Midland Old English Sheepdog Club

Caring for Sheepdogs

OES & The MDR1 Gene Defect / Ivermectin Sensitivity

MDR1 is a genetic disorder found in many dog breeds(including Australian Shepherd, Border collie, Collie, German Shepherd, Old English Sheepdog, Shetland Sheepdog (Sheltie), Rough Collie, Smooth Collie). Affected dogs, when treated with certain common drugs such as Ivermectin and loperamide (Imodium), are unable to pump out these drugs from the brain resulting in poisoning and neurologic symptoms ranging from tremors, anorexia and excess salivation to blindness, coma and even death. Some of these drugs such as Ivermectins, used for the treatment of parasite infections, are able to cause toxicity at 1/200th of the dose required to cause toxicity in healthy dogs.

Affected dogs lack a protein (P-Glycoprotein), which is responsible for pumping out many drugs and toxins from the brain, and that affected dogs show signs of toxicity because they are unable to stop drugs from permeating their brains. Researchers have identified that this condition is due to a mutation in the multi-drug resistance gene [MDR1].

List Of Drugs That Cause Sensitivity To Dogs With MDR1 Mutation

Class A Do not use these drugs in dogs with MDR1 Gene Defect Ivermectine substance"Anti parasites": (Diapec®, Ecomectin®, Equimax®, Eqvalan®, Ivomec®, Noromectin®, Paramectin®, Qualimec®, Sumex®, Virbamec®)
Doramectine substances "Anti parasites": (Dectomax® )
Loperamide substances "ant diarrheal ": (Imodium®)
Moxidectine substances "Anti Parasites" (Cydectin®, Equest®) Ivermectine substance “Anti parasites”
Class B Use only under close control of veterinarian Cytostatics "Chemotherapy": (Vinblastine, Vincristine, Doxorubicine, Paclitaxel, Docetaxel, Methotrexat, Vincristine)
Immunosuppressive: (Cyclosporine A)
Heart glycosides: (Digoxine, Methyldigoxine)
Opioids: (Morphium)
Antiarrhythmics: (Verapamil, Diltiazem, Chinidine)
Antiemetics (Ondansetron, Domperidon, Metoclopramide )
Antibiotics (Sparfloxacin, Grepafloxacin, Erythromycin)
Antihistamin (Ebastin)
Class C Can be used only in the permitted application form and dose Selamectin (Stronghold®), Milbemax® and Advocate® .

* In dogs with the MDR1 mutation, acepromazine and butorphanol tend to cause more profound and prolonged sedation in dogs . It is recommended to reduce the dose by 25% in dogs heterozygous for

Clear x Clear 100% Clear
clear x carrier 50%  Clear + 50% carriers
clear x affected 100% carriers
carrier x Clear 50%  Clear + 50% carriers
carrier x carrier 25% clear + 25% affected + 50% carriers
carrier x affected 50% carriers + 50% affected
affected x Clear 100%  carriers
affected x carrier 50% carriers + 50% affected
affected x affected 100% affected

Genotype: N / N [ Homozygous normal ]
The dog is noncarrier of the mutant gene.
The dog will never develop MDR1 Gene Defect / Ivermectin Sensitivity * and therefore it can be bred to any other dog.

Genotype: N / MDR1 [ Heterozygous ]
The dog carries one copy of the mutant gene and one copy of the normal gene.
The dog may develop MDR1 Gene Defect / Ivermectin Sensitivity.
Since it carries the mutant gene, it can pass it on to its offspring with the probability of 50%.

Genotype: MDR1 / MDR1 [ Homozygous mutant ]

The dog carries two copies of the mutant gene and therefore it will pass the mutant gene to its entire offspring.
The dog will develop MDR1 Gene Defect / Ivermectin Sensitivity * and will pass the mutant gene to its entire offspring

By DNA testing the mutation can be shown directly, testing is carried out by The Animal Health Trust and Laboklin.