VIRUS TRANSMISSION THROUGH EMBRYO TRANSFER IN SWINE
Abstract
The potential for infectious disease dissemination through embryo transfer was investigated using porcine embryos exposed to pseudorabies virus (PrV), porcine parvovirus (PPV), or enteric cytopathic orphan viruses 3 and 6 (ECPO-3, ECPO-6). Embryos were exposed to PrV by cultivation on virus inoculated cell monolayers, cultivation in a virus suspension, or by inoculation of embryo donors before ovulation. Cultivation on virus inoculated cell monolayers was the only method used for embryo exposure to the other three viruses. Electron microscopy (EM) procedures were used to study the interactions that occurred between each of the viruses and the embryos. In addition, embryos exposed to PrV in vitro or in vivo were transferred to susceptible recipients. PrV was transmitted to 5 of 9 recipients of embryos exposed for 1 hour to virus in vitro, and 2 of 8 recipients of embryos from PrV exposed donors. Through the use of EM procedures, it was discovered that PrV adsorbed to the zona pellucida of the embryo within 1 hour of in vitro exposure to virus. Longer exposure times increased the number of virions on the zona pellucida. PrV resisted removal from the zona pellucida when embryos were washed by serial passage through aliquots of cell culture medium before fixation. PrV was also observed in sperm tracks within the zona pellucida both before and after the embryos were washed. PPV, ECPO-3, and ECPO-6 were discovered enmeshed in cell debris on the zona pellucida surface, or in the pores that were interspersed among the fibers of the zona pellucida. Examination of the ultra-structure of embryos exposed to the viruses did not provide evidence of penetration of the zona pellucinda and interaction between the viruses and the cells of the embryo.
Degree
Ph.D.
Subject Area
Veterinary services
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