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.


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Congenital anomalies of the cardiovascular system are defects present at birth, and often lead to perinatal death 56 in dogs. However, in some cases, congenital heart diseases are asymptomatic and undetected until later in life, 57 so the percentage of dogs with congenital heart diseases that survive to adulthood to breed can be rather high.

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To decrease the incidence of CHDs in the dog population as a whole, the early identification of affected dogs 59 could inform a breeding program. Furthermore, some of the most common CHDs could be successfully treated 7 where Y is the vector of observations, β is the vector of the fixed effect (breed * period interaction) and var[ε] = 169

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This retrospective study was based on the 1,779 clinical records that fulfilled the inclusion criteria. Single cardiac 171 defects were present in 1,568 dogs (88.14%), and 2 or more concurrent defects were found in 211 dogs (11.86%).

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The total observed cases of congenital heart defects are reported in Table 1, including information on sex and 173 age at presentation.

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In addition to Boxers, PS was very common in other brachycephalic breeds, including French and English Bulldogs.

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Interestingly, PS was also the most common CHD in Pinschers, in which the only other congenital heart disease 236 observed was PDA (Table 2). 14 In Tables 3 and 4, the frequency of the most common CHDs by sex are reported for the purebreds and crossbreds,   238 respectively.

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PS and PDA were also the most common cardiac defects in crossbreds, and PDA was detected significantly more 260 frequently in females, and PS was detected more frequently in males (Table 4).

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In 189 purebred dogs and in 22 crossbreds, two or more defects were detected.

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The number of the CHDi found in the selected breeds, the OR for the overall CHDi, the popularity of the breeds 296 and the volatility for each breed are reported in Table 6.

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The clinic involved in this study is a valuable site from which to monitor the evolution of trends among different 331 breeds because it has been a referral center for CHDs studies in the authors' country since 1997 and is based in

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The probability of admitting a Boxer affected by PS decreased from 1997 (35%) to 2017 (23.8%) in the overall 349 population of the RC (Fig 2). This result can be explained as an effect of the screening program that has been in  Golden Retrievers was due more to the influence of movies (Fig 3) [12].

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Type 3 (23.76%). It interesting to note that SAS was the 2 nd most common CHD in our population from 1997 to 22 in Boxers (85.8%), and the screening program at this center was aimed to reduce the incidence of both (Fig 4).

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The reduction of SAS in Boxers is an interesting result because it demonstrates the effectiveness of the screening 405 and breeding program in Boxers. In other words, the increased prevalence of PS in 20 years is not a failure of the 406 Boxer screening and breeding program, but rather the result of the large increase in fashion breeds, such as the 407 French Bulldog, English Bulldog and American Staffordshire Terrier, that are not screened.

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AS was the 4 th most common CHD in our population. AS was significantly more frequent in males (7.51% CI 4.57-409 7.05, P< 0.005) ( Table 3) than in females, and Bull Terriers were the most affected breed (30%) ( Table 2).

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The dogs diagnosed with AS were older than the dogs affected by other CHDs, and the extreme ages at 411 presentation were 50 months (AS) and less than 12 months (TOF) (Fig 1).

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Many complex defects were found in our population, and PS was the most common CHD detected in association 417 with the other CHDs (SAS, VSD, PDA) ( Table 5). The overall prevalence of the PS-SAS association in Boxers (85.8%) 418 seems very high; however, the value has been estimated over the 20-year period (Fig 5). SAS-PDA was very 419 common in Newfoundland; this complex CHDs was found in the 84.6% of the admitted dogs belonging to this 420 breed (Fig 5).

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The influence of media, including movies, television and radio, on the audience is well known and described 10-12 . In conclusion, this study allowed us to evaluate the Boxer screening program for CHDs, whose success is 478 evidenced by the decreased prevalence of SAS and PS in this breed.

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However, the paradox that people buy breeds of dog that are predisposed to congenital heart diseases was also 480 evidenced in our study, and, as reported elsewhere, fashions and trends influence many individual choices 481 [11,12,29,30].