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Multi-drug
Resistance in Rough Collies (MDR1)
The problem first came to light some twenty years ago when several Collies died from Ivermectin poisoning and, since then, the veterinary profession has accepted this drug should never be given to Collies. More recently a Rough Collie died from eating horse faeces (Ivermectin is used for worming horses and any excess drug passes out with their faeces). Researchers have since found that some Collies appear to be susceptible not only to Ivermectin, but to a wide range of other drug substances. The MDR1 (multi-drug resistant) gene is responsible for enabling the body’s blood-brain barrier to function normally. In MDR1-affected dogs the function of the blood-brain barrier is compromised allowing certain drug compounds to leak into the major organs or across the blood-brain barrier, where they enter the central nervous system causing toxic reactions and even death. Symptoms include excessive salivation, ataxia, blindness, coma, and respiratory problems. An MDR1 Normal dog (+/+) receives a healthy MDR1 gene from each of its parents and can therefore only pass on healthy genes to its offspring. Such animals do not exhibit drug toxicity. A ‘Carrier’ (+/-) is a dog that has received a normal MDR1 gene from one of its parents, and a defective gene from the other parent. Although a ‘carrier’ will not develop multi-drug hypersensitivity itself, it will pass both normal and defective genes onto its offspring resulting in approximately 50% of the puppies inheriting a defective MDR1 gene. An Affected dog (-/-) receives a defective MDR1 gene from both its parents, so such dogs will display toxic reactions to a wide range of drug compounds. Researchers estimate that approximately 60% of Collies are affected with MDR1. Since the original American research of Kate Mealy and Ian Neff, the components of several other drugs (thought to be safe a few years ago) have since been found to cause toxicity in MDR1-affected (-/-) dogs. If you have an MDR1-affected Collie (-/-) you could be in a position to save its life by informing your veterinary surgeon of the Collie’s MDR1 status, and providing him/her with the following list of drug compounds that could be life-threatening to your dog. Please note that not all vets keep up to date with the latest research findings! The table here shows three classes of drug compounds: Class A includes substances that have been proven to pass through the blood-brain barrier in MDR1-affected dogs; Class B lists substances which have shown interactions in animal tests, whereas Class C substances can be given without problems, even to affected dogs:
Laboklin
[Manchester] carry out MDR tests at a cost of £65.
DNA swabs are freely available from Dr Mansour Makki "In view
of an article in "Our Dog's" entitled "KC advises
care with DNA tests - but concerns over new lab unfounded" 08/08/08'
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