Emerging insights into the genetic basis of canine hip dysplasia

Abstract

Canine hip dysplasia (CHD) is the most common inherited polygenic orthopedic trait in dogs with the phenotype influenced also by environmental factors. This trait was described in the dog in 1935 and leads to a debilitating secondary hip osteoarthritis. The diagnosis is confirmed radiographically by evaluating signs of degenerative joint disease, incongruence, and/or passive hip joint laxity. There is no ideal medical or surgical treatment so prevention based on controlled breeding is the optimal approach. The definitive CHD diagnosis based on radiographic examination involves the exposure to ionizing radiation under general anesthesia or heavy sedation but the image does not reveal the underlying genetic quality of the dog. Phenotypic expression of CHD is modified by environmental factors and dogs with a normal phenotype can be carriers of some mutations and transmit these genes to their offspring. Programs based on selection of dogs with better individual phenotypes for breeding are effective when strictly applied but remain inferior to the selection of dogs based on estimation of breeding values. Molecular studies for dissecting the genetic basis of CHD are ongoing, but progress has been slow. In the future, the recommended method to improve hip quality in controlled breeding schemes, which will allow higher selection pressure, would be based on the estimation of the genomic breeding value. Since 2012, a commercial DNA test has been available for Labrador Retrievers using a blood sample and provides a probability for development of CHD but we await evidence that this test reduces the incidence or severity of CHD.

Keywords: GWAS; breeding stock; canine hip dysplasia; diagnosis; phenotype; screening.

Figure 1

Ortolani test performed with the dog in lateral recumbency. Notes: The hip is positioned in a neutral position with the femur parallel to the table and firm pressure is applied along the long axis of the femur (arrow), which causes subluxation of the femoral head when there is increased hip joint laxity (A). While still applying proximal force, the limb is slowly abducted (arrow), and the femoral head brought back into position within the acetabulum eliciting a typical palpable and/or audible clunk (B). Reprinted from The Veterinary Journal, 184(3), Ginja MM, Silvestre AM, Gonzalo-Orden JM, Ferreira AJ. Diagnosis, genetic control and preventive management of canine hip dysplasia: a review, 269–276. Copyright (2010), with permission from Elsevier.