The last decade has seen unprecedented discussion in relation to perceived health differences between purebred and crossbred dogs.¹ These discussions have promoted some notable developments in purebred dog health strategies and data collection. However, cats have also not been immune to concerns about health differences between purebred and crossbred types.² This presentation will explore some aspects of the state of knowledge on longevity and diseases in cats with a particular focus on differences between purebred and domestic varieties.

Cats are often considered as just small dogs but there are huge differences between the species in terms of breed structure, morphology and biology that demand separate epidemiological paradigms. Thanks to the indefatigable desire of mankind for 'better' morphology, the dog is now the most phenotypically diverse mammalian species on the planet. Wide variation in the longevity and common diseases across breeds of dogs have been well documented.³ Pet cats have been much less altered in terms of their size and variation from their wild progenitors. However, this does not mean that mankind has not played god with feline breeds as well and imprinted modern cat breeds with their own unique disease and longevity profiles.

In order to investigate longevity and disease in pet cats, representative and multifaceted data sources are required. Veterinary epidemiological research has relied on referral data for many decades. However, it is now increasingly recognised that selection biases in the disorders and cats that are referred conspire to make referral data highly unrepresentative of the wider population and therefore poorly useful for general epidemiological research.⁴

Insurance data have also been widely investigated in cats and offer a useful research resource. Research application is more reliable in countries with high insurance update.⁴ However, insurance data are limited by omission of clinical events that are excluded from policy cover, disorders where the cost exceeds the deductible excess and recurrent events for some disorders and death data are often constrained beyond the age specified as the cut-off for claiming life-cover.⁴ Despite these limitations, several useful insurance studies have been published on overall morbidity⁵ and mortality⁶ in cats. Among insured cats in Sweden from 1999 to 2006, 8.4% of cats had at least one claim per year. At a breed level, many pure breeds had significantly higher proportions of cats with at least one claim per year than the domestic cat. Siamese (13.77%, 95% CI 12.00–15.54), Burmese (13.39%, 95% CI 11.26–15.53) and Abyssinian group (13.33%, 95% CI 10.99–15.66) were among some breeds that were at significantly higher risk compared with the domestic cat (8.04%, 7.85–8.24).⁵

There is now renewed emphasis on primary-care veterinary clinical data for clinical research in the UK with the development of the VetCompass™ Programme. VetCompass™ at the Royal Veterinary College in London collects anonymised clinical record data on 2.5 million cats from a network of 600 UK practices. A VetCompass™ study of 4,009 confirmed deaths randomly selected from 118,016 cats attending 90 practices in England reported that the median overall longevity overall in cats was 14.0 years (IQR 9.0–17.0; range 0.0–26.7).⁷ This study reported that the median longevity of crossbred (domestic) cats (14.0 years, IQR 9.1–17.0; range 0.0–26.7) was greater than purebred cats (12.5 years; IQR 6.1–16.4; range 0.0– 22.0) (p<0.001).⁷ However, there were pure breeds with longevity values on both sides of the crossbred longevity (Table 1).

Table 1. Longevity of cat breeds attending primary-care veterinary practices in England (n=4,009)

Adapted from⁷.

Another VetCompass™ study characterised all disorders recorded in 3,584 cats from a study population comprised of 142,576 cats attending 91 clinics in England.⁸ The most common disorders recorded were periodontal disease (13.9%; 95% CI, 12.5–15.4), flea infestation (8.0%; 95% CI, 7.0–8.9), obesity (6.7%; 95% CI, 5.7–7.6), heart murmur (5.0%; 95% CI, 4.1–5.8) and traumatic injury (4.6%; 95% CI, 3.8–5.3). In relation to our questions of main interest, this study compared purebred and crossbred cats across the twenty most common disorders and identified that crossbreds had higher prevalence for two disorders (abscess [excluding cat bite abscess], p=0.009; hyperthyroidism, p=0.002), whereas purebreds had higher prevalence for one disorder (coat disorder; p<0.001; Table 2).

Table 2. Prevalence values in purebred and crossbred cats attending primary veterinary practices in England for commonly recorded disorders

Adapted from⁸.

These results tell a complicated story on longevity and health of purebred versus crossbred cats.

References

1.  Bateson P. Independent inquiry into dog breeding. Cambridge: University of Cambridge; 2010.

2.  Gunn-Moore D, Bessant C, Malik R. Breed-related disorders of cats. Journal of Small Animal Practice. 2008;49(4):167–8.

3.  O’Neill DG, Church DB, McGreevy PD, Thomson PC, Brodbelt DC. Prevalence of disorders recorded in dogs attending primary-care veterinary practices in England. PLoS One. 2014;9(3):e90501(pages 1–16).

4.  O’Neill DG, Church DB, McGreevy PD, Thomson PC, Brodbelt DC. Approaches to canine health surveillance. Canine Genetics and Epidemiology. 2014;1(1):2.

5.  Egenvall A, Bonnett BN, Häggström J, Ström Holst B, Möller L, Nødtvedt A. Morbidity of insured Swedish cats during 1999–2006 by age, breed, sex, and diagnosis. Journal of Feline Medicine and Surgery. 2010;12(12):948–59.

6.  Egenvall A, Nødtvedt A, Häggström J, Ström Holst B, Moller L, Bonnett BN. Mortality of life-insured Swedish cats during 1999–2006: age, breed, sex, and diagnosis. Journal of Veterinary Internal Medicine. 2009;23(6):1175–83.

7.  O’Neill DG, Church DB, McGreevy PD, Thomson PC, Brodbelt DC. Longevity and mortality of cats attending primary care veterinary practices in England. Journal of Feline Medicine and Surgery. 2015;17(2):125–33.

8.  O’Neill DG, Church DB, McGreevy PD, Thomson PC, Brodbelt DC. Prevalence of disorders recorded in cats attending primary-care veterinary practices in England. The Veterinary Journal. 2014;202(2):286–91.