Feline Atopic Dermatitis – A Study Review by Professor Richard Halliwell

Feline atopic dermatitis: A retrospective study of 45 cases (2001-2012)

                                       PA Ravens, BJ Xu, LJ Vogelnest

                                       Vet Dermatol 2014, 25: 95-102

Summary:

The database of a referral practice in Australia was searched for cases consistent with a diagnosis of atopic dermatitis. Of 225 potential cases, strict inclusion criteria limited the study series to 45 cases. Abyssinian, Devon Rex and domestic mixed bred were over-represented. The median age of onset was 2 years with 62% commencing their disease at < 3yrs, and 22% over 7 years. Pruritus was reported as severe in 82%, and was perennial in 33%, waxing and waning or intermittent in 44% and distinctly seasonal in 18%. Patchy alopecia, crusting and excoriations were reported in 64% with severe excoriations, erosions and ulcerations in 20%. A further 20% presented with miliary dermatitis and 27% had lesions of the eosinophilic granuloma complex (7 with eosinophilic plaques, 4 with granulomas and 4 with eosinophilic ulcers). The face/head was most frequently affected including the pinnae (40%), pre-auricular area (31%), peri-ocular area (22%), lips (20%), chin (13%), muzzle/cheek (9%) and dorsal head (4%).  The ventral abdomen and neck were affected in 51% and limbs in 38%. The dorsolumbar area was affected in 31% of cats (18% lacked concomitant flea allergy dermatitis). Otitis externa was diagnosed in 16% and 7% also suffered from respiratory signs. Thirteen percent had concurrent adverse food reactions and 24% had co-exiting flea allergy dermatitis. Secondary superficial pyoderma was diagnosed in 22 cats (49%) and malassezzia dermatitis in three cats (7%). Pollens were the most commonly encountered inciting cause followed by insects and house dust mites.

A variety of treatment regimens were used – some sequentially. Glucocorticoids resulted in a good response in 22/42 cases and a partial response in a further 10. Type 1 antihistamines were used in 31 cases resulting in a good response in two cats and a partial response in 20, with loratadine giving the best results. Allergen-specific immunotherapy was administered to 23 cats for > 12 months with a good response in 13 and a partial response in a further 6. Ciclosporin was used in 10 cats with 100% success rate, but with severe side-effects in 3 cases – two due to toxoplasmosis and one to nodular cryptococcosis.

Comments:

This is a nice well-written study with much good information. Atopic dermatitis in cats is underdiagnosed, and symptomatic treatment is often administered without a proper workup. Firstly, it is important to rule out flea allergy and adverse food reactions as either the sole cause or a concomitant cause. Noteworthy were the facts that, similarly to dogs, secondary pyoderma was common and there was a predilection for younger animals with 62% of cases commencing < 3yrs of age. However in contrast to the dog, 22% commenced at >7 yrs. Similarly also to dogs, otitis externa was a fairly common presenting sign. Allergy testing and allergen-specific immunotherapy, gave generally good results, but not as good as reported by some other studies. Oclacitinib has been used in one small study with some 50% of cats showing improvement, but the immunosuppressive effects of ciclosporin mandates that its use should be restricted to cats shown to be free from toxoplasmosis. For many dermatologists allergen-specific immunotherapy is the preferred treatment.

Written by Professor Richard Halliwell.

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