Clinical Epidemiology of congenital heart diseases in dogs: prevalence, popularity and volatility throughout twenty years of clinical practice

The epidemiology of Congenital Heart Diseases (CHDs) has changed over the past twenty years. We evaluated the prevalence of CHDs in the population of dogs recruited in a single referral center (RC); compared the epidemiological features of CHDs in screened breeds (Boxers) versus nonscreened (French and English Bulldogs and German Shepherds), investigated the association of breeds with the prevalence of CHDs, determined the popularity and volatility of breeds over a 20-year period; and analysed the trends of the most popular breeds in the overall population of new-born dogs registered in the Italian Kennel Club from 1st January 1997 to 31st December 2017. This was a retrospective observational study, the cardiological database of the RC was analysed, and 1,779 clinical records fulfilled the inclusion criteria. Descriptive statistics and frequencies regarding the most representative breeds and CHDs were generated. A logistic regression model was used to analyse the trends of the most common CHDs found in single breeds (French Bulldog, English Bulldog, Boxer, and German Shepherd), and in groups of breeds (brachycephalic breeds and the most represented large breeds). The relationships between the breed popularity and the presence of CHDs was studied. The most common CHDs were Pulmonic Stenosis (34,1%), Patent Ductus Arteriosus (26,4%), Subaortic Stenosis (14,6%), Ventricular Septal Defect (4,8%), Aortic Stenosis (4,7%), Tricuspid Dysplasia (3,4%), Atrial Septal Defect (1,9%), Double Chamber Right ventricle (1,8%), Mitral Dysplasia (1,6%), and reverse Patent Ductus Arteriosus (0,7%). The most represented pure breeds were Boxer (19,4%), German Shepherd (9,4%), French Bulldog (6,2%), English Bulldog (4,9%), Maltese (3,7%), Newfoundland (3,1%), Rottweiler (3,1%), Golden Retriever (3,0%), Chihuahua (2,8%), Poodle (2,5%), Cavalier King Charles Spaniel (2,2%), American Staffordshire Terrier (2,1%), Labrador Retriever (2,3%), Dobermann (2,1%), Miniature Pinscher (2,0%), Cocker Spaniel (2,0%), Yorkshire Terrier (1,7%), Dogue de Bordeaux (1,6%), Dachshund (1,6%), and Bull Terrier (1,5%). Chihuahuas, American Staffordshire Terriers, Border Collies, French Bulldogs, and Cavalier King Charles Spaniel were the most appreciated small and medium breeds, all of which showed a high value of volatility. In conclusion, this study found evidence for the value of the screening program implemented in Boxers, which decreased the prevalence of Subaortic Stenosis and Pulmonic Stenosis. However, fashions and trends influence dog owners’ choices more than the worries of health problems frequently found in a breed. Effective breeding programs are needed in order to control the diffusion of CHDs without impoverishing the genetic pool; in addition, dog owners should be educated, and the breeders supported by a network of veterinary cardiology centers.