Equine intradermal test threshold concentrations for house dust mite and storage mite allergens and identification of stable acari fauna.

This study concerns the determination of specific intradermal test threshold concentrations (how much is needed to trigger a reaction) for certain types of mites in horses in the midwestern USA. It also identifies the types of mite species present in the tested area during different seasons.

Methods

• The researchers studied 38 clinically normal horses. They used a process called intradermal testing (IDT) which involves injecting a small amount of mite allergens under the horse’s skin and observing the reaction. The purpose was to identify the threshold concentrations (TCs) – the smallest amount of an allergen which can trigger a reaction.
• The reactions were recorded using subjective measurements and a statistical model was used to analyze the data.
• The serum IgE concentrations (a type of antibody that the body produces in response to an allergen) for the same mite species were quantified using a technique known as an enzyme-linked immunosorbent assay.
• The types of mites (either house dust mites (HDMs) or storage mites (SMs)) were identified using a modified flotation method where the mites are made to float in a specific liquid solution and examined under a microscope.

Results

• The research identified various threshold concentrations for different types of mites in two seasons (spring and late summer). For example, a concentration of 1:80,000 w/v (weight/volume) was determined as the threshold for Dermatophagoides farinae mite in both seasons.
• Additionally, it was observed that there were statistical correlations between elevated serum IgE levels and a positive IDT reaction for D. farinae in spring and for Dermatophagoides pteronyssinus in both seasons.
• The study also identified the presence of four mite genera but did not detect two HDM and the storage mite Acarus siro species in the stables.

Conclusion and clinical significance

• The research established the IDT dilution concentrations for both house dust mites (HDM) and storage mites (SM) in horses in the tested region.
• It also suggested that exposure to a diverse range of acaridae (a large family of mites) could contribute to the development of allergy-related illnesses in horses.

This informs veterinary professionals of the potential allergens in this region and the concentration levels that could elicit a reaction, which can assist in the diagnosis and management of allergic reactions in horses.