Risks of transmitting mycoplasmas by semen and embryo transfer techniques in cattle, sheep, goats and pigs.
2007
Wrathall, A. E. | Ayling, R. D. | Simmons, H. A.
This object of this review is to consider whether mycoplasmas, particularly those that are important pathogens in cattle, sheep, goats and pigs, are likely to be transmitted by semen and embryo transfer techniques, and if so, what can be done to prevent such transmission. The first part gives a brief overview of semen and embryo transfer techniques, focusing on general risks of disease transmission and on routine disease control strategies. Subsequent parts provide information about mycoplasmas, including their classification, pathogenesis, diagnosis and control. Details are then given of the specific mycoplasmas of cattle, sheep, goats and pigs, and the seriously pathogenic species are distinguished from the opportunist pathogens and harmless commensals. It is emphasized, however, that within species the virulence of different strains can vary widely. An important feature of the mycoplasmas is that they often reside in the reproductive tracts of their hosts and therefore tend to pose a higher risk of being transmitted by semen and embryos than do many other micro-organisms. They also tend to adhere to cells and tissues, including semen and embryos, and can be difficult to remove. Some mycoplasmas can also invade and reside within non-phagocytic cells. Their resistance to routine disease control procedures such as semen and embryo washing, and to the inclusion of antibiotics in semen diluents and in embryo media, adds further challenges. It remains true, nevertheless, that semen and embryo transfer techniques offer great advantages over the movement of live animals for transferring genetic material, and will minimize the risks of disease transmission between different farms or countries. The review concludes by recommending control strategies, uniquely rigorous ones in this case, to avoid the transfer of mycoplasmas via semen and embryos.
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