We are happy to announce our platform for molecular testing of IgE sensitizations is ready for commercial allergy testing in horses. 

The Pet Allergy Explorer (PAX®) for horses is very similar to the PAX® for dogs. Like its canine counterpart, the equine test is based on macroarray cartridges and uses equipment that is comparable to the testing done in humans. The test is developed by the ALEX2 of the Macroarray Diagnostics (MADx) company in Vienna, Austria. However, there are some differences when compared to the test for canines, as listed below. 

An expanded list of allergens

Our Head of R&D, Prof. Thierry Olivry, scouted the existing literature looking for molecular allergens that are already described in sensitizing horses with allergic dermatitis, insect-bite hypersensitivity and asthma or reactive airway diseases. Specific relevant horse allergens were then added to the existing cartridges used for dogs, as they overlap. Added allergens fall in three main categories: biting insect extracts and components, seed extracts and latex components. Here are notable additions:

• Biting insects. PAX® now includes whole-body extracts of biting insects like Aedes mosquitoes, Culicoides  midges, Stomoxys stable flies and Tabanus horse flies. An important addition are the salivary allergens from Culicoides obsoletus that have been shown to help with the diagnosis of equine insect bite sensitivity.
• Seed extracts. Horses have been shown to develop IgE sensitization to some of the seeds they eat, and such extracts were added (e.g., cottonseed, sunflower seed, linseed, lupine seed, Sorghum). Fag e 2 from buckwheat was also added as a component reported as important for horses.
• Latex components. Latex may not be the first substance that comes into mind when thinking about proteins. Still, we added five individual latex proteins, because there are several reports in the equine asthma literature of IgE sensitization to latex, which might have occurred after training or walking on rubber mats and aerosolization of latex particles. After all, latex-induced asthma is also an occupational allergy in horse trainers. 

A well characterized anti-IgE monoclonal antibody

After testing a few antibody candidates, our R&D team selected the monoclonal antibody 3H10, which was first developed in Dr. Douglas Wilson’s laboratory in Bristol. This monoclonal only recognizes horse IgE, and does not cross-react with other equine immunoglobulin types. Moreover, this mAb had already been used in several important equine allergy studies.

The PAX® test for horses was then validated using the same criteria as for the human test. The chosen mAb passed the tests with flying colors except for one minor point: hemolysis in the serum might reduce the positivity of low-positive sensitizations, so a good sample collection is important.
Once the test had passed its validation, our laboratories tested 1,150 equine sera in July. This testing allowed us to select the same positivity threshold as for dogs, being 28 ng/ml.

A sneak preview of the main sensitizations in horses

Here are the top five sensitizations in the of the main allergen categories, which confirm previously reported findings:

Environmental allergens 

• Tyrophagus storage mite extract
• Dermatophagoides farinae house dust mite extract
• American cockroach tropomyosin Per a 7
• Latex component: Hev b 11
• Culicoides obsoletus salivary component Cul o 8

Food allergens

• Apple component Mal d 1
• Cottonseed extract
• Apple component Mal d 3
• Lentil component Len c 2
• Pea extract

Venom allergens

Yes, horses are stung (and then sensitized) by bees (Api m 1 and 3 components) and wasps (Ves v extract and Ves v 5 components).

For more detailed information about PAX®, read our PAX® blog.