EVALUATION OF THE AGAR-GEL IMMUNODIFFUSION TEST FOR THE DETECTION OF PRECIPITATING ANTIBODIES AGAINST PROGRESSIVE PNEUMONIA VIRUS OF SHEEP

Various cell cultures were evaluated for their ability to support progressive pneumonia virus infection in vitro. Ovine trachea cells supported progressive pneumonia virus infection for an extended time, were extremely durable and could be passaged up until 30 passages. Progressive pneumonia virus-infected ovine trachea cells were then used for the production of antigen [Ag] for agar-gel immunodiffusion. A method for concentrating Ag, diafiltration, was compared to dialysis against polyethylene glycol. Using diafiltration, the concentrated virus was easily quantitated, less viscous (and easier to apply) and only produced 1 precipitation line. Agar-gel immunodiffusion was used to survey 401 animals from 2 sheep flocks. One flock (96 sheep) was free of progressive pneumonia while the other flock had 111 of 305 total animals positive for precipitating antibodies [Ab]. The incidence of precipitating Ab in sheep ranged from 23% for yearling ewes to 80% in ewes 7 yr old.