Walking On Volume 4, Issue 9, September 2017 - Page 8

For the Health of It Equine Coronavirus – An Emerging Enteric Virus of Adult Horses Reprinted with permission from the January 2017 issue of Equine Disease Quarterly Equine coronavirus (ECoV) is classified within the Betacoronavirus genus, along with bovine coronavirus, porcine hemagglutinating encephalomyelitis virus, mouse hepatitis virus, rat coronavirus (sialodacryoad- enitis virus), and certain human coronaviruses such as OC43, HKU1, Severe Acute Respiratory Syndrome coronavirus, and Middle East Respiratory Syndrome coronavirus; the latter two viruses have caused ep- idemic outbreaks of respiratory disease in human beings in the last decade. ECoV has been recently asso- ciated clinically and epidemiologically with emerging outbreaks of pyrogenic and enteric disease in adult horses in Japan and anorexia, lethargy, and fever in the United States. Coronavirus infection typically begi ns in the prox- imal small intestine and subsequently spreads to the colonic epithelial cells, leading to blunting of the intestinal villi and subsequent villous atrophy. Loss of epithelial cells results in malabsorption and maldigestion of nutri- ents and acute diarrhea. Following a short incubation period of 48-72 hours, adult horses develop fever, anorexia, and depression. Changes in fecal character, ranging from soft-formed stools to watery consistency, and colic are seen in less than 20% of affected horses. A small number of horses develop acute neurologic signs due to hyperammonemia, which may manifest as se- vere depression, head pressing, ataxia, proprioceptive deficits, recumbency, nystagmus, and seizure. Com- mon hematological abnormalities are leucopenia due to neutropenia and/or lymphopenia. ECoV infection generally resolves within 1-4 days with supportive care consisting of the administration of anti-inflammatory drugs and oral or intravenous fluids. Fatalities have been associated with septicemia, endotoxemia as well as metabolic abnormalities leading to encephalopathy (hyperammonemia). Historically, the detection of ECoV has relied on 8 • Walking On either electron microscopy, antigen-capture ELISA, or viral isolation from the feces. All of these detection modalities lack sensitivity, especially if viral particles are not present in sufficient numbers. Quantitative polymerase chain reaction (PCR) assay for the de- tection of ECoV nucleic acid has supplanted many conventional virological assays, mainly due to its short turn-around-time, high throughput capability and increased analytical sensitivity and specificity. the overall agreement between clinical status and PCR results for ECoV is over 90%, making fecal PCR the diagnostic tool of choice. Infected horses can shed ECoV up to 14 days. Due to the fecal-oral transmission route and the highly infectious nature of ECoV, common-sense biosecurity protocols should be instituted during an outbreak of ECoV. ECoV PCR positive horses (clinical or sub- clinical) should always be isolated from the rest of the equine population to decrease the exposure risk and environmental contamination. Potentially exposed horses should not be moved until their definitive infection status has been determined. For isolation purposes, use an empty barn or an isolation unit. In a barn situation, close one end of the barn and use it as isolation area. Caretakers and owners should wear gloves, protective clothing (coveralls or disposable gowns), and dedicated footwear. Good hand hygiene should be instituted (faucet with warm/cold water or hand sanitizer). Barrier nursing techniques should be established in the form of footbath or mats in front of the isolation unit and each stall. This will minimize the spread of pathogens from stalls to clean areas. It is very import- ant to control traffic and minimize contact of infected horses with the general public. Hygiene should be maximized by regular cleaning and disinfecting. Contact: Nicola Pusterla, DVM, PhD, Diplomate ACVIM npusterla@ucdavis edu, (530) 752-1360 Department of Medicine and Epidemiology, School of Veterinary Medicine UC Davis, California