Promise made, promise kept: it is the cat's turn.

Abstract

When the original Task Force was created in 1999 and throughout the following years as the group evolved, the question was always “What about the cat? When will you do the same for the cat?” No matter when or to whom you asked this question, the answer was always: “Don’t worry, we will get to the cat”. The promise was kept – they finally “got to the cat”. The International Committee on Allergic Diseases of Animals (ICADA) Cat Team (ICT) has provided the veterinary dermatology community with four foundational papers: “Feline allergic diseases: introduction and proposed nomenclature”, “Clinical signs and diagnosis of feline atopic syndrome: detailed guidelines for a correct diagnosis”, “Immunopathogenesis of the feline atopic syndrome”, and “Treatment of the feline atopic syndrome – a systematic review.” Reader be forewarned: these are well-written, relatively concise papers, but they are not “easy breezy reads”. They are information-dense papers. Take it slow – it’s worth it. It is very tempting to skip to the end of the Introduction paper and read the proposed nomenclature. That would be a mistake. Although name changes often are proposed based upon the slimmest of evidence, that is not the case here. The ICT makes a careful argument for these changes by reviewing what is known in man and then makes a case by asking and answering: “To what extent do feline allergic diseases satisfy the criteria as being atopic in nature?”; “Is there evidence of a genetic basis?; Is there evidence for the involvement of immunoglobulin (Ig)E?”; “Is the spectrum of allergic diseases in cats similar to the atopic diseases of man and has an atopic march been shown to exist in this species?” Strong justification was made for grouping allergic skin diseases caused by environmental allergens, food allergy and asthma under the umbrella term “Feline Atopic Syndrome” (FAS) with the caveat that flea allergy can both mimic and/or contribute to the syndrome. Feline atopic skin syndrome (FASS), as one of the subsets of FAS (take care with those “s”s!), is proposed to describe skin disease presumed to be associated with IgE to environmental allergens, again with the caveat that food allergy and flea allergy can both mimic and/or contribute to the FASS. Feline asthma is well-recognized by veterinarians, and now veterinary dermatologists are charged with the task of working harder to recognize it as part of FAS. The second paper focuses on the clinical spectrum and diagnosis of FASS. I was surprised to see only 107 references from 1950 to 2020, yet upon careful inspection they are almost exclusively original data papers. A quick Google Scholar trawl for the search terms revealed thousands of citations. This emphasizes how little original research has been done on the clinical aspects of feline allergic diseases and how much we recycle what little we know. The literature overflows with variations on the theme of “cutaneous reaction patterns in cats” and the ICT has simplified this to four major patterns: military dermatitis (MD), self-infected alopecia/hypotrichosis (SIAH), head and neck pruritus (HNP) and the eosinophilic granuloma complex (EGC). The major take-homes are that more was missed for not looking, than not knowing: cats have a surprising number of extracutaneous clinical signs with FASS; feline asthma is underdiagnosed and/or under recognized in specialty and general practice; and, finally, there is no escaping strict flea control (9–12 weeks). The summary of feline asthma and the algorithm of clinical signs with FAS were unexpected pearls. The third paper is a testament to the dedication of the ICT to organize and make sense of a wide range of investigations on the serological and cellular immunopathogenesis of FAS. Not unexpectedly the research varied in quality, was often limited in its case criteria, and comparisons complicated by advances in diagnostic and/or molecular testing. Despite these challenges, the evidence argued for a role of IgE in the pathogenesis of FASS and asthma, albeit not strong. Studies on the inflammatory cell infiltrate of FASS and asthma along with cytokine expression supports a T helper 2 immune dysregulation in some cats. It is important to note that much of the work done on feline asthma was in experimental models. The challenge is to study the disease in spontaneous cases. The fourth and final paper in this series is a systematic review of treatment for FAS. Readers familiar with ICADA will recognize the format of quality of evidence and strength of recommendation. A very thorough literature search retrieved an unsurprisingly small number of papers (58 clinical trials, eight case reports, four safety and pharmacokinetic studies, and one retrospective safety study) deemed suitable for evaluation. Treatment interventions evaluated included allergen avoidance, allergen-specific immunotherapy, systemic glucocorticoids, topical and inhaled glucocorticoids, ciclosporin, oclacitinib, bronchodilaters, H-1 receptor blocking antihistamines, essential fatty acids and palmitoylethanolamide, maropitant, antibiotics, inhaled lidocaine and meschenchymal stem cell therapy. Table 10 is a quick treatment reference for both FASS and feline asthma. It is not a spoiler to reveal that glucocorticoids are 1-A treatments for both FASS and feline asthma. The ICT has got their work off to a great start. Without a doubt there will be some controversy and arguments. So, what do we do with this information? First, I’d like to suggest that we embrace and adopt the recommended nomenclature and four reaction patterns. Second, read, reread and re-reread the papers to look for those clinical pearls to help improve patient care and – of equal importance – debunk folklore (e.g. recommending allergen avoidance to cat owners). Third, for those with any type of educational platform (e.g. clinic web page, client handouts, lectures), start disseminating the information. As it turns out, 21 years was worth the wait!