Occurrence of Salmonella in tortoises in a rescue centre in Italy

enter sperm cells and oocytes. More recently, the proviral DNA of bovine immunodeficiency virus was detected in association with frozen bull semen, but the transmission ofthe virus to oocytes by infected sperm during fertilisation was not investigated (Nash and others 1995). Since the swim up procedure generates a practically clean motile sperm fraction which is free of other cells, it is conceivable that BLV becomes associated with some sperm cells and is carried through the zp into oocytes during fertilisation which most likely were resistant to the viral infection. Since all IVF embryos tested negative, it can be speculated that the sensitivity of the PCR was insufficient to detect the proviral DNA associated with a single sperm cell introduced into embryos during fertilisation. It is also possible that the proviral DNA was adversely affected by the incubation conditions of embryos during the eight days after fertilisation. Although in this study, all embryos tested negative for proviral DNA, it is advisable for IVF practitioners to use semen from bulls free of BLV. Also, in view of the fact that as little as 1 [d of BLV-infected blood can be sufficient to transmit the disease (Evermann and others 1986), efforts should be made to limit the amount of aspirated blood associated with the follicular fluid during oocyte retrieval, and special attention should be paid when washing embryos (Stringfellow and Seidel 1998). In conclusion, these results indicate that IVF embryos generated in the presence of BLV do not appear to be associated with infectious BLV, as previously demonstrated for in vivo produced embryos. However, experiments involving the transfer of IVF embryos are needed to verify these studies. Further studies on the interaction of BLV with sperm cells also appear to be warranted.