In situ hybridization of eye from bioassay. Example of confocal photomictographs of the fasciculated zone of the eye of a challenged shrimp specimen from test 2, postive for both LSNV and ICE by RT-PCR. a) Phase image; b) Image showing positive fluorescence for LSNV in the fasciculated zone under the retinal layer that is below the false-positive fluorescence of the crystalline tracts; c) Image showing positive fluorescence for ICE in the fasciculated zone with false-positive fluorescence as in image (b). d) Combined images showing co-localized positive fluorescence (yellow) for ICE and LSNV in the fasciculated zone and false positive fluorescence in the crystalline tracts. Negative control images are shown in Additional file 5.