| Description:
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Canine
coronavirus (CCV) is a cause of sporadic outbreaks of
enteritis in dogs. Dogs of all ages appear to be susceptible
to CCV; however, young pups are more highly susceptible
to the development of clinical infections. The natural
route of transmission is fecal-oral. Virus in feces
is the major source of infection. Infected dogs shed
CCV in the feces for 6-9 days, but shedding can be prolonged
in some pups, after clinical signs have ceased. CCV
is acid resistant and passes unaltered through the stomach.
The surface epithelium of the small intestine is the
main target of CCV, while the colon is resistant to
the infection.
The incubation period is short. Vomiting and diarrhea
may be seen by 1 - 3 days post infection and, when clinical
illness occurs, it spreads rapidly. The virus is highly
contagious and often may cause clinical signs in some
dogs, with no illness occurring in contact animals.
Feces may be mucoid or watery, sometimes streaked with
blood, and it is exceptionally malodorous. Pups become
dehydrated, even if fluid therapy is started early,
depressed and anorexic. The infection is generally afebrile
although elevated body temperature has been observed
in some cases. In contrast to CPV-2 infection, leukopenia
has not been observed. Vomiting, which is much less
severe than with CPV-2 infection, usually subsides after
the first day of illness, but diarrhea persists several
days, even for 3 - 4 weeks. Secondary infections by
bacteria, parasites or other viruses, such as parvoviruses
or rotaviruses, may protract the illness. However, dogs
usually recover spontaneously within a week, but illness
may last 2 weeks or longer. The mortality rate of CCV
infection alone is usually very low, but deaths have
been reported in some kennels, especially in pups.
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| Diagnosis:
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CCV
infection is difficult to distinguish clinically from
enteritis caused by other agents. It is important to
rule out other causes of vomiting and diarrhea such
as enteric bacteria, parasites, poisonings and non-infectious
causes of diarrhea. Assays, which have been used for
the detection of CCV in fecal samples, include electron
microscopy (EM), isolation on appropriate cell cultures
and nested-polymerase chain reaction (PCR). Of the several
methods used for the detection of CCV, EM appears to
be a valuable diagnostic tool. EM has been reported
to be more sensitive and useful than virus isolation
for detecting coronaviruse. However, the frequency of
CCV disease has probably been overestimated by diagnostic
laboratories, which applied EM as the principal diagnostic
method. The common presence of coronavirus-like particles
in feces presents difficulties in the diagnosis of CCV
by EM and requires confirmation by other tests. Immuno-electronmicroscopy
with a specific immune serum permits confirmation of
the EM diagnosis, but it requires specialized laboratories
and qualified experts.
Nested PCR assay for the diagnosis of CCV infection
has been devepoled. The target sequence for amplification
is a segment of the gene encoding for transmembrane
(M) protein of CCV. The test revealed high specificity
and sensitivity. The PCR allows the diagnosis of CCV
more rapidly than traditional tests (EM or isolation
on tissue cultures), and would be suitable for the diagnosis
of CCV in fecal samples when the virus is inactivated,
or when the number of virions is low and cannot be detected
by EM examination.
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