Congenital infections with nonarbo togaviruses

The present review deals with the similarities and differences of selected aspects of prenatal pestivirus infections of domestic animals and congenital rubella of man. Hog cholera virus, bovine virus diarrhoea virus and border disease virus are antigenically closely related, but unrelated to rubella virus. The nonarbo togaviruses are capable of producing congenital infections resulting in a wide spectrum of abnormalities. The infected foetus can die in utero, in the neonatal period, or it may be born with teratogenic defects. In addition, apparently healthy progeny can be delivered that develop a late onset disease, months, or years after birth, or remain clinically normal for life. The ultimate outcome of a congenital infection is mainly determined by the stage of foetal development, at which infection occurs. Foetuses exposed to rubella virus raise an antibody response to the virus, whereas domestic animals frequently fail to respond immunologically to a congenital pestivirus infection. In congenital rubella the virus usually disappears from the host's body 1-2 years after birth. However, congenital pestivirus infections may be characterized by a lifelong and widespread persistence of virus in clinically healthy animals. Such animals are of significance in the epizootiology of bovine virus diarrhoea, border disease or hog cholera.