Complete Guide to Border Collie Genetic Conditions — Critical Warning on MDR1 Drug Side Effects

ImmunityBreed HealthMeongsiljang Veterinary Advisory Board

Border Collies are a breed that requires special attention to genetic conditions such as the drug sensitivity gene (MDR1), Collie Eye Anomaly (CEA), and hip and elbow dysplasia. We’ve compiled essential tests and care points to check before and after adoption.

What Genetic Conditions Should You Watch for in Border Collies?

A Border Collie sitting before its health check-up at the clinic.

Border Collies are a medium-sized breed that requires careful attention to genetic conditions such as the MDR1 drug sensitivity mutation, Collie Eye Anomaly (CEA), and hip and elbow dysplasia. The most important step is to conduct a single genetic test immediately after adoption. Dogs carrying the MDR1 mutation must avoid specific medications throughout their lives, while CEA can be confirmed through fundoscopic examinations and breed-specific genetic testing during puppyhood. Since CEA often shows no outward symptoms and may only be detected during a fundoscopic exam, it is highly recommended to have this check performed at least once. Completing these assessments around the age of one ensures much safer veterinary care for the rest of your dog’s life.

Top 5 Genetic Conditions You Must Know

Here’s a summary of genetic conditions commonly seen in Border Collies.

MDR1 gene mutation (drug sensitivity): This genetic variation can cause an exaggerated reaction to certain medications, including some dewormers and heartworm preventives.

Collie Eye Anomaly (CEA): Abnormal development of the retina and choroid can lead to vision impairment or retinal detachment. However, most affected dogs show no outward symptoms.

Hip dysplasia: An orthopedic condition in which the hip joint develops loosely, potentially leading to osteoarthritis and lameness.

Elbow dysplasia: A group of developmental abnormalities affecting the elbow joint, which may occur alone or in combination, often causing lameness at a young age.

Neutropenia syndrome (TNS): An autosomal recessive genetic disorder reported in Border Collies, characterized by low neutrophil counts that can result in recurrent infections and fever, sometimes accompanied by developmental abnormalities of the face and limbs.

Testing Timing and Methods for Each Genetic Condition

Item	MDR1 mutation	Collie eye anomaly	Hip dysplasia
Recommended testing time	2–3 months of age	6–12 weeks of age	12–24 months of age
Test method	Buccal mucosa swab or blood-draw genetic test	Fundus exam by an ophthalmology specialist (breed-specific genetic testing can be done alongside)	X-ray (general anesthesia recommended)
Need for retesting	One test valid for life	One test valid for life	Retest if pain or lameness occurs
Expected cost range	Included in genetic testing panel	Ophthalmology specialty service item	Orthopedic imaging exam item

Please contact your veterinary clinic directly for exact costs and scheduling.

Why Is the MDR1 Mutation So Important?

The multidrug resistance 1 (MDR1) gene produces P-glycoprotein, which pumps certain drugs out of the blood-brain and intestinal barriers. Deletion mutations in this gene are common in Collie-type breeds (reported in approximately 70% of Collies), and Border Collies, as herding dogs, also require caution. When the mutation is present, insufficient P-glycoprotein allows certain drugs, such as some dewormers, to accumulate to toxic levels even at therapeutic doses. This can cause lethargy, ataxia (staggering), drooling, dilated pupils, and vision impairment, and in severe cases, can be fatal. Always record test results in the medical chart, and it is safest for owners to proactively inform any new veterinary clinic about the status.

A veterinarian collecting a genetic test sample from the buccal mucosa of a Border Collie

Drugs to Be Especially Cautious of with MDR1 Mutation

If your dog tests positive or heterozygous for the MDR1 gene mutation, always inform your veterinarian before administering any medications. Certain drugs are known to pose risks in these cases, particularly when used at high doses, including macrocyclic lactone dewormers and preventives such as ivermectin, milbemycin, moxidectin, and emodepside, as well as the anti-diarrheal loperamide and the anti-nausea medication grapiprant. However, genuine heartworm preventatives have been reported to be safe for dogs with the MDR1 mutation when used at recommended doses. Dosage and drug selection must be determined by a veterinarian based on your dog’s weight and genetic profile, and owners should never administer medications without veterinary guidance. Your veterinarian can also help review a list of medications to avoid.

Collie Eye Anomaly (CEA) Check Points

Collie eye anomaly is a congenital, hereditary eye condition in puppies caused by abnormal development of the retina and choroid at birth. According to veterinary ophthalmology textbooks, it can manifest in various forms, including choroidal hypoplasia, retinal pigment epithelium (RPE) defects, abnormal blood vessels, peripapillary scleral defects, and, in severe cases, retinal detachment. Although it typically affects both eyes, the severity may not be symmetrical. Most cases show no outward symptoms and are often detected only during a fundus examination; breed-specific genetic testing can also be utilized. Therefore, it is important to have a fundus examination performed early in life to confirm the condition. The severity ranges from mild cases with minimal impact on vision to severe cases involving retinal detachment or anterior chamber hemorrhage that can lead to blindness, so please ensure your puppy is checked at least once.

A Border Collie puppy undergoing a fundus examination

Hip and Elbow Dysplasia: Lifelong Management Points

Border Collies are highly active, which places significant stress on their joints. Hip dysplasia occurs when the hip joint becomes loose and can progress to osteoarthritis over time. Once joint and bone changes have occurred, they are difficult to reverse. Therefore, it is crucial to maintain an appropriate body weight and manage exercise during the growth period to reduce joint strain. Studies show that proper exercise helps maintain healthy weight and muscle mass while preserving joint range of motion.

Maintain an appropriate weight: The ribs should be lightly palpable.

Prevent slipping: Place mats or rugs on hardwood floors.

Limit jumping: Restrict jumping on and off sofas and stairs until the dog is one year old.

Regular walks: Short, frequent walks are better than long, infrequent ones.

Visit the Vet If You See These Signs

If your Border Collie exhibits any of the following symptoms, they may be linked to a genetic disorder, so please seek veterinary care promptly: lifting one leg while walking or hopping on both hind legs like a rabbit; repeatedly bumping into objects or hesitating when walking in dim light; seizures with loss of consciousness and trembling lasting more than 1–2 minutes; or appearing unsteady or disoriented after taking standard deworming medication, which could indicate an emergency.

Recommended Health Schedule Up to Age 1

Early detection of genetic conditions is the most effective way to reduce lifelong veterinary costs. For cost efficiency, combine a basic health checkup with MDR1 gene testing right after adoption. When your dog is young, have a veterinary ophthalmologist perform a fundus exam to screen for Collie Eye Anomaly, and consider additional breed-specific genetic tests. Around one year of age, obtain hip and elbow X-rays to establish an orthopedic baseline. If there is a family history of Neutropenia Syndrome (TNS), closely monitor for recurring infections and fever, and we recommend confirming neutrophil counts through blood tests.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Where can I get an MDR1 gene test?

You can get this test at a veterinary clinic or a specialized pet genetic testing facility. The procedure involves either a buccal swab or a small blood sample, and we recommend keeping the results in your pet’s lifelong health records.

Is Collie eye anomaly treatable?

While a definitive cure is challenging, mild cases often have little to no impact on vision. Additional treatment is considered only if progressive changes such as retinal detachment or hemorrhage occur, and regular fundus examinations are recommended to monitor any changes over time.

Can hip dysplasia be prevented?

While we can’t prevent the genetic predisposition, maintaining an appropriate weight during growth, using non-slip flooring, and limiting excessive jumping can help delay the onset and progression of the condition. Taking baseline X-rays around the age of one makes future comparisons easier.

Does pet insurance for Border Collis cover genetic conditions?

Insurance policies vary by provider, so be sure to review the coverage scope and exclusions for breed‑prone genetic conditions—such as MDR1 mutations, Collie eye anomaly, and hip dysplasia—before enrolling.

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References

[1] Esson DW, Calvarese S, Clinical Atlas of Canine and Feline Ophthalmic Disease, 2nd Edition, Chapter 134 Collie Eye Anomaly, 2022

[2] Lowe JK, Kukekova AV, et al., Linkage mapping of the primary disease locus for collie eye anomaly, Genomics, 2003;82(1):86-95

[3] Parker HG, Kukekova AV, et al., Breed relationships facilitate fine-mapping studies, Genome Research, 2007

[4] The Dog Care Handbook, Things I Wish My Vet Had Told Me, Chapter 7 Hip Dysplasia in Predisposed Breeds

[5] Mealey KL, et al., Ivermectin sensitivity in collies is associated with a deletion mutation of the mdr1 gene, Pharmacogenetics, 2001