Frequently Asked Questions
Can Collie crosses or other herding breed crosses carry the
mutant MDR1 gene and have an adverse reaction to a normal dose of drugs?
Yes, it is less likely in a mixed breed, but still possible. We have
found the mutant gene in a Saint Bernard mix that had an adverse drug
reaction. The veterinarian did note that each eye was a different color,
like some Australian Shepherds.
How old must a dog be before it can be tested?
A puppy can be tested as soon as it is weaned from its mother. Why do we
recommend waiting until the puppy is weaned? Since we sample the inside
of the dog's mouth, and milk can contain a few cells from the mother, it
is possible that the puppy's sample could contain enough of the dam's
DNA to generate a false result.
Can mixed breed dogs have the MDR mutation?
YES! We have found the MDR1 mutation in many mixed breed dogs - even
dogs that don't look like herding breed dogs. Mixed breed dogs should be
tested for the mutation before receiving anti-mange doses of ivermectin.
Why are affected dogs called "mutants"?
A gene is a section of DNA that is responsible for producing a
particular protein in the body. When a dog (or other organism) has a DNA
sequence that produces a defective protein, that animal is said to have
a mutation in that gene. Individual animals that have a mutation in a
particular gene are considered to have the mutant form of the gene.
Unfortunately, the word "mutant" in lay language often carries a
negative connotation.
What heartworm prevention products can I use if my dog has the
MDR1 mutation?
Fortunately, the dose of ivermectin, selamectin, milbemycin and
moxidectin in the commercial heartworm preparations are low enough to be
used safely even in dogs with the MDR1 mutation. It is only when the
drugs are used at high doses, such as those used to treat mange (50
times higher dose than the heartworm prevention dose), that dogs with
the mutation will develop neurological toxicity. Attempting to use large
animal formulations of these drugs is likely to cause neurological
toxicity because it is difficult to accurately measure
Can individuals outside the United States order a test kit?
Yes, we can run samples from any country except
Australia , New Zealand or European countries (including Britain). For
those countries, please see the links below. If you have questions
please contact us at
VCPL@vetmed.wsu.edu.
03-9538-2559
Keith.byron@gribbles.com.au
1868 Danenong Rd, Clayton, Victoria, Australia, 3168
- For individuals in Europe, the exclusive
licensee for MDR1 genotyping is Genetic Counseling Services, and
they may be contacted as listed below.
http://www.gencouns.nl
info@gencouns.nl
0252 532 284
Genetic Counseling Services
Weeresteinstraat 45
2182 GR Hillegom
The Netherlands
