Procedures for a viral replication in excised fin tissue (VREFT) assay were adapted to Pacific herring, Clupea pallasii, and optimized both to reduce processing time and to provide the greatest resolution between naïve herring and those previously exposed to viral haemorrhagic septicaemia virus (VHSV), Genogroup IVa. The optimized procedures included removal of the left pectoral fin from a euthanized fish, inoculation of the fin with >10(5) plaque-forming units (PFU) mL(-1) VHSV for 1 h, rinsing the fin in fresh medium six times to remove unadsorbed virions, incubation of the fin in fresh medium for 4 days and enumeration of the viral titre in a sample of the incubation medium by plaque assay. The optimized VREFT assay was effective at identifying the prior exposure history of laboratory-reared Pacific herring to VHSV. The geometric mean VREFT value was significantly greater (P < 0.01) among naïve herring (1.2 × 10(3) PFU mL(-1) ) than among groups that survived exposure to VHSV (1.0-2.9 × 10(2) PFU mL(-1) ); additionally, the proportion of cultures with no detectable virus was significantly greater (P = 0.0002) among fish that survived exposure to VHSV (39-47%) than among naïve fish (3.3%). The optimized VREFT assay demonstrates promise for identifying VHSV exposure history and forecasting disease potential in populations of wild Pacific herring.

Previous reports of difficulties using immunohistochemical methods on mummified tissues attributed the problems mostly to the antiquity of the material. We examined mummified examples of contemporary human tissues (carotid endarterectomy specimens) obtained for research purposes, using 1) desiccation as an example of natural mummification, and 2) natron treatment (Egyptian mummification) followed by desiccation in controlled simulated desert conditions lasting up to 20 months and various reconstitution regimens. The remaining untreated tissues, fixed routinely in formalin and processed to paraffin blocks, served as a control. Additionally, we examined a contemporary human sural nerve bundle mummified in the Egyptian manner by the LIU-UMAB Mummy Project. All tissues were subjected to the same immunohistochemical procedures. There were differences in the degree of antigenicity between matching samples (desiccated only and natron treated) when comparing the same antigens. Thus, the initial mummification procedure has a crucial effect on the preservation of tissue antigenicity.