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Small Genome-wide association study of insect bite hypersensitivity in Hucul horses.
Abstract: Insect bite hypersensitivity (IBH) is a prevalent allergic skin disease in horses that significantly affects animal welfare and shows evidence of genetic predisposition. Objective: Understanding the genetic basis of IBH can improve management and breeding strategies. The Equine80K BeadChip microarray was used to identify genomic regions associated with the occurrence of IBH in Hucul horses. Methods: Hair samples were collected from 127 Hucul horses, including both affected individuals and controls. DNA was extracted and genotyped. A genome-wide association study (GWAS) was performed to identify loci associated with IBH susceptibility. Results: No genome-wide significant SNPs were detected; however, five loci showed suggestive associations on ECA5, ECA15, and ECA20. The strongest signal was on ECA20, with three SNPs located within a ∼5.32 Mb region upstream of the DST gene, suggesting potential regulatory effects. DST encodes dystonin, a cytoskeletal linker protein with an epidermal isoform expressed in keratinocytes and localized to hemidesmosomes at the dermal-epidermal junction, supporting its biological relevance to skin integrity and hypersensitivity-related pathology. Additionally, several additional genes in this interval (COL21A1, KIAA1586, ZNF451, PRIM2, BAG2, RAB23, KHDRBS2, LGSN, PTP4A1, PHF3, BEND6) may contribute to IBH susceptibility. Conclusions: These findings support a genetic component in IBH susceptibility and highlight potential regulatory variants on chromosome 20 as key contributors. Further functional studies and fine mapping are needed to identify causal mutations and validate candidate gene involvement, which could guide future breeding and management practices to reduce IBH prevalence in Hucul horses.
Copyright © 2026. Published by Elsevier Inc.
Publication Date: 2026-03-20 PubMed ID: 41865909DOI: 10.1016/j.jevs.2026.105857Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
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Overview
- This study investigated the genetic factors associated with insect bite hypersensitivity (IBH), an allergic skin condition, in Hucul horses by using genome-wide association analysis.
- The research identified suggestive genomic regions, particularly on horse chromosome 20, which may influence susceptibility to IBH, providing insight for future breeding and treatment strategies.
Background and Objective
- Insect bite hypersensitivity (IBH) is a common allergic skin disease in horses causing discomfort and welfare issues.
- Previous evidence suggested that IBH has a genetic predisposition.
- The main goal was to identify genetic loci associated with IBH in Hucul horses to improve understanding and inform better management and breeding approaches.
Methods
- Sample collection: Hair samples were taken from 127 Hucul horses, including both IBH-affected and unaffected individuals (controls).
- DNA extraction and genotyping: DNA was extracted from samples and genotyped using the Equine80K BeadChip microarray, which assays around 80,000 single nucleotide polymorphisms (SNPs) across the horse genome.
- Genome-wide association study (GWAS): Statistical analysis was performed to detect associations between SNPs and IBH status, seeking to find genetic markers linked to the disease.
Key Results
- No SNP reached genome-wide significance: The study did not find any SNPs that met strict criteria for significance across the entire genome, likely due to sample size limitations or genetic complexity.
- Suggestive loci detected: Five genomic regions showed suggestive associations, located on chromosomes ECA5, ECA15, and ECA20.
- Strongest association on ECA20: Three SNPs clustered in a ∼5.32 Mb region upstream of the DST gene, indicating a potential regulatory region affecting gene expression relevant to skin health.
Biological Significance of DST and Nearby Genes
- DST gene: Codes for dystonin, a cytoskeletal linker protein crucial for skin integrity.
- Dystonin role: Particularly important in epidermal cells (keratinocytes), where it anchors hemidesmosomes at the dermal-epidermal junction, maintaining structural stability of the skin.
- Alterations or regulatory mutations near DST could influence skin barrier function and immune responses, contributing to IBH pathology.
- Additional candidate genes in region: Other nearby genes—COL21A1, KIAA1586, ZNF451, PRIM2, BAG2, RAB23, KHDRBS2, LGSN, PTP4A1, PHF3, BEND6—may also influence susceptibility by affecting skin structure, immune function, or cell regulation.
Conclusions and Future Directions
- The study supports a genetic component in IBH susceptibility in Hucul horses.
- Highlighting the chromosome 20 locus near DST as a promising target for further research.
- Recommended functional studies and fine mapping to:
- Pinpoint causal mutations/variants.
- Confirm candidate gene roles in IBH pathogenesis.
- Results may guide breeding decisions and management practices aiming to reduce IBH prevalence and improve welfare in this horse breed.
Cite This Article
APA
Błaszczak A, Olczak K, Stefaniuk-Szmukier M, Tomczyk-Wrona I, Musiał AD, Grzegorczyk J, Długosz B, Szmatoła T, Ropka-Molik K.
(2026).
Small Genome-wide association study of insect bite hypersensitivity in Hucul horses.
J Equine Vet Sci, 105857.
https://doi.org/10.1016/j.jevs.2026.105857 Publication
Researcher Affiliations
- Department of Farm Animal Biodiversity Conservation and Horse Breeding, National Research Institute of Animal Production, Krakowska 1, 32-083 Balice, Poland.
- Department of Farm Animal Biodiversity Conservation and Horse Breeding, National Research Institute of Animal Production, Krakowska 1, 32-083 Balice, Poland; Department of Animal Genetics, Breeding and Ethology, University of Agriculture in Kraków, al. Mickiewicza 24/28, 30-059 Kraków, Poland.
- Department of Animal Molecular Biology, National Research Institute of Animal Production, Krakowska 1, 32-083 Balice, Poland. Electronic address: monika.stefaniuk@iz.edu.pl.
- Department of Farm Animal Biodiversity Conservation and Horse Breeding, National Research Institute of Animal Production, Krakowska 1, 32-083 Balice, Poland.
- Department of Animal Molecular Biology, National Research Institute of Animal Production, Krakowska 1, 32-083 Balice, Poland.
- Department of Animal Molecular Biology, National Research Institute of Animal Production, Krakowska 1, 32-083 Balice, Poland.
- Department of Animal Reproduction, Anatomy and Genomics, University of Agriculture in Kraków, al. Mickiewicza 24/28, 30-059 Kraków, Poland.
- Department of Animal Molecular Biology, National Research Institute of Animal Production, Krakowska 1, 32-083 Balice, Poland; Center for Experimental and Innovative Medicine, the University of Agriculture in Kraków, Rędzina 1c, 30-248 Kraków, Poland.
- Department of Animal Molecular Biology, National Research Institute of Animal Production, Krakowska 1, 32-083 Balice, Poland.
Conflict of Interest Statement
Declaration of competing interest None of the authors has any financial or personal relationships that could inappropriately influence or bias the content of the paper.
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