Human and animal scientists have been researching ways to stimulate the immune system in order to prevent or mitigate disease, especially just prior to or during stressful events. Options include vaccination, antimicrobial therapy, and immunomodulation (altering the immune system).

Just prior to the annual convention of the 2005 American Association of Equine Practitioners in early December, Pfizer Animal Health held an educational session for veterinarians on equine immunology. Included in the presentations was a report of a study on an immunomodulator used in Europe since the 1990s and which was scheduled to be available in the United States in early February of 2006.

Rob Holland, DVM, PhD, discussed the contact challenge study (done in conjunction with John Donecker, VMD, MS) with the product Zylexis against equine herpesvirus (EHV), which can cause abortion as well as respiratory and neurologic problems.

The respiratory form of EHV-1 and EHV-4 were used to challenge yearlings in two different studies. Half were treated with Zylexis three days and one day prior to exposure to the virus, and again treated two and five days after challenge. Daily temperatures and nasal exudate scores were noted, daily blood samples were obtained for white blood count assays, and nasal swabs were used for virus isolation