Wary about Wormers: Understanding Ivermectin Risks in Herding Dogs

As a responsible dog owner, particularly those with herding breeds like the Border Collie and other related breeds (Old English Sheepdog, Rough Collie), understanding the risks associated with ivermectin, a common anti-parasitic medication, is crucial. Ivermectin is widely used to treat parasite infestations but can be dangerous, especially in certain breeds.

Why Are Some Dogs Affected by Ivermectin?

Ivermectin and related dog wormers belong to a class called macrocyclic lactones. These drugs are effective anti-parasitic drugs commonly used to control worms, mites, and other parasites. For most dogs, ivermectin is safe when used as directed, as it targets parasite cells specifically but normally does not affect mammalian cells at normal dosages.

However, in herding dog breeds such as collies, Australian Shepherds, Rough Collies, and Old English Sheepdogs, a genetic mutation known as ABCB1 (sometimes called MDR1) impairs the blood-brain barrier. This mutation allows ivermectin to enter the brain at higher levels, potentially causing neurological toxicity even at doses safe for other dogs.

Research suggests that up to 70-75% of certain herding breeds may carry this mutation, making ivermectin use a risk factor for those dogs unless genetically tested. Collies in particular have a higher incidence, which is why most vets advise caution or avoidance of ivermectin-containing drugs in these breeds.

It’s important to note that not all herding breeds carry this mutation – for instance, Border Collies are usually not affected. Genetic testing via a simple cheek swab is widely available and recommended for herding dog owners to safely guide deworming and parasite treatment choices.

Symptoms of Ivermectin Overdose

Ivermectin toxicity in dogs manifests primarily through neurological signs. Early symptoms often include behavioural changes such as lethargy, unusual sleepiness, or reduced responsiveness. Affected dogs may display weakness, loss of coordination, wobbliness, or difficulty standing.

• Excessive drooling
• Vomiting and diarrhoea
• Tremors or muscle twitching
• Seizures or convulsions in severe cases
• Slow heart rate and breathing difficulties
• Coma in extreme toxicity

If you notice any of these symptoms following parasite treatment, immediate veterinary evaluation is essential.

Treatment for Ivermectin Overdose

Treatment involves intensive symptomatic care under veterinary supervision. There is no specific antidote for ivermectin toxicity; hence supportive care is critical. This may include:

• Hospitalisation with close monitoring and nursing
• Intravenous fluids to maintain hydration and support circulation
• Medications to control seizures and tremors
• Antiemetics to manage vomiting
• In severe situations, mechanical ventilation or medically induced coma may be required
• Intravenous lipid therapy, a procedure that helps bind and remove ivermectin from the bloodstream more rapidly

Recovery times vary greatly due to ivermectin's enterohepatic recirculation—the drug cycles through the liver and intestines, slowing its clearance from the body.

Safer Anti-Parasitic Alternatives

If you have a herding dog known or suspected to carry the ABCB1 mutation, safer alternatives to ivermectin are advisable. Drugs such as selamectin, milbemycin, and moxidectin are in the same drug family but generally have a lower risk of causing neurotoxicity in these breeds when properly dosed.

Always check the active ingredients carefully in any anti-parasitic product, especially if combining flea treatments with wormers, to avoid accidental overdosing. Consultation with your vet before starting any parasite control program is essential to ensure your dog's safety.

Veterinary Advice for Responsible Owners

For owners of herding dogs, knowledge and caution with anti-parasitic medications are key to preventing ivermectin toxicity. Genetic testing for the ABCB1 mutation offers peace of mind and customises treatment plans to your dog’s unique needs. Always work with your vet, follow dosage instructions carefully, and never administer medication without professional advice.

Responsible ownership includes understanding your dog’s breed-specific health risks and maintaining regular health checks to ensure safety in parasite prevention and treatment. Protect your loyal herding companion by being informed, cautious, and proactive.

Conclusion

Ivermectin remains a valuable medication for parasite control but requires care when used in herding breeds vulnerable to the ABCB1 mutation. Avoiding ivermectin in collies and related breeds, using safer alternatives when possible, and seeking veterinary guidance ensures your dog stays healthy and protected from parasite-related illnesses and medication risks.