| Abstract: | A key factor in the hygienic application of embryo transfer (ET) and its associated technologies is effective risk management. This depends on knowing what the risks of infectious disease transmission are and how they can be reduced or removed. Risk assessment depends on a knowledge of the pathogenesis of the disease, the procedures used in ET and its associated technologies and the results from research into infectious disease transmission by embryos or through ET. Two approaches can be taken to ensure the safe health status of the embryo: 1) by determining that the donor animals (male and female) are free from specific diseases, or 2) by ensuring that the zona pellucida (ZP)-intact embryo is collected in a sanitary manner and handled (washed, treated, evaluated, etc.) according to recommended procedures. The former approach is applicable to diseases on which no or insufficient research has been done to determine the risk of their being transmitted by embryos or where the results of research done indicate a risk of the disease being transmitted. The latter approach is a preferred option with diseases where results of research done indicate that the risk of their being transmitted by embryos collected from infected or recovered donors is negligible. Infectious diseases for which research results indicate negligible risk of transmission by ZP-intact (ZP-I) embryos collected from infected or recovered donors include: pseudorabies (Aujesrky's disease), hog cholera (swine fever), foot and mouth disease, and swine vesicular disease. Infectious diseases on which insufficient research has been done include: African swine fever, vesicular stomatitis, enterovirus disease, parvouirus disease and leptospirosis. A problem associated with this approach is ensuring that procedures shown to be effective under experimental conditions are properly carried out under field conditions: the use of nationally accredited embryo collection teams may solve this problem. Healthy recipients and good record keeping are also critical factors in the hygienic application of ET. The health status of an embryo collected from a specific disease-free donor will not be adversely affected by damage to its ZP. Where research has shown that ZP-I embryos that have been exposed to particular pathogens are not infected or contaminated after proper washing or washing and treatment, it can be assumed that the risks of transmission of the diseases caused by these pathogens will not be increased by deliberate (micromanipulation) or accidental damage to the ZP after the washing/treatment procedures have been carried out. The risks of infectious disease transmission when embryos are produced by in vitro fertilization or blastomere transplantation to mature oocytes, followed by culture, have yet to be determined. |
