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, [phone]
Department of Medicine and Epidemiology,
School of Veterinary Medicine
UC Davis, California