Descriptive epidemiology of feline upper respiratory tract disease in an animal shelter

Abstract

Upper respiratory tract disease (URTD) is common and spreads quickly in cats residing in animal shelters in the United States. Estimates of the actual incidence of URTD are sparse, yet this information is very important for welfare, economic and research purposes. In a large urban shelter in the northeastern US, 531 individual kittens, 701 litters, and 2203 adult cats were observed for signs of URTD during their stays. The median lengths of stay for adult cats and kittens were 5 and 4 days, respectively. Observations were made over a 50-week period. Approximately 1/3 exhibited signs of infectious respiratory disease. The crude incidence density estimates of URTD were 6.2, 6.7, and 5.6 cases per 100 cats per day among individual kittens, litters and adult cats, respectively. Increasing time of residence in the shelter increased risk of URTD. Using the Kaplan-Meier product limit method, the cumulative probability of developing URTD by day 7 in the shelter was approximately 32% (based on n=211) for litters, 31% (n=120) for individual kittens and 26% (n=763) for adult cats. By day 14, these cumulative probabilities had risen to 84% (n=18), 86% (n=7), and 80% (n=51) among litters, individual kittens and adult cats, respectively. The Kaplan-Meier failure function curve (probability of developing URTD overtime) for adults was significantly lower than those for litters or individual kittens (P<0.04). Among adult cats, those 11 years of age and older had a significantly higher risk of URTD compared to younger adult cats (P<0.05). Male cats (neutered and castrated) had higher URTD rates than ovariohysterectomized females, and purebred cats had a higher risk than those of mixed breeding. In this shelter, cats identified as strays were more likely to exhibit URTD than owner-surrendered cats. Affected cats spent a median of 3 more days than unaffected cats before they developed URTD. Approximately 1/3 (31.4%) of the observed individual kittens and 2/3 (61.8%) of the observed adult cats were euthanased with URTD in this shelter. Other factors such as space and behavior, especially among affected adult cats, were also cited as reasons leading to euthanasia.