Drug Sensitivity Testing in Dogs (MDR1)

  Many dogs, especially herding dogs and herding cross breeds, carry an abnormality in the multidrug resistance gene (MDR1).  This makes them very sensitive and reactive to certain drugs.  Such drug reactions can cause serious neurologic disease and even death.

 
Collies and Australian shepherds are very commonly affected but English Shepherds, herding cross breeds, German Shepherds, Long-Haired Whippets, Shelties, McNabs, Old English Sheepdogs, Border Collies, Silken Windhounds, and mixed breed dogs may also be affected.  Since herding breeds and their crosses are so over-represented with this problem, and commonly have white feet, you can remember it as “white feet, don’t treat”.
P-glycoprotein 1 (permeability glycoprotein) is the multidrug resistance protein.  It sits in membranes in many areas of the body, like the intestinal tract, kidneys, liver, adrenal glands, and nervous system.  MDR1’s job is to pump things out of the cells and regulate what things get into the brain and nervous system.  When animals have a mutation of the MDR1 gene, drugs and toxins can accumulate in unexpected and dangerous levels.  Dogs can have 0, 1 or 2 copies of the gene.  One copy of the gene may result in sensitivity and mild reactions to a given drug; two copies would lead to more severe reactions.

The drugs implicated include a broad range of medications.  The antidiarrheal medication imodium, the antibiotic erythromycin, and antiparasitic drugs such as ivermectin, milbemycin, selamectin, moxidectin, and emodepside [Profender] may cause neurologic toxicity.  Some medications will have an increased sensitivity.   These drugs include the sedative acepromazine, the pain medication butorphanol, and the chemotherapy agents doxorubicin, vincristine, and vinblastine.

The signs of toxicities may vary and will have an onset of 24-48 hours post administration.  Animals most commonly show excessive sedation, salivation, vomiting, and a slow heart rate.  They may also have dilated pupils, tremors, a wobbly gait, and disorientation.  There is no antidote or specific treatment.  Patients have to be supported until the medications can completely wear off.  This may involve many days, or even weeks, of hospitalization including fluids, nutritional support and sometimes a ventilator.  The diagnosis is based on medication exposure and suspicion.

Thanks to the discovery of the mutation of the multidrug resistant gene and the establishment of testing by the Washington State University College of Veterinary Medicine (my school), we can predict these drug sensitivities.  The American Animal Hospital Association and the American Veterinary Medical Association together offer a set of Canine and Feline Preventive Healthcare Guidelines. They recommend that dog owners use genetic testing—like the MDR1 test —as part of an overall healthcare plan for their pets.  The Lien Animal Clinic recommends testing all dogs with potential herding ancestry and considers testing mixed breed dogs. Testing at our clinic involves taking a cheek swab or a blood sample and submitting it to the WSU laboratory.  

Timothy R Kraabel, DVM, DABVP (Canine/Feline Practice)

Outreach Chairman, American Board of VeterinaryPractitioners

Spay and Neuter Project in Costa Rica

Veterinary Medicine On Location

  Welcome to my first blog post!  I have intended to start a blog for some time.  I love to write and there is so much medicine to discuss and many stories to tell in veterinary medicine.

Dr. Fritzler and I love to travel.  We have long thought we could combine travel with providing veterinary care in under-served areas of the world.  Such an opportunity presented itself this spring and our family went to Costa Rica with Critter Care International on a spay and neuter project.  Our friends and colleagues, Dr. Stan Diment and Susan Savage from Orlando, Florida, have been traveling to Arenal, Costa Rica with this group since 2011.  They asked us to join them on this trip and it was a worthy journey. 

Several days of the trip were spent at a local Arenal home providing low cost spays and neuters.  The home had an outdoor area made up into a surgery ward and there were many willing volunteers and lots of animals.  We felt a bit like rock stars pulling up in our van full of the veterinary health care team.  Dr. Diment, Dr. Mario (a local veterinarian), Dr. Fritzler and myself performed the spays and neuters.  Our kids, Geoffrey, Aubrey and Nicholas, were along as assistants along with Keri, a volunteer who came with Dr. Diment and Susan.  We treated a few sick animals as well and repaired a wound on a dog that showed up.  A bunny also came in for me that needed extensive dental work.  Susan Savage is a licensed technician and handled all the anesthesia.  The group of volunteers handled everything else including admissions and manning the recovery ward in the homeowner’s bedroom.  It was certainly different than what we are used to in the United States but we provided good care and helped a lot of animals.  Dr. Diment and Susan have seen the pet overpopulation in the town of Arenal drop significantly over the years they have been visiting.

Costa Rica is a beautiful country.  We stayed in a small bed and breakfast with an innkeeper from New York named John.  He had 3 wonderful great Danes and a lovely house with a view of Lake Arenal.  We took a few days off and went on a river cruise near the Nicaraguan border.  We saw Caiman and monkeys and tons of birds and had a relaxing day on the river.  We also spent a day zip lining, which was very cool, but not relaxing.  We loved the local cuisine and the people were welcoming and gracious.  The people of Arenal in particular were thankful for our help.  A husband and wife team, Balo and Emily, were our drivers and we loved and bonded with them immediately.  We spent the last two days in the town of La Fortuna before flying home.

The experience was life changing.  It was difficult to do surgery outside of our comfort zone, but we adjusted to the conditions and everyone did well.  Our kids, at least two of whom want to be veterinarians, got exposure to lots of surgery.  We all saw another unique and beautiful part of the world while feeling like the place was a bit better off for our visit.

 

 

Timothy R Kraabel, DVM, DABVP (Canine/Feline Practice)

Outreach Chairman, American Board of VeterinaryPractitioners