This community talks about MDR1 constantly, and for good reason: it is the test that decides whether a routine prescription can kill a herding breed. But MDR1 is one entry on a longer list. Herding breeds carry a handful of inherited conditions, some detectable by a cheek swab and some only by a physical exam, and a dog whose only documented test is MDR1 still has an incomplete health file.
The eye conditions are the clearest example. Progressive retinal atrophy is not one disease but a family of mutations, each tied to specific breeds, each progressing toward blindness at its own pace. A canine retinal genetics resource built from two decades of veterinary ophthalmology practice maps those variants breed by breed and explains how carriers can still be bred without producing affected puppies.
Which herding-breed conditions have a DNA test?
Several of the inherited problems that matter in collies, shelties, aussies, and their relatives can be read straight off a swab:
- MDR1 (ABCB1), the drug-sensitivity mutation this site exists to explain.
- Progressive retinal atrophy, with variants like prcd-PRA shared across many breeds and rcd dysplasias specific to a few lines.
- Collie eye anomaly, caused by the NHEJ1 mutation and present at high frequency in collies and related breeds.
- Degenerative myelopathy (SOD1), the late-onset spinal cord disease that most often surfaces in seniors.
- Merle status (PMEL17), which is not a disease test but a breeding safety check, since merle-to-merle pairings produce puppies at risk of deafness and eye defects.
Many consumer panels bundle all of these into one kit. The laboratory that pioneered MDR1 testing, Washington State University’s veterinary pharmacogenetics service, remains the reference for the MDR1 result specifically, while broader panels cover the rest of the list in a single report.
Which conditions still need a physical exam?
Not everything on the screening list is a DNA test, and treating it that way is a common owner mistake. Hip and elbow dysplasia have a genetic component but no reliable single-gene test: they are graded on radiographs through schemes like OFA or PennHIP, and a normal DNA panel says nothing about a dog’s hips. Eye examinations by a veterinary ophthalmologist serve a similar role, because they catch conditions whose genetic tests are incomplete or unavailable and confirm what a DNA result predicts.
The practical rule is simple. DNA tests answer “what did this dog inherit,” while exams answer “what does this dog have.” A complete file for a herding breed usually holds both.
How do you keep all the results straight?
Each test has its own vocabulary, and the MDR1 habits transfer directly. Record the exact genotype rather than “tested clear,” keep the lab reports together, and hand the full set to every veterinarian rather than the single result you happen to remember. Our guide to reading an MDR1 genotype report shows what that looks like for one gene; the same discipline applies to each line of the panel.
For breeders, the panel is the working document behind every pairing decision. For owners, it is the answer you give at the first vet visit and the reason a specialist never has to guess.
The short version
MDR1 is the test that protects a herding dog from the pharmacy, but it does not cover the eyes, the joints, or the spinal cord. PRA, collie eye anomaly, degenerative myelopathy, and merle status are readable from the same kind of swab, while hips and elbows still need radiographs. A dog with a complete screening file is a dog whose owner, breeder, and veterinarian are all working from the same facts.