Population management

Crowding and the attendant stress is undoubtedly the single greatest risk factor for severe respiratory (and other) disease outbreaks in populations. Increased population density leads to a greater risk of disease introduction, higher contact rate, reduced air quality, and often, compromises in housing and husbandry. Unfortunately, crowding in shelters is not uncommon, either due to insufficient facilities to provide even minimal care for the stray population, or (as is increasingly common) a well-intended attempt to decrease euthanasia by housing more animals. Tragically, such efforts may not only fail to improve the number of animals adopted, they may actually lead to increased disease and death[1]. Even in a boarding facility or vet clinic, it is important to anticipate times of peak population, recognize that these will be periods of increased risk for respiratory disease outbreaks, and plan sufficient additional staff that husbandry is not compromised.

An under appreciated strategy for respiratory disease prevention is to simply reduce the amount of time each cat spends in the shelter environment. Length of stay has been shown in several studies to be a significant risk factor for development of feline URI[2, 3]. Reducing length of stay may not be possible (or desirable) in a boarding facility or vet hospital, but management practices that increase length of stay for shelter cats should be carefully assessed to ensure the benefit of these practices outweighs the risk of disease they may create. This could include routine quarantine of apparently healthy animals, delays created by backlogs in behavior assessment or surgery, or failure to move cats to public-viewing areas of the shelter as soon as they are available for adoption.  Increased time for each cat in the shelter also contributes substantially to increased crowding with all the associated risks.

Stress reduction

Because clinical signs and shedding of FHV-1 are activated by stress, reduction is crucial to feline URI control. Even moving cats from cage to cage is enough to induce reactivation in some cats[4, 5]. “Spot cleaning” where possible and prioritizing housing for cats that does not require extensive movement or handling for care is likely key to control of URI. Providing hiding places, decreasing noise exposure, maintaining light/dark cycles and comfortable temperatures, and providing toys and scratching surfaces are also important to relieving feline stress. Unnecessary aversive handling should be minimized – the theoretical benefit of interventions that involve handling or forceful medication must be weighed against the certain stress these procedures cause.

Feline socialization programs can be helpful in relieving stress but must be implemented and monitored with care. Being removed from a cage, cuddled by a stranger and carried to an unfamiliar room to play may provide welcome relief from boredom for some cats, but may be highly stressful for others, as well as serving to efficiently spread disease.

Vaccination

Vaccination does not prevent infection or development of a carrier state for any URI pathogen, and many strains of feline calicivirus are vaccine resistant. At best, vaccination reduces severity and duration of disease. Vaccines should be given immediately upon shelter entry for best effect, or at least one week prior to entry for boarding kennels and catteries.

Modified live (MLV) parenteral vaccines are available containing feline herpesvirus, feline calicivirus and feline panleukopenia (FVRCP). Intranasal MLV two-way (FVRC) or three-way (FVRCP) vaccines are also available. Modified live vaccines are generally preferred for the more rapid protection induced (5-7 days parenteral, 3-5 days intranasal). However, modified live vaccines (especially intranasal) may cause mild clinical signs. In shelters that euthanize cats for any sign of URI, the risk of these mild signs must be weighed against the likely benefits of modified live vaccines.

Because URI and panleukopenia vaccines are generally delivered in combination, this is a consideration in vaccine selection. Panleukopenia is recognized with increasing frequency throughout the US, and the superior protection provided by the MLV parenteral vaccine against this disease makes it the best choice in most situations. In one study the 2-way intranasal FVRC vaccine given in addition to a killed SC FVRCP vaccine provided modestly improved protection against URI. No data has been published regarding the efficacy of combing SC modified live with an intranasal modified live vaccine for herpes/calici, although the possibility exists that administration by both routes simultaneously would provide superior protection.  Anecdotal reports from shelters are extremely varied regarding the efficacy of this strategy  (from those that report a significant apparent decrease to those that report no change or even increased URI). If a modified live intranasal vaccine is used in addition to a subcutaneous 3 way FVRCP vaccine, an effort should be made to track the impact on URI within an individual shelter (see data collection section below).

A MLV Bordetella vaccine for cats is available, but is not generally recommended for shelters except when repeated problems are demonstrated by laboratory diagnostics. Killed and modified live vaccines are available for C.  felis (often given in combination with FVRCP). This vaccine is not generally recommended, as it has a short duration of effect, is only partially effective, and may have a relatively high frequency of adverse reactions. Frequent recognition of clinical Bordetella or Chlamydophila in cats is often an indicator of overall husbandry problems, and prevention should focus on improvement of environmental management, rather than control of these agents specifically. The need for this vaccine, if used, should be periodically revisited. No Mycoplasma vaccine is available for cats. For more information on vaccination for feline URI, see the American Association of Feline Practitioners Vaccine Guidelines, available online. This document includes specific recommendations for shelter cats.

Air Quality

Air quality is undoubtedly important to URI control. The relevant air quality is at the level of the cat’s nose, not the room at large. Although fresh air exchange is often emphasized, reduction of airborne contaminants is equally or more effective (e.g. through reducing population density, frequent litter box cleaning, low dust litter, use of disinfectants at correct dilution).  Air filtration (i.e. HEPA filter) may be tried, although it is less effective than fresh air exchange or contaminant reduction. Filters need to be replaced frequently to prevent them from becoming a nidus of infection in themselves. Ozone based air filters should be avoided, as ozone itself may be a respiratory irritant.

Disinfection

Most URI pathogens survive in the environment no more than a few hours (FHV-1) to a few weeks (Bordetella) and are inactivated by routinely used disinfectants. Feline calicivirus is a notable exception, and may survive for up to a month or even longer in dried discharge. FCV is inactivated by household bleach (5% sodium hypochlorite) diluted at 1:32, or by potassium peroxymonosulfate (Virkon® or Trifectant®).[6, 7] Calicivirus is NOT reliably inactivated by alcohols, and hand sanitizers commonly used in shelters may not be completely effective. Sanitizers containing 60-90% ethanol and propanol are more effective than other alcohols.[8]  As noted above, the stress and fomite transmission associated with cleaning a typical box style single cat cage may outweigh the benefit of thorough disinfection. If possible, cages should be spot-cleaned while cats are in residence, and thoroughly cleaned, disinfected and dried between residents.

Isolation

Many cats shed URI pathogens without showing clinical signs, hence the need for careful hygienic precautions even when handling apparently healthy cats. Cats with active signs of infection are likely to be shedding much greater amounts, and isolation of these cats from the general population is a requirement for even a minimal disease control program. Many cats are still shedding increased amounts for a few weeks following recovery. Although not always practical, ideally these cats will not be mixed directly back into the general population, or at least not with vulnerable populations such as kittens or recent arrivals.