Dogs Needed For Dwarfism Study

A study into chondrodysplasia (dwarfism) in Chesapeake Bay Retrievers is underway at the University of California at Davis Veterinary Medical Teaching Hospital. The study was begun after a litter of seven puppies was whelped; five of which showed some form of dwarfism.

A search has begun to locate other dogs medically diagnosed with dwarfism. Pedigree analysis of the known affected dogs shows some common ancestry among them. However, most of the general population of Chesapeakes also shares common ancestry with these affected dogs; therefore pedigree analysis alone is not sufficient to eliminate the gene from the population. It is hoped that a genetic marker or mutation test can be developed to detect carriers. This study is privately funded, so no ACC funds are needed; however, the researchers are looking for affected dogs in order to help with development of a gene test. Anyone with an affected dog can contact:

Amy Young
Staff Research Associate
Bannasch Laboratory
University of California School of Veterinary Medicine
Davis, CA

Dr. John Switzer formerly coordinated the effort to obtain dogs for this research. A blood sample and copy of the pedigree from affected dogs are what is needed right now. The DNA swab-testing kits are free.

Below are excerpts from a preliminary report sent by Dr. Switzer.

"Six 14 week old pups from a litter of seven puppies were examined for dwarfism. Physically, the dwarfed pups were short legged and much smaller in stature. There was extreme pronation of the carpal joints and carpal laxity. The ears were extremely long in proportion to head size. The seventh pup appeared physically normal and was sold prior to this study. Upon X-Ray examination of the six pups, 3 showed severe dystrophic changes, 2 showed abnormal bone remodeling, and 1 appeared normal.

"A test breeding of two of the affected pups produced a litter of abnormal pups. Radiographs and growth measurements have been taken on this litter and compared to growth rates in a normal litter (note-all offspring from test matings have been placed in homes with vet students. LVL) By 10 weeks of age, growth and radiographic changes are noticeable and by 14 weeks, growth and radiographic changes are obvious. It also appears that the dwarfism is due to an autosomal recessive gene and that multigenic factors may be involved. Blood samples are being obtained for DNA analysis at UC Davis, and hopefully a genetic marker can be located which could assist in the screening of carrier dogs."

Dr. Switzer’s brief also included a detailed radiographic description by Paul W Poulos, DVM, PhD, Diplomate of the American College of Veterinary Radiologists. This description is very useful for veterinarians who may wish to do radiographic workups on dwarfism in Chesapeakes or other breeds prone to this form of dwarfism. A copy of Dr. Switzer’s complete brief is available from Lisa Van Loo.

Please contact Dr. Amy Young directly with information about affected dwarves. Spread the word to non-ACC members, we need as many affected dogs as possible for this research effort.