EQUINE CORONAVIRUS – A DECADE LONG JOURNEY TO INVESTIGATE AN EMERGING ENTERIC VIRUS OF ADULT HORSES DR. NICOLA PUSTERLA, DACVIM
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3 THE DIAGNOSIS It is the lack of gastrointestinal signs that often misleads the equine veterinarian into ruling out an enteric pathogen. Leukopenia due to neutropenia and/or lymphopenia is a consistent hematological abnormality and, although not specific for ECoV, should direct the diagnostic work-up toward a viral disease. The laboratory support of ECoV infection is based on the detection of the virus in feces. Historical detection modalities such as electron microscopy and antigen capture ELISAs have been supplanted by quantitative real-time PCR (RT- qPCR). RT-qPCR has the advantage of being highly sensitive and specific, has a quick turn-around-time and is cost-effective. Further, the quantitative capability of RT-qPCR allows the study of viral kinetics and the ability to determine the horse’s contagious nature and prognosis. Experimental studies have shown that ECoV RNA can be detected as early as 72-96 hours post-inoculation and continues to be detected until 10-14 days post infection. In naturally infected horses, ECoV can be detected by RT-qPCR for 3-9 days with a detection time occasionally extending up to 25 days from onset of clinical disease. Histological changes have only been reported in a very small number of horses and showed morphological changes similar to BCoV infection. The histological hallmarks of ECoV infection were diffuse necrotizing enteritis, marked villus attenuation, epithelial cell necrosis of the tips of the villi, neutrophilic and fibrin
potential infectious pathogens, have been ruled in or out. ECoV qPCR- positive horses should be isolated and stable- or herdmates closely monitored until the outcome of past-exposure has been determined. Outbreaks of ECoV are generally short lasting, especially when strict biosecurity measures have been followed, and quarantine can routinely be lifted 2-3 weeks following the resolution of clinical signs in the last affected horse. While common disinfectants inactivate ECoV, it is unknown as to how long ECoV remains infectious in the environment. Severe acute respiratory syndrome (SARS)- CoV has been shown to persist up to 2 days in wastewater and dechlorinated tap water, 3 days in feces and 17 days in urine at room temperature. The survival of the virus is even longer at lower temperatures.
extravasation into the small intestinal lumen, as well as crypt necrosis, microthrombosis and hemorrhage. Post-mortem diagnosis of ECoV can be achieved by RT-qPCR on feces or small intestinal contents, and ECoV can be detected in intestinal tissue by electron microscopy, immunochemistry and direct fluorescent antibody testing using BCoV reagents. 4 PREVENTION Specific preventive measures are scarce, and there are yet no licensed vaccines against ECoV. The cornerstone of ECoV prevention resides in strict biosecurity measures aimed at reducing the risk of introducing and disseminating ECoV on equine premises. It is important to be vigilant when working-up horses presenting with fever, anorexia and lethargy, with or without concurrent enteric signs. Such horses should be isolated until ECoV, as well as other
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