3 Aug 2015
Libby Sheridan
Job TitleWe can forget sometimes just how lucky we are living on a relatively small island – protection from invasion and disease, beautiful beaches within a few hours’ drive. Stay with me here – and access to a concentrated pool of talent within our shores.
The latter was on my mind when I attended the 2015 International Society of Feline Medicine (ISFM) pre-BSAVA feline symposium in Birmingham. It struck me just how lucky we are in the UK to have such a large pool of knowledgeable and passionate veterinary experts at our disposal – people who are also genuinely committed to sharing their expertise.
Further, this willingness to share reaches across many disciplines and species, and helps to maintain our enviably high standards of veterinary medicine in this country. Plus, we have access to all this knowledge without having to travel very far to access it.
ISFM has always been very good at bringing together la crème de la crème in feline CPD and this year’s symposium was no exception. The topic, which had been well thought through to provide CPD at just the right pitch for the many general practitioners who attended, was practical feline oncology and ophthalmology.
If, like me, you struggle to spell ophthalmology, let alone excel at it, the choice of having a range of topics that included common clinical presentations such as uveitis and corneal ulcers, as well as an interesting mix of surgical cases, proved pitch perfect.
With the emphasis on practical, the ophthalmology speakers – Marian Matas Reira and Chiara Leo from the RVC, Mike Lappin from Colorado State University, and Christine Heinrich, then working at Willows Referrals, and Heidi Featherstone also from Willows – spent the afternoon taking us through the presentation, diagnosis and treatment of ocular neoplasia, infectious and idiopathic uveitis, feline corneal sequestrum and common eyelid surgeries.
As with any ophthalmology CPD, being able to view numerous high-quality photos of various case presentations was especially valuable; by the end of the afternoon I was gaining confidence in being able to pick out clear identifying features of the more common diseases.
Mike Lappin, always an entertaining speaker, tackled the tricky subject of infectious causes of uveitis and serological testing. The most common infectious agents include Toxoplasma gondii, feline leukaemia virus (FeLV), feline immunodeficiency virus (FIV) and feline infectious peritonitis (FIP) virus, along with mycoses, such as cryptococcosis, coccidioidomycosis, histoplasmosis, candidiasis and blastomycosis.
Dr Lappin reminded us detection of an infectious agent did not confirm disease aetiology. The best use of serological testing is in negative predictive value, which implies a decreased risk of that disease, but does not rule out the agent, due to the occurrence of false negatives.
Positive results are equally frustrating: positive results for infectious diseases occur in healthy cats as well as diseased cats, and have poorer predictive value than negative results. ELISA FIV antibody test results are sometimes falsely positive, and enteric coronaviruses induce serum antibodies that cannot be distinguished from FIP-inducing strains, making coronavirus antibody titres very difficult to interpret.
The presenters contemplated whether aqueous humour testing was a useful tool for narrowing down the differentials and while the procedure is carried out in cats, they agreed the payoff between risks posed by sticking a needle into the eye versus potential yield, was probably too low. It is probably a more appropriate technique in dogs, where it can be helpful in diagnosing neoplasia.
While infection is most certainly a known cause of feline uveitis, in Ms Heinrich’s experience, the aetiology remains obscure in most of the cases she sees, despite extensive work-up. Idiopathic uveitis accounts for the majority of cases seen in the UK. Interestingly, the condition is classically bilateral so look carefully for signs in the other eye or have the patient back to check regularly (Figures 1 and 2).
A combination of topical prednisolone or ketorolac eye drops together with prednisolone tablets and a course of clindamycin (in case of undiagnosed T gondii infection) is a good starting point, with anti-inflammatories gradually reduced to a minimum maintenance dose as clinical signs go into remission. In the long term, few patients will stay in remission with topical treatment alone and many will require prednisolone at an ongoing low dose (1.0mg/kg daily).
There is no published information on the use of other immunomodulatory drugs, such as ciclosporin, in the management of feline idiopathic uveitis, and Ms Heinrich reported she has not had success with off-label use in two cats. The routine use of atropine to prevent synechiae formation was not recommended due to its unpleasant side effect of causing the cat to froth excessively.
While the management of idiopathic uveitis hasn’t changed much through the years, the treatment of feline cancer has advanced much further. Here, specialists Sue Murphy from the Animal Health Trust, Laura Blackwood from the University of Liverpool and Northwest Surgeons’ John Williams, gave comprehensive reviews of the management options for feline lymphoma, cutaneous and visceral mast cell tumours and feline mammary carcinomas, together with Dr Matas Reira and Dr Leo covering ocular neoplasia.
The most common neoplasm in cats is lymphoma, and while accurate categorisation of subtypes and, therefore very targeted treatment, is not yet available to feline patients as it is in people, chemotherapeutic management is becoming more common. Other treatment modalities, such as external beam radiotherapy is also becoming more accessible. Lymphocytes are very radiosensitive, and low doses of radiation have been found to be very useful treatments for nasal and CNS lymphoma, as well as providing an option for treating resistant alimentary lymphoma.
Response rates to common chemotherapeutic protocols will vary according to the site of the neoplasm, but the initial response to therapy remains a very valuable prognostic indicator. 30% to 50% of cats with high-grade lymphoma treated with vincristine, cyclophosphamide and prednisone (COP) or vincristine, cyclophosphamide, doxorubicin and prednisone (CHOP) can achieve long-term remission of about 30 to 40 weeks. Lower grade, usually gastrointestinal, lymphomas are generally treated with chlorambucil and prednisolone, and commonly achieve a clinical remission of more than two years. With lymphoma being more commonly found in older animals, urea and creatinine levels should be monitored with all these therapies.
Unfortunately, mediastinal lymphoma, classically associated with FeLV infection in young cats, still carries a very guarded prognosis, with a median survival time of one to two months. Some countries – Australia, Holland, the US and UK – have found some oriental breeds do slightly better and can have longer survival times with CHOP or COP.
Other types of gastrointestinal neoplasms are not so amenable to treatment. Feline mast cell tumours (MCTs) can occur in the gut and viscera, where they are generally very aggressive, with metastases common. Interestingly, visceral MCTs in cats can metastasise to the skin and vice-versa. While diagnosis of MCT is relatively straightforward on a fine needle aspirate, acute degranulation caused by the procedure has been known to lead to fatalities, so premedication with antihistamines (H1 antagonists) is advisable.
Grading of MCTs in cats is problematic, making prognostic prediction difficult. The grading systems used for cutaneous MCTs in dogs cannot be applied to cats and identifying histological predictors of malignancy has proved tricky. Fortunately, the majority of cutaneous MCTs (between 50 and 90%) in cats are well-differentiated and behave benignly (Figures 3 and 4).
Finally, the wrap-up to the day was typically ISFM-friendly, with an interesting presentation on new uses for synthetic pheromone Feliway by behaviourist Claire Hargrave on behalf of CEVA, followed by drinks and canapés. Chatting to the other delegates, it was clear everyone had enjoyed the day and found the speakers excellent – and I clocked up seven hours of really worthwhile CPD all within easy reach and just a few hours’ drive from home.
