Equine Culicoides hypersensitivity: evaluation of a skin test and of humoral response.

The research article presents a study on the use of intradermal testing and serum analysis to detect Culicoides hypersensitivity (CHS) in horses. The authors found that both methods were highly effective, with the skin test exhibiting 100% sensitivity and specificity in detecting CHS, even in winter when clinical symptoms may not be apparent.

Research Methodology

• The study was conducted on a sample of 18 horses showing clinical signs of CHS and 23 horses without any noticeable signs of CHS.
• For intradermal testing, the horses were injected with a sterile Culicoides extract, histamine as a positive control, and physiological saline as a negative control. All injections were made in the dermis of the mid-region of the neck.
• The researchers analyzed the reactions at 24 hours after the injections. A valid cut-off for identifying horses with CHS was established at a 1 cm wheal and a skinfold thickness increase of more than 10%.
• In parallel with intradermal testing, serum samples from the horses were analyzed using SDS-PAGE and Western blotting (W-B). The Culicoides extract was run on a 12% polyacrylamide gel for the W-B assay.

Findings of the Study

• Using the established cut-off values, the intradermal test demonstrated 100% sensitivity and specificity for detecting CHS, even during winter seasons when visible signs of hypersensitivity may be absent.
• The Western blot assay revealed multiple bands in a molecular weight range of 6 to 200 kDa. Among them, a 65 kDa band was found predominantly in horses with hypersensitivity, as detected by an anti-IgE antibody. The same band was primarily detected in normal horses using an anti-IgG antibody.
• This result suggests that the 65 kDa band probably represents the allergen responsible for CHS in hypersensitive horses.

Significance of the Research

• The results of this study show that the intradermal test is a valid diagnostic tool for CHS in horses, with high sensitivity and specificity.
• The identification of a probable allergen for CHS in the form of the 65 kDa band can contribute to furthering our understanding of equine hypersensitivity conditions and aid in the development of targeted treatments.