2 Sept 2025
Deborah Caunter RVN provides information VNs need to know about the types of infections that can impact the feline upper and lower respiratory tracts
Deborah Caunter
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Different conditions can affect the upper and lower respiratory tract of cats, and veterinary nurses are highly involved in managing such cases.
Many upper respiratory tract infections can affect and damage the nose or oropharynx.
Some of the most common causes of chronic upper respiratory tract infections are as follows, as outlined by International Cat Care (2025a):
Cat flu is the most common term that everyone in the industry has heard of, and that is what we will discuss now.
Cat flu is the term used to describe multiple infectious diseases that affect, mainly, the upper respiratory tract. It can cause rhinosinusitis, conjunctivitis and oral ulceration in addition to increased lacrimation, salivation and pyrexia (Jones, 2025a).
It can affect a variety of groups, including cats that live in groups, for example, catteries or rescue centres; unvaccinated cats; kittens; elderly and immunosuppressed cats; and cats under stress (International Cat Care, 2025b).
Cat flu can be separated into viral causation and bacterial causation. Viral causes are feline calicivirus (FCV) and feline viral rhinotracheitis or feline herpes virus (FHV). More than 90% of upper respiratory infections are caused by one or both of these (International Cat Care, 2025b).
These are highly contagious and will generally shed the period when they display clinical signs – normally during times of stress or illness and otherwise can be latent and display no clinical signs (Jones, 2025a). Bacterial infections, such as Mycoplasma felis or Chlamydia felis have been identified as potential causes of cat flu, but more commonly they are seen alongside a viral cause and can complicate treating these patients.
In most cases, regardless of whether it is viral or bacterial, patients will present with pyrexia, sneezing, nasal discharge, conjunctivitis, rhinitis, salivation, anorexia and dehydration. In addition to this, cats can go on to develop ulcerative keratitis, conjunctival oedema or blepharospasm and severely affected patients can develop ulcerative stomatitis (Jones, 2025a).
Stertorous breathing (noisy breathing through the mouth) and changes or swelling to the face (International Cat Care, 2025b) can also indicate an upper respiratory tract disease could be occurring.
Calicivirus presents in different ways because there are various different strains. Some cause ulceration and gingivostomatitis, some cause pulmonary oedema and pneumonia, and some cause joint pain and shifting leg lameness (Jones, 2025a).
Mycoplasma felis affects the eyes and upper respiratory tract – normally presenting as conjunctival oedema and less severe nasal signs (Jones, 2025).
The preferable testing method is to run a polymerase chain reaction (PCR) test using swabs taken from the conjunctiva or oropharynx. Running feline leukaemia virus (FeLV) and feline immunodeficiency virus (FIV) tests will prove useful, as these diseases are associated with immunosuppression.
Topical and systemic antiviral agents, in addition to antibiotics, will be the initial port of call. Analgesia is worth a trial in these patients as they are going to be sore if they have ulcers and antiemetics can be given if nausea is seen.
Dependent on the patient’s hydration status, IV fluid therapy can also be considered.
But what about the nursing side? Well, supportive care is then the key recipe for success with these patients and, therefore, nurse-heavy. Nutrition, fluid balance, sense care, cleaning, monitoring and infection control are the main areas to focus on. As aforementioned, these patients are highly infectious, and so housing these patients in an isolation ward and implementing strict barrier nursing is imperative.
Nutrition wise, some of these patients will be kittens who already have additional needs and almost all the patients will be inappetent. Warming food up to make it super-smelly will help, but if they are not eating enough then a feeding tube should be considered.
Anorexia, hypersalivation and secretions from the nose all add to fluid losses and can lead to dehydration. We need to monitor our patients for this and introduce IV fluid therapy where required to support them.
Remember: a patient’s fluid requirement will not remain the same throughout the period it is with you. Ensure this is regularly assessed and amended where necessary.
Nebulising these patients is a real godsend and something owners can do at home, too. Acquiring a nebuliser (my practice purchased a human one from Boots) and using warm tap water or saline in addition to cleaning their ocular and nasal discharge will make an enormous difference in making them feel better and, eventually, wanting to eat. The application of eye lubrication on a regular basis is recommended as these patients are at high risk of corneal ulceration (Jones, 2025a).
Chlamydophila felis is a Gram-negative bacterium that targets the conjunctiva in our feline patients, with most occurring in kittens and pedigree cats (Griffith, 2009). It is thought to be the cause of 30% of chronic conjunctivitis cases in cats (Cats Protection, 2025).
Clinical signs of this disease include: unilateral ocular disease progressing to bilateral, chemosis of the conjunctiva, ocular discharge, transient fever, inappetence and weight loss (Griffith, 2009).
In addition to this, their eyes may be red and held fully or partly closed (Cats Protection, 2025). Respiratory signs in these cats are normally quite uncommon, but nasal discharge and stertor can be present (European Advisory Board on Cat Diseases, 2009).
It is normally diagnosed via PCR ocular swabs and treated with antibiotics such as doxycycline or clavulanic acid and amoxicillin (European Advisory Board on Cat Diseases, 2009), supportive care and vaccination (Griffith, 2009).
In cats, two main disorders are associated with the lower respiratory tract and are known as feline lower airway disease (FLAD) – feline asthma and feline chronic bronchitis.
Most cats presenting with feline asthma present with dyspnoea and a chronic cough, with signs of airway changes. Younger to middle-aged cats, around the ages of six to nine years (International Cat Care, 2025c) are more likely to present with this condition and Siamese and oriental shorthairs are more commonly affected, with a breed prevalence of up to 5% (Sharp, 2013). In latest available data, female cats are overrepresented (Sharp, 2013).
Feline asthma can often be triggered by allergens within the household environment, such as dusty cat litter, air fresheners and cleaning chemicals, perfumes, cigarette smoke, pollen and dust mites, and so exposure to these should be minimised where possible (Jones, 2025b).
Of the two, feline chronic bronchitis is less-well understood. Patients present in a similar way, with a chronic cough and airway remodelling and narrowing, but unlike feline asthma, acute episodes are uncommon. Instead, increased mucous production because of the inflammation and airway changes will decrease the diameter of the airway and so will significantly affect the air flow (Jones, 2025b).
Most clients will initially report that their cat is trying to bring up a hairball. Those patients in acute respiratory distress will also present with signs such as tachypnoea and dyspnoea, open mouth breathing and wheezing. In addition to this, our patients may have a persistent cough, or owners may report that their cat looks like they are trying to be sick or bring up a hairball (International Cat Care, 2025c).
You may find clients report that they seem more lethargic, too, or that they are eating less because of their cough or breathing interfering with their eating ability (Jones, 2025b). If a client is reporting their cat is open-mouth breathing then it could be a sign of an asthma attack (International Cat Care, 2025c).
When conducting a vital signs check, either when the patient is admitted as an inpatient or if you are triaging it, the heart rate and temperature can aid in differentiating if you are dealing with a patient suffering from FLAD or a patient with heart failure.
Cats that are normothermic and have a normal heart rate are more likely to have FLAD; those that are tachycardic and hypothermic are more likely to have heart failure, with the parameters indicating cardiogenic shock (Sharp, 2013).
Regardless of if these patients are presenting as an emergency or stable, they require careful management as they can easily go into a respiratory episode because of stress.
Step 1. Stabilise, stabilise, stabilise
These patients are trying to balance an increased demand for oxygen, but with a reduced ability to get oxygen. Focus on a minimal stress approach; hands off.
If your cat doesn’t have an IV catheter placed already and isn’t tolerant of placing one, then don’t force it. Instead, consider giving IM butorphanol under the vet’s discretion and oxygen therapy.
Remaining calm and quiet while monitoring this patient is vital. You as a nurse play a key advocacy role in ensuring these patients have time to stabilise and you do not rush them into having x-rays or other invasive procedures that could decompensate them quicker.
Step 2. Diagnostics
Once your patient is stabilised (and not before), nurses can assist with the diagnostic element. Chest radiographs are probably the initial first step. Inflated chest views, where possible, will give the best possible diagnostic image and allows you to have full airway access; conscious chest x-rays require restraint, and this could destabilise your patient.
If your veterinary practice has it, then a CT scan would also be beneficial as it could highlight problems that an x-ray cannot, such as lung consolidation or bronchial thickening (Jones, 2025b). Bronchoalveolar Lavage can then be performed.
This diagnostic test can show which cells are present in the airway, if any, and rule out other bacterial or infectious diseases. This can be performed blind or, if your practice has access to them, via an endoscope.
Cats have narrow and sensitive airways, so minimising anaesthetic time and monitoring their oxygen saturation (Sp02) is vital in reducing the risk as much as possible and, as ever, if there are any signs of desaturation then tell your vet to stop.
It may also be prudent to ask about the worming status of your patient. Lungworm can cause coughing and if your feline patient is not up to date with its preventive treatment then they could be at risk. Running a Baermann faecal sample test will help eliminate this possibility (International Cat Care, 2025c). Testing for heartworm and FeLV/FIV is recommended, as heartworm can cause respiratory signs. If the patient has FeLV/FIV, it could affect the prognosis (Sharp, 2013).
Step 3. Treating our patients
Normally, these patients require steroids as an initial injection before transitioning to oral versions, and, in the case of asthmatic patients, inhaled versions with or without bronchodilators (Jones, 2025b).
Supportive treatment should always be provided where necessary, such as oxygen and anxiolytics.
Glucocorticoids could be administered to reduce inflammation in the airways while symptomatic control can be controlled with bronchodilators (Today’s Veterinary Practice, 2014).
If lungworm is suspected or confirmed, then treatment with fenbendazole is indicated (Today’s Veterinary Practice, 2014).
Step 4. Managing our patients as outpatients
The key thing to remember and to remind our cat owners is that these diseases are long-term conditions and require careful ongoing management for the rest of their cats’ lives. As nurses, we can support clients through this and guide them on how to prevent further episodes. Obesity will increase their oxygen demand, inevitably increasing pressure on the respiratory system. Preventing obesity or managing obesity with weight loss clinics is essential. Educating clients in eliminating or minimising the use of potential triggers, such as cleaning products or perfumes, can help reduce those acute onset episodes that can be so distressing to witness.
Finally, for our feline patients requiring long-term steroid treatment, targeted administration via the use of an inhaler will be required and, as nurses, we can introduce the clients to this process and guide them through it.
Client compliance is of the utmost importance, and as nurses we can try to make this process as painless and as stress-free as possible by getting the cat desensitised to the face mask and then slowly building (Jones, 2025b). International Cat Care (2025a,b,c) and Aerokat (Trudell Animal Health, 2023) have fabulous resources to give to owners or to use for your own personal training as well.
Follow-up consultations with the nurse and follow up phone calls to check in with owners, encourages compliance and prompts owners to discuss any issues or concerns they have (Taylor, 2017).
As nurses and technicians, we are highly involved in stabilising and managing these cases, both in the hospital and long term.
Veterinary nurses are vital throughout the process with these patients, from triage and initial presentation to investigating and, most crucially, during the treatment process, when they spend time with the owners. Explaining and demonstrating techniques and medications will increase the chances of client compliance in the long term.
These patients can be intensive and isolating at times, but they can be really rewarding cases.
Deborah Caunter qualified from Hartpury College in 2017 with a BSc in Veterinary Nursing Science and works as team leader at Vets Klinic. She has completed an ISFM Certificate in Feline Nursing and is currently in her second year of her MSc in Veterinary Nursing at the University of Glasgow. She has two cats at home: Tipsy, a 10-year-old hand-reared cat, and six-year-old Frank. In her spare time, you can find Deborah snuggled with a book or teaching and participating in pole fitness and aerial arts.
