An interview with veterinary dermatology expert, Dr. Hilary Chan.

Hilary Chan is a current Dermatology resident at the Animal Dermatology Clinic in Murdoch, Western Australia. After obtaining her Bachelor of Veterinary Science (Hons I) in 2017 from the University of Sydney, Hilary began practicing in a small animal veterinary clinic in the Northern Beaches of Sydney where her passion for veterinary dermatology grew and led her to join her current team in Western Australia.

What are the top 5 dermatological conditions that affect cats at your practice?

1. Feline atopic syndrome, food allergies (includes eosinophilic granuloma complex)
2. Flea allergy dermatitis
3. Aural polyps
4. Dermatophytosis
5. Pemphigus foliaceus

What are the top 5 dermatological conditions that affect dogs?

1. Canine atopic dermatitis (includes otitis externa, secondary bacterial pyoderma)
2. Cutaneous adverse food reactions
3. Hyperadrenocorticism
4. Hypothyroid
5. Pemphigus foliaceus

What are some common misconceptions about dermatologic conditions?

Most of the misconceptions are related to allergies:

• Fleas – no visible fleas means they do not need to be on flea prevention; the definition of flea allergies does not equate to flea infestation or having fleas
• Food – often thought to be grain-related but realistically it is more commonly protein-related; common to see blood tests performed to diagnose food allergies but gold standard remains to be an elimination diet trial; dietary rechallenges are required to diagnose the food allergy
• Atopy – more can be done to manage atopy than just lifelong anti-pruritic therapy, eg immunotherapy; anti-pruritics “not working” but is actually due to concurrent infection
  • Cutaneous manifestations of endocrinopathies often get overlooked, eg recurrent bacterial pyoderma in a middle-aged to old dog and they are often treated symptomatically again and again
• In the same vein, endocrinopathies may present only with cutaneous signs, without the classical systemic signs
• Not all erythema, alopecia and pruritus is allergy-related, eg actinic dermatitis, neoplastic, parasitic, viral, immune-mediated

Allergies are a very frustrating condition for all involved. What are your tips on how to approach these cases?

• Intervene early: after 1-2 episodes of otitis externa/pruritus/bacterial pyoderma, commence investigation into the underlying issue. Explain that symptomatic treatment with recurrent of signs is the main source of frustration for owners, vets and the animal so it is crucial to rule out infectious causes, investigate food allergies and diagnose atopy by exclusion of other conditions, then refer. There is no cure but immunotherapy gives the dog the best chance to alter the underlying course of allergies.
• Some owners also come to us frustrated as they are referred when the animal is middle aged or older so they don’t see the benefit of proceeding with immunotherapy compared to if they were referred younger; ultimately, a lifetime of symptomatic treatment may be as costly or even more costly than immunotherapy
• Perform cytology and rule out infection, as anti-pruritics will not be effective in the presence of infection.

Are there any emerging or rising dermatological issues facing pets at the moment that general veterinary practitioners should be aware of?

MRSP – liberal use of first-line to third-line antibiotics has led to an increased incidence of MRSP. Skin cultures are under-utilised in general practice so animals often present with partial or no response to amoxiclav/cephalexin. I think it is important for practitioners to understand when to culture, what tests to order to detect MRSP; the need to increase use of topical antibacterials to reduce the need for oral antibiotics.

What dermatological conditions have a better prognosis when picked up earlier? What tips do you have to help general veterinary practitioners with early diagnosis?

• Allergies as described above – early diagnosis improves human-animal bond, improved welfare for the animal
• Immune-mediated conditions, eg pemphigus foliaceus – general practitioners are pretty good at detecting atypical lesions and recommend referral, but diagnosing early helps reduce the duration of immunomodulating medication and therefore side effects.
• Tips – understand when to biopsy as well as specific tests requested (histopathology, cultures); once all the dermatological diagnostics have been exhausted, or first-line treatment fails, then refer.

Can you share any updates in animal dermatology that would be relevant to the general veterinary practitioner?

• A new intratumour injection Stelfonta has been developed to treat mast cell tumours. It induces necrosis and has shown to be effective in 75% of dogs for the first round so it can be used for MCTs that are non-surgical or on distal limbs. Unfortunately this is not out in Australia yet, and had only been approved by the FDA in the US in Nov 2020.
• There is increasing research into the multifactorial nature of atopic dermatitis: genetics, environment, skin microbiome and skin barrier function. There is greater emphasis on topical therapy, improving skin barrier function and restoring the skin microbiome (DHA and EFAs – omega-3 and omega-6 via fish oils, evening primrose oils etc); regular antiseptic baths
• Daily dilute bleach spray (1:10 ratio) applications are highly effective in resolving superficial MRSP infections
• Sonotix is a newer cerumenolytic ear flush that we have found to be very effective; it can cause irritation to some external ear canals and can only be used with an intact tympanum so owners should be warned.

Pet owner compliance is key in managing dermatological conditions. What is your advice in getting clients to comply and achieving the best outcomes?

• Firstly understand the lifestyle of the owner (young family with small children? Elderly lady with arthritis? FIFO worker?), behaviour of the animal (tolerates bathing? Spits out tablets and capsules?) and ask how feasible it is for the owner to give tablets vs topical therapy, and centre treatment plans around what is most convenient for the owner without jeopardising the medical aspect of the treatment plan. Some examples include having the animal brought into the clinic for injections or paws cleaned with antiseptic wipes weekly; having multiple medications compounded into one capsule to minimise the number of pills given; if animal spits out oral medication, use topical treatment or injectables.
• Educate the owners about the disease process so they understand why treatments are required and signs of improvement and deterioration; troubleshooting at home – often they have the necessary medications so it is helpful to explain situations in which certain medications would be helpful.
• Present a detailed step-by-step treatment plan for the owner, particularly where multiple medications are required.

What areas of dermatology do you feel general practitioners could help in driving better pet owner education?

• The concept of antimicrobial resistance – understanding that one day, we have a very limited number of (if at all) effective antibiotics if animals receive repeated courses without having the underlying cause addressed, short courses or underdosing of antibiotics; dispensing oral antibiotics without bacterial cultures. Also emphasising the efficacy of topical treatment.
• The pathogenesis of otitis externa and how it is a multifactorial disease. Symptomatic treatment and relapsing ear infections without addressing the underlying cause leads to further frustration for the owner and animal. As such, explaining the anatomy of the ear, differentials for chronic or recurrent otitis externa and giving a full run down into the pathogenesis, diagnostics to investigate the underlying cause could help improve better pet owner education.
• Allergies – debunking some of the myths presented on Facebook groups, google, and providing well-researched evidence to the owner could help with understanding the disease better.