Prevalence and genetic analysis of spondylosis deformans in the Italian boxer dog population

The dog is the non-human species for which the largest number of genetic disorders is known, and, to date, over 370 genetic diseases have been documented (Ostrander et al., 2000). Some skeletal diseases, namely hip and elbow dysplasia, have been investigated, and genetic parameters for such disorders have been reported (Maki et al., 2000; Lippanen et al., 2000). Conversely, genetic determinism of other diseases like spondylosis deformans has been less considered. Spondylosis deformans is a degenerative disease of the spine characterised by the presence of one or more osteophytes, showing different degrees of development, placed on the vertebral bodies (Hansen, 1952; Morgan, 1967). Severe spondylosis deformans causes stiffness in the back, lameness, change of gait and pain. Hence, reduction of incidence of spondylosis is advisable for increasing welfare and longevity of dogs. In a survey on approximately 7,000 dogs, spondylosis was the most common disorder in the group of degenerative spinal diseases (Empel and Blenau, 1999). Incidence of spondylosis is particularly large in the Boxer breed (Murlebach and Freudiger, 1973; Eichelberg and Wurster, 1982), is higher in females (Eichelberg et al., 1989) and tends to increase and to be more severe at increasing age of dogs (Mattoon and Koblick, 1993). Some studies (Murlebach and Freudiger, 1973; Eichelberg and Wurster, 1982) postulated that spondylosis has a genetic basis. Langeland and Lingaas (1995), in a study based on 353 boxers progeny of 24 sires, reported heritability estimates ranging from 0.42 to 0.62 for the maximum degree of osteophyte development and from 0.13 to 0.47 for the number of affected discs, but these estimates exhibited very large standard errors and did not differ significantly from zero. The present study aimed to assess the prevalence and to investigate genetic aspects of spondylosis deformans in the Italian Boxer dog population. CONCLUSION Results from this study provide evidence that spondylosis deformans is a polygenic genetic disorder showing estimates of h2 for linear scores for the degree of osteophytes development of intermediate magnitude. This ensures feasibility of selection programs to reduce prevalence of the disease and offers the opportunity of implementing genetic evaluation procedures mostly based on phenotypic observations, i.e. x-ray assays, of candidates to selection. Definition of a selection index considering appropriate weighting factors for different sites will be the aim of a future study