Feline Health
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A Winn Feline Foundation Report On ...
Feline Infectious Peritonitis - Virus Shedding and Infection - The American
Experience
FECV (feline enteric coronavirus) in the Cattery
By Janet Foley, DVM, PhD
University of California at Davis
The last year was rewarding in
terms of what has been learned about the pathogenesis (course of
infection) of FECV (feline enteric coronavirus) infection in large
pedigreed catteries and shelters.
FECV is apparently endemic (common) in
all such multi-cat households, with from 40-70%+ of cats shedding the
virus in their feces at any given time. Susceptible cats entering shelters
are infected almost immediately, while kittens born in pedigreed catteries
are infected when their maternal immunity wanes (usually from five to ten
weeks of age). Three types of FECV infection have been observed in older
breeding cats. About 10-20% of cats are seropositive but never shed the
virus; these animals are presumably solidly immune for life. A similar
proportion of cats shed the virus more or less persistently, and are
probably chronic carriers. The bulk of cats, however, shed the virus
intermittently, indicating that they are infected, become immune, lose
their immunity, and then are reinfected at intervals.
Preliminary attempts
in this study to eliminate FECV by isolation of pregnant queens and early
weaning of their kittens (by the procedures of Addie and Jarrett) gave
mixed results. This procedure, as conducted within private cattery
facilities, was doomed in all instances. In most cases, it was a total
failure with kittens getting infected only slightly later than
non-isolated cats. In one cattery, elimination was almost achieved, but a
break in containment occurred and the infection status returned to
pre-control levels. Attempts in laboratory facilities were more
successful, but even with this level of containment, two litters were
inadvertently infected by virus brought in by caretakers. Moreover, it was
discovered that litters born to persistent high level FECV shedders were
often infected before early weaning could be achieved at five weeks of
age.
The final conclusion was that isolation of queens and early weaning
could only work if:
- Queens that were high level persistent FECV
shedders were eliminated from the breeding program, and
- The very
strictest level of isolation, sanitation, and control of virus spread
could be employed.
Based on laboratory and field experience, we feel that
isolation of queens and early weaning is not feasible for control of FECV
in catteries, shelters and facilities of the type employed in the United
States. Statistical modeling, based on data collected from our studies,
suggests that FECV infection will be self-perpetuating in any group of
indoor cats containing six or more animals. The successes with isolation
and early weaning in the United Kingdom have far fewer cats on average
than catteries in the US, leading to a higher likelihood of success using
this approach. The most effective way to eliminate FECV would be by
determining the FECV carrier status of individual cats by repeated fecal
PCR (testing) and eliminating all high level persistent carriers. This
procedure would be very costly, however, and from our preliminary work
would not meet with a high rate of breeder compliance (it is hard for
breeders to eliminate healthy-appearing cats from their catteries and
breeding programs, especially if they are valuable for show or breeding).
Risk factors for FIP within pedigreed catteries were determined. After
comparing a number of different possible co-factors, only three seemed to
be important:
- Age (the young are most susceptible).
- Genetic susceptibility (accounting for about 50% of FIP incidence).
- The proportion of persistent FECV carriers in the environment.
Articles based on other studies by the University of California at Davis on Feline
Infectious Peritonitis have been published in volume 20 of JAVMA (Journal
of the American Veterinary Medical Association).
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