Given the close relationship between Irish Wolfhounds and Scottish Deerhounds and the clinical similarities between recurrent/chronic pneumonia in the two breeds, the Wolfhound pneumonia story may have important implications and benefits to offer to our own breed.
by John Dillberger, DVM, PhD
Reprinted from the September/October 2013 Claymore
Based on the results of the 2011 Deerhound Health Survey, one of the more important health problems in Deerhounds is pneumonia, which was reported for 14 (5%) of 273 males and 12 (4%) of 315 bitches. Several people reported single bouts of pneumonia, but many others said their dogs had more than one episode. For example, one male “had kennel cough after the first dog show of his 2nd and 3rd years of age that progressed to pneumonia each time.” A 1½-year-old bitch also had pneumonia that “began as kennel cough,” but she “also had frequent aspiration pneumonia due to megaesophagus.” A 2-year-old male had “chronic pneumonia from aspirated food.” A 3-year-old male was “treated twice for tandem episodes of pneumonia.” For a young bitch, “the first episode was after whelping, and she had repeated episodes as she aged.” In all, nine Deerhounds (four males and five bitches) had chronic and/or recurrent pneumonia.
Pneumonia is a serious disease in all animals, and Deerhounds are no exception. Pneumonia was the cause of death for eight Deerhounds, making it an important cause of death for our breed.
I was not surprised by the survey results. Over the past 25 years, I have had conversations with many Deerhounders whose dogs had pneumonia—sometimes more than one episode.
Recently I learned of research being done to investigate pneumonia in Irish Wolfhounds, under the joint direction of Dr. Margret Casals at the University of Pennsylvania and Dr. Iris Reichler at the University of Zurich. Because of the close relationship between Wolfhounds and Deerhounds, the Wolfhound research may shed some light on pneumonia in our breed. This month I will share what I learned.
The Wolfhound Story Begins with Rhinitis
Rhinitis is the medical term for inflammation of the nasal passages. A rhinitis syndrome in Irish Wolfhounds was first described in 1969. The primary symptoms of Wolfhound rhinitis syndrome were sniffling, sneezing, and a watery nasal discharge that sometimes became a thick white/yellow/green discharge and could even be tinged with blood. Symptoms usually began at a very early age and often were continuous or would recur at short intervals. Many affected Wolfhounds would develop a moist cough and die at a young age from pneumonia.
Typically only a few pups in a litter would come down with the illness, and the rest never would, even though all pups were housed together and shared food and water. The original theory was that rhinitis was caused by a virus to which only some dogs were susceptible or that it was the result of an inherited defect in the immune system. However, repeated attempts failed to isolate a virus, and recent sophisticated studies by Drs. Casals and Reichler have shown that the immune system of affected Wolfhounds is normal.
Drs. Casals and Reichler have discovered that the underlying cause of Wolfhound rhinitis syndrome is an inherited defect in the microscopic hairs called cilia that line the airways from the nose to the lungs. The cilia are covered by a layer of mucus that traps inhaled dust, pollen, bacteria, and fungi. In a normal dog, the cilia beat in unison like oars on a galley, moving the mucus up from the lungs. Together the cilia and mucus function like an escalator, moving trapped particles up the windpipe to the throat, where they are swallowed or coughed out. In the upper respiratory tract, the cilia and mucus layer do the same thing, trapping particles and moving them out of the sinuses and into the nasal passages where they can be blown out the nose or swallowed.
In Wolfhound rhinitis syndrome, the cilia are not lined up in orderly rows and do not beat in unison. As a result, the mucus layer and the particles trapped in it do not move at a normal speed, and often do not move at all. As you can imagine, this predisposes an affected dog to respiratory infections—not just rhinitis but also sinusitis and pneumonia.
The cilia of Irish Wolfhounds with rhinitis syndrome are indistinguishable from the cilia in a disease called Primary Ciliary Dyskinesia (PCD), which has been reported in many other dog breeds, in many other animal species, and in humans. In all species studied to date, PCD is congenital—meaning present from birth—and inherited. In Wolfhounds, careful pedigree analysis has shown that PCD/rhinitis syndrome is inherited as an autosomal recessive trait, meaning it takes two copies of the defective gene to produce the disease. Thus, an affected dog inherits the defective gene from both parents.
At present, no genetic test exists for PCD/rhinitis syndrome in Wolfhounds, but the Irish Wolfhound Foundation and Drs. Casals and Reichler are actively working to identify the responsible gene. If they succeed, a genetic test would soon follow.
I am not aware of a rhinitis syndrome in Scottish Deerhounds, although that doesn’t mean there isn’t such a syndrome. However, while the Wolfhound story begins with PCD/rhinitis syndrome, it doesn’t end there. And the rest of the Wolfhound story sounds a lot more like the situation that exists in Deerhounds.
A Second Syndrome: Chronic Pneumonia
As already noted, Irish Wolfhounds with PCD/rhinitis syndrome often develop pneumonia. But that doesn’t explain all cases of recurrent or chronic pneumonia in Wolfhounds. Instead, there is a second, fairly common syndrome in Wolfhounds, currently termed “chronic pneumonia syndrome.”
Wolfhounds with chronic pneumonia syndrome may be as young as 6 months old when they first become sick, but they never show any signs of rhinitis before their first episode of pneumonia. Most affected dogs will have repeated episodes of pneumonia, but these are often misdiagnosed by those unfamiliar with the disease. Why? Because affected dogs may not show the signs and symptoms typical of pneumonia.
When a Wolfhound with chronic pneumonia syndrome experiences a flare-up, the only sign may be restlessness, reluctance to lie down (especially on the side), or loss of appetite. Contrary to what one would expect, dogs with chronic pneumonia syndrome rarely cough in the early stages of a flare-up, even though they may be running a fever. A Wolfhound experiencing a flare-up also may not have any dramatic changes in the lungs visible on X-rays. And finally, the breathing of a Wolfhound in the early hours of a flare-up often looks normal, although some dogs will exhibit rapid, noisy, or labored breathing.
No one knows why Wolfhounds with chronic pneumonia syndrome often lack the usual signs and symptoms of pneumonia in the early stages of a flare-up, but it is clear that a Wolfhound having a flare-up can become very sick very fast—in a matter of hours. Survival depends upon prompt treatment with antibiotics, often before taking time to make a diagnosis. Wolfhound owners familiar with chronic pneumonia syndrome, either through education or experience, become hyper-vigilant for any change in behavior that might signal an episode of illness and immediately start treatment. Waiting for a diagnosis can mean a fatal outcome. Deerhounders with whom I have spoken whose dogs have recurrent pneumonia report the same rapid onset and vague symptoms when a flare-up occurs. Like Wolfhound owners, they have learned to be vigilant and start antibiotic treatment at the least sign of a flare-up.
One theory about the cause of Wolfhound chronic pneumonia syndrome is that affected dogs are “carriers” of a single copy of the gene that, in double dose, causes PCD/rhinitis syndrome. Such carriers may have cilia that function less than perfectly, making them more susceptible to lung infections. But until the gene for PCD/rhinitis syndrome is identified, this theory cannot be tested.
Given the close relationship between Irish Wolfhounds and Scottish Deerhounds and the clinical similarities between recurrent/chronic pneumonia in the two breeds, the unfolding Wolfhound pneumonia story may have important implications and benefits to offer to our own breed. I will follow the story closely and share any breakthroughs that might apply also to pneumonia in Deerhounds.