ABSTRACT. The enzyme-linked immunosorbent assay (ELISA) and the fluorescent antibody test (FAT) were compared for their sensitivity in detection of Renibacterjum salmoninarum (Rs) in kidney tissues of Alaskan salmonids. The ELISA appeared to be more sensitive in detecting Rs infections. The FAT did not detect Rs in 80 % of the ELISA-positive samples but was positive for Rs in 28 'K, of the samples that were ELISA-negative. This contradiction may have been due to low-level washover of Rs cells from smears containing large numbers of Rs cells when slldes containing nlultiple samples were rinsed in d common vessel during the FAT procedures. The FAT routinely did not detect infections in Rs-positive fish the tissues of which produced a mean ELISA optical density value 50.173, and inconsistently detected infections in fish with ELISA values > 0.173 but < 0.978. The 0.978 optical density was the mean ELISA value at which the FAT routinely detected Rs-positive fish. Based on the ELlSA results, Rs occurred in only 9 % of the Alaskan Pacific salmon tested in both wild (85 "/U) and hatchery (81 %) stocks. The very high stock prevalences and levels of Rs antigen detected in wild trout Oncorhynch~~s spp., char Salvelinus spp., and grayling Thymallus arcticus having no clinical signs of bacterial kidney disease suggest these species may be somewhat resistant hosts and important freshwater reservoirs of Rs.

Kldney tissues from 5231 chinook salmon Oncorhynchus tshawytscha and 3793 coho salmon 0. kisutch adults used for spawnlng were examined for soluble antigen of Renibacterium salmo-11inarum (Rs) by the enzyme-linked lmmunosorbent assay (ELISA). The purpose of this study was to develop an extens~ve data base for establishing a negative-positive threshold optical density value for Rs-negative and-positive fish uslng commercially available ELISA reagents. Statistical evaluation of the estimated distribution of Rs-negative optical density values from coho a n d chinook salmon indicated the preliminary estimated negative-positive threshold value of 0.1 was not conservative enough. i.e. there was an unacceptably high probability that a large number of low-level Rs-positive fish were not identified. Consequently, a more conservative threshold value of 0.095 was chosen that erred in ~dentifying an acceptably low number of negative fish a s positive. At this threshold optical density value the ELISA could detect about 20 ng of Rs antigen ml-l of kidney homogenate.

A universal childhood VZV vaccination strategy will need to take account of the increase in incidence of VZV infection in children under the age of 4 years; hence, the suggested target age would be between 12 and 18 months---soon after the disappearance of maternal antibody.

Rodent sentinel screening for adventitious pathogens is an integral part of many biomedical research institutes and universities that use rodents in research. Typical screening programs involving live sentinel animals typically purchase young SPF sentinel animals that are sampled and replaced quarterly. Previous reports suggest that mice as old as 6 mo are effective sentinels for various agents. In efforts to reduce the number of animals used in our sentinel program, we wanted to investigate the possibility of keeping sentinel animals inhouse for 12 mo at a time. We exposed mice (age, 40 to 48 wk) to murine norovirus (MNV) to test whether they could reliably produce detectable levels of antibodies (similar to younger mice) to this adventitious pathogen. Mice first exposed to MNV at 40 to 48 wk of age seroconverted to MNV after both direct inoculation (through gavage) and indirect exposure (from soiled-bedding transfer) at the same or greater frequency than mice first exposed at 8 to 12 wk of age. These findings indicate that, at least for MNV, sentinel residence time can be extended from 3 to 12 mo without compromising the reliability of seroconversion, thus ultimately reducing sentinel animal numbers. This practice, combined with nonanimal testing modalities (for example, exhaust duct sampling), can increase the sensitivity and specificity of rodent surveillance programs and minimize the use of live animals.

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