A dot immuno-gold filtration assay(DIGFA)for porcine reproductive and respiratory syndrome virus(PRRSV)was developed.Rabbit anti-PRRSV IgG was obtained from the rabbit immunized with the purified PRRSV and confugated t o immunogold.15 clinical samples were detected,3 of which were positive both in DIGFA and cell culture,and the virus particles of PRRSV could be seen by EM.It s howed that the DIGFA is a sensitive,specific,simple and rapid assay for detectin g PRRSV.

A pair of oigonucleotide primers appropriate for PCR amplication were selected based on the two conserved regions of the 5^ end of the gene encoding the S protein of TGEV. A reverse transcription-polymerase chain reaction (RT-PCR) assay was developed for the detection of TGEV after optimization of the reaction conditions. The sandwich ELISA was also used for control. Out of 56 fecal samples, 20 were positive detected by RT-PCR, meanwhile only 14 were positive detected by sandwich ELISA. The corresponding rate of the two methods was 89%. It suggests that RT-PCR is more sensitive than sandwich ELISA and should be quite useful for detection of TGEV and the epidemiiological survey of TGE.