Testing for Insect Hypersensitivity

Allergy testing is done in many species, including horses and humans. Unfortunately, testing to determine a horse is hypersensitive to insect bites is difficult.

According to a Swedish study, an IgE serum test is not specific enough and has too many false positive results to be used as a screening test for insect hypersensitivity (overreaction to insect bites).

"This disease (insect hypersensitivity) occurs seasonally, in horses of all ages and breeds, causing dermatitis and self mutilation," Maria Lendau, VDM, a researcher at the Swedish University of Agricultural Sciences, said at the 2006 American College of Internal Medicine Forum. "It would be useful to have a blood test to differentiate hypersensitive horses from those that are normal horses, but insect bitten."

Lendau and her colleagues examined the results of an IgE test on 22 horses during the summer of 2004. Half of the horses had been previously diagnosed with insect hypersensitivity and the other half (controls) were horses with no history of insect allergies. Each control horse was stable/pasture matched to one of the study horses to provide a control for that particular environment.

Blood samples were analyzed for IgE with a commercially available ELISA test. the results showed a large number of false positive results in the control group, but the test group had significantly higher levels of IgE in relation to the control group.

"The test results showed a high sensitivity and a low specificity (100% sensitivity, 20% specificity) for Culicoides (a type of biting insect)," Lendau explained. "Identification of a specific allergen is the first step to institute allergy reduction and avoidance measures."

About the Author

Chad Mendell

Chad Mendell is the former Managing Editor for TheHorse.com .

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