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

ABSTRACT

BACKGROUND: House dust mite (HDM) and storage mite (SM) stable fauna and their associated equine intradermal test (IDT) threshold concentrations (TCs) for the midwestern region of the USA are unknown. HYPOTHESIS/OBJECTIVES: To determine IDT TCs and serum IgE concentrations for two HDM and three SM species in clinically normal horses over two seasons, and to identify the mite taxa and habitats in a stable. ANIMALS Thirty-eight clinically normal horses. METHODS: Threshold concentrations for HDMs and SMs were determined using IDT subjective measurements and a statistical model. An enzyme-linked immunosorbent assay was used to quantify serum IgE concentrations for the same mite species. A modified flotation method was used to identify morphologically HDMs and SMs. RESULTS: Subjective IDT TCs were as follows 180,000 w/v for Dermatophagoides farinae in both seasons; 180,000 w/v in spring and 1160,000 w/v in late summer for Dermatophagoides pteronyssinus; 140,000 w/v in spring and 120,000 w/v in late summer for Acarus siro; 120,000 w/v for Lepidoglyphus destructor in both seasons; and 120,000 w/v in spring and 110,000 w/v in late summer for Tyrophagus putrescentiae. Statistically significant associations for increased serum IgE and a positive IDT reaction were evident for D. farinae in the spring and D. pteronyssinus in both seasons. One mite from all four genera specific to this study was identified; however,two HDM and A. siro species were not detected.Conclusions and clinical importance ­ This study established HDM and SM IDT dilution concentrations for the horses in this region. Exposure to diverse acaridae fauna may contribute to the pathogenesis of equine allergic disease.