How do hereditary diseases occur?

In all living beings, genetic information is stored in the form of DNA (deoxyribonucleic acid). During reproduction, this information is passed on from both the mother and the father to the offspring. Hereditary diseases are the result of changes in the DNA and they are also called variants or mutations. Variants naturally arise random and are not targeted. Depending on the changes the variants bring about in the organism, they can trigger serious hereditary diseases or be beneficial for the individual. Basically, mutations and variants are what enable evolution and thus the adaptation of living organisms to their environment. There are also variants that do not trigger any changes. In this case, we speak of silent mutations.

How important are variants and mutations for breeding?

Through targeted breeding of animals with special characteristics, breeds have been formed, that are optimally adapted to the respective use of the animals or to the respective living conditions. Thus, different breeds with great differences in character as well as in external appearance have been created. Due to targeted breeding, however, the breeding lines are isolated or only partially crossed with each other, so that in some breeds the genetic diversity (also called gene pool) has been significantly reduced. Variants can be passed on unnoticed from generation to generation, and breed-specific predispositions to certain inherited diseases have emerged.

What are the benefits of genetic testing for hereditary diseases?

A genetic test can also detect variants that are not externally visible. In so-called recessive diseases, carriers can be present, which can inherit the variant but do not suffer from the disease themselves. In addition, there are also hereditary diseases with a late onset of the disease, so possible symptoms can emerge later than the onset of the breeding age. On the basis of the genetic examination, such variants can be reliably detected or excluded already at a young age. Genetic tests can be performed regardless of age and the current health status of the animal.

Genetic tests offer breeders the possibility to carry out selective mating. For example, with appropriate breeding planning, carriers of recessive variants can still be used for breeding. Thus, the gene pool is not further restricted and nevertheless the occurrence of hereditary diseases is avoided as far as possible. In addition, certain breeding associations require certain genetic tests before breeding permission and only allow animals for breeding where the corresponding hereditary diseases have been excluded.

Some hereditary diseases are associated with an increased risk, especially in certain situations. Examples are ivermectin intolerance due to the MDR1 gene defect or genetic bleeding tendencies. If the owners of the affected animals are informed of the presence of such diseases and their consequences, critical situations can often be avoided or certain precautions can be taken.

In addition, genetic testing supports veterinarians in diagnostics. A hereditary disease can be confirmed in the case of a positive result, or excluded in the case of a negative finding. If the genetic cause of a disease has not yet been identified, tests for genetic risk factors may still give an indication of present diseases. A further advantage of genetic testing is that veterinarians can treat the animals more specifically and/or create appropriate preventive plans if present genetic variants are known.