Canine Primary Ciliary Dyskinesia (PCD)
Dog Primary Ciliary Dyskinesia (PCD) is an inherited disorder that causes defects in upper and lower respiratory tract, as well as in the flagella of sperm cells, causing infertility. Previously it was known as immotile cilia syndrome (ICS). Until now, primary ciliary dyskinesia has been identified in more than 19 breeds, such as Bichon frises, Border collies, Bull Mastiffs, Chihuahuas, shar peis, chow chows, Dalmatians, Doberman pinschers, English cocker spaniels, English pointers, English setters, English springer spaniels, golden retrievers, Gordon setters, long-haired dachshunds, miniature poodles, Old English sheepdogs, Newfoundlands, Rottweilers, and Staffordshire bull terriers, however, the causative mutation has so far been identified only in the Bobtail dog breed.
Characteristics and Symptoms
A cilium is an organelle found in eukaryotic cells. Cilia cells that are in the lining of the trachea have an important role of sweeping mucus and dirt out of lungs. When the ciliary function becomes ineffective, it results in poor mucus clearance from the airways. This with time results in chronic mucus plugging and inflammation of nasal cavities, trachea and lower airways. Progressively this can lead to rhinosinusitis, bronchitis, bronchopneumonia and bronchiectasis, all known as chronic respiratory abnormalities. Other than that, other known clinical signs are bilateral mucopurulent nasal discharge, hyperpnea, increased upper airway sounds, orthopnea and cyanosis. Symptoms occur in an early age, which is already in few weeks or months after the cub’s birth. Exceptional cases of affected dogs that remained asymptomatic for prolonged periods have been reported. These dogs remained asymptomatic from six months to ten years.
Respiratory signs are the most prominent, but there are other symptoms of the primary ciliary dyskinesia, such as otitis media, renal fibrosis or dilation of renal tubules and infertility in males and females.
Methods used by veterinarians in order to establish diagnosis of PCD, except the clinical signs, are radiography, bronchoalveolar lavage, sperm samples, cilia function tests and electron microscopy of cilia.
Dog Primary Ciliary Dyskinesia (PCD) is inherited as an autosomal recessive disorder. Dog carrying one copy of the mutated gene is heterozygous and will not show the PCD symptoms. When mating two carriers (heterozygotes) at conception each cub has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Currently there is no cure for PCD and the only way to avoid obtaining affected cubs is to breed dogs which are not carriers of the mutation. Defected genes for autosomal recessive disease can be passed for many generations without affected individuals occurring until two carriers are bred to one another. The only way to find out if there is a chance of getting an affected puppy is to do genetic testing.