Are the Rare Anomalies Seen in Hedlund Huskies Truly of Heritable Genetic Origin?

When confronted with an apparently congenital defect one must determine whether that defect is caused by one or more genetic mutations. Not all abnormalities in puppies or dogs are a result of heritable genetic defects and some that are known to be genetic may also be caused by non-heritable causes. Phenocopies are traits known to be genetic, but that can also be produced by something in the environment.  For example, cleft palate is a defect seen in nearly all breeds of dogs, but there are also 22 other causes of cleft palate including excessive vitamin A or steroidal drugs such as prednisone or prednisolone given during pregnancy

All of the following are known to cause birth defects and diseases that can mimic genetic diseases in puppies:

-  Trauma (an injury caused by an outside force), including trauma while in the uterus, injury during birth or early development.

-  Bacterial or viral infections while in the uterus or acquired shortly after birth.

-  Dietary insufficiencies or excesses.

-  Toxins

Some genetic diseases are "multifactorial" diseases, requiring both a genetic predisposition combined with environmental components in order to express the undesirable trait.  One hallmark of multifactorial diseases is the problem is identified in puppies raised in one kennel, but not seen in littermates raised in others.  This may be why some puppies in the Hedlund Husky Preservation Project have had what is thought to be developmental head tremors (which they later outgrew) while some closely related puppies raised in other kennels have not. It's also possible that the laryngeal dysfunction seen in half-Hedlund Husky puppies from a single outcross litter is multifactorial.

As a general rule, if a trait is known to be inherited in sled dogs, in other breeds or in other species it should be considered inherited in our dogs unless proved otherwise.  Overbite, primary hypothyroidism and bilateral cryptorchidism are known to be inherited in other lines of sled dogs as well as other breeds of dogs, so it is safest to assume that the cases we've seen within the project are heritable genetic disorders. The zinc responsive dermatosis present in one dog is definitely known to be a heritable genetic disease.

It isn’t certain that all of these disorders seen in our dogs are of genetic origin, but it also isn’t certain that they are not. Since the population of Hedlund Huskies is extremely low and consists of dogs with pedigrees that show numerous shared ancestors, members of the Hedlund Husky Preservation Project have chosen to take an aggressive approach toward ensuring minimizing the risks of genetic disorders such as those that threaten the existence of many purebred dogs to ensure that our Hedlund Huskies remain vibrant, healthy working dogs.