Primary ciliary dyskinesia is a relatively rare genetic disorder that has recently been recognised in several breeds, including the Newfoundland. A genetic mutation affects the cilia of cells. Cilia are microscopic hair-like projections of cells that are able to move, and in the respiratory tract these cilia beat together to create movement of the thin fluid film that sits on top of the cells. The fluid moves up the airways into the trachea, then up to the larynx where it is coughed up and usually swallowed. This acts to remove bacteria and foreign material from the respiratory tract, helping to protect the lungs.
Primary ciliary dyskinesia means that the respiratory cilia are unable to move properly, and so the airways are not cleared of fluid, bacteria and other foreign material. Dogs affected by primary ciliary dyskinesia therefore tend to be affected by recurrent upper and lower respiratory tract infections (most importantly pneumonia). Another noticeable function of cilia in the body is in the reproductive tract, and affected dogs tend to have reduced fertility.
Signs are first seen in the first few days or weeks of life, with young puppies developing a mucoid nasal discharge and/or pneumonia. It is thought that some cases of primary ciliary dyskinesia may be missed as “fading puppies” at this age. Signs may include sneezing, cough, lethargy, exercise intolerance, lack of appetite and dyspnoea (fast and/or laboured breathing).
Older puppies and dogs with primary ciliary dyskinesia will have bouts of broncho-pneumonia that respond to treatment with antibiotics, but then recur. The pneumonia tends to become worse over time, and bronchiectasis can occur due to mucous plugging of bronchioles. Other organ pathology that may be seen includes renal tubular fibrosis, otitis media and hydrocephalus. Animals may succumb to the disease at a variable age ranging from puppyhood to middle age or older.
Diagnosis is by special electron microscope examination of the cilia to visualise them and the abnormality present. This is usually from a biopsy of nasal or tracheal/bronchial mucosa. Some dogs can be managed for years with careful use of antibiotics, but as time goes on the response to antibiotics becomes less and less complete. Eventually death results or euthanasia is carried out due to the severe disease and suffering in the affected dog.
As yet the genetic defect has not been determined, except for the Old English sheepdog, for which a DNA test does exist.