Equine atopic skin disease and response to allergen‐specific immunotherapy: a retrospective study at the University of California‐Davis (1991–2008)

Abstract

This retrospective study reports on the clinical presentation of equine atopic skin disease and evaluates response to treatment with allergen-specific immunotherapy (ASIT) based on intradermal testing and/or serum testing. Computerized medical records from January 1991 to December 2008 yielded 54 horses included in the study. Presenting clinical signs (CS) included urticaria (n=28), pruritus (n=8) or both (n=18). Forty-one of 54 horses received ASIT, and response to ASIT (n=32) was evaluated via telephone survey. Eighty-four per cent (n=27) of owners reported that ASIT reduced their horse's CS; 59% (n=19) were able to manage CS by ASIT alone. Three horses (9%) were managed with ASIT in combination with doxepin and discontinued use of corticosteroids. There was no statistical significance between type of test performed and reported success of ASIT (χ(2) analysis, P=0.53). Ninety-three per cent (n=30) of owners reported use of antipruritic medications prior to starting ASIT; 57% (n=17) of these owners reported discontinuing those medications due to success of ASIT. Adverse effects were limited to swelling at the injection site, seen in 16% (n=5). Seventy-five per cent (n=24) of owners elected to discontinue ASIT after 6 months to 8 years (mean 2.2 years): 15 due to resolution of CS, six due to persistent CS, two because the horse was sold, and one due to cost. Ten owners reported no recurrence of CS after discontinuing ASIT; five had recurrence within a median of 2 years of discontinuing ASIT (range 1-12 years). Allergen-specific immunotherapy is a safe and effective way to manage equine atopic skin disease.

A diagnostic approach to the pruritic horse

“…In general, approximately 70% of atopic horses improve with ASIT (Stepnik et al . ); other researchers have reported even better results, albeit in a noncontrolled report (Tallarico and Tallarico ).…”

“…However, a full 12 months of ASIT should be given before fully evaluating its effectiveness, and veterinarians should maintain consistent communication with the client to monitor the progress of the treatment and to encourage the owner to continue with the injections for the full year. While in other domestic species it is thought that most patients will need to be maintained on the injections for life, this may not be true in the horse, as some horses had the ASIT injections stopped and did not relapse (Stepnik et al 2012). In general, approximately 70% of atopic horses improve with ASIT (Stepnik et al 2012); other researchers have reported even better results, albeit in a noncontrolled report (Tallarico and Tallarico 1998).…”

“…Atopic dermatitis has been successfully managed with allergen-specific immunotherapy, with horses showing improvement as early as 2 months into treatment (Rees 2001;Stepnik et al 2012). However, a full 12 months of ASIT should be given before fully evaluating its effectiveness, and veterinarians should maintain consistent communication with the client to monitor the progress of the treatment and to encourage the owner to continue with the injections for the full year.…”

Skin Diseases in Horses

“…16 Horses of a wide range of ages have been diagnosed with atopy. 48 No study has found any breed, age or sex predilections.…”

“…Urticaria, both pruritic and nonpruritic, is a reported common clinical sign. 47,48 Alopecia, self-trauma, and pitting edema are also relatively common. Lesions are most common on the face, pinnae, trunk, and distal part of the legs.…”