title: The importance of the zona pellucida for disease control in livestock by embryo transfer.
abstract: From the point of view of disease risk, the movement of livestock by embryo transfer is undoubtedly much safer for trading than the movement of live animals or semen. Nevertheless, strict governmental control by veterinary certification of health of embryos is still vital. In cattle, sheep and pigs, unlike laboratory species such as the mouse, infectious agents do not appear to pass through the zona pellucida (ZP) into the embryo proper. Some agents do, however, adhere firmly to the outer surface of the ZP, especially onto those of the pig. Disease risks associated with the inadvertent transmission of infectious agents when embryos are moved are, therefore, intimately connected with the nature and properties of the ZP. This article reviews current knowledge on the physical and adhesive properties of the ZP and discusses how risks associated with the possible presence of infection on its surface can be minimized. Further research is urgently needed so that realistic but safe veterinary certification of the health of embryos for international trade can be devised.
authors.forename: S S
authors.initials: SS
authors.lastname: Chen
authors.forename: A E
authors.initials: AE
authors.lastname: Wrathall
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D018407:Bacterial Physiological Phenomena; D004624:Embryo Transfer / Q000662:veterinary*; D007239:Infections / Q000635:transmission / Q000662:veterinary*; D010063:Ovum / Q000382:microbiology*; D018406:Virus Physiological Phenomena; D015044:Zona Pellucida / Q000382:microbiology*