Australian Shepherd Health Testing Requirements for Stud Dogs

Australian Shepherds are athletic, highly intelligent herding dogs — and they carry one of the most clinically significant genetic mutations in all of dog breeding: MDR1, which causes life-threatening drug reactions to common medications.

The Australian Shepherd Club of America (ASCA) maintains CHIC requirements for the breed. Any responsible Aussie stud dog must be tested for MDR1 in addition to conventional health screenings.

CHIC Requirements for Australian Shepherds

• OFA or PennHIP Hip Evaluation
• OFA Elbow Evaluation
• OFA Eye Examination (CAER)
• DNA test for MDR1 (ABCB1)
• DNA test for Hereditary Cataracts (HSF4)

MDR1 — The Most Critical Test

MDR1 (Multidrug Resistance Gene 1, also called ABCB1) causes abnormal sensitivity to a wide range of commonly used medications, including:

• Ivermectin (common heartworm preventive and antiparasitic)
• Loperamide (Imodium)
• Acepromazine (common sedative)
• Butorphanol (pain medication)
• Vincristine (chemotherapy)
• Many other drugs

MDR1 is semi-dominant — one copy causes partial sensitivity; two copies causes severe sensitivity. A dog with two copies of the mutation can die from a dose of ivermectin that would not harm a normal dog.

MDR1 carrier frequency in Australian Shepherds is approximately 50%. This is not a rare condition — it is foundational to how Aussie breeders must operate.

Stud dogs should be MDR1 Clear (N/N) or at minimum Heterozygous (MDR1/N) with the result disclosed. Breeding Heterozygous × Heterozygous produces 25% two-copy (severely affected) offspring.

Hereditary Cataracts (HSF4)

HSF4 hereditary cataracts cause posterior polar subcapsular cataracts that progress to blindness. Autosomal dominant with incomplete penetrance — one copy can cause cataracts. This means Carrier dogs (one copy) are at risk for developing the disease themselves, not just their offspring.

Stud dogs should be HSF4 Clear (no copies). Using an HSF4 Carrier stud dog risks producing cataracts in offspring and may indicate the stud himself will develop cataracts.

Collie Eye Anomaly (CEA)

CEA occurs in Australian Shepherds. DNA testing is available. CEA can cause retinal detachment and blindness in severely affected dogs. Stud dogs should be DNA tested; Carriers can be bred to Clear dams safely.

Progressive Retinal Atrophy

Multiple PRA variants occur in Aussies. prcd-PRA testing is recommended, as well as testing for additional Aussie-specific PRA mutations.

Epilepsy

Australian Shepherds have elevated epilepsy rates. The genetic basis is complex (polygenic), and no single DNA test covers this risk. Selecting from low-epilepsy pedigrees and avoiding breeding affected dogs is the current management approach.

Hip and Elbow Evaluations

Hip dysplasia occurs at moderate rates in Aussies. OFA Good or Excellent hips are the standard for stud dogs. OFA Normal elbows are required.

Summary

A responsible Australian Shepherd stud dog must have: MDR1 genetic testing (with results disclosed to dam owners), HSF4 Clear status, OFA/PennHIP hips, OFA Normal elbows, and current CAER eye exam. CEA and prcd-PRA testing reflects best practice. MDR1 is not optional — it is a safety-critical test that affects medical care throughout the dog's life and the lives of all offspring.