FCV is often a problem in cat shelters. Management to limit or even prevent virus
transmission is as important as vaccination in control. Shelter design and management should
be aimed at avoiding cross infection of cats. Cats should be housed individually unless they
are known to originate from the same household.
If acute respiratory disease occurs in a shelter, identification of the agent involved (with
differentiation of FCV from FHV-1, Chlamydophila felis, Bordetella bronchiseptica, and
Mycoplasma spp.) may be useful in deciding on the appropriate preventative measures. In
case of an FCV outbreak, it should be considered that FCV can persist in the environment for
about one month and is resistant to many common disinfectants. Effective substances include
sodium hypochlorite (5% bleach diluted at 1:32), potassium peroxy-monosulfate, chlorine
dioxide and commercial products that have been approved for their virucidal activity.
New healthy cats should be vaccinated as soon as possible. Modified live virus vaccines are
preferred in shelters because of the earlier onset of protection.
FCV can be a major problem for cat breeders. Infection most often appears as upper
respiratory disease in young kittens, typically at around 4-8 weeks as MDA wanes. Disease in
such young kittens can be severe and frequently involves all the kittens in the litter; some
kittens may die. Vaccination of the queen will not prevent virus shedding, but may be
beneficial in ensuring that the kittens benefit from higher levels of MDA through the
colostrum and milk, providing protection for the first month or so of life.
Booster vaccinations should take place prior to mating. Vaccination during pregnancy is not
recommended. Modified live virus vaccines are not licensed for use in pregnant cats and if
considered at all, an inactivated vaccine must be used.
Queens should kitten in isolation, and in order to avoid the risk of exposure to potential
carrier cats, the litter should not mix with other cats until it has been fully vaccinated. Early
vaccination should be considered for litters from queens that had infected litters previously or
for which there is concern of infection. The earliest age for which FCV vaccines are licensed
is six weeks, but vaccination may be considered even earlier in kittens deemed to be at risk.
When levels of MDA may be too low to protect, vaccination should be repeated every two
weeks until the primary vaccination course is concluded at twelve weeks.
When all other control strategies have failed, early weaning into isolation from around four
weeks of age is an alternative approach to protect kittens against infection from their mothers.
Vaccines cannot generate optimum protection in animals with compromised immune function, such as deficient nutrition, genetic and acquired, viral immunodeficiencies, systemic disease, concurrent administration of immunosuppressive drugs and environmental stress. Efforts should be made to protect immunocompromised cats from exposure to infectious agents and to correct these conditions prior to vaccination; if this cannot be assured, vaccination should be performed nevertheless and repeated after the animal has fully recovered. Based on safety considerations, ABCD recommends inactivated vaccines in these circumstances. Modified live FCV vaccines should not be used in immunocompromised individuals, as the failure to control replication of the vaccine virus could lead to clinical signs.
Vaccination of FIV-infected cats is controversial. FIV-infected cats are capable of mounting immune responses to administered antigens except during the terminal phase of infection, but also primary immune responses may be delayed or diminished (Dawson et al., 1991; Reubel et al., 1994; Foley et al., 2003). FCV vaccination was less effective in cats shortly after experimental infection with FIV, as compared to uninfected cats, and vaccination might enhance long-term shedding of FCV (Dawson et al., 1991). Immune stimulation of FIV-infected lymphocytes in vitro promotes FIV replication. In vivo, vaccination of chronically infected cats with a synthetic peptide was associated with a decrease in the CD4+/CD8+ ratio (Lehmann et al.1992; Reubel et al., 1994). Therefore, a potential trade-off to protection from FCV-related disease is the progression of FIV infection as a result of increased virus production. Thus, only FIV cats with a high risk of exposure to infectious agents that are clinically healthy or in a stable medical condition should be vaccinated, and only killed vaccines used.
FeLV-infected cats should be kept indoors and isolated, to avoid exposure to FCV, but also to diminish the likelihood of retrovirus transmission to other cats. Asymptomatic FeLV-infected cats should be vaccinated against FCV. Although there is no evidence that FeLV-infected cats are at increased risk of vaccine-induced disease from residual virulence of modified-life virus vaccines, killed vaccines are preferable. FeLV-infected cats may not mount adequate immune responses to rabies vaccines and perhaps neither to other vaccines. Protection of FeLVinfected cats may therefore not be comparable to that achieved in uninfected cats, and more frequent vaccination should be considered.
Exceptions from the general rule to vaccinate only healthy animals apply for cats with chronic
illness, where vaccination may sometimes be necessary. Manufacturers evaluate vaccine
safety and efficacy in healthy animals and accordingly, vaccines are labelled for use in
healthy animals only. Nonetheless, cats with stable chronic conditions such as renal disease,
diabetes mellitus or hyperthyroidism should receive vaccines at the same frequency as healthy
cats. In contrast, cats with acute illness, debilitation, or high fever should not be vaccinated.
In cats with chronic stomatitis and FCV infection, administration of modified live FCV
vaccine is best avoided (Pedersen et al., 1995).
In cats under corticosteroid treatment, vaccination should be considered carefully. Depending on dosage and duration, corticosteroids may cause functional suppression of cell-mediated immune responses in particular. In dogs, corticosteroids do not hamper effective immunization if given for short periods of time at low to moderate doses (Nara et al., 1979), but the effect of corticosteroids on vaccine efficacy in cats is not known. Hence the use of corticosteroids and/or other immunosuppressants at the time of vaccination should be avoided.