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The Demographics of Canine Hip Dysplasia in the United States and Canada.

1. Introduction

Canine hip dysplasia (CHD) is a well-known disorder in veterinary medicine [1-4], especially amongst certain breeds. The human counterpart of CHD, developmental dysplasia of the hip (DDH), is also a well-known problem with differences in prevalence by race/ethnicity [5], analogous to breed differences in CHD. Comprehensive literature reviews of DDH have shown various demographic patterns regarding sex, laterality, latitude, and seasonal variation in birth month [5, 6]. Variation in birth month/season has been described in a few small series of CHD [7-12]. There has been no study of the demographics of CHD using a large data set. The purpose of this study was to investigate the demographics of CHD using a large North American data base and analyze the differences by breed, sex, laterality, seasonal variation in birth, and latitude. Comparison with the demographics of DDH may shed further light on the etiology ofboth conditions and specifically support the use of CHD as an animal model for DDH, as well as DDH pointing towards further comparative research areas in CHD.

2. Materials and Methods

2.1. Data Source. The data for this study was the complete hip dysplasia registry (both public and private) collected by the Orthopedic Foundation for Animals (OFA) through April 2015. There were a total of 1,430,979 records. The OFA hip score uses the American Veterinary Medical Association grading system: 1 = excellent, 2 = good, 3 = fair, 4 = borderline CHD, 5 = mild CHD, 6 = moderate CHD, and 7 = severe CHD. These scores were divided into two groups: those with CHD (scores 5-7) and those without CHD (scores 1-3); the borderline score of 4 was excluded. Duplicate records, feline cases, and those with an indeterminate score were deleted. The country of origin was known in 1,130,478 dogs; the vast majority (1,121,961-99.25%) were from the USA (1,046,249) or Canada (75,712). Dogs less than 24 or greater than 60 months of age at the time of the radiograph were next deleted, leaving 921,046 unique records which are the data for this study.

2.2. Data Groups. Each dog was classified into related breed groups using both the American Kennel Club (AKC) (http://www.akc.org) [13] and Federation Cynologique Internationale (FCI) (http://www.fci.be/en/Nomenclature) [14] systems. Each dog was separately given an AKC and FCI group designation and analyzed separately; the two different systems were not merged. Dogs in each of these groups are relatively similar genetically [15, 16] and thus could be expected to respond to environmental triggers similarly, compared to dogs that do not share a common genetic background. The AKC categories are herding, hound, working, sporting, nonsporting, terrier, toy, native, hybrid, and miscellaneous groups. The FCI categories are (1) sheep and cattle dogs; (2) pinscher, schnauzer, molossoid, and Swiss mountain and Swiss cattle dogs; (3) terriers; (4) dachshunds; (5) spitz and primitive dogs; (6) scent hounds; (7) pointers; (8) retrievers, flushers, and water dogs; (9) companion and toy dogs; and (10) sighthounds.

The variables analyzed were sex, breed, season of birth, hip score, and latitude. Season of birth was arbitrarily defined as follows: winter, December through February, spring, March through May, summer, June through August, and autumn, September through November. Each state and province was grouped by latitude. The latitude where each dog was living at the time of the radiograph was placed into 4 groups defined as (1) <30[degrees]N, (2) 30-39[degrees]N, (3) 40-49[degrees]N, and (4) >50[degrees]N. Those <30[degrees]N were Florida, Hawaii, Louisiana, Puerto Rico, Virgin Islands, and Guam. Those 30-39[degrees]N were Alabama, Arkansas, Arizona, California, Colorado, District of Columbia, Delaware, Georgia, Indiana, Kansas, Kentucky, Maryland, Missouri, Mississippi, North Carolina, New Mexico, Nevada, Oklahoma, South Carolina, Tennessee, Texas, Virginia, and West Virginia. Those 40-49[degrees]N were the states of Connecticut, Iowa, Idaho, Illinois, Maryland, Maine, Michigan, Minnesota, Montana, Nebraska, New Hampshire, New Jersey, New York, Ohio, Oregon, Pennsylvania, Rhode Island, South Dakota, Utah, Vermont, Washington, Wisconsin, and Wyoming and the provinces of New Brunswick, Newfoundland, Nova Scotia, Ontario, Prince Edward Island, and Quebec. Those >50[degrees]N were the state of Alaska and the provinces of Alberta, British Columbia, Manitoba, Northwest Territories, Saskatchewan, and Yukon Territory. Although a few of the states and provinces straddle these latitude lines, each state/province was placed into the group corresponding to the major population areas.

2.3. Statistical Analysis. Demographic variables were first analyzed using bivariate analyses (Pearson's [chi square] test) to determine differences between those with and without CHD. Next, binary multivariate logistic regression analyses were performed to determine adjusted odds ratios (OR) and 95% [upper, lower] confidence intervals of a dog having CHD. While the American Veterinary Medical Association grading system is a numerical value, it is not a continuous variable such as the Norberg angle, but rather a categorical ordinal variable determined by subjective criteria (http://www.ofa.org/hd_grades.html--hip dysplasia, OFA X-ray procedures). For this reason, CHD grade was considered to be a categorical variable. All statistical analyses were performed with Systat[TM] 10 software (Chicago, IL, 2000), and p < 0.05 was considered statistically significant.

3. Results

3.1. Overall Results. The hip dysplasia scores were 1 in 74,931 dogs; 2 in 601,893; 3 in 95,154; 4 in 6,772; 5 in 86,321; 6 in 47,971; and 7 in 8,004, resulting in an overall CHD prevalence of 15.56%. There was significant variability in the prevalence of CHD by AKC and FCI groups, gender, latitude, and season of birth (Table 1). CHD was overall slightly more common in females, those born in spring and winter (Figure 1(a)), and those born in the more southern latitudes (Figure 1(b)). Within AKC groups, CHD was most prevalent in hybrid breeds (21.5%) and least prevalent in hounds (10.5%) (Figure 1(c)). Within FCI groups, it was most prevalent in group 2 (pinscher, schnauzer, molossoid, and Swiss mountain/Swiss cattle dogs) (20.4%) and least common in group 10 (sighthounds) (5.2%) (Figure 1(d)). Although there was a statistically significant difference in the prevalence of CHD by age at the time of radiography (Figure 1(e)), the variability was less than 2% and considered to not be clinically significant, especially since the oldest group of dogs had a lower prevalence of CHD than the youngest cohort. Age was thus deleted from all further analyses. There was significant variation by individual breeds. The prevalence of CHD by breeds in this study is very similar to that given on the OFA website http://www.ofa.org, even though dogs outside of Canada or the USA were excluded in our study. The complete CHD prevalence data set is given in Supplemental Table 1 in Supplementary Material available online at https://doi.org/10.1155/2017/5723476; the highest prevalence was in the bulldog (77.7%) and the lowest in the Italian greyhound (0.0%).

3.2. Results by Demographic Parameters. The overall OR for CHD was higher in females (1.05 [1.064, 1.039]; p < [10.sup.-6]), those born in spring (1.143 [1.16,1.13]; p < 0.004), and those living in more southern latitudes (<30[degrees]N) (OR 2.12; [2.21, 2.04]; p < [10.sup.-6]). These results from the composite data set obviously reflect the proportion of breeds in the OFA database and could likely be different if the breed composition differed. Therefore, analyses for each AKC and FCI group, as well as individual breeds, were performed (Table 2). Due to small numbers in certain groups, those in the native, hybrid, and miscellaneous were excluded when analyzing by AKC groups and the dachshunds when analyzing by FCI groups. Within AKC groups, working dogs had the highest risk of CHD (OR 1.882) with hounds being the reference group. Within FCI groups, group 2 (pinscher, schnauzer, molossoid, and Swiss mountain/Swiss cattle dogs) had the highest risk of CHD (OR 4.168) with sighthounds being the reference group. Those born in spring had the highest risk of CHD (OR 1.14) as well as those living in latitudes < 30[degrees]N (OR 2.1), with a minimally higher risk in females (OR 1.05).

3.3. Results by AKC and FCI Groups. Analyses by each of the AKC and FCI groups were next performed (Table 3). Again, many of the groups showed an increase in CHD in those living in latitudes <30[degrees]N, except for toy dogs (where the opposite was noted with a higher risk in the most northern latitudes >50[degrees]N); hounds had no variation in CHD by latitude. When there was an increased OR by season of birth, winter and spring seasons most commonly demonstrated the increased risk with a few demonstrating an autumn increase; no group demonstrated a summer increase. A few groups demonstrated an increased CHD risk in females (AKC herding, working and sporting groups and FCI sheep/cattle and pinscher groups); sighthounds had an increased risk in male dogs.

Analyses within subgroups of AKC and FCI groups (Supplemental Table 2) as well as the most common 25 breeds in the data set (Supplemental Table 3) were also performed. Here again, similar findings are as seen for individual AKC and FCI groups. The detailed ORs of CHD for all dogs with n > 1000 as well as all dogs with n > 100 and a CHD prevalence of >15% (the median value) are given in Supplemental Table 4.

3.4. Severity and Laterality of CHD. For those dogs with CHD, severity of the CHD was analyzed (Table 4). Severe CHD (score of 7) was more common in those with bilateral involvement, AKC groups of herding and working dogs, FCI groups of pinscher and sheep/cattle dogs, those living in the most southern latitudes (<30[degrees]N), and those born in spring. Males had a slightly higher proportion of severe CHD. Regarding unilateral or bilateral involvement, bilateral disease was most prevalent in terriers and least prevalent in hybrid dogs within AKC groups (Figure 2(a)); bilateral disease was most prevalent in terriers and least prevalent in sighthounds within FCI groups (Figure 2(b)).

4. Discussion

Limitations of this study need to be acknowledged. Although we used a very large data set, it may not give the true prevalence of CHD, since it only represents the data on those dogs whose radiographs were submitted to the OFA. This predisposes to selection bias as it is not a truly random sample of the canine population [17]. Determination of the "true" prevalence would require a prospective radiographic exam between 2 and 5 years of age of every dog consecutively born, with a population of at least 1 million. Obviously such a study is impossible to perform. The OFA data set is therefore likely the best that can be presently obtained in the North America with the possible exception of the PennHIP[TM].

With these limitations in mind, there are several important findings. CHD is slightly more common in females, but with a large variation, ranging from 3.36 times more frequent in female Polish Tatra Sheepdogs to 1.63 times more frequent in male Afghan Hounds (Supplemental Table 1). CHD prevalence varies by breed, which was again demonstrated in this study, ranging from 77.7% in the bulldog to 0% in the Italian Greyhound. Many breeds demonstrated a mild increase in risk for CHD when born in winter and spring. CHD was unilateral in 33% of all dogs with CHC. Unilateral involvement was more common in herding/sporting dogs and they had lower hip dysplasia scores. Finally, a new finding is that the prevalence of CHD is more common in dogs living in more southern latitudes.

This study confirms the marked variability in CHD prevalence by breed. In France, the highest prevalence of CHD was in the Cane Corso (59.7%) and the lowest in the Siberian Husky (3.9%) [18]. In a national Veterinary Medical Database from the entire USA [19], the OR of CHD was 10.2 in the Kuvasz with mixed breed dogs being the reference group. In a more recent study using the Veterinary Medical Database [20] the highest prevalence of CHD was 17.16% in the Newfoundland and 0.12% in the Scottish Terrier. In USA veterinary teaching hospitals, the prevalence of CHD was highest in the Rottweiler (35.4%) and lowest in the miniature schnauzer dogs (1.5%) [21]. In a Norwegian study comprised of Newfoundland, Leonberger, Labrador Retriever, and Irish Wolfhounds (n = 501), the highest prevalence of CHD was in the Newfoundland and the lowest in the Irish Wolfhound (OR 0.22 that of the Newfoundland) [22]. In Turkey, a study of 484 dogs from 7 different breeds revealed the highest prevalence in Doberman Pinschers (70.6%) and the lowest in Golden Retrievers (50%); the prevalence in Doberman Pinschers in this study in North America was low at 5.1%. It must be remembered that many of these studies used a different grading system than the OFA scores; however, it still confirms marked variability within breeds within each study.

The quoted prevalence of CHD is frequently different between different studies for a particular breed. When comparing the data of Witsberger et al. [20] to ours, the prevalence of CHD for the Newfoundland was 17.2% versus 20.0%, Saint Bernard 14.7% versus 36.8%, Rottweiler 10.3% versus 12.5%, German Shepherd 10.3% versus 16.3%, Golden Retriever 8.5% versus 14.9%, Labrador Retriever 7.4% versus 9.2%, Bulldog 4.4% versus 68.9%, Doberman Pinscher 1.3% versus 5.1%, and Greyhound 0.4% versus 2.1%, respectively. This demonstrates that the sampling technique/composition of the data set markedly impacts the prevalence value as previously mentioned. Prevalence amongst each breed within a country, or region, is likely a result of gene flow, bottle necks, popular sire effects, and the efforts of individuals and breed clubs to impact the prevalence and severity of CHD in a particular breed.

We noted a slight increase in CHD in females with marked differences by breed. Several studies noted no sex difference in the prevalence of CHD. In Norway, Turkey, and the United Kingdom no sex differences were noted for the various breeds studied [22-25]. In Sweden, CHD was 1.14 times more common in female German Shepherds compared to males [26]. In the United States, sex differences were noted in Golden Retrievers [27]; the prevalence of CHD was 5.1% in intact males, 10.3% in males neutered early, 0% in males neutered late, 39% in intact females, 4.5% in females neutered early, and 0% in females neutered late. The status of neutering in the OFA registry is not given, so we cannot compare our findings to those of Torres de la Riva [27].

The prevalence of unilateral CHD was 33% in this study. The prevalence of unilateral CHD was 35% in a New York study of 1022 dogs consisting of Labrador Retrievers, Golden Retrievers, German Shepherds, and crossbreeds [2]. In Pennsylvania, it was 6% in 133 Greyhounds. A recent study of multiple breeds from Italy noted an overall percentage of unilateral CHD of 31.5% [28], strikingly similar to the 33% in this study and the 35% of Lust et al. [2]. This is the first study to investigate the proportion of unilateral CHD by AKC/FCI groups; for AKC groups it was highest in herding dogs (35.4%) and lowest in terriers (27.5%); for FCI groups it was highest in sheep/cattle dogs (35.4%) and lowest in terriers (25.1%) (Table 1).

Few studies discuss season of birth and CHD. In Norway [29], the OR for CHD (Newfoundland, Leonberger, Labrador Retriever, and Irish Wolfhounds) was 3.94 times higher in autumn and 1.85 times higher in winter compared to spring. In another Norwegian study [9], pointers had an increase in CHD in those born in August to February, Labrador Retrievers September to February, with no seasonal effect on CHD in German Shepherds or Golden Retrievers. In Finland [7], German Shepherds born in spring or summer had less CHD. In England [10], Labrador Retrievers and Gordon Setters had less CHD when born in July through October. In New Zealand [8], Labrador Retrievers and Rottweilers had less CHD when born in autumn, but no seasonal variation was observed for German Shepherds or Golden Retrievers. In aggregate, the previous studies in the Northern Hemisphere noted that dogs born in autumn and/or winter months demonstrate a higher prevalence of CHD. In this study we noted an increase of CHD primarily in winter and spring months. When reviewing the data from Supplemental Table 3, 563,403 of the 619,825 dogs (81.4%) showed a seasonal variation. Of these 536,403, 313,202 (55.6%) had the highest percentage in winter, 229,925 (40.8%) in spring, and 20,276 (3.6%) in autumn.

There are several postulated reasons for seasonal differences in CHD. One is the relationship between hip muscle development and season. The most critical time for canine hip joint development is between 3 and 9 months of age [8, 30]; cage confinement during this crucial period has a protective effect on the hip [30]. The proposed explanation is that puppies born in winter spend more time in cages/indoors than in free activities, and indoor confinement may keep the hips in flexion and abduction lessening the development of CHD [29]. The same has been noted in human DDH, where carrying the infant in positions of hip abduction and flexion reduces the incidence of DDH [31-35] while swaddling in extension increases the incidence of DDH [5, 36, 37]. Our results refute a winter protective effect in CHD. A second explanation is that puppies born in late autumn or early winter, compared to those born in spring or early summer, do not get as much physical exercise. Puppies getting less physical exercise may develop weaker hip musculature than those with a lot of outdoor activity, which when combined with rapid skeletal growth results in weakened constraints on the hip, subsequent subluxation, and CHD [8, 22, 29, 30]. This can explain the increase in CHD in dogs born in late autumn/early winter and corroborates the findings from New Zealand, England, and our study, while conflicting with the data from Norway, Finland, and Sweden.

Another postulated mechanism for CHD seasonal variation is diet and weight gain in puppies. Dogs with limited weight gain in early life have a lower prevalence of CHD [2, 22, 29, 38, 39]. In cold winter months dogs have increased food intake [40, 41], and if not accompanied by an increase in energy consumption (e.g., activity), the dog will gain weight. Increased body weight increases the stress across the developing hip joint leading to subluxation [17, 42, 43]. Vitamin D plays a role in DDH, as humans with homozygosity for the mutant Taq1 vitamin D receptor t allele demonstrate increased acetabular dysplasia [44]. Vitamin D levels may vary by season due to seasonal variation in vitamin D dietary content in both humans and animals [45-52]. Low vitamin D levels and increased body fat in winter may result in more CHD. Finally, various dietary factors differ by season and could result in seasonal differences in hormones in milk (vitamin D, relaxin, and vitamin C) and secondarily influence hip development [52-57].

This is the first description of an increased prevalence of CHD in more southern latitudes. This was true even when multivariate regression logistic analysis was performed adjusting for breed group, gender, and season of birth. One potential explanation is that the generally warmer climate in more southern latitudes may result in a general increase in physical activity at all times, with the hips being less abducted and flexed, resulting in more CHD. Another potential explanation is that the gene pools may be different in different latitudes. Finally, other environmental factors such as diet as discussed above maybe involved, resulting in increased CHD. Perhaps the dogs in the more southern latitudes are heavier and place more stress across the hip. It could also be that the dogs in the warmer more southern latitudes grow more rapidly early in life, which is a well-known contributing factor to CHD [38, 39]. This finding and potential explanations will require further study.

There are marked differences and similarities between DDH and CHD (Table 5). The most striking is the difference in incidence/prevalence by race/breed. Prevalence/incidence variation in humans is higher (950-fold difference in Native Americans compared to Africans in Africa) than canines (96-fold difference in the bulldog compared to the whippet) (Supplemental Table 1). DDH occurs predominantly in females (75%) for all races [5], while for CHD the prevalence was only slightly higher in females compared to males (Table 1). However there are large sex variations in CHD which ranged from 3.4 times more frequent in female Polish Tatra Sheepdogs to 1.6 times more frequent in male Afghan Hounds. DDH is usually unilateral (63.4%) [5] compared to CHD which is usually bilateral (67%). DDH demonstrates a seasonal variation in ~91.0% of cases [6], and 81.4% in CHD, which is remarkably similar. DDH was most prevalent when the baby was born in winter months (70.3%); CHD was most prevalent when the puppy was born in winter and spring. DDH is more common in northern latitudes, while CHD is more common in southern latitudes [5, 6]. This latitudinal difference has also been noted in children with Perthes' disease [58]. Within DDH there are two different types, the typical infantile DDH and the late onset adolescent/adult acetabular dysplasia [59]. The older group, when compared to the infantile group, demonstrated a lower female predominance (88.0 versus 98.0%) with more bilateral involvement (61.2% versus 45.1%). Our findings in CHD more closely mirror the demographics of DDH in the late onset group.

In conclusion, the prevalence of CHD differed markedly by breed, having a slight female predominance but with significant variability by breed, was unilateral in about one-third of cases, and often demonstrated a seasonal variation with a mild increase when the dog was born in spring and winter months. Most interestingly, CHD was more prevalent in the more southern latitudes. This information is important to owners/breeders, suggesting that monitoring of puppies for signs of CHD should be undertaken during the birth months when there is an increased OR of CHD for those affected breeds and/or AKC groups, especially in more southern latitudes. The similarities between CHD and DDH are striking, especially late onset DDH, and suggest that comparative studies of both disorders should lead to a better understanding of a problem that leads to debilitating hip osteoarthritis in both canines and humans.

https://doi.org/10.1155/2017/5723476

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Acknowledgments

The authors wish to thank Mr. Eddi Dzuik and Jon Curby, Orthopaedic Foundation for Animals, for granting the authors access to the entire hip dysplasia registry. This research was supported in part by the Garceau Professorship Endowment, Indiana University, School of Medicine, Department of Orthopaedic Surgery, and the Rapp Pediatric Orthopaedic Research Endowment, Riley Children's Foundation, Indianapolis, Indiana.

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Randall T. Loder (1) and Rory J. Todhunter (2)

(1) Department of Orthopaedic Surgery, Indiana University School of Medicine and James Whitcomb Riley Children's Hospital, Indianapolis, IN 46202, USA

(2) Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853-6401, USA

Correspondence should be addressed to Randall T. Loder; rloder@iupui.edu

Received 28 December 2016; Accepted 27 February 2017; Published 12 March 2017

Academic Editor: Antonio Ortega-Pacheco

Caption: Figure 2: Unilateral and bilateral involvement in CHD. (a) By AKC group. (b) By FCI group.
Table 1: Prevalence of CHD by demographic variables.

                                            CHD versus no CHD

Parameter                        All      Dogs without      Dogs
                                               CHD        with CHD

All dogs                       914,274       771,978       142,296
Sex
  Female                       582,990       490,884       92,106
  Male                         331,281       281,091       50,190
AKC group
  Herding                      181,497       153,857       27,640
  Hound                         24,017       21,490         2,527
  Working                      217,397       178,178       39,219
  Sporting                     404,008       343,284       60,724
  Nonsporting                   51,153       44,226         6,927
  Terrier                       19,234       16,812         2,422
  Toy                           11,005        9,197         1,808
  Native                          36           32             4
  Hybrid                        2,514         1,973          541
  Miscellaneous                 3,413         2,929          484
FCI group
  Sheep and cattle             185,969       157,713       28,256
  Pinscher Schnauzer,          176,144       140,164       35,980
    molossoid, and Swiss
    Mtn/cattle dog
  Terrier                       14,542       12,374         2,168
  Dachshund                       70           63             7
  Spitz and primitive           64,683       58,132         6,551
  Scent hounds                  16,509       14,782         1,727
  Pointing dogs                 71,170       63,403         7,767
  Retrievers, flushers,        340,551       286,489       54,062
    and water dogs
  Companion and toy dogs        37,085       32,071         5,014
  Sighthounds                   5,129         4,860          269
Latitude
  <30[degrees]N                 43,929       34,779         9,150
  30-39[degrees]N              404,336       343,861       60,475
  40-49[degrees]N              425,790       357,670       68,120
  [greater than or equal        37,506       33,364         4,142
    to]50[degrees]N
Season of birth
  Autumn                       215,003       182,842       32,161
  Winter                       218,849       183,276       35,573
  Spring                       255,064       213,377       41,687
  Summer                       225,358       192,483       32,875

                                      CHD versus no CHD

Parameter                      % CHD   % without        p value
                                           CHD

All dogs                       15.56      84.44           --
Sex
  Female                       15.80      84.20      <[10.sup.-6]
  Male                         15.15      84.85
AKC group
  Herding                      15.23      84.77      <[10.sup.-6]
  Hound                        10.52      89.48
  Working                      18.04      81.96
  Sporting                     15.03      84.97
  Nonsporting                  13.54      86.46
  Terrier                      12.59      87.41
  Toy                          16.43      83.57
  Native                       11.11      88.89
  Hybrid                       21.52      78.48
  Miscellaneous                14.18      85.82
FCI group
  Sheep and cattle             15.19      84.81      <[10.sup.-6]
  Pinscher Schnauzer,          20.43      79.57
    molossoid, and Swiss
    Mtn/cattle dog
  Terrier                      14.91      85.09
  Dachshund                    10.00      90.00
  Spitz and primitive          10.13      89.87
  Scent hounds                 10.46      89.54
  Pointing dogs                10.91      89.09
  Retrievers, flushers,        15.87      84.13
    and water dogs
  Companion and toy dogs       13.52      86.48
  Sighthounds                  5.24       94.76
Latitude
  <30[degrees]N                20.83      79.17      <[10.sup.-6]
  30-39[degrees]N              14.96      85.04
  40-49[degrees]N              16.00      84.00
  [greater than or equal       11.04      88.96
    to]50[degrees]N
Season of birth
  Autumn                       14.96      85.04      <[10.sup.-6]
  Winter                       16.25      83.75
  Spring                       16.34      83.66
  Summer                       14.59      85.41

                            Bilateral versus unilateral CHD

Parameter                      Bilateral     Unilateral
                                   CHD           CHD

All dogs                         95,376         46,918
Sex
  Female                         17,079         50,189
  Male                           29,839         92,105
AKC group
  Herding                         9,770         27,639
  Hound                            782          2,527
  Working                        12,215         39,219
  Sporting                       20,628         60,723
  Nonsporting                     2,005         6,927
  Terrier                          633          2,422
  Toy                              497          1,808
  Native                            2             4
  Hybrid                           196           541
  Miscellaneous                    190           484
FCI group
  Sheep and cattle               18,250         10,005
  Pinscher Schnauzer,            24,919         11,061
    molossoid, and Swiss
    Mtn/cattle dog
  Terrier                         1,623          545
  Dachshund                         7             0
  Spitz and primitive             4,588         1,963
  Scent hounds                    1,207          520
  Pointing dogs                   5,045         2,721
  Retrievers, flushers,          35,797         18,265
    and water dogs
  Companion and toy dogs          3,484         1,530
  Sighthounds                      148           121
Latitude
  <30[degrees]N                   6,428         2,721
  30-39[degrees]N                40,594         19,880
  40-49[degrees]N                45,283         22,837
  [greater than or equal          2,777         1,365
    to]50[degrees]N
Season of birth
  Autumn                         21,362         10,798
  Winter                         23,695         11,878
  Spring                         28,146         13,540
  Summer                         22,173         10,702

                            Bilateral versus unilateral CHD

Parameter                      % bilateral        %
                                              unilateral

All dogs                          67.03          32.97
Sex
  Female                          65.97          34.03
  Male                            67.60          32.40
AKC group
  Herding                         64.65          35.35
  Hound                           69.05          30.95
  Working                         68.85          31.15
  Sporting                        66.03          33.97
  Nonsporting                     71.06          28.94
  Terrier                         73.86          26.14
  Toy                             72.51          27.49
  Native                          50.00          50.00
  Hybrid                          63.77          36.23
  Miscellaneous                   60.74          39.26
FCI group
  Sheep and cattle                64.59          35.41
  Pinscher Schnauzer,             69.26          30.74
    molossoid, and Swiss
    Mtn/cattle dog
  Terrier                         74.86          25.14
  Dachshund                       100.00         0.00
  Spitz and primitive             70.04          29.96
  Scent hounds                    69.89          30.11
  Pointing dogs                   64.96          35.04
  Retrievers, flushers,           66.21          33.79
    and water dogs
  Companion and toy dogs          69.49          30.51
  Sighthounds                     55.02          44.98
Latitude
  <30[degrees]N                   70.26          29.74
  30-39[degrees]N                 67.13          32.87
  40-49[degrees]N                 66.48          33.52
  [greater than or equal          67.04          32.96
    to]50[degrees]N
Season of birth
  Autumn                          66.42          33.58
  Winter                          66.61          33.39
  Spring                          67.52          32.48
  Summer                          67.45          32.55

                                 Bilateral       Right versus
                            versus unilateral   left unilateral
                                    CHD              CHD

Parameter                         p value        Left     Right
                                                  CHD      CHD

All dogs                            --           21,657   18,140
Sex
  Female                       <[10.sup.-6]      8,039    6,444
  Male                                           13,618   11,696
AKC group
  Herding                      <[10.sup.-6]      4,346    3,922
  Hound                                           359      307
  Working                                        5,076    4,898
  Sporting                                       10,006   7,694
  Nonsporting                                    1,031     238
  Terrier                                         341      238
  Toy                                             277      194
  Native                                           1        1
  Hybrid                                          117       66
  Miscellaneous                                   103       77
FCI group
  Sheep and cattle             <[10.sup.-6]      4,465    4,004
  Pinscher Schnauzer,                            4,571    4,462
    molossoid, and Swiss
    Mtn/cattle dog
  Terrier                                         291      209
  Dachshund                                        0        0
  Spitz and primitive                             915      740
  Scent hounds                                    238      200
  Pointing dogs                                  1,293    1,073
  Retrievers, flushers,                          8,912    6,746
    and water dogs
  Companion and toy dogs                          815      586
  Sighthounds                                      48       54
Latitude
  <30[degrees]N                <[10.sup.-6]      1,172    1,074
  30-39[degrees]N                                9,131    7,865
  40-49[degrees]N                                10,650   8,619
  [greater than or equal                          655      546
    to]50[degrees]N
Season of birth
  Autumn                          0.0016         5,020    4,099
  Winter                                         5,582    4,555
  Spring                                         6,151    5,278
  Summer                                         4,904    4,208

                              Right versus left unilateral CHD

Parameter                      % left   % right       p value

All dogs                       54.42     45.58          --
Sex
  Female                       55.51     44.49         0.001
  Male                         53.80     46.20
AKC group
  Herding                      52.56     47.44     <[10.sup.-6]
  Hound                        53.90     46.10
  Working                      50.89     49.11
  Sporting                     56.53     43.47
  Nonsporting                  81.25     18.75
  Terrier                      58.89     41.11
  Toy                          58.81     41.19
  Native                       50.00     50.00
  Hybrid                       63.93     36.07
  Miscellaneous                57.22     42.78
FCI group
  Sheep and cattle             52.72     47.28     <[10.sup.-6]
  Pinscher Schnauzer,          50.60     49.40
    molossoid, and Swiss
    Mtn/cattle dog
  Terrier                      58.20     41.80
  Dachshund                      --         --
  Spitz and primitive          55.29     44.71
  Scent hounds                 54.34     45.66
  Pointing dogs                54.65     45.35
  Retrievers, flushers,        56.92     43.08
    and water dogs
  Companion and toy dogs       58.17     41.83
  Sighthounds                  47.06     52.94
Latitude
  <30[degrees]N                52.18     47.82        0.0037
  30-39[degrees]N              53.72     46.28
  40-49[degrees]N              55.27     44.73
  [greater than or equal       54.54     45.46
    to]50[degrees]N
Season of birth
  Autumn                       55.05     44.95         0.10
  Winter                       55.07     44.93
  Spring                       53.82     46.18
  Summer                       53.82     46.18

Table 2: Odds ratios of CHD by AKC/FCI groups, sex, season of
birth, and latitude.

                                          (a)

                                      By AKC group

                              OR         95% CI           p value

Sex
  Female                     1.056   (1.069, 1.044)    <[10.sup.-6]
  Male                       1.0 R         --               --
Season of birth
  Autumn                     1.025   (1.042, 1.008)    <[10.sup.-6]
  Winter                     1.131   (1.149, 1.112)        0.081
  Spring                     1.146   (1.165, 1.128)    <[10.sup.-6]
  Summer                     1.0 R         --               --
Latitude
  <30[degrees]N              2.116   (2.203, 2.034)    <[10.sup.-6]
  30-39[degrees]N            1.428   (1.477, 1.381)    <[10.sup.-6]
  40-49[degrees]N            1.552   (1.605, 1.501)    <[10.sup.-6]
  [greater than or           1.0 R         --               --
    equal to]
    50[degrees]N
AKC group
  Herding                    1.535   (1.602, 1.470)    <[10.sup.-6]
  Toy                        1.675   (1.788, 1.570)    <[10.sup.-6]
  Working                    1.882   (1.965, 1.804)    <[10.sup.-6]
  Sporting                   1.504   (1.569, 1.442)    <[10.sup.-6]
  Nonsporting                1.348   (1.415, 1.284)    <[10.sup.-6]
  Terrier                    1.236   (1.311, 1.164)    <[10.sup.-6]
  Hound                      1.0 R         --               --

                                           (b)

                                       By FCI group

                              OR         95% CI           p value
Sex
  Female                     1.053   (1.065, 1.040)    <[10.sup.-6]
  Male                       1.0 R         --               --
Season of birth
  Autumn                     1.021   (1.038, 1.004)        0.016
  Winter                     1.124   (1.142, 1.105)    <[10.sup.-6]
  Spring                     1.143   (1.161, 1.125)    <[10.sup.-6]
  Summer                     1.0 R         --               --
Latitude
  <30[degrees]N              2.047    (2.13, 1.967)    <[10.sup.-6]
  30-39[degrees]N            1.410   (1.458, 1.363)    <[10.sup.-6]
  40-49[degrees]N            1.546   (1.599, 1.496)    <[10.sup.-6]
  [greater than or           1.0 R         --               --
    equal to]
    50[degrees]N
FCI group
  Sheep and cattle           3.229   (3.653, 2.854)    <[10.sup.-6]
  Pinscher schnauzer,        4.618   (5.224, 4.082)    <[10.sup.-6]
    molossoid, and
    Swiss Mtn/cattle dog
  Terrier                    3.163   (3.605, 2.774)    <[10.sup.-6]
  Spitz and primitive        2.059   (2.334, 1.816)    <[10.sup.-6]
  Scent hounds               2.096   (2.393, 1.836)    <[10.sup.-6]
  Pointing dogs              2.184   (2.473, 1.927)    <[10.sup.-6]
  Retrievers, flushers,      3.386   (3.830, 2.994)    <[10.sup.-6]
    and water dogs
  Companion and toy dogs     2.824   (3.204, 2.489)    <[10.sup.-6]
  Sighthounds                1.0 R         --               --

Table 3: Odds ratios of CHD for each AKC/FCI group by sex,
season of birth, and latitude *.

                                             Sex

                                n          Female
                                         OR (95% CI)

By AKC group
  Herding                    180,911     1.14 (1.171,
                                            1.110)
  Toy                         11,011    0.948 (1.052,
                                            0.853)
  Working                    216,599    1.069 (1.903,
                                            1.045)
  Sporting                   402,911    1.027 (1.046,
                                            1.009)
  Nonsporting                 51,045    0.988 (1.042,
                                            0.938)
  Terriers                    19,156    0.978 (1.071,
                                            0.894)
  Hounds                      23,974    1.024 (1.114,
                                            0.941)

By FCI group
  Sheep and cattle           185,366    1.138 (1.169,
                                            1.109)
  Pinscher schnauzer,        175,562    1.078 (1.104,
molossoid, and Swiss                        1.053)
Mtn/cattle dog
  Terrier                     14,507    1.013 (1.115,
                                            0.921)
  Spitz and primitive         64,393    1.014 (1.069,
                                            0.961)
  Scent hounds                16,490    1.095 (1.215,
                                            0.987)
  Pointing dogs               70,962    0.998 (1.048,
                                            0.951)
  Retrievers, flushers,      339,651    1.015 (1.035,
and water dogs                              0.995)
  Companion and toy dogs      37,025     0.99 (1.054,
                                            0.930)
  Sighthounds                 5,111     0.739 (0.945,
                                            0.578)

                                  Sex             Latitude

                                p value        (<30[degrees]N)
                                                 OR (95% CI)

By AKC group
  Herding                    <[10.sup.-6]#      2.129 (2.323,
                                                    1.052)
  Toy                             0.31          0.457 (0.620,
                                                    0.339)
  Working                    <[10.sup.-6]#      2.345 (2.519,
                                                    2.182)
  Sporting                      0.0038#         2.179 (2.328,
                                                    2.038)
  Nonsporting                     0.94          1.588 (1.881,
                                                    1.341)
  Terriers                        0.63          2.489 (3.281,
                                                    1.887)
  Hounds                          0.58           1.31 (1.748,
                                                    0.980)

By FCI group
  Sheep and cattle           <[10.sup.-6]#      2.105 (1.295,
                                                    1.931)
  Pinscher schnauzer,        <[10.sup.-6]#      2.227 (2.409,
molossoid, and Swiss                                2.059)
Mtn/cattle dog
  Terrier                         0.79          2.131 (2.864,
                                                    1.585)
  Spitz and primitive             0.62          1.709 (2.022,
                                                    1.444)
  Scent hounds                   0.085           1.15 (1.573,
                                                    0.841)
  Pointing dogs                   0.93          1.412 (1.722,
                                                    1.164)
  Retrievers, flushers,           0.14          2.305 (2.471,
and water dogs                                      2.149)
  Companion and toy dogs          0.75           1.02 (1.234,
                                                    0.850)
  Sighthounds                    0.016#         2.607 (6.622,
                                                    1.027)

                                          Latitude

                                p value        (30-39[degrees]N)
                                                  OR (95% CI)

By AKC group
  Herding                    <[10.sup.-6]#       1.383 (1.489,
                                                     1.285)
  Toy                        <[10.sup.-6]#        0.54 (0.678,
                                                     0.430)
  Working                    <[10.sup.-6]#       1.489 (1.584,
                                                     1.401)
  Sporting                   <[10.sup.-6]#       1.523 (1.609,
                                                     1.441)
  Nonsporting                <[10.sup.-6]#       1.258 (1.443,
                                                     1.096)
  Terriers                   <[10.sup.-6]#       1.414 (1.776,
                                                     1.126)
  Hounds                         0.067           1.044 (1.336,
                                                     0.815)

By FCI group
  Sheep and cattle           <[10.sup.-6]#       1.371 (1.475,
                                                     1.274)
  Pinscher schnauzer,        <[10.sup.-6]#        1.52 (1.628,
molossoid, and Swiss                                 1.419)
Mtn/cattle dog
  Terrier                      0.000001#         1.287 (1.651,
                                                     1.003)
  Spitz and primitive        <[10.sup.-6]#       1.121 (1.263,
                                                     0.995)
  Scent hounds                    0.38           0.911 (1.192,
                                                     0.700)
  Pointing dogs                 0.0005#          1.179 (1.384,
                                                     1.004)
  Retrievers, flushers,      <[10.sup.-6]#       1.578 (1.672,
and water dogs                                       1.488)
  Companion and toy dogs          0.83           0.958 (1.102,
                                                     0.832)
  Sighthounds                    0.044#          1.482 (3.421,
                                                     0.642)

                                          Latitude

                                p value        (40-49[degrees]N)
                                                  OR (95% CI)

By AKC group
  Herding                    <[10.sup.-6]#       1.531 (1.648,
                                                     1.422)
  Toy                        <[10.sup.-6]#       0.499 (0.628,
                                                     0.397)
  Working                    <[10.sup.-6]#       1.558 (1.657,
                                                     1.465)
  Sporting                   <[10.sup.-6]#     1.7 (1.796,1.609)

  Nonsporting                   0.0011#          1.266 (1.454,
                                                     1.103)
  Terriers                      0.0028#          1.492 (1.870,
                                                     1.190)
  Hounds                          0.74           1.165 (1.493,
                                                     0.909)

By FCI group
  Sheep and cattle           <[10.sup.-6]#       1.512 (1.623,
                                                     1.405)
  Pinscher schnauzer,        <[10.sup.-6]#       1.626 (1.743,
molossoid, and Swiss                                 1.518)
Mtn/cattle dog
  Terrier                        0.047#          1.412 (1.810,
                                                     1.102)
  Spitz and primitive             0.06           1.164 (1.311,
                                                     1.033)
  Scent hounds                    0.50           0.922 (1.212,
                                                     0.702)
  Pointing dogs                  0.045#          1.288 (1.509,
                                                     1.098)
  Retrievers, flushers,      <[10.sup.-6]#       1.781 (1.886,
and water dogs                                       1.681)
  Companion and toy dogs          0.55            0.97 (1.117,
                                                     0.842)
  Sighthounds                     0.36           2.122 (4.872,
                                                     0.924)

                               Latitude      Season of birth

                                p value          Autumn
                                               OR (95% CI)

By AKC group
  Herding                    <[10.sup.-6]#    0.996 (1.035,
                                                  0.958)
  Toy                        <[10.sup.-6]#    0.918 (1.062,
                                                  0.794)
  Working                    <[10.sup.-6]#    0.979 (1.011,
                                                  0.948)
  Sporting                   <[10.sup.-6]#    1.082 (1.111,
                                                  1.056)
  Nonsporting                   0.0008#       0.975 (1.046,
                                                  0.938)
  Terriers                      0.0005#       0.987 (1.118,
                                                  0.872)
  Hounds                          0.23         0.99 (1.115,
                                                  0.879)

By FCI group
  Sheep and cattle           <[10.sup.-6]#    0.987 (1.026,
                                                  0.951)
  Pinscher schnauzer,        <[10.sup.-6]#    1.006 (1.041,
molossoid, and Swiss                              0.972)
Mtn/cattle dog
  Terrier                       0.0064#       0.999 (1.142,
                                                  0.875)
  Spitz and primitive            0.012#       1.007 (1.081,
                                                  0.938)
  Scent hounds                    0.56         0.97 (1.121,
                                                  0.839)
  Pointing dogs                 0.0018#       1.124 (1.207,
                                                  1.046)
  Retrievers, flushers,      <[10.sup.-6]#    1.044 (1.073,
and water dogs                                    1.016)
  Companion and toy dogs          0.67        0.938 (1.054,
                                                  0.930)
  Sighthounds                    0.076         1.45 (2.073,
                                                  1.014)

                                     Season of birth

                                p value          Winter OR
                                                  (95% CI)

By AKC group
  Herding                         0.83          1.148 (1.191,
                                                   1.107)
  Toy                             0.25          1.073 (1.239,
                                                   0.930)
  Working                         0.19          1.075 (1.109,
                                                   1.041)
  Sporting                   <[10.sup.-6]#      1.189 (1.219,
                                                   1.159)
  Nonsporting                     0.19          1.004 (1.081,
                                                   0.932)
  Terriers                        0.84          1.102 (1.245,
                                                   0.975)
  Hounds                          0.87          0.933 (1.046,
                                                   0.832)

By FCI group
  Sheep and cattle                0.51          1.145 (1.187,
                                                   1.105)
  Pinscher schnauzer,             0.74          1.076 (1.113,
molossoid, and Swiss                               1.041)
Mtn/cattle dog
  Terrier                         0.99          1.125 (1.281,
                                                   0.988)
  Spitz and primitive             0.85          1.008 (1.084,
                                                   0.937)
  Scent hounds                    0.68          1.09 (1.254,
                                                   0.947)
  Pointing dogs                 0.0014#         1.257 (1.346,
                                                   1.173)
  Retrievers, flushers,         0.0021#         1.15 (1.182,
and water dogs                                     1.120)
  Companion and toy dogs          0.14          1.031 (1.123,
                                                   0.946)
  Sighthounds                    0.042#         1.24 (1.784,
                                                   0.860)

                                      Season of birth

                                p value          Spring
                                               OR (95% CI)

By AKC group
  Herding                    <[10.sup.-6]#    1.102 (1.141,
                                                  1.063)
  Toy                             0.34        1.041 (1.200,
                                                  0.903)
  Working                      0.000008#      1.146 (1.182,
                                                  1.111)
  Sporting                   <[10.sup.-6]#    1.195 (1.224,
                                                  1.167)
  Nonsporting                  0.000008#      1.067 (1.146,
                                                  0.994)
  Terriers                        0.12        1.082 (1.216,
                                                  0.963)
  Hounds                          0.23         0.92 (1.031,
                                                  0.820)

By FCI group
  Sheep and cattle           <[10.sup.-6]#    1.098 (1.137,
                                                  1.060)
  Pinscher schnauzer,           0.00002#      1.168 (1.207,
molossoid, and Swiss                              1.131)
Mtn/cattle dog
  Terrier                        0.076        1.089 (1.233,
                                                  0.961)
  Spitz and primitive             0.84         0.92 (0.992,
                                                  0.853)
  Scent hounds                    0.23        0.939 (1.074,
                                                  0.820)
  Pointing dogs              <[10.sup.-6]#    1.184 (1.260,
                                                  1.112)
  Retrievers, flushers,      <[10.sup.-6]#    1.188 (1.213,
and water dogs                                    1.158)
  Companion and toy dogs          0.49        1.113 (1.207,
                                                  1.026)
  Sighthounds                     0.25        1.177 (1.661,
                                                  0.834)

                            Season of birth

                                p value

By AKC group
  Herding                    <[10.sup.-6]#

  Toy                             0.58

  Working                    <[10.sup.-6]#

  Sporting                   <[10.sup.-6]#

  Nonsporting                <[10.sup.-6]#

  Terriers                        0.19

  Hounds                          0.15

By FCI group
  Sheep and cattle           <[10.sup.-6]#

  Pinscher schnauzer,        <[10.sup.-6]#
molossoid, and Swiss
Mtn/cattle dog
  Terrier                         0.18

  Spitz and primitive            0.031

  Scent hounds                    0.36

  Pointing dogs              <[10.sup.-6]#

  Retrievers, flushers,      <[10.sup.-6]#
and water dogs
  Companion and toy dogs         0.001#

  Sighthounds                     0.35

* The reference groups were male, latitude [greater than or
equal to]50[degrees]N, and summer.

The p values for statistically significant variables
are in bold type.

Note: The p values for statistically significant
variables indicated with #.

Table 4: Severity of CHD by demographic parameters.

Parameter                                    CHD severity

                                     Mild                Moderate

Age (mos [+ or -] 1 sd)        31.4 [+ or -] 8.4     32.0 [+ or -] 8.9
Sex
  Male                              55,390                31,452
  Female                            30,931                16,519
Laterality
  Bilateral                         51,085                36,754
  Unilateral                        35,236                11,217
AKC group
  Herding                           17,011                 8,906
  Hound                              1,329                  427
  Working                           22,469                14,379
  Sporting                          36,994                20,498
  Nonsporting                        4,452                 2,062
  Terrier                            1,757                  605
  Toy                                1,622                  800
FCI group
  Sheep and cattle                  17,387                 9,106
  Pinscher schnauzer,               20,179                13,430
molossoid, and Swiss
Mtn/cattle dog
  Terrier                            1,563                  552
  Spitz and primitive                4,106                 2,120
  Scent hounds                       1,142                  511
  Pointing dogs                      4,981                 2,496
  Retrievers, flushers,             32,742                18,344
and water dogs
  Companion and toy dogs             3,710                 1,178
  Sighthounds                         181                   85
Geographic group
  <30[degrees]N                      2,760                 1,183
  30-39[degrees]N                   41,628                22,781
  40-49[degrees]N                   36,358                20,619
  [greater than or                   5,335                 3,235
equal to]50[degrees]N
Season of birth
  Autumn                            19,795                10,644
  Winter                            21,512                12,101
  Spring                            24,728                14,456
  Summer                            20,286                10,770

Parameter                        CHD severity      % severity

                                    Severe            Mild

Age (mos [+ or -] 1 sd)        32.5 [+ or -] 9.3       --
Sex
  Male                               5,264            60.14
  Female                             2,740            61.63
Laterality
  Bilateral                          7,537            53.56
  Unilateral                          465             75.10
AKC group
  Herding                            1,723            61.54
  Hound                               52              73.51
  Working                            2,371            57.29
  Sporting                           3,232            60.92
  Nonsporting                         413             64.27
  Terrier                             60              72.54
  Toy                                 105             64.19
FCI group
  Sheep and cattle                   1,763            61.53
  Pinscher schnauzer,                2,371            56.08
molossoid, and Swiss
Mtn/cattle dog
  Terrier                             53              72.09
  Spitz and primitive                 325             62.68
  Scent hounds                        74              66.13
  Pointing dogs                       290             64.13
  Retrievers, flushers,              2,976            60.56
and water dogs
  Companion and toy dogs              126             73.99
  Sighthounds                          3              67.29
Geographic group
  <30[degrees]N                       199             66.63
  30-39[degrees]N                    3,711            61.11
  40-49[degrees]N                    3,498            60.12
  [greater than or                    580             58.31
equal to]50[degrees]N
Season of birth
  Autumn                             1,722            61.55
  Winter                             1,960            60.47
  Spring                             2,503            59.32
  Summer                             1,819            61.71

Parameter                          % severity          p value

                               Moderate     Severe

Age (mos [+ or -] 1 sd)           --          --     <[10.sup.-6]
Sex
  Male                           34.15       5.72    <[10.sup.-6]
  Female                         32.91       5.46
Laterality
  Bilateral                      38.54       7.90    <[10.sup.-6]
  Unilateral                     23.91       0.99
AKC group
  Herding                        32.22       6.23    <[10.sup.-6]
  Hound                          23.62       2.88
  Working                        36.66       6.05
  Sporting                       33.76       5.32
  Nonsporting                    29.77       5.96
  Terrier                        24.98       2.48
  Toy                            31.66       4.16
FCI group
  Sheep and cattle               32.23       6.24    <[10.sup.-6]
  Pinscher schnauzer,            37.33       6.59
molossoid, and Swiss
Mtn/cattle dog
  Terrier                        25.46       2.44
  Spitz and primitive            32.36       4.96
  Scent hounds                   29.59       4.28
  Pointing dogs                  32.14       3.73
  Retrievers, flushers,          33.93       5.50
and water dogs
  Companion and toy dogs         23.49       2.51
  Sighthounds                    31.60       1.12
Geographic group
  <30[degrees]N                  28.56       4.80    <[10.sup.-6]
  30-39[degrees]N                33.44       5.45
  40-49[degrees]N                34.10       5.78
  [greater than or               35.36       6.34
equal to]50[degrees]N
Season of birth
  Autumn                         33.10       5.35    <[10.sup.-6]
  Winter                         34.02       5.51
  Spring                         34.68       6.00
  Summer                         32.76       5.53

Table 5: Comparisons between DDH and CHD.

(a)

                                    Human DDH *

                       Incidence
Race                   per 1000     % M   % F   % bilateral
                         births

Indigenous peoples

Native American           95.0      30    70         50

Sami                      40.0
Aboriginal                3.7

Caucasian

Eastern Europe            44.2      21    79         19

Mediterranean             14.3
Islands
Australia/New             12.0      16    84         43
Zealand
Western Europe            8.1       21    79         19
United Kingdom            8.0
Scandinavia               7.3       21    79         41
South America             4.6       24    76
North America             0.8       19    81         13
Indo-Mediterranean        5.5       21    79         50
Indo-Malay                0.4
Africans
North America             0.5
Africa                    0.1

                              Canine CHD ([dagger])

Race                   % unilateral         AKC groups

Indigenous peoples                        Sporting dogs

Native American             50              Retrievers

Sami                                     Movers/flushers
Aboriginal                              Pointers/ setters
                                        Versatile sporting
Caucasian                                    Herding

Eastern Europe              81               Working

Mediterranean                              Nonsporting
Islands
Australia/New               57               Terrier
Zealand
Western Europe              81                 Toy
United Kingdom                                Hound
Scandinavia                 59             Scent hounds
South America                              Sighthounds
North America               87
Indo-Mediterranean          50
Indo-Malay
Africans
North America
Africa

                                Canine CHD ([dagger])

Race                   Prevalence    % bilateral    % unilateral

Indigenous peoples        15.03         66.03           33.87

Native American           16.52         65.68           34.32

Sami                      12.71          68.7           31.3
Aboriginal                12.13         65.96           34.04
                          8.42          60.16           39.84
Caucasian                 15.23         64.65           35.35

Eastern Europe            18.04         68.85           31.15

Mediterranean             13.54         71.06           28.94
Islands
Australia/New             12.59         73.86           66.14
Zealand
Western Europe            16.43         72.51           27.49
United Kingdom            10.52         69.05           30.95
Scandinavia               12.97          71.0           29.0
South America             4.64           54.2           45.8
North America
Indo-Mediterranean
Indo-Malay
Africans
North America
Africa

                                 Canine CHD ([dagger])

Race                         FCI groups          Prevalence

Indigenous peoples        Sheep and cattle          15.19
                              Pinscher
                             schnauzer,
Native American         molossoid, and Swiss        20.43
                           mountain/cattle
                                 dog
Sami                           Terrier              14.91
Aboriginal               Spitz and primitive        10.00
                            Scent hounds            10.13
Caucasian                  Pointing dogs            10.46
                             Retrievers,
Eastern Europe              flushers, and           10.91
                             water dogs
Mediterranean              Companion and            15.87
Islands                       toy dogs
Australia/New                Sighthounds            13.52
Zealand
Western Europe
United Kingdom
Scandinavia
South America
North America
Indo-Mediterranean
Indo-Malay
Africans
North America
Africa

                         Canine CHD ([dagger])

                           %            %
Race                   bilateral    unilateral

Indigenous peoples        64.6         35.4

Native American           69.3         30.7

Sami                      74.9         25.1
Aboriginal                70.0         30.0
                          69.9         30.7
Caucasian                 65.0         35.0

Eastern Europe            66.2         33.8

Mediterranean             69.5         30.5
Islands
Australia/New             55.0         45.0
Zealand
Western Europe
United Kingdom
Scandinavia
South America
North America
Indo-Mediterranean
Indo-Malay
Africans
North America
Africa

(b)

Seasonal variation              n         %
([double dagger])

Single winter peak            16,425    70.3
Single summer peak            1,280      5.5
Spring and autumn peaks       3,450     14.8
No variation                  2,205      9.4

Seasonal variation              n         %
([dagger])

Autumn (Sept-Nov)             20,276    2.93
Winter (Dec-Feb)             312,202    45.27
Spring (March-May)           229,925    33.23
Summer (June-Aug)               0         0
No variation                  128422    18.56

* Data extracted from [5].

([double dagger]) Data extracted from [6].

([dagger]) Present study.

Figure 1: Prevalence of CHD by various demographic parameters. (a)
By season of birth. (b) By latitude. (c) By AKC groups. (d) By FCI
groups. (e) By age at time of radiograph. The numbers in the boxes
are the percentage within each column bar.

(a)

Season    Prevalence of CHD (%)

Winter    16.25
Spring    16.34
Summer    14.59
Autumn    14.96

(b)

Latitude           Prevalence of CHD (%)

<30[degrees] N     20.83
30-39[degrees] N   14.96
40-49[degrees] N   16.00
>50[degrees] N     11.04

(c)

AKC group        Prevalence of CHD (%)

Hybrid           21.52
Working          18.04
Toy              16.43
Herding          15.23
Sporting         15.03
Nonsporting      13.54
Terriers         12.59
Native           11.11
Hounds           10.52

(d)

FCI group                    Prevalence of CHD (%)

Pinscher                     20.43
Schnauzer, molossoid,
and Swiss Mtn/cattle dog

Retrievers,                  15.87
flushers, and water dogs

Sheep and                    15.19
cattle

Terriers                     14.91

Companion                    13.52
and toy dogs

Pointing dogs                10.91

Scent hounds                 10.46

Spitz and                    10.13
primitive dogs

Sighthounds                   5.24

(e)

Age at radiograph   Percentage of
                       cases (%)

                    CHD    No CHD

24-35 mos          16.7     83.3
36-48 mos          17.6     82.4
49-60 mos          15.7     84.3

Note: Table made from bar graph.
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Article Details
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Title Annotation:Research Article
Author:Loder, Randall T.; Todhunter, Rory J.
Publication:Journal of Veterinary Medicine
Article Type:Report
Geographic Code:1CANA
Date:Jan 1, 2017
Words:10370
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