Veterinarians have been using an antibody product to treat West Nile virus (WNV) clinical signs, but its use for this purpose is currently off-label (not approved by the USDA). Currently, the hyperimmune plasma product HiGamm-Equi, by Lake Immunogenics, is being examined by the USDA for conditional approval.

HiGamm-Equi is typically used for failure of passive transfer in foals–the horses from which the plasma is taken are heavily vaccinated against a multitude of diseases so that antibodies get passed on to the plasma recipient. In recent years, donor horses have been vaccinated against WNV, and tests have been performed to determine that grown horses given the plasma develop a WNV antibody titer of 1:20, which James L. Bowman, DVM, president of Lake Immunogenics, said is effective. He also reported that the firm’s study in hamsters indicates that the product is effective in eliminating the virus in the bloodstream when given before or after WNV challenge