First clinical expression of equine insect bite hypersensitivity is associated with co-sensitization to multiple Culicoides allergens.
Authors: Birras Jasmin, White Samuel J, Jonsdottir Sigridur, Novotny Ella N, Ziegler Anja, Wilson A Douglas, Frey Rebecka, Torsteinsdottir Sigurbjörg, Alcocer Marcos, Marti Eliane
Journal: PloS one
Summary
# Editorial Summary Insect bite hypersensitivity (IBH) represents a significant welfare and economic concern in horses exposed to Culicoides midges, yet the immunological mechanisms underlying initial sensitization remain poorly understood. Using IgE microarray profiling against 27 recombinant Culicoides allergens, researchers tracked sensitization patterns in 110 horses imported from Iceland (where IBH is absent) to Switzerland, plus a longitudinal cohort of 31 affected horses sampled across three summers relative to first clinical signs. The critical finding was that horses developing IBH showed a dramatic increase in allergen sensitization specifically in the year of first clinical expression, with median IgE reactivity to 11 allergens (including nine major ones) compared to just 3 allergens in the preceding year and 1 in healthy controls—and this peak did not increase further in subsequent years. The multi-allergen sensitization pattern indicates true co-sensitization rather than cross-reactivity, suggesting horses mount a coordinated immune response to multiple salivary components simultaneously upon initial exposure. These findings carry immediate implications for practitioners: identifying the nine major primary sensitizing allergens opens possibilities for targeted preventive allergen immunotherapy before clinical disease develops, whilst the distinct sensitization window during TIBH suggests that immune intervention strategies may be most effective during this critical period. For horses at risk (particularly naive imports to endemic regions), serological monitoring could enable early detection and intervention before dermatitic lesions emerge, potentially altering disease trajectory.
Read the full abstract on PubMed
Practical Takeaways
- •Horses exported from Culicoides-endemic regions show rapid multi-allergen sensitization in the year before clinical signs appear—serological testing could enable early intervention before symptoms develop
- •Nine identified major allergens could be used to develop preventive allergen immunotherapy, potentially reducing IBH incidence in at-risk imported horses
- •Origin matters more than disease duration: horses born in Iceland remain more sensitized after export than European-born horses, suggesting inherent susceptibility factors worth investigating
Key Findings
- •At first clinical signs of IBH (TIBH), horses were sensitized to a median of 11 recombinant allergens compared to 3 allergens the previous summer (TIBH-1) and 1 allergen in healthy controls
- •Nine major Culicoides allergens were identified as primary sensitizing agents, indicating co-sensitization rather than cross-reactivity
- •IBH-affected horses exported from Iceland showed significantly higher degree of sensitization than those born in Europe, while disease duration did not affect sensitization levels
- •Significant IgE sensitization to Culicoides allergens is detectable only in the year of first clinical IBH signs