EXPOSURE OF IN VITRO-PRODUCED BOVINE EMBRYOS TO FOOT-AND-MOUTH-DISEASE VIRUS

The aim of this study was to investigate whether foot and mouth diseas e virus (FMDV) interacts with in vitro produced (IVP) bovine embryos. One milliliter of a suspension of FMDV (2x10(7) TCID50/mL) was added t o several batches of these embryos 7 d after in vitro fertilization, b y which time they had either developed to the morula / blastocyst stag e (n = 256) or degenerated (n = 260). Six experiments were performed i n which developed or degenerated batches of embryos were incubated wit h FMDV for periods of 1 h (3), 2 h (2) or 4h (1). After this, the embr yos were washed 10 times according to the International Embryo Transfe r Society GETS), then pooled and ground up to form a suspension, and a ssayed on cell cultures for FMDV. The cell cultures were observed dail y for cytopathic effects for 3 d post exposure. In addition to the cel l culture method, the polymerase chain reaction (PCR) technique was us ed to assay for the presence of the virus in the washing fluids. Assay s for FMDV were also conducted on the first and second wash and on the pooled sample constituting the eigth, ninth and tenth wash. With the exception of the second wash from a batch of embryos exposed to FMDV f or 2 h, all samples of the first and second wash produced FMDV cytopat hic effects, but none occurred with the pooled samples of the 8th, 9th and 10th wash. FMDV was also isolated from ail but 1 of the batches o f embryos after 1 h of incubation, from 1 of 4 batches after 2 h of in cubation and from all batches after 4 h incubation. By contrast, the p resence of virus could not be demonstrated by PCR based on the techniq ue used here. These results show that 7 d old IVP bovine embryos can r etain FMDV after washing, unlike in vivo-derived embryos, which do not appear to carry risks of FMDV transmission when washed according to I ETS recommendations. Stricter controls are, therefore, necessary when using NP embryos from cattle in a non-FMD-free zone in domestic or int ernational trade. (C) 1998 by Elsevier Science Inc.