THE snuffly cat is a common encounter for most vets in practice but actually getting to the root of these cats’ problems can be challenging.
Last month’s webinar organised by The Webinar Vet discussed the investigation and management of common chronic nasal and nasopharyngeal disease in the cat, and with Martha Cannon at the helm, this webinar proved itself to be practical and relevant to the cases we see so frequently in practice.
Martha, demonstrated the diagnostic trail for working up these sometimes complex cases by citing an example presented at her practice, the Oxford Cat Clinic.
Simba, a 12-year-old MN DSH had a three-month history of gradual onset recurrent unilateral nasal discharge. Simba responded well to antibiotics but his nasal discharge always recurred.
The majority of The Webinar Vet’s audience agreed that this was a case for further investigation with neoplasia, chronic rhinitis, foreign body, dental disease and pharyngeal polyps all being potential diagnoses.
Martha pointed out that a frustration of these cases is that most of the key diagnostic tests that are required to investigate them require the affected cat to go under a general anaesthetic.
Upper respiratory virus tests can be carried out consciously and one would assume bacterial culture and sensitivity could also be performed without a general anaesthetic. However, superficial swabs often result in the culture of commensals and/or contaminants, and the most sensitive sample for bacterial culture appears to be a nasal lavage and this would, of course, need to be performed under a general anaesthetic.
After endoscopic examination of the nasopharynx, Simba had intra-oral x-rays performed showing a unilateral loss of turbinate detail and the presence of a soft tissue opacity (see Figure 1). These changes, along with displacement of the midline and evidence of bone invasion, are all radiographic signs associated with nasal neoplasia. They are not, however, diagnostic, making a biopsy always necessary.
Simba had a biopsy of his nasal cavity performed using endoscopy biopsy forceps which, according to Martha, are an investment well worth making even if you don’t own an endoscope. Martha advocates taking several biopsies from each side of the nasal cavity as there is often inflammation on the periphery of tumours which could lead to an incorrect diagnosis.
When performing a biopsy it is always necessary to measure from the nostril to the medial canthus of the eye (see Figure 2) to ensure the biopsy isn’t performed too deeply which could damage the cribiform plate and potentially perforate into the brain.
Martha also described the forced flush technique which can be very useful in gaining soft tissue material from a soft tumour such as lymphoma. The cat’s throat should be packed and the ET tube cuffed. A seal should be formed over one nostril using a syringe filled with saline attached to a kennel cough applicator (see Figure 3).
The contralateral nostril should be blocked and a firm flush of saline administered. Often large chunks of tissue can be retrieved this way (see Figure 4) and in some cases clinical signs will also be relieved.
Unfortunately the histology performed on Simba’s biopsy revealed the presence of an adenocarcinoma. These tumours respond poorly to chemotherapy, unlike lymphoma where treatment can give a median survival time of an impressive 749 days, and combined with radiotherapy gives a median survival of 955 days.
Nasal surgery is often poorly tolerated by cats so radiotherapy or palliative care were the best options for Simba. The owner opted for palliative care and after the use of antibiotics, antiinflammatories and nebulisation, Simba survived 10 months after his diagnosis.
Neoplasia accounted for 39% of cases of chronic nasal discharge and sneezing in a study of a referral population of cats, and chronic rhinitis came a close second at 35%. Martha explained that most cases of chronic bacterial rhinitis have had a previous infection with feline herpes virus, but most will be FHV negative when tested as most infections are latent and not active when the chronic rhinitis develops.
Aerobic bacteria, anaerobic bacteria, Bordetella bronchiseptica and Mycoplasma may be found on culture but these can all be isolated from normal cats’ noses so interpreting culture results can be difficult.
Intra-oral x-rays tend to show subtle changes with some loss of a distinct turbinate pattern. As many of the diagnostic findings are vague with chronic rhinitis, biopsy is always necessary if confirmation of the diagnosis is required.
Repeated long courses
Treatment of chronic bacterial rhinitis involves repeated long (e.g. four week) courses of broad-spectrum antibiotics as required and Martha suggests using a “low rung” antibiotic such as amoxycillin/clavulanic acid initially as it has good bone penetration.
Doxycycline also has good activity against Bordetella bronchiseptica and Mycoplasma and is thought to cause immunomodulation which may reduce inflammation. Antibiotics such as the cephalosporins and fluoroquinolones should be reserved and only used if absolutely necessary.
Maintaining tissue hydration is an essential part of the treatment, by the use of nebulisers or by placing the affected cat in a steamy environment such as a shower room. Antiinflammatories such as meloxicam may also be useful. If NSAIDs aren’t tolerated, inhaled steroids such as fluticasone might prove useful, administered via an Aerokat inhaler.
For more refractory cases, oral prednisolone can be effective, especially in cats with lymphoplasmacytic or eosinophilic rhinitis. Other suggestions offered by Martha for cases that have not responded to all other treatments include intranasal gentamicin drops and diphenhydramine (Nytol) as a decongestant at a dose of 2-4mg/kg P/O q 6-8 or less often as required.
There are, of course, diseases other than neoplasia and chronic rhinitis that cause signs in the snuffly cat. Martha explained that differentiating signs of nasal disease and nasopharyngeal disease can be helpful. Cats with nasopharyngeal disease usually have more noise but less nasal discharge than expected with nasal disease and less sneezing too, as any discharge tends to be passed backwards and swallowed. They may also have stertor and voice change.
Conditions involving the nasopharyngeal area include foreign bodies such as grass, nasopharyngeal polyps and strictures. It is also a very common site for neoplasia such as lymphoma and adenocarcinoma as seen with Simba (discussed earlier within this report).
Martha’s webinar gave a very clear approach for diagnosing these sometimes challenging cases, ensuring there is very little opportunity for anything to be missed – this being so important when nasal tumours such as lymphoma are so responsive to chemotherapy.
Martha discussed a lymphoma case where complete remission was achieved and which has remained healthy two years after ceasing all chemotherapy, which really brings home why getting to the root of the problem is so important and how effective treatment can make all the difference to the outcome of these cases.
