MORPHOMETRIC ANALYSIS OF GROWTH-RETARDATION IN FETAL LAMBS FOLLOWING EXPERIMENTAL-INFECTION OF PREGNANT EWES WITH BORDER-DISEASE VIRUS

The onset of growth retardation was investigated in fetal lambs follow ing experimental infection of pregnant ewes with Border Disease virus (BDV) on day 53 of pregnancy. Fetuses from control and infected ewes w ere harvested at weekly intervals between day 60 and day 95 of gestati on and morphometric studies were completed on tibial radiographs and t ibial growth cartilage metaphyseal junctions. Mean tibial areas were s ignificantly reduced (P<0.01) in fetuses from infected ewes at 35 and 42 days after infection and growth cartilage metaphyseal junctions wer e less mature in fetuses from infected ewes at 42 days after infection . Positive immunostaining for BDV antigen was demonstrated in the brai ns of all fetuses from infected ewes between 14 and 42 days after infe ction. Attempts to demonstrate BDV antigen in bone proved unsuccessful . It is concluded that intrauterine growth retardation is an early man ifestation of BDV infection in lambs and that the process is initiated shortly following infection of the fetus.