First clinical expression of equine insect bite hypersensitivity is associated with co-sensitization to multiple Culicoides allergens

Background Insect bite hypersensitivity (IBH) is an IgE-mediated allergic dermatitis in horses incited by salivary allergens from Culicoides spp. IBH does not occur in Iceland, as the causative agents are absent, however a high prevalence is seen in horses exported to Culicoides-rich environments. Aims To study the natural course of sensitization to Culicoides allergens and identify the primary sensitizing allergen(s) in horses exported from Iceland utilizing a comprehensive panel of Culicoides recombinant (r-) allergens. Method IgE microarray profiling to 27 Culicoides r-allergens was conducted on 110 serological samples from horses imported to Switzerland from Iceland that subsequently developed IBH or remained healthy. Furthermore, a longitudinal study of 31 IBH horses determined IgE profiles the summer preceding first clinical signs of IBH (TIBH-1), the summer of first clinical signs (TIBH) and the following summer (TIBH+1). In a group of Icelandic horses residing in Sweden, effects of origin (born in Iceland or Sweden) and duration of IBH (<4 years, 4–7 years, >7 years) on Culicoides-specific IgE was evaluated. Sero-positivity rates and IgE levels were compared. Results At TIBH, horses were sensitized to a median of 11 r-allergens (range = 0–21), of which nine were major allergens. This was significantly higher than TIBH-1 (3, 0–16), as well as the healthy (1, 0–14) group. There was no significant increase between TIBH and TIBH+1(12, 0–23). IBH-affected horses exported from Iceland had a significantly higher degree of sensitization than those born in Europe, while duration of IBH did not significantly affect degree of sensitization. Conclusion Significant sensitization is only detected in serum the year of first clinical signs of IBH. Horses become sensitized simultaneously to multiple Culicoides r-allergens, indicating that IgE-reactivity is due to co-sensitization rather than cross-reactivity between Culicoides allergens. Nine major first sensitizing r-allergens have been identified, which could be used for preventive allergen immunotherapy.

Insect bite hypersensitivity in horses

Allergic skin disease is a very common cause of itching in horses. The itching can severely affect the horse?s quality of life, leading to the horse wounding itself by biting or scratching, and it can reduce the utility of the horse. This 4-page fact sheet written by Rosanna Marsella, Nicky Craig, Carissa Wickens, and Samantha Brooks and published by the UF/IFAS Department of Animal Sciences explains how to manage allergic skin disease, control itching, treat secondary infections, and prevent the insect bites in the first place.https://edis.ifas.ufl.edu/an359

New Strategies for Prevention and Treatment of Insect Bite Hypersensitivity in Horses

Purpose of Review Treatment of equine insect bite hypersensitivity (IBH) needs to be improved. Allergen-specific immunotherapy (ASIT), the only curative treatment of allergy, currently has only a limited efficacy for treatment of IBH. This review highlights the latest findings in prophylactic and therapeutic strategies. Recent Findings Prophylactic vaccination against IBH using recombinant Culicoides allergen has been developed in unexposed Icelandic horses and is ready to be tested. Therapeutic virus-like particle (VLP)–based vaccines targeting equine interleukin- (IL-) 5 or IL-31 improved clinical signs of IBH by induction of anti-cytokine antibodies thus reducing eosinophil counts or allergic pruritus, respectively. Summary First studies for development of ASIT using pure r-Culicoides allergens have yielded promising results and need now to be tested in clinical studies for both prevention and treatment of IBH. Therapeutic vaccines inducing neutralizing antibodies against IL-5 or IL-31 will be valuable future treatments for reduction of clinical signs of IBH.