In situ hybridization for the detection of transmissible gastroenteritis virus in pigs and comparison with other methods

Archived formalin-fixed, paraffin-embedded tissues from 25 pigs naturally i nfected with transmissible gastroenteritis virus (TGEV) were examined by in situ hybridization for TGEV nucleic acid using a nonradioactive digoxigeni n-labeled cDNA probe that targeted the nucleocapsid sequence of TGEV strain s. The results of in situ hybridization for the detection of TGEV were comp ared with virus isolation (VI), a fluorescent antibody test (FAT), and tran smission electron microscopy (TEM). VI, FAT, and TEM were tested over a cou rse of time before the in situ hybridization was performed. Positive hybrid ization signals were detected in duodenal, jejunal, and ileal enterocytes f rom 21 pigs. Hybridization signals were confined to the cytoplasm. Intestin al specimens from 25 piglets were evaluated by 4 tests. Twenty-one of 25 we re positive by in situ hybridization. Of these 21 samples, 5 (24%) were pos itive for TGEV by all 4 tests, 15 (71%) were positive by FAT, 14 (67%) were positive by VI, and 6 (29%) were positive by TEM. In situ hybridization fo r the detection of TGEV in formalin-fixed, paraffin-embedded tissues provid es a rapid means of confirmation of a histopathological diagnosis of TGEV w ithout virus isolation, or when only formalin-fixed intestinal specimens we re available.