This is an article written by Dr. Danièlle Gunn-Moore, which you may wish to print off and share with your vet.

Since writing these notes, Dr. Gunn-Moore is now testing the Aerokat feline spacer in practice.

Dyspnoea in Cats
Dr. Danièlle Gunn-Moore BSc BVM&s PhD MACVSc MRCVS
Nestlé Purina Lecturer in Feline Medicine
University of Edinburgh

Localisation of the cause dyspnoea
Upper respiratory tract (URT) disease
Acute URT disease
Chronic URT disease
Diagnosis of URT disease
Treatment of URT disease
Lower respiratory tract (LRT) disease and thoracic cavity disease
Causes of LRT disease
Causes of thoracic cavity disease
Diagnosis of LRT disease and thoracic cavity disease
Treatment of LRT disease and thoracic cavity disease

Dyspnoea is a clinical sign that is seen relatively commonly in cats. It describes difficulty in breathing. This can result from a decreased ventilatory capacity, or an increased ventilatory demand. Dyspnoea can therefore result from respiratory or non-respiratory causes.

LOCALISATION OF THE CAUSE OF DYSPNOEA

The first step in diagnosing the cause of dyspnoea is to determine if it is due to non-respiratory causes, URT disease, LRT disease or disease affecting the pleural space. This differentiation should be possible by taking a detailed history and performing a thorough physical examination (Table 1). Inspiratory dyspnoea is usually associated with URT disease resulting in airway obstruction, or pleural disease preventing full lung expansion. URT disease may be accompanied by sneezing, nasal discharge, wheezing, snoring, snorting, facial deformity, obstructed nares, or dysphagia. Laryngeal disease may cause a change in the animal’s voice. Expiratory dyspnoea is usually a sign of LRT disease. Tachypnoea (rapid breathing) or orthopnoea (dyspnoea when recumbent) do not help in localising the cause of the dyspnoea.

UPPER RESPIRATORY TRACT DISEASE

Acute URT disease - Cat ‘flu’

Cat ‘flu’ is the common name used to describe infectious acute URT disease. It is frequently seen in unvaccinated cats and kittens, particularly when they are kept in large groups, either in private homes, or rescue centres. While the disease can be caused by a number of different organisms, over 80% of cases are caused by infection with either feline calicivirus (FCV), or feline rhinotracheitis virus (FRV, also called feline herpes virus). Other organisms may also be involved, including feline coronavirus (FCoV), mixed bacteria; Bordetella bronchiseptica, Pasturella multocida and Mycoplasma species, and Chlamydophila felis (formerly Chlamydia psittaci). Many cases of cat ‘flu’ involve infection with a number of different organisms. Environmental factors, such as poor ventilation, high humidity, and over-crowding may exacerbate the problem.

Factors involved in cat ‘flu’:

· Feline rhinotracheitis virus (FRV)
· Feline calicivirus (FCV)
· Feline coronavirus (FCoV)
· Bordetella bronchiseptica
· Pasturella multocida
· Mycoplasma species
· Chlamydophila felis
· Poor ventilation, high humidity, dusty environment, over-crowding.

Clinical signs of cat ‘flu’:

· Sneezing
· Conjunctivitis
· Ocular and nasal discharge – initially serous progressing to mucopurulent
· Ulceration of the tongue and mouth
· Excessive salivation
· Inappetence
· Depression
· Fever
· Coughing
· Limping syndrome (FCV)

Diagnosis of cat ‘flu’:

· A presumptive diagnosis is usually made on the presence of typical clinical signs and a history of possible exposure to causal organisms. While different organisms tend to produce characteristic changes in the laboratory situation, in mixed natural infections it is not usually possible to determine which organisms are involved from clinical signs alone. That said, FRV tends to cause more severe disease than FCV, with more prominent conjunctivitis, perfuse nasal discharge, and obvious coughing. FCV tends to be associated with milder clinical signs, and oral ulceration. Chlamydophila felis is usually associated with conjunctivitis, which may initially be unilateral. Bordetella bronchiseptica may cause coughing, and is generally seen when kittens are kept in over-crowded conditions.

· Nasal or oropharyngeal swabs can be taken for isolation and culture. Care should be taken when interpreting the results since FRV is shed only intermittently, and FCV shedding may result from infection with either pathogenic or non-pathogenic field strains of virus, or vaccine virus. Bacteriology is generally of little value unless the diagnostic laboratory is instructed to look for specific agents e.g. B. bronchiseptica, Mycoplasma spp., or C. felis. It is advisable to speak to the laboratory prior to collecting the samples since specific transport media may be required.

· Serology can be used to determine whether or not a cat has been previously exposed to FCV or FRV. However, it is of limited value since most cats have usually been vaccinated.

Treatment of cat ‘flu’:

Treatment usually involves symptomatic therapies and good nursing care.
· Antivirals – although cat ‘flu’ is usually caused by FCV or FRV, specific antiviral therapy is rarely used. Where FRV infection is present, the use of oral L-lysine may be beneficial @ 200 mg/day, PO with food.
· Antibiotics – ideally, where specific organisms are detected, antibiotics should be selected by culture and sensitivity. If not, a safe broad-spectrum antibiotic, that is active against bacteria commonly found in the feline oropharynx, should be given for 2-3 weeks.
e.g. Amoxycillin-clavulanic acid or a cephalosporin
Doxycycline is a good choice where B. bronchiseptica, Mycoplasma spp., or C. felis have been detected.
· Nutritional and fluid support – this usually entails giving intravenous fluids and placing a feeding tube. Care should be taken when placing naso-oesophageal tubes as the cat’s nasal turbinates are already inflamed. Affected cat’s should be encouraged to eat by use of warmed tempting food. Use of appetite stimulants is controversial; the author’s preference is cyproheptadine (Periactin) @ 0.1-0.5mg/kg PO q8-12 hours. Diazepam is used less frequently because of its association with fatal idiosyncratic hepatic necrosis.
· Supportive nursing care – it is important to keep the cat’s eyes and nose clean, and it’s coat groomed.
· Multivitamins – anorexia can result in a lack of certain vitamins, especially B vitamins. This can in turn exacerbate anorexia. Supplementation can be beneficial.
· Mucolytics – mucolytics may help to ease respiratory tract congestion; e.g. bromhexine (Bisolvon) @ 3mg/cat IM q24 hours, or 1mg/kg PO q24 hours.
· Nebulised air – the use of steam or nebulised air can help to clear the airways. Where necessary, bronchodilators can be added to the air current.
· Decongestants – intranasal oxymetazoline (Afrazine) may give temporary relieve to nasal congestion @ 1 drop/nostril q12 hours for 48 hours maximum.
· Non-specific immune stimulation – while many non-specific immune stimulants are currently available, few have proven efficacy and safety. The ones that the author recommends are interferon a and w which can be obtained as recombinant human interferon alpha (hrIFNa) or recombinant feline interferon w (frIFN w - Virbagen Omega from Virbac). hrIFNa can be obtained as 3M IU, which can then be diluted in one litre of saline, aliquoted into 1ml volumes, and frozen for up to a year. It can then be defrosted as required, diluted to the appropriate concentration, and kept refrigerated for up to a week. It is usually given @ 1-30 IU, PO, q24h. Given parenterally at high doses it will cause toxicity and induce antibody production.

Prevention of cat ‘flu’:

To reduce respiratory disease within a group of cats it is necessary to address infectious and non-infectious causes. This may require instigating a suitable vaccination and/or isolation programme, treating with suitable antibacterials, improving ventilation, and reducing over-crowding.

· Introduce a suitable vaccination program
· Decrease stocking density
· Increase air flow
· Ensure good sneeze barriers are present between separate groups of cats
· Improve overall hygiene, and use suitable disinfectant
· Have individual cats give birth and then wean their kittens in isolation
· Have a suitable quarantine facility and quarantine all incoming cats for three weeks
· Stop breeding – kittens are the most susceptible to infection

Causes of chronic URT disease

· Chronic post-viral rhinitis / idiopathic chronic rhinitis:
The majority of cases of chronic URT disease are defined as chronic post-viral rhinitis/sinusitis. The initial viral infection causes damage to the nasal mucosa, which allows secondary infection with oro-pharyngeal bacteria, and hence the establishment of chronic osteomyelitis of the turbinate bones. However, since it is usually not possible to detect FRV or FCV at this late stage of disease, the condition should more correctly be termed chronic idiopathic rhinitis.

· Chronic bacterial rhinitis:
While this is usually associated with chronic post-viral rhinitis, occasional cases have been seen associated with more unusual bacteria, such as Mycobacteria species.

· Fungal rhinitis:
Cryptococcus neoformans infection is seen world wide, it is rare in the UK and Ireland but is seen commonly in Australia. Saprophytic fungi (e.g. Pseudoallescheria boydii) have caused occasional cases of fungal rhinitis. These are typically associated with plant material that has become lodged in the nasopharynx.

· Allergic rhinitis:
Allergic rhinitis has occasionally been diagnosed in cats. Typical allergens include cat-litter dust, certain aerosol sprays, and cigarette smoke. In some cases, allergic rhinitis may occur concurrently with ‘feline asthma’.

· Nasopharyngeal polyps:
These inflammatory polyps are usually associated with chronic inflammation of the middle ear, from where they are believed to originate. While they are usually seen in young cats, they can be seen in cats of all ages. Nasopharyngeal polyps usually cause obstructive URT disease. When they extend into the caudal nasopharynx they may also cause dysphagia or gagging. When they extend from the middle ear into the outer ear they may cause ear pain, otitis externa and otorrhoea.

· Nasonasal polyps:
Nasonasal polyps originate within the nasal chambers. They arise secondary to chronic inflammation. Since their mucosa is very friable they may be associated with epistaxis.

· Nasopharyngeal stenosis:
This is seen when an inflammatory membrane develops across the caudal nasopharynx. It usually arises secondary to chronic inflammation.

· Neoplasia:
The most common tumours of the nasal cavity are lymphosarcoma (LSA) and adenocarcinoma. Other tumours that may be seen in this location include undifferentiated carcinoma, squamous cell carcinoma (SCC), fibrosarcoma, and chondrosarcoma. Tumours may arise secondary to chronic inflammation. The author has seen nasal LSA develop in cats that have had very chronic idiopathic (lymphocytic/plasmacytic) rhinitis. One cat, which had chronic idiopathic rhinitis, later developed nasonasal polyps, then undifferentiated carcinoma.

· Foreign body:
Intranasal foreign bodies typically consist of plant material, and usually enter via the nasopharynx. Fungal spores associated with the plant material may occasionally lead to a secondary fungal rhinitis. Removal of the foreign body, and any associated fungal cast, usually results in a good recovery.

· Trauma:
Trauma is usually caused by road traffic accidents or cat fights. Road traffic accidents may cause hard palate separation, the generation of oro-nasal fistulae, or damage to the maxillary bones. Cat fights occasionally result in the loss of teeth within the opponent’s nose, or maxillary bone fractures. This type of damage may in turn lead to infected sequestra.

· Dental disease:
Severe peridontal disease can result in the generation of an oronasal fistula.

· Congenital defects:
Cleft palate, defects of the external nares or nasal septum can all result in chronic URT disease.

Larynx

· Paralysis / Trauma / Oedema / Polyp / Granulomata / Neoplasia:
Laryngeal disease is seen far less frequently than rhinitis. Paralysis is seen most commonly secondary to neck trauma. While tumours of the larynx are uncommon, they are usually of similar types to those seen in the nose or pharynx, with SCC and LSA being seen most often.

Trachea
· Infection: Viral - FRV / FCV
Bacterial - Bordetella bronchiseptica
- Secondary opportunistics from the oropharynx
Parasitic - Aelurostrongylus abstrusus
Infectious tracheitis is typically associated with more generalised respiratory tract infection, either acute cat ‘flu’ (discussed previously), or bronchopneumonia (see later).

· Foreign body / Trauma:
Tracheal foreign bodies are occasionally seen in cats. Tracheal trauma may be associated with being attacked by a dog, or result from traumatic endotracheal intubation. Healing may occasionally result in tracheal stenosis.

· Congenital Stenosis / Tracheal Collapse / Neoplasia:
These are seen only rarely in cats.

DIAGNOSIS OF URT DISEASE

Diagnosis of URT disease, as with all diagnostic investigations, relies on a combination of knowing the signalment of the patient (i.e. its age, sex and breed), gaining a complete medical history, performing a thorough physical examination, then undertaking selected further investigations.

The signalment can be of help since congenital detects will usually cause clinical signs within a few days of birth. However, cat ‘flu’ is seen most frequently in older kittens, and neoplasia is seen most typically in old cats. While the breed rarely has a bearing on URT disease, the author has seen nasonasal polyps most frequently in Oriental breeds of cat.

From the history it is important to determine;
· what type of environment the cat lives in
· what other animals it lives with
· where it has previously lived
· whether or not it has been vaccinated, and if so, with what
· whether there is any history of previous illness, facial trauma, dental disease or ear infections
· at what age signs of URT developed
· what was the pattern of onset of clinical signs
· were other animals from the same household affected
· did the cat ever have cat ‘flu’ (remember - chronic post-viral rhinitis is the most common cause of chronic URT disease)
· how has the disease progressed
· have the clinical signs ever responded to previous treatments

Physical examination;
The main signs of URT disease are sneezing, nasal discharge and difficulty in breathing. The exact nature of the discharge, whether both sides of the nose are affected, and the presence of other clinical signs are dependent on the nature of the underlying disease, and on the presence of any other illness the cat may have.

Particular points to look out for include:
· The presence of nasal discharge, and whether it is bilateral or unilateral. Some diseases tend to show unilateral signs (e.g. foreign bodies, or neoplasia), while others more often cause bilateral signs (e.g. chronic post-viral rhinitis). While the nature of discharge can be helpful (e.g. haemorrhage is seen commonly with neoplasia, fungal infections and nasonasal polyps), it can be misleading (haemorrhage can occasionally be seen with foreign bodies, or severe chronic post-viral rhinitis).

· The character of breathing, and whether or not the breathing is noisy when the cat breathes through its mouth, may help to localise disease to the nasal area or the larynx. Generally, the breathing is more stertorous (snoring) when disease is in the nose, but more stridorous (high pitched and harsh) when disease affects the larynx.

· Facial examination may reveal a lack of symmetry or facially swelling (most typically associated with neoplasia or fungal infections). Facial pain and resentment of facial examination is common among cats with URT obstruction, especially those with intranasal foreign bodies, or polyps. In Siamese cats the facial hair overlying the inflamed nasal chambers may become de-pigmented.

· Ocular examination should involve assessment of the periocular area, the anterior and posterior chambers, and the retina. Examination may reveal a serous ocular discharge resulting from tear duct damage associated with previous URT viral disease, or occasionally associated with cancer within the nose. Previous FCV, FRV or C. felis infections can result in chronic conjunctivitis, which in the case of FRV infection may also result in keratitis. Retinal lesions may be seen associated with intranasal neoplasia or fungal rhinitis.

· Aural examination may reveal evidence of painful or infected ears associated with inflammatory polyps.

· General body condition and body weight. Cats with URT obstruction often have a poor appetite and so experience a degree of weight loss. Marked weight loss is more suggestive of neoplasia, fungal disease or severe systemic disease.

· Cats with chronic URT disease frequently have mild to moderate submandibular lymphadenopathy. If submandibular lymphadenopathy is marked, or if lymph nodes elsewhere in the body are also affected, neoplasia or fungal infections are most likely to be the cause.

· Kidneys should be assessed for size and shape since nasal LSA may be associated with renal LSA.

Since different diseases can present very similarly it is important not to over-interpret the presence of a particular clinical sign. A few general rules usually hold true, e.g. facial deformity with associated pain, especially if accompanied by a unilateral nasal haemorrhage or marked lymphadenopathy, is usually suggestive of nasal neoplasia or fungal infection. However, a lack of these findings does not rule out these diagnoses; some cases of nasal LSA cause bilateral nasal obstruction and little nasal discharge of any kind. Also, although post-viral rhinitis usually presents with chronic bilateral purulent discharge, it can also present with unilateral discharge, sometimes blood tinged and occasionally with frank haemorrhage.

FURTHER INVESTIGATIONS

Assessment of serum biochemistry, haematology, and FeLV/FIV status will help to gain an overall picture of the cat’s health.

Attempts to make a diagnosis from nasal swabs taken from a conscious cat are rarely successful (unless C. neoformans is detected). If C. neoformans is detected its presence should be confirmed by culture and/or serology. Bacteria detected in this manner usually represent only secondary contaminants.

The detection of FRV or FCV by oro-pharyngeal swab and viral culture is rarely helpful. Vaccinated cats and cats that have been previously infected with FCV may also be shedding virus. Since FRV is shed only intermittently, failure of its detection does not negate against it playing a causal role in disease.

It is usually only by performing a detailed examination of the URT (for which the cat has to be anaesthetised), taking radiographs, and collecting samples for microbiological and histopathological examination, that a definitive diagnosis may be made. These procedures are performed under general anaesthesia; anaesthesia is induced, the mouth and larynx are examined as the cat is intubated, radiographs are taken, and then the nasopharynx and nasal chambers are examined. The investigations can be performed under the same anaesthetic. Radiographs should be taken before the introduction of flushing solutions, an endoscope, or biopsy instruments since these procedures may result in haemorrhage that will alter the radiographic appearance.

Radiographic investigations:

To prevent head movement radiographic investigations should be performed with the cat under general anaesthetic. When taking the radiographs it is advisable to remove the endotracheal tube to prevent it obscuring essential details.

The investigation should include:
• Whole skull radiographs (lateral and VD views) – to assess the overall structure of the skull, the frontal sinuses, the size and content of the pharynx, etc.
• Intraoral view – to assess the nasal chambers and the maxillary dental arcade.
• Open mouth view – to assess the tympanic bullae.
• Lateral oblique views – to look for the presence of dental disease and to highlight the tympanic bulla.

Lateral oblique view Open mouth view Intraoral views

Radiographs should be assessed for the presence of dental disease, evidence of middle ear infection, obstruction of the nasopharynx by soft tissue, soft tissue density within the frontal sinuses, loss of integrity of the nasal septum, and loss of turbinate detail. Whether the loss of turbinate detail is unilateral or bilateral, and its position within the nasal chambers may help to localise the disease. The loss of turbinate detail may be due to an overall loss of turbinate bone, or an overlying increase in soft tissue. While the nature of the change should be assessed, it is rarely specific. An overall loss of turbinate bone may be seen with chronic destructive post-viral rhinitis, neoplasia, a focal reaction to a foreign body, or fungal rhinitis. An overlying increase in soft tissue may be seen with chronic post-viral rhinitis, neoplasia, nasonasal polyps and allergic rhinitis.

Physical examination
• Teeth, hard palate, soft palate, oro-pharynx and tonsils:
This examination is performed under general anaesthesia, with a cuffed endotracheal tube in place. The teeth, hard and soft palates, oro-pharynx and tonsils are examined visually and digitally for signs of disease.

• The nasopharynx:
The caudal nasopharynx is then examined using a dental mirror and a bright light, or a retroflexed bronchoscope. If the soft palate needs to be drawn forward to improve visualisation this should be done by placing ‘stay sutures’ though its caudal margin, or using atraumatic tissues forceps (not Alice tissue forceps). Any unusual findings should be biopsied.

• The rostral nasal chambers:
Prior to investigating the nasal chambers it is important to pack the caudal oro-pharynx with surgical swabs. This is done because even minor trauma to the nasal mucosa can result in significant haemorrhage. It is important to prevent this blood from entering the trachea. For this reason it is also advisable to use a cuffed endotracheal tube. While the rostral nasal chambers can be assessed using an auroscope fitted with a small cone, this approach generally affords very poor visualisation. Where available, a narrow rigid rhinoscope/arthroscope is more suitable, and in large cats may even permit biopsies to be collected with endoscope guidance. When using either a rhinoscope or taking blind biopsies it important that the instrument is measure against the animal’s face, and marked with a tape tag at the distance from the tip of the nose to the medial canthus of the eye on the same side. This prevents iatrogenic damage to the brain when the instrument is introduced into the nose.

Sample collection:
Samples for cytological and microbiological examination can be collected by a number of methods. Pros and cons exist for each of the methods.

• Direct swabs:
While direct nasal or pharyngeal swabs are non-invasive they rarely yield useful information (see earlier section in “further investigations”).

• Direct aspirates/flushes:
Flushing sterile saline through the nasal chambers may help to clear away mucus and debris, and the resultant flush can be used for analysis. Unfortunately, analysis of this fluid is likely to detect only surface contaminants.

• Traumatic flush:
A traumatic flush entails scarification of the intranasal mucosa at the same time as flushing the nose with saline. While the cellular yield is increased using this technique, the cellular detail is generally poor and the risk of haemorrhage considerable.

· Forced flush:
A forced flush is performed after firmly packing the caudal pharynx, then forcing approximately 10ml of saline up one nostril while holding the other nostril shut. This technique can be used to dislodge foreign bodies, inspissated pus, necrotic debris, and occasionally, tumours or polyps. The solid tissue collects on the pharyngeal swabs. The procedure should be performed carefully, as excessive force may flush material through the cribriform place if it has already been damaged by local pathology.

• Pinch biopsies:
Pinch biopsies are most easily collected using endoscopic biopsy grabs. Only in very large cats can the biopsies be endoscopically guided. Blind biopsies are usually adequate, provided that 2-3 samples are collected from each side of the nose.

• Nasal core biopsy:
Nasal core biopsies can be collected by cutting down a 16 gauge over-the-needle IV catheter, and using it like an ‘apple corer’ to collect a nasal biopsy.

• Surgery:
The most representative and diagnostic biopsies will be gained during surgical exploration of the nose.

Haemorrhage:
While many methods of sample collection have been devised it is important to remember that the larger the biopsy sample, the better the chance of an accurate diagnosis, but the greater the risk of haemorrhage. Since nasal investigations frequently result in bleeding it is strongly recommended that all patient’s have their clotting times checked prior to beginning the procedure. If intra-operative haemorrhage does occur the intranasal instillation of ice-cold saline or adrenaline may help, along with packing of the pharynx and closing the nostrils.

Non-specific findings:
Unfortunately, the collection of suitable samples does not always lead to a definitive diagnosis. Since most cases of chronic URT disease result from chronic post-viral damage, many of the tests will give negative or non-specific results, at best confirming the presence of chronic-active inflammation. A diagnosis of chronic post-viral rhinitis is usually a diagnosis of exclusion.

TREATMENT of CHRONIC URT DISEASE

When undertaking the treatment of a cat with chronic URT disease it is helpful (where possible) to differentiate between the possible underlying causes (see diagnosis). This allows for the correct treatment to be given and a prognosis to be considered. However, since most cases of chronic URT disease result from chronic post-viral damage, it is important to remember that the likelihood for full recovery is poor.

Where a specific disease is diagnosed, specific treatment should be given:
• Nasopharyngeal polyps can be removed by gentle traction, pulling the polyp towards the oro-pharynx. To reduce the risk of recurrence inflammatory material should also be removed from the middle ear. This is usually achieved via an ipsilateral ventral bulla osteotomy.
• Nasonasal polyps can be surgically resected, as can the inflammatory membrane of nasopharyngeal stenosis.

• Foreign bodies can be removed. Local infection can be reduced by curettage.

• Fungal rhinitis should be treated with antifungal drugs (e.g. itraconazole, fluconazole, ketoconazole).

• Laryngeal paralysis can be ameliorated by performing a unilateral ‘laryngeal tie-back’. Any underlying cause should be corrected.

• Post-viral rhinitis/idiopathic rhinitis is rarely curable. The emphasis is on management not cure. Many of the therapeutic options discussed in the section on treatment of cat ‘flu’ also apply here (see earlier section).
Antibiotics – While antibiotics rarely result in a cure, their strategic or long-term use can reduce the severity of clinical signs, and so improve the cat’s quality of life. A good response is sometimes gained using a long course of antibiotics (6-8 weeks), starting immediately following intranasal investigations.
Therapeutic flush – A therapeutic flush entails adding an antibiotic, antiseptic or other therapeutic agent (e.g. 1ml of 300iu/ml hrIFNa) to the intranasal flush. This can have beneficial effects when performed at the end of a nasal investigation.
Nasal curettage – While this procedure results in a degree of improvement in some cases, other cases benefit little. Also, the procedure is not without risk, and can be very painful. This procedure should not be undertaken lightly, and post-operative analgesics are essential.
Frontal sinus ablation, trephination and irrigation – These procedures may be considered where inflammation has extended into the frontal sinuses. Response to these procedures is not always favourable and post-operatively the cat’s can be in considerable pain. Analgesics are essential.

Lower Respiratory Tract Disease in Cats

Danièlle Gunn-Moore
Nestlé Purina Senior Lecturer in Feline Medicine
University of Edinburgh

CAUSES OF LOWER RESPIRATORY TRACT (LRT) DISEASE (Table 1)

• Chronic bronchopulmonary disease:

This describes a commonly occurring, yet poorly understood, group of conditions that affect the airways and alveolar space. It includes ‘feline asthma’, bronchitis, broncho-pneumonia, chronic obstructive pulmonary disease, and emphysema. In many cases, the exact aetiopathogenesis of the different conditions remains unclear.

The main clinical signs are coughing, wheezing and respiratory distress. Coughing arises because of:
• Tracheobronchial inflammation and irritation
• Excessive airway secretion
• Bronchoconstriction

Disease is seen most frequently in young to middle aged cats (2-8 years of age), with female cats and the Siamese and Burmese breeds perhaps being over-represented. Historically, the cats may have previously experience cat ‘flu’, have initially shown a degree of seasonality to their disease, or had their clinical signs exacerbated by airway irritants (smoke, temperature changes, aerosols, dusty cat-litter). Coughing may conclude with a terminal retch to clear mucus from the pharynx.

In cats with episodic signs clinical examination is often unremarkable. During an episode of coughing or in cats with more protracted disease, increased lung sounds can be heard on auscultation (wheezes and crackles), the chest may take on a barrel-shape, and a ‘heave line’ may be evident.

• Pneumonia:
This can be caused by various infectious agents, including viruses (feline calicivirus [FCV], feline rhinotracheitis virus [FRV, also called feline herpes virus], feline coronavirus [FCoV], cow pox), bacteria (Pasturella multocida, Bordetella bronchiseptica, Escherichia coli, Mycoplasma species, Mycobacterium bovis), parasites (Toxoplasma gondii, Aelurostrongylus abstrusus, Capillaria aerophilia), or inhaled or circulating toxins or irritants (lipid or food aspiration, smoke inhalation, uraemia, sepsis).

Bacterial pneumonia is seen most frequently in immunocompromised individuals. Mixed and pure cultures of B. bronchiseptica have been found in pneumonic kittens of 5-10 weeks of age that have come from poor environments. Bacterial bronchopneumonia usually presents with a cough, tachypnoea, dyspnoea, nasal discharge, fever and depression. Auscultation may reveal increased lung sounds, crackles, wheezes, and silent areas.

Parasitic pneumonia: A. abstrusus is probably the most common lungworm of cats, although C. aerophilia infection may also occur. While A. abstrusus may be present in up to 20% of free-roaming cats, it rarely causes disease. Clinical signs are more prevalent in immunosuppressed individuals. The infection is gained by eating infected slugs or snails (the intermediate host), or infected rodents, lizards or birds (the transport hosts). Affected cats may present with a chronic cough, with associated crackles and wheezes. Perhaps the most important consideration of A. abstrusus infection is its differentiation from chronic bronchopulmonary disease, particularly ‘feline asthma’. Since both conditions can result in a eosinophil-rich bronchoalveolar lavage (see later), it is advisable to treat all coughing cats with a therapeutic course of fenbendazole (see later), prior to undertaking further investigations.

• Neoplasia:
Pulmonary neoplasia may be primary or metastatic. Primary neoplasia is rare in the cat. It may include adenoma, bronchoalveolar adenocarcinoma, and bronchial gland carcinoma. Affected cats are usually older (average 10-14 years), with clinical signs consisting of coughing, wheezing and/or dyspnoea, depending on the location and extent of the tumour. Lameness may be seen in ~25% of cats with malignant lung tumours due to secondary metastasis to the digits.

• Pulmonary oedema:
In cats, most cases of pulmonary oedema result from congestive heart failure. Occasional cases of non-cardiogenic pulmonary oedema may result from severe uraemia or pancreatitis, shock, sepsis, near-strangling, near-drowning, electrocution, smoke-inhalation or cranial trauma. The history and other clinical findings are likely to indicate the cause of the disease.

• Pulmonary contusion (trauma):
Blunt trauma to the chest (road traffic accidents, ‘high-rise’ falls) can result in pulmonary contusion, haemorrhage, oedema, atelectasis, and gas-filled cyst formation. Other injuries may include fractures of ribs, sternebrae, mandible or fore-limbs, pneumothorax or pneumomediastinum.

DIAGNOSIS OF LRT DISEASE

The signalment of the patient can be of help: Young cats from unhygienic multi-cat households are most likely to develop B. bronchiseptica associated bronchopneumonia, Siamese and Burmese middle-aged cats are over-represented in cats with chronic bronchopulmonary disease, and primary lung tumours are seen mainly in older cats.

From the history it is important to determine;
• what type of environment the cat lives in
• whether or not it is allowed outside, and whether it hunts
• what other animals it lives with
• whether there is any history of previous illness, or trauma
• what was the age of onset of clinical signs
• what was the pattern of onset of clinical signs
• are other animals from the same household affected
• how has the disease progressed
• have the clinical signs ever responded to previous treatments

A cough that starts seasonally may be suggestive of ‘feline asthma’ or lungworm infection. ‘Asthmatic’ cats may cough more at night when sleeping on their owner’s bed, or at the end of a bout of play, and their clinical signs may be exacerbated by their owner’s smoking. Cats that go outside, hunt, or eat snails are more likely to become infected with Aelurostrongylus abstrusus (lungworm). A history of a road traffic accident may suggest pulmonary contusion.

Physical examination:

Particular points to look out for include:

• The character of breathing: Generally, LRT disease is associated with expiratory dyspnoea. Severely ‘asthmatic’ cats may have a very exaggerated expiratory effort. An increased abdominal effort is seen in many dyspnoeic cats. Tachypnoea (rapid breathing), or orthopnoea (dyspnoea when recumbent), are generally associated marked respiratory compromise.

• The presence and character of a cough: A cough may be seen in LRT disease when the larger airways are affected. A dry harsh cough is found most commonly associated with tracheal or bronchial irritation, while a productive moist cough is usually associated with bronchopneumonia.

• The presence of tracheal sensitivity confirms inflammation of the upper airways.

• Assessment of the mucous membranes can help to assess the level of general peripheral perfusion, determine whether or not the animal is cyanotic (an indication of severe respiratory dysfunction), assess the patient’s level of hydration, and see whether or not the patient is septic (injected dirty-red membranes). The presence of petechial haemorrhages may suggest a clotting disorder.

• Thoracic palpation should be used to check for the presence of trauma (bruises, pain, fractured ribs), or congenital defects (‘flat-chested’ kittens, or kittens with sternal deformities). Thoracic palpation will also help to localise the position of the apex beat of the heart, and detect whether or not a cardiac thrill is present. In severely ‘asthmatic’ cats the exaggerated expiratory effort may lead to a barrel-chested appearance, and enhanced musculature (a ‘heave line’).

• Thoracic compression may be reduced in cases of air-trapping, associated with severe ‘asthmatic’ change. It may also be reduced in cases with pleural fluid accumulation or when an intrathoracic mass is present.

• Thoracic percussion can help to determine the extent of the thoracic cavity. Significant caudal extension of the pulmonary field may result from air-trapping, associated with ‘asthma’. Percussion may also help to detect fluid or soft tissue masses within the chest (a reduction in resonance, especially ventrally), or unusual gas accumulations (an increase in resonance, usually located dorsally).

• Thoracic auscultation can be used to detect the presence of wheezes and crackles, an increase or decrease in respiratory noise, to detect the extent of the respiratory field, and as part of the cardiac examination. Wheezes are generally associated with narrowing of the airways, while crackles indicate fluid within the alveoli. Respiratory noise may be increased in LRT disease, referred for the upper respiratory tract, or amplified due to the presence of air in the pleural space. To determine which is the case it is necessary to auscultate over the trachea to determine how much of the sound is referred. Percussion may help to differentiate LRT disease from a pneumothorax. A decrease in respiratory noise may be associated with fluid or soft tissue within the pleural space.

• Physical examination of cardiac function; this includes an assessment of the capillary refill time, mucous membrane colour, quality of peripheral pulses, position of the apex beat, presence of a cardiac thrill, presence of jugular distension, a jugular pulse, or a hepatojugular reflex, and cardiac auscultation. The presence of a cardiac thrill, jugular distension, a jugular pulse, a positive hepatojugular reflex, or abnormalities detected on cardiac auscultation warrants a more detailed cardiac examination. It is worth noting that while cardiac disease in cats can lead to either LRT disease (pulmonary oedema), or thoracic cavity disease (pleural fluid), unlike the situation in dogs, it very rarely causes coughing.

• Regurgitation may be present when disease within the thoracic cavity impedes the transit of food through the oesophagus (e.g. with thymic LSA). When regurgitation and coughing are seen together mixed disease is usually present, e.g. megaoesophagus resulting from mediastinal disease, with secondary aspiration pneumonia and coughing. Mediastinal disease alone only occasionally cause coughing. This usually results from marked enlargement of the hilar lymph nodes.

• General body condition and body weight. Severely dyspnoeic cats often have a poor appetite and so experience a degree of weight loss. Marked weight loss is more suggestive of neoplasia, or severe systemic disease, such as congestive heart failure.

• General physical examination: Many intrathoracic diseases have systemic involvement. Ocular examination may suggest the presence of uveitis or retinitis in cases of FIP, or signs of hypertension associated with hypertrophic cardiomyopathy (HCM). Detection of goiter may be helpful as hyperthyroid cats may develop HCM. Examination of the abdomen may reveal ascites in cases of FIP, congestive heart failure, or generalised neoplasia. Generalised or regional lymphadenopathy is seen most frequently in cases of neoplasia or mycobacterial infection.

FURTHER INVESTIGATIONS

Prior to undertaking further investigations, or even completing a full physical examination, it may be necessary to stabilize the patient. This can be done most simply by placing the cat in an oxygen enriched environment (oxygen box, tent, or mask).

While assessment of serum biochemistry, haematology, and FeLV/FIV status will help to gain an overall picture of the cat’s health, they rarely lead to a definitive diagnosis. For this, radiography, and the collection of samples for cytological, histopathological, and microbiological examination, are usually required.

Haematology may support a diagnosis of pneumonia (a raised neutrophil count with a left shift, and possibly the presence of toxic changes within the neutrophils). Lymphopenia may be associated with FeLV or FIV infections, or with FIP. Hypereosinophilia may be associated with ‘feline asthma’ or lungworm infection, or be unrelated to the thoracic disease (e.g. concomitant flea infestation). Serum biochemistry may on occasion be of help, and FeLV/FIV status should be assessed as an aid to determining prognosis. Any cat found to have HCM should have its serum total T4 assessed.

In theory, lungworm larvae (A. abstrusus) can be detected by faecal examination. However, it is generally more convenient to perform a therapeutic trial, using fenbendazole @ 50mg/kg/day PO for 3 days.

Where there is suggestion of cardiac dysfunction a more detailed cardiac examination should be performed. This may include ECG, thoracic radiographs, assessment of blood pressure, and echocardiography.

Radiographic investigations:

Ideally, the investigation should include good quality dorsoventral (DV – good for cardiac detail), ventrodorsal (VD – good for pulmonary detail), and lateral views. A general anaesthetic may be helpful as it allows control of respiration, enabling radiographs to be taken at the end of inspiration. It also allows the patient to have an increased oxygen supply.

Radiographs should be assessed for the integrity of the thoracic skeleton, presence of pleural or mediastinal fluid, masses or gas shadows, lung density and position, heart size and position, the presence of masses within the lung-fields, and the integrity of the diaphragm. Abdominal radiographs may be needed to assess the positions of the abdominal organs, the size of the liver, and the presence of ascitic fluid.

Care should be taken when assessing thoracic radiographs since on some occasions they may show no changes, despite the presence of severe disease. This is often true of chronic bronchopulmonary disease, or pulmonary thrombosis. To assess these cases further radiography may need to be repeated at a later date. Where fluid is present radiography should be repeated after thoracocentesis.

Radiography of cats with chronic bronchopulmonary disease usually reveals a prominent bronchial pattern, with or without interstitial changes, and/or patchy alveolar infiltrates. The right middle lobe may occasionally be collapsed, presumably due to occlusion of the bronchi with mucus and debris. The lungs may appear over-inflated due to air-trapping, with flattening of the diaphragm and peripheral emphysema. In very severe cases rib fractures may be evident.

Ultrasound examinations:

Ultrasound examination can be useful at detecting masses located within the thoracic fluid. It can also be used to provide guidance for fine needle aspiration (FNA) or True-Cut needle biopsy of thoracic masses, and in the assessment of cardiac function.

Collection of samples:

Tracheal wash
Bronchio-alveolar lavage (BAL)
Bronchial mucosal biopsy
Transthoracic FNA of a soft tissue mass
Ultrasound guided True-Cut needle biopsy of a soft tissue mass

• Tracheal washes can rarely be performed in conscious cats, and the technique can only sample the upper respiratory tree. The author finds this procedure unrewarding.

• Bronchio-alveolar lavage (BAL). This technique is much more rewarding. The cat is lightly anaesthetised, and placed in lateral recumbency. Where a human pediatric bronchoscope is available an endoscopically guided BAL can be collected. When performing the technique without endoscopic guidance a sterile catheter (canine urinary catheter, or an endoscopic catheter) is measured against the cat’s chest and marked at a level 2/3 of the way down the chest. The catheter is then introduced through the endotracheal tube and advanced gently until it can be advanced no further (approximately to the level at which it was pre-marked). Sterile saline is then flushed down the catheter (~5-10ml/cat). Very little of this first flush can ever be re-aspirated. A second and third flush/aspiration is then made. The cat’s chest can be coupáged (clapped) between each flush. The second flush is generally used for microbiological examination (culture), while the third flush is usually assessed cytologically. The third flush usually has the best harvest of alveolar cells. Fluid that is aspirated back should be slightly cloudy (cellular) and frothy (denotes the presence of surfactant). After performing a BAL the cat should be given oxygen enrichment for a few minutes.
Normal BAL fluid from cats contains: 150-450 nucleated cells/l
60-90% macrophages
2-30% eosinophils

Cats with bacterial bronchopneumonia usually have elevated levels of neutrophils, while chronic bronchopulmonary disease usually results in increased neutrophils, macrophages, hyperplastic epithelial cells, or excessive amounts of mucus. Cats with allergic lung disease (‘feline asthma’) may have raised numbers of eosinophils, mast cells, neutrophils and macrophages.

• Bronchial mucosal biopsy can be performed with or without endoscopic guidance. It is usually achieved using endoscopic biopsy grabs. The procedure should not be undertaken lightly as the generation of a full-thickness perforation may lead to pneumothorax or pyothorax. The collection of bronchial cells using an endoscopic brush is considerably less traumatic.

• Transthoracic FNA of a soft tissue mass can be performed with or without ultrasound guidance. When collecting FNA samples from masses in close association with the heart or major vessels, or collecting samples by True-Cut needle biopsy, ultrasound guidance is recommended. In both cases it is strongly advised that the patient be anaesthetized. The skin overlying the area of interest must be aseptically prepared.

BAL fluid should be assessed by culture and cytology:

• Culture: This requires a sterile container. All of the air should be removed from the container if anaerobic culture is to be performed. Ideally, all fluids should be assessed for both aerobic and anaerobic bacteria, fungi and yeasts. It is often beneficial to contact the laboratory that will be performing the culture prior to sending the samples. In order to detect some infections specific transport medium will be required, and the lab has to be specifically requested to look for others, e.g. B. bronchiseptica, Mycoplasma species.

• Cytology: Heparin or EDTA tubes are used for cytology. They should be processed promptly before cellular detail is lost. Where samples are to be sent away for assessment 4-6 slides should be prepared at the time of collection, and prepared as preferred the cytologist (air dried, spray fixed or fixed in alcohol). If few cells are present, the sample can be spun (200 rpm for 2-4 minutes), then smears can be made with the cell pellet. For in-house assessment, Gram stain and ‘Diff-Quik’ are suitable stains. Cell counts can be performed on EDTA anti-coagulated samples.

TREATMENT

With LRT disease the treatment will generally depend on the specific diagnosis.

• Management of bronchopulmonary disease:

The treatment of chronic bronchopulmonary disease aims to control clinical signs rather than achieve a cure. Therapy should be tailored to each individual case.
It aims to:

• Alter life-style
• Reverse bronchoconstriction: (-adrenergic agonists, theophylline)
• Reduce inflammation: (corticosteroids, anti-serotonergics, antibiotics, or leukotriene receptor antagonists)

Alter life-style:
A marked improvement in the cat’s well being can often be achieved by reducing its exposure to airway irritants (smoke, cat-litter, aerosol, dusty environments, sudden changes in temperature), preventing its access to drugs that can cause bronchoconstriction (-blockers, aspirin), avoiding stressful situations, and, in obese cats, instigating a weight loss program.

Medical therapy:
In all cases altering the life-style is usually beneficial (see above). The first line of therapy is to treat any infection and give a bronchodilator. It is only if this does not work, or when the disease is more severe, that corticosteroids are added. While oral medication has previously been the mainstay of treatment, inhaled medications are now being used more widely, particularly in more complicated cases. Their major advantage is their general lack of systemic side effects. That said, it is important to remember that few medications (oral or inhaled) have been scientifically trialed in cats, and even fewer have undergone long-term studies.

Inhaled medication (approximate prices as of January 2004):
While the successful use of an inhaler, drug-chamber and small face mask does take a little practice by the owner and the patient, many cats do very well on inhaled medications. (It is best to have the owner introduce the mask to the cat at home, rather than in the clinic, as this leads to more rapid acceptance). The AeroKat Chamber (~£50, €49), see later for details) has been specifically designed for cats and is the preferred choice. While the Babyhaler or Paediatric Volumatic chambers from Allen & Hanburys can also be considered, they usually require higher doses of medication. (These chambers are cheaper; ~£10, €13, but the higher drug dosages soon accumulate costs).

Suggested treatment regimens:
Mild cases: Salbutamol (100 mg metered dose inhaler [MDI] ~£3, €4), give one dose (one puff), as needed.

Moderate cases: i.e. clinical signs are occurring on a daily basis.
Salbutamol, 1-2 doses, 2-4 times daily.
Inhaled steroids may also be required:
• Fluticasone has been used most frequently in cats. It is very expensive, 125 mg MDI (~£40, €52): 1-2 doses, twice daily.
• Beclomethasone may be considered as an alternative. 100 or 200 mg MDI (~£15, €20): 1-2 doses, twice daily.
• Qvar is a form of beclomethasone that is currently under investigation as its smaller particle size may allow for using lower doses. 50 mg MDI (£12, €16): 2 doses, 2-3 times daily.
• Budesonide, like fluticasone is minimally absorbed from the lungs. Dose as for fluticasone.
Where more than one dose is required put one dose into the Chamber then place the mask on the cat’s face for 5-10 seconds. Then repeat this for the second dose.

Severe cases: Treat as for moderate cases (i.e. Salbutamol [1-2 doses, 2-4 times daily] + inhaled steroids [1-2 doses, twice daily]). However, since inhaled steroids may take 1-2 weeks to achieve maximal effect oral steroids are also required. These can usually be reduced or discontinued once the disease is under better control, typically over 2-4 weeks. (i.e. 5mg prednisolone twice daily for 1 week, then 5mg prednisolone once daily for 1 week, then 5mg prednisolone every other day for 1 week, then stop).
Salmeterol, may be added as a night-time dose to give bronchodilation throughout the night, or given twice daily in more severe cases. 120 mg MDI (£40, €52): 1-2 doses, 1-2 daily.

Oral medication:
Where oral medication is to be used the author usually starts with a two-week trial of long-acting theophylline. If this fails to achieve sufficient control of the clinical signs, prednisolone is usually added. Where one bronchodilator (e.g. long-acting theophylline) fails to give a positive response, a different class of bronchodilator (e.g. terbutaline) may be used instead. (Some authors prefer to use terbutaline as their first choice of treatment). Where prednisolone cannot be given (recurrent infections, intolerance, diabetes mellitus), and inhaled medication will not be tolerated, the author then tries an anti-serotonergic or, occasionally, a leukotriene receptor antagonist. Over-weight cats that prove hard to diet may benefit from a reduced corticosteroid dose, which may be compensated for by the inclusion of inhaled medication, or in some cases, a leukotriene receptor antagonist.

Reverse bronchoconstriction:
• Beta 2 adrenergic agonists:
Salbutamol (Albuterol, ‘Ventolin’), single dose MDI, give as required, effective within 5-10 minutes. (i.e. it is more rapidly acting when given by inhalation than PO, SQ or IM). (See above for treatment regimens). Use of high doses can result in tachycardia and muscle twitching.

Salmeterol (‘Serevent’), is a long-term bronchodilator that takes up to 1-2 hours to take effect but lasts ~8-12 hours. (See above for treatment regimens). Use of high doses can result in tachycardia and muscle twitching.

Terbutaline (‘Bricanyl’) 0.625-1.25 mg PO q12h
As with all of these drugs, this drug is not licensed for use in cats. However, it has been used frequently with few problems reported. Side effects include GI upset, weakness, tachycardia and hypotension. Care should be taken when used concurrently with corticosteroids.

• Theophylline: Slow release theophylline (‘Corvental-D’) 20-25mg/kg PO q24h.
Theophylline is a weak bronchodilator that also improves mucociliary transport, stabilizes mast cells, and increases the strength of respiratory muscle contractions. It has a narrow therapeutic window, with toxicity resulting in GI upset, hyperactivity, seizures, and cardiac arrhythmia. Efficacy is very dependent on formulation; Corvental-D and Theo-Dur are recommended.

Reduce inflammation:
• Corticosteroids:

Fluticasone propionate (‘Flixitide’), Beclomethasone bipropionate (‘Becotide’,‘Qvar’) and Budesonide (‘Pulmicort’) are available as inhaled medications. They have virtually no systemic effects (especially Fluticasone and Budesonide). In cats they can occasionally cause airway irritation. (See above for treatment regimens).

Prednisolone 0.25-2 mg/kg PO q12h, then taper off slowly.
Corticosteroids are very effective at reducing airway inflammation, and in prolonged dosing may reduce airway hyper-responsiveness. Short-term high-dose therapy should be avoided as a rebound hyper-responsiveness may result.

• Anti-serotonergics: Cyproheptadine (‘Periactin’) 0.1-1.0mg/kg PO q8-24h
Given that feline mast cells release high concentrations of serotonin, a number of clinicians have been using anti-serotonergic drugs to treat refractory cases of ‘feline asthma’. While cyproheptadine has been used successfully to control a number of difficult cases, it has a considerable appetite stimulatory effect that can be unhelpful. It can also cause drowsiness and inco-ordination. This drug is not licensed for veterinary use.

• Leukotriene receptor antagonists: Zafirlukast (‘Accolate’) 5-10mg/cat PO q12 h.
In humans, a number of other anti-inflammatory drugs have come into use, including the leukotriene receptor antagonists. While, in cats, experimental data suggests that this group of drugs is unlikely to give major benefits, the author has found them to be useful in some cases. They often need to be given for four weeks before their full effect is seen. These drugs are not licensed for veterinary use.

• Antibiotics: Cats with chronic bronchopulmonary disease are very susceptible to opportunistic airway infections. Whenever infection is found it should be treated. Ideally, selection of antibiotics should be made on culture and sensitivity. However, empirical choices include doxycycline, penicillins, and fluoroquinolones. Treatment for 4-6 weeks is often required. Recommended treatment for mycoplasmosis is doxycycline 5mg/kg PO q12h.

• Mucolytics: Bromhexine (‘Bisolvon’) 3mg/cat IM/day, or 1mg/kg PO/day.
While the author has rarely found mucolytics to be beneficial, some authors recommend them to help ease respiratory tract congestion.

Acute decompensation:
This requires very prompt intervention. It is important to keep restraint to a minimum, and increase the oxygen concentration of the air the cat is breathing (oxygen tent or box).
Rapidly acting drugs include;
Methylprednisolone Na succinate@ 50-100mg/cat SQ, IM, IV
Dexamethasone @ 0.2-2.2 mg/kg SQ, IM, IV
Terbutaline @ 0.01 mg/kg SC, IM, IV q4h (is also absorbed very rapidly PO)
Aminophylline @ 5 mg/kg IV q8-12 hours (is also absorbed very rapidly PO). This is painful when given IM or SC.

In severe respiratory distress;
Adrenalin @ 0.1ml of a 1:1000 solution SC, IM, IV or via ET tube
Atropine @ 0.015 mg/kg IV, 0.04 mg/kg SC – will block vagal bronchoconstriction and reduced bronchial secretions, but increases heart rate and can cause cardiac arrhythmia.

Some drugs can be administered via an inhaler or in nebulised air. Unfortunately, administration via nebulised air can result in their therapeutic concentrations taking a longer time to be reached. e.g. Salbutamol (two doses every 30 minutes for up to 2-4 hours) and/or Fluticasone (see above).

2. Bacterial bronchopneumonia:
Treatment of bacterial bronchopneumonia usually includes a protracted course of antibiotics. Ideally, antibiotics should be selected by culture and sensitivity. Useful broad-spectrum antibiotics include amoxycillin, cephalosporins, doxycycline, trimethoprim-sulpha, and aminoglycosides. Combinations of these drugs may be required. An oxygen enriched environment, fluid therapy, airway humidification, bronchodilators, and daily coupáge may also be helpful.

3. Lungworm infection:
In mild cases supportive therapy may be sufficient. In more severe cases intervention may be needed. The first choice of treatment is Fenbendazole @ 50mg/kg/day PO for 10-21 days as this has minimal toxicity. In addition to this it is advisable to give bronchodilators (see above), antibiotic cover to prevent secondary infection of the damaged lung tissue, and an anti-inflammatory dose of glucocorticoid to reduce the inflammation that tends to arise as the cat’s immune system removes the dead and dying worms. Alternatives to fenbendazole are ivermectin (0.4 mg/kg SQ), and levamasole (25-30 mg/kg divided into 8 hourly doses and given on alternate days for 5 treatments). Care should be taken when using levamasole as it can be very toxic to cats (and tastes very bitter).

Figure 1. Causes of lower respiratory tract disease in cats

Bronchi
• Chronic bronchitis
• ‘Feline asthma’
• Parasitic - Aelurostrongylus abstrusus
(Capillaria aerophilia)

Lungs
• Broncho-pneumonia
• Neoplasia
• Pulmonary oedema
• Pulmonary contusion (trauma)
• Pulmonary emphysema
• Parasitic - Aelurostrongylus abstrusus

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