Porcine Circovirus Type 2
Dr. Peter Bahnson
November 3, 2000
In the past few years, controversy has arisen over the
importance of Porcine Circovirus type 2 (PCV 2) infection
in growing pigs.
In the late 1990s, circovirus was reported in clinical cases
of a wasting syndrome that affected multiple organ systems
in weaned pigs (hence the name and acronym,
"post-weaning multisystemic wasting syndrome," PMWS).
Since that time, evidence has continued to mount that PCV
2 may cause the syndrome. Although infection with the virus
alone causes little or no clinical signs, infection together with
parvovirus, a common virus circulating in pig herds, has
been shown to cause a wasting syndrome quite similar to
that in reported clinical cases. There is also the potential
that PRRS virus infection may increase susceptibility to
PCV 2 infection.
Field-based evidence includes a Canadian study showing
more nursery-pig diseases at infected farms than at
non-infected farms. In addition, a descriptive study
comparing cases of PMWS with cases of an apparently
unrelated disease, Streptococcus suis infection, showed that
PCV 2 was found in all of the PMWS cases, but none of
the Strep. suis farms. The authors concluded that this was
evidence to "confirm and extend previous findings
documenting a consistent association of PCV 2 with
Diagnostic testing for PCV 2 generally includes
histopathology, specific staining of samples for virus
(immunohistochemistry), and serologic testing. The specific
stains are effective in documenting the virus.
The potential for PCV 2 to cause a wasting syndrome is
relatively well established, and the infection is being
detected at an increasing rate. The Iowa State University
diagnostic laboratory, for example, reported nearly a
four-fold increase in laboratory diagnosis of PCV/PMWS
from 1998 to 1999. However, the impact of this infection
relative to other growing-pig infections in commercial
production is still up for debate, since it is not clear that
infections necessarily cause disease.
No vaccines or treatments are currently available. The best
protection at this point is strictly enforced principles of
biosecurity, including strict sanitation and age segregation.
Since infection with other viruses can increase the severity
of the infection, steps to control concurrent disease may be
justified. Good supportive care--including careful attention
to environmental control--is especially important. Where
indicated to control secondary or concurrent bacterial
infection, antibacterial therapy can also be used.
Since controversy remains as to the relative importance of
this infection in commercial production, producers need to
keep an open mind, and veterinarians and producers alike
need to keep abreast of the developing science in the area.
For further reading, see the reference list at:
At least one thing is clear: Pigs are effective at reproducing
viruses, and disease control or elimination remains, as
always, an important component of efficient pig production.
Peter Bahnson, DVM, PhD
Veterinary Clinical Medicine and Veterinary
Continuing Education/Public Service-Extension
University of Illinois at Urbana Champaign
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