May 1, 2002

BATON ROUGE–LSU researchers in the School of Veterinary Medicine have begun a study to investigate the effect of viral infections on the immune response of neonatal foals, specifically if exposure to influenza virus reduces the risk for developing recurring airway obstruction (RAO) later in life.

"This study is an evolution of many things we’ve been investigating to understand equine airway disease. It’s become pretty obvious that RAO disorders are a result of allergic reactions," said Dr. David Horohov, principal investigator and professor of veterinary immunology. "With this study, we’re hoping to provide insight into the consequence of early viral exposure and the tendency of horses to develop allergic immune response in their lungs," said Horohov.

Fifteen to 20 percent of horses worldwide suffer from RAO, a condition similar to human asthma, representing a significant impact on the equine population and industry. While RAO typically affects older horses, younger horses may have a less severe form of the disease. There is also evidence of a relationship between other inflammatory airway disease in young performance horses and RAO in older horses. All breeds of horses are affected.

Although it is believed that RAO develops from allergic reactions, researchers still question why the other 80 percent of horses worldwide are not susceptible to the allergic airway response even though they may be exposed to the same allergens.

It is currently believed that exposure to infectious agents early in life may help prevent later allergic complications. In other related studies, heavily parasitized horses were protected, while other horses were more susceptible to the development of allergic airway response. According to Horohov, this is similar to what may be seen in humans in underdeveloped countries. "Asthma problems were not typical in underdeveloped countries until the incidence of parasitism and other infectious diseases was reduced through the use of modern drugs and vaccinations," he said.

It has also become clear through research that the programming of children for allergic diseases happens early on, and it is believed a similar situation occurs in horses to predispose airway problems.

Taking the past research into consideration and hoping to clarify new questions, the study will focus on the immune function of the foal’s respiratory system with two approaches. The first part of the study will focus on the immunologic capability of the foal’s lung during the first year of life. The second part will determine what effect a viral infection will have on the lung’s immune responsiveness.

Drs. Dale Paccamonti, Dennis French and Ralph Beadle from the Department of Veterinary Clinical Sciences are co-investigators of the study. This study is one of 22 research projects sponsored this year by the Grayson-Jockey Club Research Foundation of Lexington, Ky., which funds equine health research. Horohov received $57,680 for the first year of study and will receive $70,000 for the second year.

This is the second study Horohov has conducted through the assistance of Grayson-Jockey Club. The first study explored Summer Pasture-Associated Obstructive Pulmonary Disorder, a form of equine RAO that affects horses in the southern United States. He determined that the disorder is a result of an allergic response to inhaled allergens. The current study hopes to identify immunological events that lead to the allergic response in the affected horses.

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