Embryo transfer from Brucellosis-positive donors: A field trial

Relative risks and approaches to biosecurity in the use of embryo technologies in livestock

Embryo technologies have been integrated into production systems for a variety of livestock species. As relates to transmission of infectious diseases, our working hypothesis has been that use of embryo transfer for distribution of germ plasm within and between herds and flocks is likely safer than the movement of postnatal animals. Indeed, research and experience generally have been supportive of this hypothesis. However, the relative risks of transmitting infectious agents via embryo transfer vary among donor species. Further, different methods of producing embryos appear to present different risks. This paper provides a comparative overview of the risks of transmitting infectious diseases via transfer of both in vivo- and in vitro-derived embryos in common domesticated livestock species. Also discussed are universal approaches to biosecurity in embryo production and transfer.

The dangers of disease transmission by artificial insemination and embryo transfer

This review summarizes the major infectious diseases of the three major agricultural species (cattle, sheep and pigs) and horses, and presents the evidence for and against the possibility of infectious agents being transmitted between animals via the venereal route or by the use of semen or early embryos in commercial artificial insemination (AI) or embryo transfer (ET). Cattle feature most prominently in the widespread distribution of frozen semen, and national and international organizations have set out guidelines to work towards disease-free bull studs with semen free from potential pathogens. With the control of major epizootic diseases, attention has been focused on such diseases as IBR, BVD and blue tongue, where clinical signs are rarely evident but the detection of virus in semen is of great importance. New information on the relevance of bacterial disease such as Mycobacterium paratuberculosis, campylobacteriosis and leptospirosis is reviewed, along with details of the mycoplasma and ureaplasma species of the bull's genital tract. Bovine spongiform encephalopathy (BSE) has attracted much research and semen is not regarded as a source of infection. New work on the pathogenesis of a number of diseases and the use of new biotechnology in diagnosis is included. The International Embryo Transfer Society (IETS) has encouraged a great deal of experimental work--much originating in Canada--on the risk of transmission of disease from donors to recipients via a 7-day-old blastocyst. There has been much success in demonstrating that with an approved protocol of handling the embryos, to date there is very little danger in disease transmission with both viruses and bacteria. The mycoplasma group appear more intractable and the role of BSE is still being evaluated. In sheep, scrapie, Brucella ovis infection and blue tongue feature in current work. In the pig there is a surge in international movement of pig semen, and Aujeszky's disease and the new so-called Blue Ear disease feature prominently. Much work is in progress on infectious agents likely to be found in the semen of stallions, with an expanding trade in the international movement of chilled and frozen semen. Equine embryo transfer experiments are hampered by the very limited number of embryos available. Reference is also made to the further risk of disease transmission by in vitro manipulated embryos.

The potential of embryo transfer for infectious disease Icontrol in livestock

This review of the general epidemiological aspects of embryo transfer indicates that the transfer of embryos provides the opportunity to introduce genetic material into populations of livestock while greatly reducing the risk for transmission of infectious diseases. Studies of specific diseases of livestock confirm that many pathogens are likely to be excluded when embryos are transferred. Twenty years of commercial embryo transfer under field conditions in a variety of species has not resulted in a single documented transmission of an infectious disease agent. Strategies for insuring that embryos are free of pathogens include the use of donors that are specific pathogen-free, washing of embryos, the trypsin treatment of embryos, or a combination of these methods. Although researchers continue to develop new procedures for the treatment of embryos to provide an even greater margin of safety, it is clear that existing techniques for the handling and transfer of embryos can be used to limit the spread of infectious diseases.

A serologic study of the progeny of a seropositive cow

This may be the first study to follow the offspring (obtained by natural mating and by embryo transfer) of a brucellosis seropositive cow. No positive reactors were found among the offspring and these findings support the hypothesis that brucellosis seropositive cows may be used as embryo donors.