Treating feline airway diseases can be tricky, and many specialists agree that the diagnosis may be just as difficult. But one thing they don’t all agree on is which diseases are the most prevalent.
“I would say the most common lower respiratory disease that cats get is asthma/bronchitis,” said Lynelle Johnson, DVM, MS, Ph.D., Dipl. ACVIM. “This is an inflammatory disease of the airways that generally responds quite well to steroids.”
However, any feline respiratory disease can have asthma-like symptoms, added Dr. Johnson, a professor of medicine and epidemiology at the University of California, Davis, School of Veterinary Medicine.
“Cats with infection caused by bacteria or parasites, aspiration pneumonia and sometimes even cancer can present with cough with or without wheezing or episodes of respiratory distress,” Johnson said.
She noted that because a practitioner may assume a cat has asthma or bronchitis, the patient is often treated with steroids before specific diagnostic tests are performed. And, in most cases, the majority of patients are likely to respond.
“However, in my experience, cats with inflammatory airway disease often require lifelong medication, and if the diagnosis is not correct, they can develop substantial complications and become nonresponsive,” Johnson said.
Other experts said feline asthma is a common airway disease they treat.
“I believe asthma is the most prevalent feline airway disease,” said Arnold Plotnick, MS, DVM, Dipl. ACVIM, of Manhattan Cat Specialists in New York City. “Infectious causes of bronchitis are less common. Heart-worm-associated respiratory disease, while greatly underdiagnosed, is even less common.”
Asthma is one of the most common feline airway diseases encountered by J.D. Foster, VMD, Dipl. ACVIM, a staff veterinarian at the University of Pennsylvania School of Veterinary Medicine.
“Bacterial pneumonia is rather uncommon in cats,” Dr. Foster said. “However, cats with asthma may develop secondary bacterial infections, particularly due to Mycoplasma, and potentially require a short treatment of antibiotics.”
Not So Common
Phil Padrid, DVM, interim medical director of specialty services at VCA Vet Care Animal Hospital and Referral Center in Albuquerque, N.M., believes the two feline airway diseases many believe are among the most common—asthma and bronchitis—are not so prevalent.
“Asthma and chronic bronchitis in cats occur in maybe 1 percent of the population—5 percent of Siamese and Siamese-derived breeds,” Dr. Padrid said. “In practice a cat with chronic daily cough and no other obvious cause of the cough may have either bronchitis or asthma.
“The standard tests in humans to distinguish, and the lack of a smoking history, make it more difficult to diagnose one or the other in cats compared to people.”
Andrew Bugbee, DVM, Dipl. ACVIM, a clinical assistant professor of internal medicine at the University of Georgia College of Veterinary Medicine, tried to shed light on the debate.
“Determining the true prevalence of various feline respiratory diseases is difficult due to occurrence in apparently healthy cats with no clinical signs, lack of standardized definitions as to what constitutes the specific disease condition or how best to diagnose it, as well as failure to often determine the definitive diagnosis,” Dr. Bugbee said.
Upper respiratory tract infections with pathogens feline herpes virus type 1 (FHV-1) or feline calicivirus (FCV) are generally encountered more often than inflammatory lower airway diseases like feline asthma, Bugbee said.
He noted that prevalence rates of greater than 50 percent have been reported for upper respiratory tract infections, particularly in multicat households and shelters. However, feline asthma has a reported prevalence rate of 1 to 5 percent, Bug-bee said.
“Contributing to the difficulty in assessing the true prevalence is that all of the above conditions have been reported in healthy cats exhibiting no clinical signs of the found disease,” Bugbee said.
When asthma is the diagnosis, treatment can be difficult. However in Foster’s experience, most cats will improve at least somewhat through therapy.
Asthma involves two adverse processes in the lungs: airway inflammation and bronchospasm, Foster said.
“The airway inflammation is treated with steroids and the bronchospasm is treated with bronchodilators,” he said. “Oral medications are quite reliable and are often the type of medications initially prescribed.
“However, there are numerous medications, including steroids and bronchodilators, that can be delivered via an inhaler. These may be more effective by delivering a high dose of the medication directly into the lungs and can spare systemic delivery.”
He added: “Asthmatic cats may have a respiratory crisis, where they become acutely dyspneic. This is typically attributed to bronchospasm and can be treated with oral or inhaled bronchodilators.”
Even when well-controlled, many asthmatic cats go through periods where the disease is more severe, Foster said.
“Evaluating for secondary airway infection with an endotracheal wash—submitted for cytology, culture and mycoplasma PCR—can help identify such complications and help guide therapy,” he said. “Inhaled medications are typically very well tolerated by cats, and there are many online resources owners can use to become familiar with the process even before they purchase inhaled medications.”
Oral or inhaled steroids usually will control signs of respiratory problems unless a cat has developed complications such as airway remodeling, mucus impaction or airway dilation, UC Davis’ Johnson said.
She offered an important reminder for practitioners: If a cat isn’t responding to steroid therapy, go back to the basics to confirm the diagnosis and search for complications that might have developed.
“Ensure that owners are administering medications properly and that the environment is free of agents that can further irritate the airways, such as dust, perfume, cigarette smoke and dirty furnace heaters,” she said.
VCA’s Padrid said asthma and bronchitis require the same treatments as in human medicine.
“Some combination of bronchodilators and anti-inflammatory steroids [are necessary],” he said. “Other approaches, like anticholinergics or antileukotrienes, are much less effective in feline species. Inhaled steroids are standards of care now in cats as well as people.
“Left untreated, chronic bronchial disease has a worse prognosis compared to dogs, for example, mostly because of a different airway and lung anatomy in cats compared to dogs.”
Most cats respond to oral medications, namely prednisolone, while some cats require adjunct therapy with a bronchodilator, said Plotnick, with Manhattan Cat Specialists.
“Cats that experience systemic side effects from oral prednisolone, such as cardiac side effects or diabetes, can be switched to inhaled steroids, which are effective at controlling the asthma but are not appreciably absorbed into the bloodstream, [thereby] lessening or mitigating their adverse effects,” Plotnick said.
Bugbee, of the University of Georgia, said that while FHV-1 and FCV are not treatable or curable infections, they can be managed for the life of the pet.
“Similar to [in human cases], FHV-1 is known to become inactive, and the cat shows no clinical signs of the infection and sheds no viral particles during this time,” Bug-bee said. “Then, following a stressful event, the virus recrudesces and begins actively replicating, which causes the cat to develop clinical signs of the infection and shed virus, which could infect other cats.
“Calicivirus is continuously shed in respiratory secretions, even during periods where the cat is not exhibiting overt upper respiratory signs.”
Treatment of both conditions, Bugbee said, centers on supportive care and dealing with secondary bacterial infections a cat may develop as a result of the primary viral infection. This may include cleaning the nose and eyes of dried discharge, feeding aromatic or warmed food to maintain appetite, providing humidified air to moisten airways, minimizing stress, and offering intermittent antibiotic therapy if signs of infection develop.
“L-lysine supplementation has been shown to reduce FHV-1 replications, with conflicting reports in its ability to reduce severity of clinical signs or viral shedding,” he said. “Anti-viral medications such as famciclovir have been reported to reduce the severity and length of time clinical signs are present as well as reduce viral shedding during flare-ups.”
Julia Veir, DVM, Ph.D., Dipl. ACVIM, an assistant professor in Colorado State University’s department of clinical sciences, emphasizes searching for underlying causes if the owner can afford the work.
“Looking for things like parasitism, plus empirical de-worming, heartworm infection and other lower airway infections—ideally with a lower airway wash of some kind—can change prognosis and not curse a cat to unneeded lifetime medications,” Dr. Veir said.
Infectious diseases, including lungworm and heartworm infections, are being recognized more commonly as causes of respiratory problems, Penn Vet’s Foster said.
“It is unknown if this is due to an increase in disease prevalence or increased awareness and testing,” he said. “It is always a reasonable consideration to test a cat with lower airway disease for these infections, as they may have new treatment options available if so.”
For dyspneic cats, newer blood tests may aid in a diagnosis when the apparent cause is cardiac or respiratory, Foster said.
“N-terminal pro-B-type natriuretic peptide (NT-proBNP) can distinguish congestive heart failure from primary respiratory disease in cats with respiratory signs with approximately 90 percent diagnostic accuracy,” Foster said. “It has been shown to significantly aid general practitioners in obtaining an accurate diagnosis towards the cause of dyspnea.”
Originally published in the October 2016 issue of Veterinary Practice News. Did you enjoy this article? Then subscribe today!