Atopy

From Dog
Atopy in a Maltese Terrier showing lichenification (blackening) of the ventral area[1]
Atopy in the feet of a dog[2]

Canine atopic dermatitis (CAD; atopy) is a common inflammatory skin disease associated with defects in the epidermal barrier, particularly in West Highland white terriers[3][4].

The condition is characterized by variable degrees of dermatitis, intertrigo and in severe cases, pyoderma.

In most cases, atopy has a chronic, progressive course and can significantly affect the quality of life of affected dogs and their owners[5]

Canine atopy can be aggravated or compounded by environmental allergens (e.g., pollen)[6], yeast such as Malassezia spp and certain food[7]. Atopy can occur even before allergic sensitization to allergens. Dust mites do not appear to be a particularly important allergen in dogs[8].

Impairment of the skin barrier has been recognized[9].

The skin of dogs with atopy is different from normal canine skin in terms of ultrastructure, lipid composition (e.g., amount of ceramides)[10], and permeability[11].

Early exposure to probiotics appears to play a protective role against clinical development of atopy in some dogs[12][13], further suggesting that modulation of the immune system in the early stages of life is important.

Clinical signs

Typically, dogs with atopy begin to show clinical signs between 1 and 3 years of age. These signs may initially be seasonal before becoming evident year round. In very mild cases, they may remain seasonal.

Erythema and pruritus on the face, paws, ears, and inguinal area are typical, as are recurrent skin and ear infections. Previously, it was accepted that primary lesions of atopy did not exist; however, it is now known that some dogs with atopy present with a primary papular eruption caused by the accumulation of eosinophils and lymphocytes in the area where the allergen is captured. This presentation seems to be more common in young dogs (e.g., younger than 1 year) and in dogs with house dust mite allergies[14].

Clinical signs are triggered in most cases by environmental allergens (the traditional definition of allergy); they can also be caused by food allergens or be nonallergic (i.e., intrinsic disease).

Diagnosis

Despite the availability of a variety of allergy tests, the diagnosis of atopy remains clinical and is based on a compatible history, clinical signs, and the exclusion of other pruritic skin diseases.

Bacterial, fungal and yeast cultures are essential. The role of Staphylococcus intermedius appears to play an important role in pathogenesis of secondary infections since over 80% of atopic dogs are affected with this bacteria[15] and it is frequently involved with atopy-associated pyoderma[16]. Despite this, both atopic and normal dogs have equal amounts of antimicrobial peptides (defensins) within their skin[17].

Allergy testing can be considered to identify the allergens to be included in immunotherapy[18].

A differential diagnosis would include allergic reactions to Demodex spp and Sarcoptes spp mites[19] and Ctenocephalides spp fleas[20].

Treatment

Broad-spectrum antimicrobials, with sensitivity against S. pseudintermedius are indicated for 2 - 4 weeks, supplemented with chlorhexidine-based shampoo[21]. Parenteral prednisolone therapy has been extensively use in general practice, based on clinical resolution of symptoms[22].

Topical hydrocortisone sprays[23] are also effective in ameliorating pruritusbut do not abate the underlying allergy.

Immunotherapy with Recombinant canine interferon-gamma may be considered if affordable, and shows good responses[24].

In terms of medical treatments to control inflammation and pruritus, evidence-based medicine has shown that very few treatments are very effective[25].

Broad-spectrum anti-inflammatory agents (e.g., prednisolone, cyclosporine[26]) are more effective than "targeted" therapies (e.g., amitriptyline[27], diphenhydramine, pentoxifylline).

Failures have been reported with use of interferon, budesonide leave-on conditioners, oral fexofenadine, masitinib or commercial diets[28]

Although clients believe antihistamines can be a useful part of multimodal therapy for canine atopic dermatitis, most dogs benefit largely with dietary modification and true clinical remission is only effective with allergen-specific immunotherapy[29].

References

  1. Darwin Vets
  2. Canine Skin Allergies
  3. Roque JB et al (2011) Real-time PCR quantification of the canine filaggrin orthologue in the skin of atopic and non-atopic dogs: a pilot study. BMC Res Notes 4:554
  4. Lauber B et al (2012) Total IgE and allergen-specific IgE and IgG antibody levels in sera of atopic dermatitis affected and non-affected Labrador- and Golden retrievers. Vet Immunol Immunopathol 149(1-2):112-118
  5. Griffin CE, DeBoer DJ. (2001) The ACVD task force on canine atopic dermatitis (XIV): clinical manifestations of canine atopic dermatitis. Vet Immunol Immunopathol 81(3-4):255-269
  6. Kubota S et al (2012) IgE reactivity to a Cry j 3, an allergen of Japanese cedar (Cryptomeria japonica) pollen in dogs with canine atopic dermatitis. Vet Immunol Immunopathol 149(1-2):132-135
  7. Olivry T, Deboer DJ, Prélaud P, et al (2007) Food for thought: pondering the relationship between canine atopic dermatitis and cutaneous adverse food reactions. Vet Dermatol 18(6):390-391
  8. Farmaki R et al (2012) Dust mite species in the households of mite-sensitive dogs with atopic dermatitis. Vet Dermatol 23(3):222-e45
  9. Reiter LV, Torres SM, Wertz PW. (2009) Characterization and quantification of ceramides in the nonlesional skin of canine patients with atopic dermatitis compared with controls. Vet Dermatol 20(4):260-266
  10. Reiter LV, Torres SM, Wertz PW. (2009) Characterization and quantification of ceramides in the nonlesional skin of canine patients with atopic dermatitis compared with controls. Vet Dermatol 20(4):260-266
  11. Hightower K, Marsella R, Creary E, Dutcher P.(2008) Evaluation of transepidermal water loss in canine atopic dermatitis: a pilot study in beagle dogs sensitized to house dust mites. Vet Dermatol 19(2):108
  12. Marsella R et al (2012) Early exposure to probiotics in a canine model of atopic dermatitis has long-term clinical and immunological effects. Vet Immunol Immunopathol 146(2):185-189
  13. Marsella R. (2009) Evaluation of Lactobacillus rhamnosus strain GG for the prevention of atopic dermatitis in dogs. Am J Vet Res 70(6):735-740
  14. Marsella R, Olivry T, Nicklin C, Lopez J. (2006) Pilot investigation of a model for canine atopic dermatitis: environmental house dust mite challenge of high-IgE-producing beagles, mite hypersensitive dogs with atopic dermatitis and normal dogs. Vet Dermatol 17(1):24-35
  15. Fazakerley J et al (2009) Staphylococcal colonization of mucosal and lesional skin sites in atopic and healthy dogs. Vet Dermatol 20(3):179-184
  16. Fazakerley J et al (2010) Heterogeneity of Staphylococcus pseudintermedius isolates from atopic and healthy dogs. Vet Dermatol 21(6):578-585
  17. Leonard BC et al (2012) Activity, expression and genetic variation of canine β-defensin 103: a multifunctional antimicrobial peptide in the skin of domestic dogs. J Innate Immun 4(3):248-259
  18. Schnabl B, Bettanay SV, Dow K, Mueller RS (2006) Results of allergen-specific immunotherapy in 117 dogs with atopic dermatitis. Vet Rec 158(3):81-85
  19. Koebrich S et al (2012) Intradermal and serological testing for mites in healthy beagle dogs. Vet Dermatol 23(3):192-e39
  20. Bruet V et al (2012) Characterization of pruritus in canine atopic dermatitis, flea bite hypersensitivity and flea infestation and its role in diagnosis. Vet Dermatol doi:10.1111
  21. Schilling J & Mueller RS (2012) Double-blinded, placebo-controlled study to evaluate an antipruritic shampoo for dogs with allergic pruritus. Vet Rec 171(4):97
  22. Kovalik M et al (2012) Short-term prednisolone therapy has minimal impact on calcium metabolism in dogs with atopic dermatitis. Vet J 193(2):439-442
  23. Nam EH et al (2012) Evaluation of the effect of a 0.0584% hydrocortisone aceponate spray on clinical signs and skin barrier function in dogs with atopic dermatitis. J Vet Sci 13(2):187-191
  24. Scott DW, Miller WT, Griffin CE. (2001) Muller and Kirk's Small Animal Dermatology. 6th ed. Philadelphia: WB Saunders; pp:598
  25. Olivry T, Mueller RS (2003) International Task Force on Canine Atopic Dermatitis. Evidence-based veterinary dermatology: a systematic review of the pharmacotherapy of canine atopic dermatitis. Vet Dermatol 14(3):121-146
  26. Kovalik M et al (2012) The use of ciclosporin A in veterinary dermatology. Vet J 193(2):317-325
  27. Miller WH et al (1992) Nonsteroidal management of canine pruritus with amitriptyline. Cornell Vet 82(1):53-57
  28. Olivry T & Bizikova P (2013) A systematic review of randomized controlled trials for prevention or treatment of atopic dermatitis in dogs: 2008-2011 update. Vet Dermatol 24(1):97-117
  29. Dell DL et al (2012) Owner assessment of therapeutic interventions for canine atopic dermatitis: a long-term retrospective analysis. Vet Dermatol 23(3):228-e47