Bluetongue and equine viral arteritis viruses as models of virus-induced fetal injury and abortion

A number of viruses have the capacity to cross the placenta and infect the fetus to cause, among other potential outcomes, developmental defects (tera togenesis), fetal death and abortion. Bluetongue virus (BTV) infection of f etal ruminants provides an excellent model for the study of virus-induced t eratogenesis. This model has shown that only viruses modified by passage in cell culture, such as modified live virus vaccine strains, readily cross t he ruminant placenta, and that the timing of fetal infection determines the outcome. Thus, cerebral malformations only occur after fetal infection at critical stages during development and the precise timing of fetal BTV infe ction determines the severity of the malformation present at birth. Fetal B TV infection also can result in fetal death, followed by abortion or resorp tion, growth retardation, or no obvious abnormalities, depending on age of the conceptus at infection. Equine arteritis virus (EAV) infection of the e quine fetus causes fetal death and abortion but not teratogenesis. These tw o fetal viral infections are useful not only for the study of teratogenesis and fetal disease, but also to further characterize and compare the comple x process that is responsible for normal induction of parturition in rumina nts and horses. (C) 2000 Elsevier Science B.V. All rights reserved.