human‐like social skills in dogs are heritable and derived. In: The Dog and its Genome (eds. E.A. Ostrander, U. Giger and K. Lindblad‐Toh), 497–514. New York: Cold Spring Harbor Laboratory Press.
Recommended Reading
1 Ackerman, L. (2011). The Genetic Connection. Lakewood, CO: AAHA Press.
2 Ackerman, L. (2019). The skinny on genes – what you should know about genetic testing. AAHA Trends 35 (6): 39–42.
3 Ackerman, L. (2020). Proactive Pet Parenting: Anticipating pet health problems before they happen. Problem Free Publishing.
4 Karlsson, E.K., Baranowska, I., Wade, C.M. et al. (2007). Efficient mapping of mendelian traits in dogs through genome‐wide association. Nat. Genet. 39: 1321–1328.
5 Modiano, J.F., Breen, M., Burnett, R.C. et al. (2005). Distinct B‐cell and T‐cell lymphoproliferative disease prevalence among dog breeds indicates heritable risk. Cancer Res. 65: 5654–5661.
3.4 Predicting and Eliminating Disease Traits
Lowell Ackerman, DVM, DACVD, MBA, MPA, CVA, MRCVS
Global Consultant, Author, and Lecturer, MA, USA
3.4.1 Summary
To be able to appropriately screen pets for disease traits, it is first critical to be able to ascertain their risk of developing problems, and then intervene at the earliest possible opportunity. This is best accomplished with a combination of genotypic and phenotypic screening.
3.4.2 Terms Defined
Allele: A variant or alternative form of a gene, found at the same location on a chromosome, and which can result in different observable traits.
Dominant: Heritable characteristics, traits, or diseases that are expressed when inherited even from one parent.
Genetics: The study of genes and how traits or conditions are passed from one generation to the next.
Genome: The complete set of genes for an animal.
Genomics: The study of the entire genome, and its combined influence on complex diseases and the impact of environmental factors such as diet, exercise, medications, and toxins on genes.
Genotype: An individual's genetic constitution.
Heterozygotev An individual with two different alleles for a given gene.
Homozygote: An individual with two identical alleles for a given gene.
Locus: A fixed position on a chromosome for a gene or marker.
Nutrigenomics: The interaction of genetics and nutrition and the role the two play in the prevention and treatment of disease.
Odds Ratio: The ratio of the odds of an event in a select group (e.g., breed) to the odds of an event in a control group.
Phene: A trait or characteristic that is genetically determined.
Phenotype: Observable characteristics or traits that result from the interaction of genotype with the environment.
Recessive: Heritable characteristics, traits, or diseases that are expressed only when inherited from both parents.
Relative Risk: The ratio of the probability of a phene, condition, or trait occurring in a specific group (e.g., breed), compared to the probability of it happening in a control group.
3.4.3 Risk Factors
Pet‐specific care is all about managing risks. All animals have certain risks that pertain to their individual circumstances (see 1.1 Overview of Pet‐Specific Care). By acknowledging and prioritizing risks, we can craft meaningful personalized care plans for our patients (see 1.3 Personalized Care Plans).
For most pets, family history or breed predisposition is a significant contributor to disease susceptibility. This is true whether the pet is purebred or mixed‐breed. In many instances, when a pet is mixed‐breed and the parents have not been identified with certainty, it may be difficult to discern any type of predisposition without performing breed composition genetic testing. Whether purebred or mixed‐breed, both genotypic and phenotypic testing can be done for disease susceptibility.
Exposure risks constitute another significant contributor to disease susceptibility. For example, a pet exposed to many other pets will be at increased risk for infectious diseases and, potentially, parasite transmission. A dog that is taken for walks in wooded areas may be exposed to ticks that are enzootic to the region and may introduce tick‐related infections to the pet. A cat that is allowed to wander the neighborhood may be exposed to a variety of infectious diseases, as well as injury from vehicles, other pets, and wildlife.
Susceptibility to medical problems is also influenced by life stages. For example, an umbilical hernia is more likely to be congenital and evident in a juvenile pet, while most cases of hypothyroidism present during adulthood (see 4.1 Canine and Feline Life Stages).
A pet's gender as well as its neuter status also influence risk. Some diseases are sex limited in nature (such as prostatic disease in males or pyometra in females), but there are also sex predispositions for a variety of disorders. For example, there may be a modest sex predisposition to females regarding cutaneous lupus erythematosus, while adrenal sex hormone imbalance (alopecia X) may be more commonly diagnosed in males. This is different from disorders transmitted genetically on the sex chromosomes. For example, hemophilia is more often clinically evident in males because the condition is transmitted on the X chromosome as a sex‐linked recessive condition, and since males only have one X chromosome (the other is a Y chromosome), they manifest the condition; in females, with two X chromosomes, it would take two copies of the hemophilia mutation before the condition would be apparent. Neuter status also affects risk. Bitches spayed before their first estrus have a reduced prevalence of mammary cancers; neutered males have a lowered risk for prostatic hyperplasia (see 4.2 Gender‐Related Considerations).
Geography also plays a significant role in disease susceptibility, partially because it influences infectious diseases that are present in the area, or the vectors that are associated with their transmission. Accordingly, when creating personalized care plans, it is important to take into consideration whether or not the pet may travel outside the region.
Even conformation and nondisease traits
