As a whole most Labs live a healthy life with minimal health problems. There are some serious genetic health problems that Lab owners should be aware of including Elbow and Hip Dysplasia, Progressive Retinal Atrophy, Muscle Myopathy, Megaesophagus and Hypothyroidism.
Hip Dysplasia
Canine hip dysplasia (CHD) results from poor development of the hip joint and affects dogs of many different breeds. It is inherited, but because of the polygenic (”multiple genes”) mode of inheritance it has proven to be difficult to eradicate. For example, it is possible for two dogs with “good” hips to produce a puppy with CHD. Additionally, environmental factors, such as trauma or excessive growth, can contribute to the problem.
The severity of CHD can vary from mild with no symptoms to severe and crippling arthritis. The first signs generally appear before a dog’s first birthday and may only appear as a slight irregularity in gait. Young, affected dogs can improve somewhat as they mature and develop a stronger musculature, but even these dogs will develop arthritis later in life.
Diagnosis can be made by x-ray as early as 4 or 5 months of age, although at this age there is a small chance of error. All dogs intended for breeding should be x-rayed once they have matured, but before being bred for the first time. Twenty-four months of age is considered the minimum age for an accurate determination and for certification by the Orthopedic Foundation for Animals (OFA). Bitches should not be x-rayed within about four weeks before or after her heat cycle because the additional hormones circulating in her system at this time may cause a false positive reading.
X-rays sent to the OFA will be examined by three veterinary radiologists who will determine whether or not the dog is dysplastic and will also assign a rating. Non-dysplastic hips will receive a rating of Excellent, Good, or Fair. Dysplastic hips will receive a rating of Mild, Moderate, or Severe. There is also a Borderline rating and the OFA will usually request an additional x-ray be taken about 6 months later. Arthritic changes over this time period will help determine whether the dog is actually dysplastic.
Costs for the x-ray and anesthesia run about $150 to $200. Evaluation by the OFA is currently $25 for a preliminary evaluation (before 24 months of age) and $30 for certification (after 24 months of age). There are discounts available if hip and elbow x-rays are submitted together or if several dogs are evaluated at the same time.
Between January 1974 and December 2001 there were 134,979 Labs evaluated by the OFA. Of these dogs, 16.1 percent were graded Excellent, while 13 percent were graded as dysplastic. Although the Lab is ranked as the most popular breed in the United States, it was ranked 67th in the number of dysplastic dogs. Breeders are slowly making headway toward eradicating this problem. Before 1980 only 10.4 percent were rated as excellent, but for dogs born in 1994/95 16.6 percent were rated excellent for an increase of 59.6 percent. During the same time period dysplastic dogs declined from 14.5 percent to 11.7 percent for a decrease of 19.3 percent.
Breeding only unaffected dogs probably accounts for the majority of the improvement. The OFA believes that environmental factors and high caloric intake do not cause CHD and that high doses of vitamin C won’t reduce or prevent CHD. However it is wise to do everything possible to prevent CHD, therefore we recommend the following: Only breed unaffected dogs and only buy puppies from unaffected parents. Line the whelping box with carpeting or towels instead of newspapers to provide better traction. Prevent excessive jumping (e.g. into the back of a pickup) or forced exercise (e.g. roadwork) until the dog is mature (at least 24 months). Keep dogs on the lean side, instead of obese. Provide a good quality diet.
Can high doses of vitamin C help a dysplastic dog? Read an article by Larry Mueller, Editor of Hunting Dogs, for his experiences.
Progressive Retinal Atrophy (PRA) and other eye problems
Labs are also at risk for several eye problems including: PRA, cataracts, and retinal dysplasia.
PRA is a progressive deterioration of the light-receptive area (retina) of the eye, and may result in complete blindness. Symptoms are subtle, often starting with night blindness and eye dilation. Typically the age of onset is between four to six years which makes it difficult to identify carriers and remove them from the breeding pool.
This disease is believed to be caused by a simple recessive gene. For the dog to be affected he must have two copies of this recessive gene. A dog that has only one copy of the gene is a carrier and will show no clinical symptoms, but can pass the recessive gene on to his descendants.
Cataracts are relatively common in dogs. Most are hereditary, however haziness or cloudiness in the eyes of an older dog is often not caused by cataracts. Some cataracts are stable while others may progress in severity. Surgery can often help dogs with severely impaired vision.
Retinal dysplasia (RD) or “folds” is inherited with dwarfism. In mild cases, sight is only slightly affected. In severe cases the dog may be blind and have skeletal abnormalities. Because RD may disappear with age, it is important to have puppies checked by a board-certified ophthalmologist, preferable between eight to ten weeks of age. At this time, folds are more easily detected. As the puppy grows the folds may straighten out and become almost impossible to diagnose. Dogs with any type of RD should not be bred because they probably also carry the gene for dwarfism. Additionally one of that dog’s parents is also probably a carrier for dwarfism.
All breeding stock should be examined annually by a board certified veterinary ophthalmologist who has the special equipment and training needed to properly examine the dog’s eyes. This exam is painless. The results can then be submitted to Canine Eye Registration Foundation (CERF).
Dwarfism
In Labradors, dwarfism has been linked with retinal dysplasia or “folds.” These problems seem to be more common in dogs with American field trial breeding.
A dog that received two copies of the gene for retinal dysplasia will probably go blind and will develop abnormally. Generally the legs will bow outward, giving a bulldog-type appearance with short legs and a disproportionately large head. Any dog with these symptoms should never be bred. Additionally the dog’s parents and most, if not all, of his siblings, should not be bred because they are carriers of the gene even though they may not show any outward signs of it.
Another form of dwarfism may be caused by an abnormality of the pituitary gland. The pituitary gland secretes a growth hormone, and if this hormone is decreased or absent the dog will not develop properly. Unlike chondrodystrophic (skeletal) dwarfs, these dogs remain proportionate, just smaller than average. Generally an owner will notice the dog failing to grow around eight to twelve weeks of age. Other signs might include: a soft, wooly coat, hyperpigmentation (darkening) of the skin, gradual alopecia (hair loss), and little, if any, sexual development. These animals may be helped with injections of growth hormones over several months, thyroid supplementation and/or cortisone replacement. Check with your vet for the best treatment of your dog. In additional, all dogs with this condition should be neutered.
Muscle Myopathy
This rare condition is known by several names, including muscle myopathy, muscular dystrophy, myotonia, generalized muscle weakness, and polyneuropathy. First diagnosed in 1976, this condition is characterized by a marked deficiency of skeletal muscle mass, abnormal posture, and a stiff hopping gait.
The first signs of this condition are generally seen in puppies between three and six months of age. They may seem reluctant to play as much as their littermates and may become tired more easily. More advanced symptoms include pronounced muscle wasting (particularly in the head, shoulders and hips), a short, stilted stride and “bunny hopping” with their rear legs, an arched back and low head posture, and a lanky appearance. Symptoms often seem worse with more exercise or exposure to cold weather, even to the point of collapse. The dog will often get worse over the course of six months to a year and then most dogs stabilize or even improve slightly.
Diagnosis can be difficult, particularly in mildly affected dogs, and may require a muscle biopsy. Unfortunately there is currently no method to determine genetic carriers.
There is no treatment, except for rest. Some dogs may respond to Diazepam or steroids. Dogs with muscle myopathy may make an acceptable house pet with a normal life span, however they are very sensitive to stress and cold.
This condition is inherited as an autosomal recessive gene, meaning both parents carry the gene even if they don’t show any symptoms. All offspring of an affected dog will carry at least one copy of the gene. Until a genetic test is developed, prevention consists of never breeding a dog that has any offspring with muscle myopathy. Offspring and siblings of these dogs may also be carriers.
Megaesophagus
Megaesophagus is so-named because of the enlargement of the esophagus caused by the loss of peristaltic function. (Peristalsis is the process of muscular contractions that move food through the esophagus.) Dogs with megaesophagus will usually regurgitate their food soon after eating. It is often seen in young puppies, but may develop later in life. Other signs include labored breathing (possibly aspiration pneumonia), fever, lethargy, and nasal discharge. Some dogs may outgrow this condition, while there is no improvement in other dogs.
To confirm the diagnosis, your veterinarian may decide to take chest x-rays, run blood tests, and run a urinalysis. Although there is no specific treatment for megaesophagus, your veterinarian may be able to identify an underlying cause and provide supportive care. Feeding small, frequent, high-caloric meals from an elevated stand may also help.
In Labs, the condition appears to be genetic, however the mode of inheritance is still unknown. In some breeds it is caused by a recessive gene and in other breeds it is caused by a dominant gene. Until more is known about this condition, it is safest to avoid breeding any affected dogs, their parents and their siblings.
Hypothyroidism
Hypothyroidism occurs when the thyroid gland does not secrete enough of the thyroid hormone called thyroxine (T4). T4 plays a major role in controlling metabolism and is necessary for growth. The other main thyroid hormone is called triiodothyronine (T3). Both T3 and T4 circulate through the bloodstream and are regulated by the thyroid stimulating hormone (TSH).
The most common cause of hypothyroidism is autoimmune thyroiditis. This occurs when the body makes antibodies against the thyroid gland which gradually destroys the gland and decreases its ability to secrete T4.
Because T4 affects many internal organs a deficiency can manifest with varied symptoms. Some possible symptoms include obesity, lethargy, mental dullness, hair loss, hyperpigmentation (darkening of the skin), mood swings, facial paralysis, and disorientation. Other possible symptoms include diarrhea, constipation, vomiting, abnormal heat cycles, lowered body temperature and even heart problems. One study found that the majority of dogs with hypothyroidism had some kind of skin abnormality, however some dogs may not have any symptoms.
The disease can occur at any age, but tends to affect dogs starting at two to five years of age. Dogs may appear normal for years, only to become hypothyroid at a later date.
Some of the tests to determine hypothyroidism include a blood test, a skin biopsy, TSH test, or a thyroid biopsy. The blood test is most commonly used, however other factors may also cause a decrease in the production of T4. These factors include using medications such as cortisone, valium, and anticonvulsants, and diseases such as Cushing’s disease, diabetes, chronic renal failure and liver disease. A skin biopsy, by itself, probably wouldn’t be conclusive evidence of hypothyroidism. The TSH test was considered quite reliable, but it can be expensive and difficult to find TSH. The thyroid biopsy is rarely used because is so invasive. Sometimes the only way to determine hypothyroidism is to administer the treatment for several months and note the results.
Treatment consists of correcting any underlying problems and, perhaps, administering a synthetic thyroid hormone. Generally a change in attitude and energy level is seen very quickly, however skin changes and hair regrowth may take several months. Dogs usually remain on this hormone for life, but the hormone level should be checked every six to 12 months to adjust the dosage amount.
Because there appears to be a genetic predisposition to hypothyroidism, breeding stock should be tested annually starting at sexual maturity. After about four years of age the dog can be tested every other year.
Of the 119 test results submitted to the OFA for Labradors between 1974 and 2002, 79 percent tested normal.
If you’re thinking about buying a Lab puppy, be sure to check with the breeder about the possibilities of these problems in their puppies. At the very least you should insist that both parents have hip and eye clearances.
The information given here is to help you learn more about your dog and not to replace your veterinarian’s advice.
