DNA Test for Drug Sensitivity in Dogs

DNA Test for Drug Sensitivity in Dogs

In 1983 researchers first described a peculiar reaction in many Collies to ivermectin, a medicine used for heartworm prevention, among different things. Although ivermectin able to cause toxicity in any dog if you give enough of it, these Collies had neurological signs (drooling, stumbling, blindness, coma, respiratory problems and even death) at doses that were 1/200th of the dose needed to cause problems in different dogs. Nobody knew why.

Soon afterward, many different breeds, most of them related to Collies, showed similar symptoms. Over the next two decades researchers continued to search for the cause, and continued to draw blanks. Now, thanks to research at Washington State University, we finally know.

The problem able to be traced to a mutation in a gene called the multi-drug resistance (MDR1) gene, which is needed to form a type of protein that's vital to flushing drugs out of the brain. When this protein is faulty, many drugs, e.g. ivermectin, remain in the brain where they build up and cause toxic effects.

It's not only ivermectin that causes problems in MDR1 dogs. Other drugs that are well-known to cause problems in these dogs are:

abamectin, selamectin, milbemycin,and moxidectin (anti-parasite agents used in heartworm, ear mites, mange mites and yard preparations; at doses used to prevent heartworm, these drugs are safe in mutant MDR1 dogs, but at levels used to treat mange, they are not.)

loperamide (antidiarrheal agent found in Imodium; this medicine is not safe at normal doses for mutant MDR1 dogs)

acepromazine (tranquilizer; this medicine produces deeper and longer sedation in mutant MDR1 dogs; it should only be given at a 75 percent dose in dogs with one copy of the mutant gene, and at 50- to 70 percent doses in dogs with two copies of the mutant MDR1 gene)

butorphanol (analgesic and pre-anesthetic agent; this medicine produces deeper and longer sedation in mutant MDR1 dogs; it should only be given at a 75 percent dose in dogs with one copy of the mutant gene, and at 50- to 70 percent dose in dogs with two copies of the mutant MDR1 gene).

vincristine, vinblastineand doxorubicin(chemotherapy agents; this medicine is more likely to cause bone marrow suppression and gastrointestinal upset in dogs with the MDR1 mutation; it should be given at 70- to 75 percent normal dose in these dogs.

Dogs with one copy of the mutant gene are said to be sensitive; they might have toxic reactions to normal doses of loperamide and many anticancer drugs, and high doses of ivermectin. Dogs with two copies of the mutant gene are said to be super sensitive and are very likely to have toxic reactions to normal doses of loperamide, many anticancer drugs and high doses of ivermectin.

Because many of these drugs are commonly used when your dog has surgery, it's a good idea to find out now if your Collie or Collie relative, or even mixed breed, has the MDR1 gene or genes. Washington State University offers the test, which requires a simple cheek swab and costs about $60. To get a test kit, go to http://www.vetmed.wsu.edu/depts-VCPL/test.aspx

About three out of four collies have the mutant MDR1 gene. The MDR1 mutation is found in Shetland Sheepdogs, Old English Sheepdogs, German Shepherds, Longhaired Whippets, Silken Windhounds, and a variety of mixed breed dogs, although not as frequently as in Collies.

Researchers are currently seeking cheek swab samples from dogs of the herding breeds, e.g. Collies and their relatives, that that have experienced unexpected reactions to normal doses of drugs. For more information contact the Veterinary Clinical Pharmacology Lab at Washington State University via e-mail at: VCPL@vetmed.wsu.edu.

Old English Sheepdog

Breed Profile

American Kennel Club

Group:

Herding

Size:

Large

Origin:

England

Color:

Grey, Black and White

The Old English Sheepdog is a big lovable companion. He likes to be with his family and get plenty of exercise everyday.

At first he looks like a shaggy bear who tumbles around like a clown. But underneath all that hair is a sturdy worker that English farmers have valued for numerous years.

Old English Sheepdogs were especially skilled in guiding sheep and cattle herds from farms to the towns where they would be sold. The dogs needed to be smart, able to predict the sheep or cattle's behavior, and quick enough to round them up if they got away. Old English Sheepdogs are believed to be descended from Bearded Collies of Scotland and, possibly, a Russian dog brought to England by sailors.

In today's families, the Old English Sheepdog is a big, lovable companion. He likes to be with his family and get plenty of exercise every day. Although the Old English Sheepdog's abundant coat might seem a problem in hot weather, it's an effective insulator in both hot and cold. The outer coat should be hard and shaggy. The undercoat is a soft, waterproof covering that sheds out. He'll need daily brushing and combing. Color able to be any shade of gray, grizzle, blue, or blue merle with or without white markings.

Excerpts from the Standard

General Appearance: A strong, compact dog, profusely coated, thickset, and muscular.

Size, Proportion, and Substance: Height--males, 22 inches or more at the withers; females, 21 inches or more.

Fun Facts

The Old English Sheepdog's nickname is the Bobtail. His tail is docked very close to the body about three to four days after birth. Since he worked as a "drover" dog, herding cattle and sheep to market towns, the Old English Sheepdog's tail was "bobbed" to show tax collectors that he was a working dog. Only Sporting dogs, owned by noblemen hunters, were taxed. The Old English able to do more than drive herds. He has been used as a retriever, sled dog, and watchdog.
Excerpted from The Complete Dog Book For Kids (c) 1996, John Wiley & Sons, Inc.

German Shepherd Dog

Breed Profile

American Kennel Club

Group:

Herding

Size:

Large

Origin:

Germany

Color:

Tan, Black and Brown

German Shepherds are courageous, active and dignified. He is the world's leading guard, police and military dog. He loves to swim and hike and is fond of children once he gets to know them.

Owner's Guide

The German Shepherd Dog (GSD), is one of the most readily recognized breeds of dog in the world. They are also in demand world wide as a respected working partner for military and law enforcement agencies.

Least: Most:
Grooming Difficulty:
Puppy Activity Level:
Adult Activity Level:
Training Difficulty:
Housetraining Difficulty:

Health Concerns

These conditions have all been seen in the breed.

* Gastric bloat and stomach torsion
* Hip and elbow dysplasia
* Allergies
* Panosteitis (bone disease)
* Pancreas problems
* Neurological problems