Multi-Drug Resistance Gene (MDR1)

Description: Found in German Shepherds

Multi-Drug Resistance Gene, (MDR) codes for a protein that is responsible for protecting the brain by transporting potentially harmful chemicals away from the brain. In certain breeds, a mutation occurs in the MDR1 gene that causes sensitivity to Ivermectin, Loperamide, and a number of other drugs. Dogs with this mutation have a defect in the P-glycoprotein that is normally responsible for transporting certain drugs out of the brain. The defective protein inhibits the dog's ability to remove certain drugs from the brain, leading to a buildup of these toxins. As a result of the accumulation of toxins, the dog can show neurological symptoms, such as seizures, ataxia, or even death.

Dogs that are homozygous for the MDR1 gene (meaning that they have two copies of the mutation) will display a sensitivity to Ivermectin and other similar drugs. These dogs will also always pass one copy of the mutation to all potential offspring. Dogs that are heterozygous (meaning they have only one copy of the mutation) can still react to these drugs at higher doses. Also, there is a 50% chance that a dog with one copy of the mutation will pass it on to any offspring.

There are many different types of drugs that have been reported to cause problems. The following is a list of some of the drugs:

Ivermectin (found in heartworm medications) Loperamide (Imodium over the counter antidiarrheal agent) Doxorubicin, Vincristine, Vinblastine (anticancer agents) Cyclosporin (immunosuppressive agent) Digoxin (heart drug) Acepromazine (tranquilizer) Butorphanol ("Bute" pain control).

The following drugs may also cause problems: Ondansetron, Domperidone, Paclitaxel, Mitoxantrone, Etoposide, Rifampicin, Quinidine, Morphine.
Arrhythmogenic Right Ventricular Cardiomyopathy

Description:  Found in Boxers

Arrhythmogenic Right Ventricular Cardiomyopathy, or ARVC, is an inherited condition that affects the muscles of the heart. ARVC is associated with sudden cardiac death and congestive heart failure. It is thought that these are a symptom of irregular heartbeats.

Dogs affected by ARVC typically begin showing symptoms around 6 years of age, however, this can vary widely. The best method to detect the symptoms of ARVC is through the use of a Holter monitor, in which the dog's health ECG is monitored for 24 hours, detecting any abnormalities such as ventricular premature complexes (VPCs) that may suggest ARVC.

Currently, there is one known mutation that is highly associated with ARVC. Testing for the mutation is a helpful tool, however, it is important to note that this mutation is not necessarily definitive. There are other unknown mutations responsible for ARVC in a smaller percent of the population, so a negative result does not ensure that the dog will not be affected. This is particularly true is the parents of a dog also test negative but experience symptoms. Additionally, dogs that test positive for ARVC will not necessarily experience symptoms, they are just at a substantially higher risk of developing the disease. Dogs that do test positive should report these results to their veterinarian; proper veterinary care can help manage the condition and promote a healthy life for the dog.
Degenerative Myelopathy (DM)

Description: Found in Both Boxers and German Shepherds. 

Degenerative Myelopathy (DM) is a progressive neurological disorder that affects the spinal cord of dogs. Dogs that have inherited two defective copies will experience a breakdown of the cells responsible for sending and receiving signals from the brain, resulting in neurological symptoms.

The disease often begins with an unsteady gait, and the dog may wobble when they attempt to walk. As the disease progresses, the dog's hind legs will weaken and eventually the dog will be unable to walk at all. Degenerative Myelopathy moves up the body, so if the disease is allowed to progress, the dog will eventually be unable to hold his bladder and will lose normal function in its front legs. Fortunately, there is no direct pain associated with Degenerative Myelopathy.

The onset of Degenerative Myelopathy generally occurs later in life starting at an average age of about 10 years. However, some dogs may begin experiencing symptoms much earlier. A percentage of dogs that have inherited two copies of the mutation will not experience symptoms at all. Thus, this disease is not completely penetrant, meaning that while a dog with the mutation is likely to develop Degenerative Myelopathy, the disease does not affect every dog that has the genotype.
  


The causes of hip dysplasia are considered heritable, but new research conclusively suggests that environment also plays a role. To what degree the causality is genetic and what portion environmental is a topic of current debate. Neutering a dog, especially before the dog has reached an age of full developmental maturity, has been proven to almost double the chance he or she will develop hip dysplasia versus intact dogs or dogs that were neutered after reaching adulthood. Other environmental influences include overweight condition, injury at a young age, overexertion on the hip joint at a young age, ligament tear at a young age, repetitive motion on forming joint (i.e. jogging with puppy under the age of 1 year). As current studies progress, greater information may help provide procedures to effectively reduce the occurrence of this condition.