Primary ciliary dyskinesia (PCD) is an inherited disorder of the cilia affecting Old English Sheepdogs. Cilia are microscopic, hair-like structures that line the nasal cavity, trachea, and bronchi of the respiratory system, the fluid filled cavities of the brain and portions of the reproductive tract. Normal cilia move in wave-like patterns to aid the movement of fluids in the brain and reproductive tracts and prevent large particles and pathogens from getting into the lungs. In PCD, affected dogs have cilia that are either malformed or do not move. Particles and pathogens cannot be removed from the upper respiratory tract and can lead to sinusitis, bronchitis and pneumonia. Affected dogs typically present a few days after birth with respiratory disease. Symptoms include coughing, sneezing, nasal discharge and frequent respiratory infections. This disorder also causes immobility of sperm, therefore affected male dogs are sterile. Dogs with PCD may also have a transposition of organs in the thoracic and/or abdominal cavities, resulting in a mirror image of the normal placement of the heart and lungs and sometimes other organs. This transposition is called situs inversus and does not usually cause clinical problems. Dogs with this disorder can live for years if their chronic respiratory infections are managed.
Genetic testing of the CCDC39 gene will reliably determine whether a dog is a genetic Carrier of primary ciliary dyskinesia. Primary ciliary dyskinesia is inherited in an Autosomal Recessive manner in dogs meaning that they must receive two copies of the mutated gene (one from each parent) to develop the disease. In general, carrier dogs do not have features of the disease but when bred with another carrier of the same Mutation, there is a risk of having affected pups. Each pup that is born to this pairing has a 25% chance of inheriting the disease and a 50% chance of inheriting one copy and being a carrier of the CCDC39 gene mutation. Reliable genetic testing is important for determining breeding practices. In order to eliminate this mutation from breeding lines and to avoid the potential of producing affected pups, breeding of known carriers to each other is not recommended. Dogs that are not carriers of the mutation have no increased risk of having affected pups due to this mutation.
There may be other causes of this condition in dogs and a normal result does not exclude a different mutation in this gene or any other gene that may result in a similar genetic disease or trait.
Merveille AC, Battaille G, Billen F, Deleuze S, Fredholm M, Thomas A, Clercx C, Lequarré AS. Clinical Findings and Prevalence of the Mutation Associated with Primary Ciliary Dyskinesia in Old English Sheepdogs. J Vet Internal Med. 2014 Article first published online: 12 MAR 2014. [Not in PubMed]
Merveille AC, Davis EE, Becker-Heck A, Legendre M, Amirav I, Bataille G, Belmont J, Beydon N, Billen F, Clément A, Clercx C, Coste A, Crosbie R, de Blic J, Deleuze S, Duquesnoy P, Escalier D, Escudier E, Fliegauf M, Horvath J, Hill K, Jorissen M, Just J, Kispert A, Lathrop M, Loges NT, Marthin JK, Momozawa Y, Montantin G, Nielsen KG, Olbrich H, Papon JF, Rayet I, Roger G, Schmidts M, Tenreiro H, Towbin JA, Zelenika D, Zentgraf H, Georges M, Lequarré AS, Katsanis N, Omran H, Amselem S. CCDC39 is required for assembly of inner dynein arms and the dynein regulatory complex and for normal ciliary motility in humans and dogs. Nat Genet. 2011 Jan; 43(1):72-8.