Authors: Pessoa Vera Carvalho, Branco-Ferreira Manuel, Jónsdóttir Sigridur, Marti Eliane, Tilley Paula
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Culicoides Allergen Testing in Equine Insect Bite Hypersensitivity Insect bite hypersensitivity (IBH) remains a significant welfare concern in horses, yet diagnostic protocols for identifying the causative Culicoides species allergens have lacked standardisation. Researchers compared intradermal and skin prick testing (SPT) using 14 distinct Culicoides allergens—including whole body extracts and recombinant salivary proteins from *Culicoides nubeculosus* and *Culicoides obsoletus*—alongside in vitro serology in 30 IBH-affected and 30 control Lusitano horses, with wheal responses measured at 20 minutes, 6 hours and 48 hours. Skin prick testing proved significantly superior to intradermal testing for diagnostic discrimination, particularly using whole body extracts and several recombinant proteins (notably Cul n 7, 8, 9 and Cul o 1P, 2P) at 100 µg/mL concentration read at 20 minutes; of the in vitro assays, sulfidoleukotriene release testing showed the strongest performance. These findings suggest practitioners should prioritise SPT over intradermal testing when investigating suspected IBH, whilst the identification of specific high-performing allergens enables more targeted and cost-effective diagnostic protocols. Further validation across different breeds and geographic populations would strengthen clinical application of this refined allergen panel.
Read the full abstract on PubMed
Practical Takeaways
- •SPT at 100 µg/mL with 20-minute assessment is more reliable than IDT for diagnosing IBH in Lusitano horses in clinical practice
- •Whole body Culicoides extracts and specific recombinant proteins (Cul n 7, 8, 9, Cul o1P, Cul o 2P) should be prioritized when selecting allergens for diagnostic testing
- •In vitro sLT release assays provide valuable adjunctive confirmation when in vivo skin testing results are unclear or inconclusive
Key Findings
- •Skin Prick Tests (SPT) at 100 µg/mL with 20-minute readings demonstrated superior diagnostic performance compared to Intradermal Tests (IDT) for IBH diagnosis
- •Cul n WBE, Cul n 7, 8, 9, Cul o1P, and Cul o 2P allergens showed best discriminatory potential in the first allergen panel (p ≤ 0.0001)
- •Sulfidoleukotriene (sLT) release assay outperformed other in vitro tests for detecting allergen-specific responses in IBH-affected horses
- •Culicoides obsoletus whole body extract and recombinant proteins from both Culicoides species produced in different expression systems showed diagnostic value (p ≤ 0.05)