Attenuation of turkey rhinotracheitis virus by alternative passage in embryonated chicken eggs and tracheal organ cultures.

Turkey rhinotracheitis virus (TRTV) was still infective for turkey poults after 30 cycles of alternate passages in 9-day-old chicken embryos and tracheal organ cultures. It caused only mild, transient respiratory signs yet protected against challenge with virulent TRTV 21 days later. It is suggested that this attenuated strain has potential for use as a vaccine.