Han So Low is a double dapple Dachshund who is deaf and
somewhat vision impaired.
Spend any time at all online, and you’ll see scads of shared photos of amazing looking pets. The recent fervor over a presumed chimera dog (a dog with two sets of DNA) got me thinking, “I wonder what medical problems come with that.”
Next time you see a dog with physical traits that make you say, “Wow,” keep its medical health in mind too.
A Quick Genetics Lesson
Some neat-looking traits are carried in the “germline” of reproductive cells. These traits can be passed to future generations. Other neat-looking traits are mutations inside cells of that dog alone, and they won’t be passed on, if that dog reproduces.
The only way to know for sure if a dog (or cat) with a split-color or calico-like coat is a true chimera or merely somatic mutation is to do genetic testing. True chimera mutations – where two embryos essentially fuse into one animal leaving some cells with the first animal’s DNA and other cells with the second animal’s DNA – are rare in the wild.
Dr. Alice Crook is a veterinarian and the coordinator at the Sir James Dunn Animal Welfare Centre, Atlantic Veterinary College/University of Prince Edward Island. She serves as the corresponding author for the Canine Inherited Disorders Database.
When asked if a true chimera would be okay, medically speaking, she says, “I think so.” Since there are so few, it’s hard to discern any trends.
As for somatic mutations that might, for example, result in a Retriever that’s both black and yellow, they affect only coat color and do not travel, genetically speaking, with health issues.
Inherited Looks and Medical Problems
Other neat-looking dogs, however, aren’t so lucky. In many cases, as dog fanciers have bred dogs for certain physical characteristics, they also have created and perpetuated medical problems.
Coloring (coats, eyes, noses) & blindness / deafness
“Genes for coat color are often associated with the genes that also govern vision and hearing,” Crook says.
Dogs that look a certain way are more likely than others to be partially or completely deaf or to suffer eye abnormalities that make them partially or totally blind. These traits can be found in many breeds, including Dachshunds, Australian Shepherds, Collies, and Great Danes.
Merle/Dapple: This gene dilutes a dog’s coat in a random or splotchy pattern, which can also affect eye color (shades of blue, one blue and one brown) and nose color (patches of pink). Some merle or dapple dogs suffer vision or hearing problems. It’s controversial to breed two merle or dapple dogs because of the likelihood of producing double merle/dapple puppies that are deaf and/or blind.
Double Merle/Dapple: The doubled merle or dapple gene impairs the animal’s ability to make pigment in the skin and coat. Mostly white, double merles/dapples can have some color patches. They often feature mostly or all pink noses and blue eyes. It’s common for double merle/dapple dogs to be blind and/or deaf. It’s even more controversial to breed double merle or dapple dogs.
Piebald: This gene dilutes a dog’s coat in an asymmetrical pattern, mainly in the body and head.
Albino: I double-checked with the canine geneticists at the UC-Davis Veterinary Medical Teaching Hospital, and they’ve never seen a true albino canine reported.
That’s probably a good thing. In horses, for example, there is a gene called “lethal white” that comes with often deadly intestinal development problems.
Read more about inherited vision problems (mycrophthalmia; ocular dysgensis) in dogs.
Flat-Faced Dogs & Breathing Problems
As certain breeds of dogs have been bred to feature flatter faces, problems with brachycephalic syndrome have increased. It isn’t merely because they have flatter noses.
Brachycephalic dogs – such as Pugs, Boston Terriers, and Bulldogs – also have real anatomical deformities, including an elongated and fleshy soft palate, narrow nostrils, larynx changes, and small tracheas.
In addition to trouble breathing – during exercise or not – brachycephalic breeds can also suffer gastrointestinal problems because it’s hard for them to breathe and swallow at the same time.
Long Bodies & Disk Disease
There are two kinds of disk diseases in dogs. One can set in as dogs of any breed age. The other is associated with chondrodystrophic breeds – breeds with long bodies and short legs such as Dachshunds, Corgis, and Basset Hounds. It’s called intervertebral disk disease type 1.
“It’s like a form of dwarfism,” Crook says. “They’ve been chosen for that, but as a result, there are problems with their backs. They have abnormal cartilage in their backs, and they develop problems much earlier than some of the other old-age changes that may develop in other breeds.”
Wrinkly Coats & Skin Disease
There is a price to pay for those super-cute skin folds in breeds like the Shar-Pei and some Bulldogs. It’s skin troubles, including infections and chronic inflammation.
Have you ever chosen a pet based on looks, only to discover medical problems that came with the neat markings or body style?
Share your story and your ideas on how to cope with such canine deficits or illnesses.
Canine Inherited Disorders Database
Dog Coat Color Genetics
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