial diagnostic kits, Pathfinder™ Rotavirus and FASTest Rota® strip, with an in-house KERI ELISA, for the detection of equine RVA. A total of 172 stool samples from Thoroughbred foals with diarrhea were analyzed. The presence of equine RVA in samples in which only one of the three methods showed positive results was confirmed by RT-PCR. A sample was considered "true positive" when RVA was detected by at least two of the methods, and "true negative" when it tested negative by the three assays. Following these criteria, 50 samples were found positive and 122 were found negative, and were handled as reference population for the assay validation. Pathfinder™ Rotavirus assay showed 32% sensitivity and 97% specificity, FASTest Rota® strip, 92% sensitivity and 97% specificity, and KERI ELISA, 76% sensitivity and 93% specificity. Pathfinder™ Rotavirus showed 77%, FASTest Rota® strip 95%, and KERI ELISA 88% accuracy to correctly classify the samples as equine RVA positive or negative. Pathfinder failed specifically to detect equine RVA G3P12I6 genotype; such performance might be related to the specificity of the monoclonal antibody included in this kit. According to our results, differences among VP6 genotypes could influence the sensitivity to detect equine RVA in foal feces, and thus assay validation of diagnostic kits for each species is necessary. In conclusion, FASTest Rota® strip is more suitable than ELISA Pathfinder™ Rotavirus for the screening of rotavirus infection in foals. The KERI ELISA showed an acceptable performance, and could be considered a proper economic alternative for equine RVA diagnosis.

Disease associated with equine coronavirus infection and high case fatality rate

BACKGROUND

Equine coronavirus (ECoV) is associated with clinical disease in adult horses. Outbreaks are associated with a low case fatality rate and a small number of animals with signs of encephalopathic disease are described.

OBJECTIVES

The aim of this study is to describe the epidemiological and clinical features of two outbreaks of ECoV infection that were associated with an high case fatality rate.

ANIMALS

14 miniature horses and 1 miniature donkey testing fecal positive for ECoV from two related disease outbreaks.

METHODS

Retrospective study describing the epidemiological findings, clinicopathological findings, and fecal viral load from affected horses.

RESULTS

In EcoV positive horses, 27% (4/15) of the animals died or were euthanized. Severe hyperammonemia (677 μmol/L, reference range ≤ 60 μmol/L) was identified in one animal with signs of encephalopathic disease that subsequently died. Fecal viral load (ECoV genome equivalents per gram of feces) was significantly higher in the nonsurvivors compared to animals that survived (P = .02).

CONCLUSIONS AND CLINICAL IMPORTANCE

Equine coronavirus had a higher case fatality rate in this group of miniature horses than previously reported in other outbreaks of varying breeds. Hyperammonemia could contribute to signs of encephalopathic disease, and the fecal viral load might be of prognostic value in affected horses.

Infection control in equine critical care settings

There is a recognizable standard of practice for infection control in veterinary medicine. Effort must be given to control and prevention of infectious disease transmission within a facility and among animal populations. In the critical care setting, patients typically have a high degree of systemic illness and immune compromise, are commonly subjected to invasive procedures and placement of indwelling devices, and frequently receive antimicrobials and gastric protectants. Every equine critical care unit is distinctive in its physical and operational features and the types of patients that are managed. Infection control programs must therefore be tailored to each facility's needs.