Norwich DNA health tests

There are currently six DNA health tests that are relevant for Norwich terriers. All of these tests are inexpensive and require nothing more than a swab of the inside of a dog's mouth in order to get a DNA sample to test. In order of importance (in my opinion).

UAS

Norwich Terrier Upper Airway Syndrome is the number one health problem in Norwich terriers. In May 2019, European researchers published a paper reporting on an association between a mutation in the ADAMTS3 gene and Norwich Terrier Upper Airway Syndrome (NTUAS). While this is not the entire story with regards to UAS, it is currently the only tool that breeders have to try to breed away from this problem. VetGen is the only lab of which I am aware that offers this DNA test.

INPP5E (Cystic Renal Dysplasia)

In September 2018, Finnish researchers published a paper reporting on a mutation in the INPP5E gene that causes kidney failure and death in Norwich terrier puppies. While this mutation was discovered among Finnish Norwich terriers, the mutation is known to exist among North American Norwich.

The only lab in North America currently offering a DNA test for the INPP5E mutation is a genetics lab at North Carolina State University. To test, one starts by ordering a (free) cheek swab kit.

PLL

Primary lens luxation (PLL) is an eye disease found mostly in the terrier breeds . Some Norwich have been diagnosed with PLL. These Norwich and related Norwich have been found to carry the mutation in the ADAMS17 gene believed to be the cause of PLL and diagnosed by the PLL DNA test. Many commercial labs offer the PLL DNA test. OFA maintains a database of PLL DNA reports. The PLL DNA test is part of the Embark panel of DNA tests.

ALT

Alanine aminotransferase, or ALT, is a common value on most blood chemistry panels and is known to be a sensitive measure of liver health. Labs give a reference range for normal ALT values. This reference value was determined from the ALT results of lots of healthy dogs of many breeds.

According to a 2015 scientific paper, dogs with one or two copies of an ALT mutation may have "low-normal" ALT activity. This is not a disease state. Rather it is a clinical finding - dogs with low-normal ALT activity have lower resting levels of ALT activity. In other words, the reference range for dogs with the ALT mutation is different (lower) than for the general dog population. This means that if the ALT activity rose, it still could fall within the range the lab reports as normal and might be missed by a veterinarian who was not aware that the dog is a "low-normal".

The low-normal ALT mutation has been seen in several Norwich who are not closely related. The only DNA lab offering to test for the ALT mutation is Embark, as part of their DNA panel test.

DM

Degenerative Myelopathy (DM) is an adult-onset, progressive spinal cord disease causing weakness in the hind limbs and eventually paralysis. Because common spinal cord injuries can mimic DM, a definitive diagnosis can only be made by a postmortem examination of the spinal cord. No Norwich has been definitively diagnosed with DM. A veterinary neurologist reported a Norwich with DM, but unfortunately the spinal cord was not postmortemly examined. A mutation in the SOD1 (exon2) gene has been associated with DM. This mutation has been found in over 100 breeds, and is believed to be an ancesteral mutation predating the segretation of dogs in breeds. This mutation exists in Norwich terriers.

DNA testing for DM has generated controversy among breeders. Some argue that since no Norwich has been definitively diagnosed with DM, that there are modifier genes that stop Norwich from getting DM. However no evidence has been presented that such modifier genes exist for Norwich nor has any search been made for modifier genes among Norwich. A 2016 paper reported that a modifier gene had been found in Pembroke Welsh Corgies.

Many commercial labs offer the DM DNA test. OFA maintains a database of DM DNA reports. The DM DNA test is part of the Embark panel of DNA tests.

D-Locus

The D-Locus is usually tested as as part of a DNA coat color panel. The recessive allele d in the "D locus", located in the MLPH gene, causes (where there are two copies of d) a color dilution in a dog's coat color. This mutation has also been associated with the disease "color dilution hairloss". To my knowledge no Norwich has been reported with "color dilution hairloss".

Many commercial labs offer the D-Locus DNA test. OFA maintains a database of D-Locus DNA reports. The D-Locus DNA test is part of the Embark panel of DNA tests.

Last updated 20200531