Introduction
The idea of this thesis was born after an unexpected and unfortunate turn of events. My new adopted 6-month old British shorthair cat was supposed to undergo a trivial spay surgery. Before that, I noticed some troubling signs, in particular — shortness of the cat’s breath. I decided to address that health issue later because I never expected it to be a symptom of a serious genetic disease. Apparently, this was a mistake on my part, as my cat suffered a cardiac arrest during the surgery. She died during what was supposed to be an ordinary veterinary intervention. A necropsy revealed that the cause of my cat’s death was an endocardial fibroelastosis (EFE), a rare cardiac condition characterized by endocardial expansion by fibrous and elastic tissues. The necropsy report concluded that such an extremely rare condition has a genetic cause, previously described in populations of Siamese, Burmese, and common domestic cats in the United Kingdom.
These results sparked my interest in the subjects of purebred animals, purebred animals’ health, and genetic diseases. Previously, my knowledge was limited to obscure information that breeding is sometimes associated with potential health risks in animals. After the issue affected me personally, I started thinking about how such cases can be diagnosed, prevented, and treated and what help can be provided to owners and their pets. I decided to perform a narrative literature review in order to analyze the current knowledge in the following areas:
- History of purebred animals and pets;
- Relationship between purebred origin and genetic diseases;
- Contemporary solutions for addressing health problems of purebred pets.
The ultimate goal of my thesis lies in synthesizing suggestions for product design that would provide a complex solution for purebred pets’ health issues. In this regard, the motivation of my thesis goes beyond the initial personal interest since such a product would be beneficial for many purebred cat and dog owners. In addition, raising awareness of purebred health problems would help amend the existing breeding practices, which often prioritize an aesthetic pleasure for the owners at the expense of pets’ health.
The scope of my research includes secondary sources — books, scholarly articles, and web resources created by animal healthcare professionals. I perceive a narrative review approach as an optimal method for conducting the research since it includes a critical analysis of the current knowledge and consecutive synthesis of the desired product. I expect that the review findings would help me obtain an understanding of the subject necessary for preparing solid interview questions for the following stakeholders: breeders, pet owners, and veterinarians. In particular, I will explore how breeding philosophy changed (for the better or worse) throughout history, what genetic diseases develop in purebred populations, and how they can be diagnosed and traced. In the end, I will supplement the narrative literature review with a series of qualitative interviews, thus creating a well-balanced research design.
Overall, I expect that the outcomes of my investigation will provide the necessary advice and peace of mind for purebred pet owners. On a bitter personal example, I learned that the lack of awareness of purebred genetic diseases might cost a pet life and bring severe emotional pain to the owner. A complex understanding of the issue is necessary for developing a solution that would prevent the untimely deaths of our beloved pets. Investigating the root causes of genetic health issues and examining which breeds are affected and what can be done to assist them would serve as a first step to mitigating the undesirable consequences of breeding.
Literature Review
In accordance with the previously outlined research design, the reviewed secondary sources are divided into three categories. The first category includes sources that define breeding and describe the evolutionary process and purposes of animal selection. The second category of sources explores genetic-related health problems in various pure breeds of cats and dogs. Finally, the third category provides an overview of the contemporary and future solutions for addressing genetic health issues prevalent in purebred pets.
History of Purebred Dogs and Cats
When it comes to breeding, it is necessary to understand that breeding purposes have significantly evolved with time. In addition, the evolution of breeding substantially differs depending on particular species. For example, an article by DogTime provides a clear and concise depiction of the history of dog breeding. When humans first domesticated dogs over 15,000 years ago, they primarily performed utilitarian duties, such as barking to scare wild animals or guarding their owners (DogTime). Early humans did not possess scientific knowledge of genetics; however, they could distinguish and breed dogs with desirable traits, for instance, loud barking (DogTime). According to Bess, humans selected early dog breeds for their ability to perform specific tasks, such as guarding, shepherding, and companionship. Therefore, one can claim that the early dog breeding process involved less inbreeding since its ultimate goal lay in achieving a certain physique or temperament rather than fostering the desired appearance. Early breeders were satisfied if a dog was fast and loyal; they did not need breeds that met strict modern selection standards.
However, the situation in dog breeding changed when the emphasis in selection shifted from utility to hobby. According to DogTime, breeders started to keep records of bloodlines and classify dogs into particular breeds only since the 19th century. The previous broad types, such as hunting dog, shepherd dog, or hound, became unsatisfactory, as people wanted to own purebred pets. Certain breeds came into fashion, and their population surged, whereas less fortunate ones plummeted in numbers. Beuchat provided a vivid illustration of this scenario on an example of the UK Kennel Club data. For example, the number of Yorkshire Terrier registrations declined from 26,000 in 1990 to only 5,000 in 2000 (Beuchat). On the contrary, annual Pug registrations gradually increased from 1,000 in 2003 to about 8,000 in a little more than a decade (Beuchat). Overall, these articles on the history of dog breeding allow making two important conclusions. First of all, purebred selection of the modern age largely replaced utilitarian generic type breeding of the past. Secondly, modern breeding is guided by strict regulations and fashion demands, which leads to increased inbreeding for the sake of fostering appearance.
The evolution of breeding with cats is significantly different due to important nuance in domestication. Whereas early humans actively domesticated dogs and bred hybrids with utilitarian purposes, the development of distinct cat breeds started only in the middle of the 19th century (Bess). As a result, even two differently looking cats are likely to be genetically similar, and 90% of the cats have no purebred bloodlines (Bess). Therefore, domesticated felines are essentially standing at the point which canines passed thousands of years ago. One can argue that domestic cats are closely related since genetically robust differences require generations of fostering through breeding. For example, the Cat Fanciers’ association distinguishes only 45 pure breeds, whereas kennel clubs worldwide recognize over 400 (Bess; DogTime). In this regard, an article by Bess provides a valuable insight — even the purebred cats can hardly be called “pure” from the genetic perspective. However, this also means that genetic diversity in cats has not developed yet. Humans did not increase diversity in the global cat population, as they barely used cats for specific utilitarian purposes. Overall, this situation can be perceived as worrying since cats have entered the stage of inbreeding in selection while still sharing nearly identical genetics.
Relationship between Purebred Cats, Dogs, and Genetic Diseases
Before touching the subject of genetics-related health issues in purebred cat and dog populations, it is necessary to provide a definition of a genetic disorder. A comprehensive veterinary guide to cat and dog breeds by Bell et al. offers a simple solution — any disorder with a hereditary component is considered genetic (2). One should distinguish between genetic and congenital disorders which are evident at birth. On the contrary, genetic disorders may reveal themselves later in an animal’s life, despite the fact that coding for the disorder is already present in birth. Purebred animals are usually more susceptible to neonatal death and various genetic disorders due to the presence of deleterious genes, which stems from lowered genetic diversity (Bell et al. 4). As discussed previously, modern-day breed standards are strict, and breeders often try to meet them through the extensive use of so-called popular sire. The breeders pick the best, award-winning male and use him for mating and gene-spreading purposes. The popular sire’s genes appear in the population more frequently; however, this also means a loss of contribution from other healthy males to the genetic pool.
As a result, various cat and dog pedigree breeds experience negative consequences in the shape of breed-specific genetic disorders. For instance, Maldarelli described the case of a bulldog, which was a sturdy and energetic breed in the middle of the 19th century. Due to the owners’ wish to meet the standards for the dog shows, the breed acquired short, bandy legs and a large head (Maldarelli). The altered physique hurt bulldogs in many ways — for instance, mating without assistance became difficult for them. In addition, about a third of all bulldogs suffer from severe breathing problems caused by the flattened muzzle (Maldarelli). Specific bulldog variations are not exempt from the general issues of the breed — for instance, the French bulldogs had significantly higher disease proportion for all organ systems, especially the upper respiratory tract (Keijser et al. 9). This story serves as a cautionary example for breeders and owners who want to mass-produce “perfect” purebred animals through the overuse of popular sire’s genetic material.
Most popular purebred cat breeds are also susceptible to various genetic disorders associated with breed-specific features. For example, Persian cats are predisposed to 29 genetic diseases; many of them are caused by the brachycephaly, flat and short skull shape typical for the breed (O’Neill et al.). In particular, ophthalmic and respiratory disorders are widespread among Persian cats due to their large flat eye sockets and reduced muzzle length (O’Neill et al.). The quantitative study by Keijser et al. revealed a significantly higher proportion of diseases in Persian cats in comparison to mixed-breed European shorthair cats (10). In regard to British shorthairs, the Aubrey Animal Medical Center (AAMC) pointed at genetically predisposed hypertrophic cardiomyopathy (HCM) — a thickening of a cat’s heart muscle. However, the British shorthairs are also predisposed to such genetic disorders as arterial thromboembolism, polycystic kidney disease, hemophilia, and cataract (AAMC). Overall, these works confirm that purebred pets tend to have significantly weaker health, as they are predisposed to genetic disorders due to the modern breeding system features.
Given this situation around the purebred animals, breeders are recommended to follow through with a set of procedures in order to bolster health and diversity in the breed’s gene pool. Most importantly, it is advised to avoid the popular sire syndrome (Bell et al. 5). Secondly, Bell et al. advise utilizing quality animals within the population to expand the gene pool (5). In addition, the breeders should conduct regular health surveys and genetic tests of their animals to monitor breed-related disorders. Lastly, Bell et al. urge the breeders to participate in open health registries (5). These measures are aimed at achieving several goals, such as stopping the production of affected animals, reducing the number of defective genes in the breed, and improving gene pool diversity. However, eliminating whole breeding lines due to the presence of a few affected individuals is not recommended (Bell et al. 6). Such an action effectively reduces genetic diversity and directly leads to an increase in genetic disorders in the population.
Overall, the sources reviewed in this section provided several valuable insights. First, the patterns of breeding systems development differ depending on the species. Second, the modern-day cat and dog breeding process is primarily guided by strict phenotype standards, which often pushes the breeders to overuse popular sires. Third, extensive popular sire use significantly reduces gene pool diversity and ultimately causes the spread of genetic disorders in purebred cats and dogs. Fourth, this issue can be mitigated through various means, such as genetic testing and health surveys, reviewed in the following section. Fifth, preventing whole lines from reproduction is inefficient for improving genetic health in purebred populations.
Review of Solutions Available for Addressing Genetic Health Problems in Purebred Pets
One may state that purebred pet owners face fewer problems than breeders. While breeders have to consider the genetic health of the whole population, owners’ concerns are limited exclusively to their pets. However, pets’ health should be treated as an ultimate value in contemporary breeding practices, which means that solutions to genetic disorders in purebreds should be applied both by owners and breeders. These solutions include the following products, projects, and measures that help purebred pets: information resources, tools for genetic evaluation, and regulatory practices. In addition to the existing solutions, this section reviews priority recommendations for enhancing genetic health in purebred animals.
First of all, the essential information on purebred’s genetics can be found in registries open to the public. Hedhammar et al. provided a review of information resources that can be used for increasing breeders’ and owners’ awareness about potential issues in purebred dogs. In the case of pedigree dogs, publicly available registries are usually kept by kennel or breed clubs (Hedhammar et al., 190). Breeders and purebred owners should realize that registries may have different levels of reliability and usefulness. A registry that contains the results of a population-based screening program would be significantly more trustworthy than the recordings of specific cases unrelated to the whole population (Hedhammar et al. 190). This issue is crucial for the breeders since the genetic health data on a particular animal would be sufficient for the pet owners. In certain countries such as Sweden, insurance companies and veterinarian clinics keep the statistics on morbidity and mortality rates in specific breeds (Hedhammar et al. 190). However, cat breeders and owners may find themselves in a disadvantageous position since cat breeding has a significantly shorter history. As a result, genetic health registries on canines may be substantially better developed.
Tools for genetic evaluation serve as a crucial source for checking the health registry data. Breeders and owners must understand that genetic tests significantly vary in regard to what they can identify. Bell et al. provided short yet clear guidance on which genetic tests exist and how they should be used (4). For instance, tests of the phenotype, such as cataract screening and skin biopsies, have limited usefulness for the breeders since they identify already affected animals, not the disorder carriers. On the contrary, direct gene tests performed through blood sampling or cheek swab allow identifying carriers not affected by the disorder (Bell et al. 3). In addition, defective genes can be linked to a genetic marker via linked-marker based tests that identify a marker of a defective gene rather than the gene itself (Bell et al. 4). Finally, susceptibility genes test identifies genes that provide liability for disease rather than act as its direct cause (Bell et al. 4). Overall, purebred pet owners are in a beneficial situation in regard to gene testing since tests that reveal whether a pet is affected with a genetic disorder are sufficient for them.
Finally, preemptive regulatory measures can be introduced in order to eliminate the harmful influence of the modern breeding system on purebred genetic health. As was discussed previously, genetic health disorders in purebred populations often stem from the popular sire syndrome and inbreeding with the purpose of meeting the strict breed standards. Rooney and Sargan conducted a survey of twenty experts in dog welfare, veterinary, and genetics who rated the offered suggestions for improving purebred health (38). In particular, the experts recommended revising registration rules, according to which offspring of mating between siblings, half-siblings, and any other closely-related animals would be considered non-pedigree (Rooney and Sargan 40). As a result, the incentive for inbreeding and popular sire overuse would disappear. Another priority recommendation encouraged openness in stud books, which would make possible the introduction of new genes into established breeds without losing the purebred status (Rooney and Sargan 40). In this regard, new regulations explicitly aimed at the root of genetic disorders in purebred animals would become an important preemptive measure. In the end, such regulations would significantly reduce the frequency of harmful practices in the breeding system.
Overall Reflection
The research of secondary sources clarified several aspects of the issue, which were previously obscure for me. First, I obtained knowledge on how the animal breeding process changed over time and what shape it took in the modern age. In particular, I learned that dog breeding has a substantially longer history which led to the emergence of various distinct breeds. On the contrary, purebred cats are still quite similar to each other from the perspective of genetics. As a result, the gene pool of cats lacks diversity, and such a lack serves as a cause of genetic disorders.
Second, I examined scholarly and veterinary evidence of genetics-related health issues in purebred dogs and cats. I realized that owning a purebred pet requires caution since these breeds are more susceptible to genetic disorders. I also identified factors harmful to the genetic diversity and health in purebred populations. In particular, popular sire syndrome and inbreeding in pursuit of the strict standards lead to genetic health disorders in various dog and cat breeds. Therefore, my future project might focus on raising genetic health awareness among the owners of such breeds.
Finally, I explored the possible solutions that may help purebred animals, their owners, and breeders. An important takeaway from the sources — genetic testing and health registries may have different values for breeders and owners. Whereas phenotype tests and data on a particular animal are sufficient for an owner, a breeder must consider the genetic conditions of the whole lines and populations. Overall, after consolidating the information from the resources, I decided that my further research should be aimed at shaping owner-oriented solutions since breeders deal with large populations. Breeders may be bearing a significant part of the responsibility for health problems in purebred animals. However, an owner must be alert and aware of the potential genetic disorders of their pet. As a former purebred cat owner who faced this issue first-hand, I realized that spreading knowledge about it is crucial.
Works Cited
Aubrey Animal Medical Center. “British Shorthair.” AAMC, Web.
Bell, Jerold S., et al. Veterinary Medical Guide to Dog and Cat Breeds. Teton NewMedia, 2012.
Bess, Emilie. “We Tried the Top Two Cat DNA Tests and Here’s What We Discovered.” The Dog People, Web.
Beuchat, Carol. “The History of Purebred Dogs in the UK.” The Institute of Canine Biology, Web.
DogTime. “A Brief History of Breeding.” DogTime, Web.
Hedhammar, Åke A., et al. “International and Collaborative Strategies to Enhance Genetic Health in Purebred Dogs.” The Veterinary Journal, vol. 140, no. 2, 2011, pp. 189-196.
Keijser, S. F. A., et al. “Disease Burden in Four Populations of Dog and Cat Breeds Compared to Mixed-Breed Dogs and European Shorthair Cats.” Preventive Veterinary Medicine, vol. 140, 2017, pp. 38-44.
Maldarelli, Claire. “Although Purebred Dogs Can Be Best in Show, Are They Worst in Health?”, Scientific American, Web.
O’Neill, Dan G., et al. “Persian Cats Under First Opinion Veterinary Care in the UK: Demography, Mortality and Disorders.” Scientific Reports, vol. 9, 2019, pp. 1-13.
Rooney, Nicola, and David Sargan. “Pedigree Dog Breeding in the UK: A Major Welfare Concern?” RSCPA, Web.