Wednesday, September 4, 2013

Four things I learned: atopic dermatitis in dogs and cats

In cases of severe atopic dermatitis, body suits may be required to prevent self trauma. This particular image depicts Percy, looking incredibly handsome in an 00 size child's spencer, which was the perfect fit. 

Last night the ASAVA hosted another excellent webinar featuring veterinary dermatologist LindaVogelnest. Dr Vogelnest consults at the Small Animal Specialist Hospital (SASH) in Sydney. She was talking about atopic dermatitis.
According to the current definition (settled by a panel in 2002), atopic dermatitis is a pruritic skin disease with characteristic clinical features and is most commonly but not always associated with IgE antibodies to environmental allergens. Next to flea allergy dermatitis it is the most common allergic skin condition I see in canine patients, and it occurs in around 8-18 per cent of dogs and cats worldwide.

Affected animals likely have immunological dysfunction which is T cell driven, as well as skin barrier dysfunction leading to increased transepidermal water loss and increased penetration of pathogens, allergens and irritants. Signs include recurrent or relapsing pruritis which may or may not be seasonal, may or may not be steroid responsive (but usually is) and in dogs at least tends to occur around the face, ears, feet, ventrum and perianal region. Some dogs have recurrent anal sacculitis and/or recurrent secondary bacterial pyoderma and malassezia (yeast) overgrowth. Onset is usually between 1-3 years of age, but 95 per cent occur before the age of 5.
  1. Interestingly, atopy accounts for 21 per cent of skin and ear disease seen in general practice and is responsible for 15 per cent of total pet insurance claims in Australia.
  2. Dr Vogelnest manages acute flare with treatment of active infections where present; soothing shampoos; anti-inflammatory (0.5mg/kg) doses of glucocorticoids and limiting self-trauma (by use of body suits or Elizabethan collars).
  3. For long term control where possible she will use antihistamines (although stresses these are not highly effective as they only target one inflammatory mediator from mast cells, notably histamines); fatty acids (eg fish or evening primrose oil at 50-100mg/kg SID; or cold-pressed sunflower or safflower oil at 2mls/kg SID) and shampoos (she will step these up to daily in acute flare-ups and recommends a 10-15 minute soak). She is also a fan of moisturisers.
  4. Where stronger anti-inflammatories are needed she uses more potent topical steroid creams such as Elacaon, Aristocort or Cortavance; glucocorticoids (if long term she uses a dose of 0.1-0.2mg/kg in dogs and double that in cats) or cyclosporine at 5-7mg/kg.

Atopic dermatitis is multifactorial but there is certainly a genetic predisposition. Breeds that are over-represented include labs, staffies, Westies, JRTs, Scotties, boxers, bulldogs, ridgies, shar peis, bichons, beagles, great Danes, pugs and schnauzers. And in cat land, Abbysinians are especially prone.
It was a comprehensive, logical presentation – timely as this is the time that veterinarians in Sydney see a lot of itchy dogs (it is also the time of year when flea eggs are hatching like there’s no tomorrow). And a good reminder that these cases require a multifactorial approach. I liked the way Dr Vogelnest talks about management of acute flare-ups as well as long-term management. Owners typically request veterinary attention during the former, but if we can institute long-term management it may reduce the incidence of flare ups.