A prospective study on insect bite hypersensitivity in horses exported from Iceland into Switzerland

• Published in: Acta Veterinaria Scandinavica
• Main Authors: Torsteinsdóttir, Sigurbjörg, Scheidegger, Stephan, Baselgia, Silvia, Jónsdóttir, Sigríður, Svansson, Vilhjálmur, Björnsdóttir, Sigríður, Marti, Eliane
• Other Authors: Tilraunastöð í meinafræði að Keldum (HÍ), Institute for Experimental Pathology, Keldur (UI), Auðlinda- og umhverfisdeild (LBHÍ), Faculty of Natural Resources and Environmental Sciences (AUI), Háskóli Íslands, University of Iceland, Landbúnaðarháskóli Íslands, Agricultural University of Iceland
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Nature 2018
• Subjects: Culicoides; Icelandic horses; Insect bite hypersensitivity; Simulium; Sulfdoleukotriene release assay; Íslenski hesturinn; Lúsmý; Skordýrabit; Iceland
• Online Access: https://hdl.handle.net/20.500.11815/1249; https://doi.org/10.1186/s13028-018-0425-1

Publisher's version (útgefin grein) Background: Insect bite hypersensitivity (IBH) is an IgE-mediated dermatitis caused by bites of Culicoides spp., which occurs frequently in horses imported from Iceland to continental Europe. IBH does not occur in Iceland because Culicoides species that bite horses are not present. However, Simulium vittatum (S. vittatum) are found in Iceland. In Europe, blood basophils from IBH-afected horses release signifcantly more sulfdoleukotrienes (sLT) than those from healthy controls after in vitro stimulation with Culicoides nubeculosus (C. nubeculosus) and S. vittatum. Aims of the study were: (I) using the sLT release assay, to test if horses living in Iceland were sensitized to S. vittatum and (II) to determine in a longitudinal study in horses imported from Iceland to Switzerland whether the sLT release assay would allow to predict which horses would develop IBH. Results: Horses in Iceland, even when living in high S. vittatum areas, were usually not sensitized to S. vittatum or C. nubeculosus. Incidence of IBH in the 145 horses from the longitudinal study was 51% and mean time until IBH developed was 2.5±1 year. Before import and after the frst summer following import, there were no signifcant diferences in sLT release between the endpoint healthy (H) and IBH groups. After the 2nd summer, when the number of clinically afected horses increased in the endpoint IBH group, a signifcantly higher sLT release after stimulation with C. nubeculosus but not with S. vittatum was observed. After the 3rd and 4th summer, the endpoint IBH group had a signifcantly higher sLT release with C. nubeculosus and S. vittatum than the endpoint H group. Some of the horses that remained healthy became transiently positive in the sLT release assay upon stimulation of their peripheral blood leucocytes with C. nubeculosus. Conclusions: Horses in Iceland are not sensitized to S. vittatum. In horses that develop IBH, sensitization to S. vittatum is secondary to sensitization to C. nubeculosus and probably a ...