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

Abstract

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.

Equine allergic skin diseases: Clinical consensus guidelines of the World Association for Veterinary Dermatology

“…When IgE microarray profiling to 27 Culicoides r‐allergens was conducted on 110 serological samples from Icelandic horses imported from Iceland to Switzerland, significant sensitisation was detected in the serum in the year of first clinical signs 63 . When a subset of these horses was tested the following summer, the increase in number of sensitisations and serum concentration of allergen‐specific IgE was not statistically significant.…”

“…Insect bite hypersensitivity is characterised by a skin infiltration with mast cells and eosinophils 11,22–88 . Injection of Culicoides antigen into the skin leads to increased infiltration with eosinophils 89 .…”

Autoimmune disorders in horses: the role of Insect Bite Hypersensitivity

“…Insect bite hypersensitivity (IBH) is a recurrent chronic seasonal allergic dermatitis triggered by the bites of different species of blood feeding dipterous insects of the genus Culicoides and Simulium. IBH in horses is one of the most common allergic skin diseases incited by salivary allergens more specifically towards Culicoides species (Birras et al, 2021). This condition is an IgE-mediated allergic dermatitis.…”

“…This condition is an IgE-mediated allergic dermatitis. IBH is also known as Culicoides hypersensitivity, summer eczema, sweet itch, Queensland itch or Kasen (Anderson et al, 1993;Kurotaki et al, 1994;Miller et al, 2019;Birras et al, 2021). IBH was first described in 1840 and is currently regarded as the best characterized allergic disease in horses (Fettelschoss-Gabriel et al, 2018).…”

Microarray molecular mapping of horses with severe asthma

“…SA diagnosis is based on clinical history and readily identified clinical signs, which correlate with severity of asthma, furthermore ancillary diagnostic tests such as BALF cytology, lung function testing, hematology, and immunological testing are used to improve diagnostic accuracy 12‐17 . While several studies address the potential benefits derived from in vitro allergen assessment in diagnosing SA, commercial applications have historically been hampered due to a lack of statistical approaches for clear disease classification, and the limited range of allergens tested 18,19 . To combat this, a microarray platform has been developed to profile allergen‐specific IgE, which enables the serological diagnosis of SA 20 .…”