November 4, 2018

Prevalence and heritability of distichiasis in the English Cocker spaniel

The authors and directors of this study researched the distichiasis disease in cocker spaniels and if it was genetic. Distichiasis is the abnormal growth of eyelashes on the inner eyelid instead of the outer, and it occurs in a variety of mammals including both humans and dogs.  


The article looked at breeding between affected dogs (dogs with the disease) and affected dogs, affected and unaffected, and unaffected and unaffected dogs. Out of the 549 dogs included in the study, it found that 157 were produced by two affected parents, 229 were produced by one affected parent and one unaffected parent, and 163 were produced by unaffected parents. It found that the risk for distichiasis is 1.3 higher in one affected parent and one not than with unaffected parents, and 1.4 times higher for two affected parents than 1 affected parent. The percent of affected dogs in the study was 50%. The article states that "The heritability (h2) of distichiasis was estimated at 0.22 when using offspring from one affected parent and 0.51 when using offspring from two affected parents." Thus, the study found that although distichiasis cannot be formally proven as autosomally dominant, distichiasis is inherited as a threshold character. Because of this, the authors conclude that the best way to reduce distichiasis is to primarily use unaffected or mildly affected dogs in breeding. 


Article reviewed by Aidan Ryan