We investigated mosquito and bird involvement in West Nile virus (WNV) transmission in July 2001 in Jefferson County, FL, and Lowndes County, GA. We detected 16 WNV-infected pools from Culex quinquefasciatus, Cx. salinarius, Cx. nigripalpus, and Culiseta melanura. In Florida, 11% of 353 bird sera neutralized WNV. Antibody prevalence was greatest in northern cardinal (Cardinalis cardinalis, 75%), northern mockingbird (Mimus polyglottus, 50%), common ground-dove (Columbina passerina, 25%), common grackle (Quiscalus quiscula, 15%), domestic chicken (Gallus gallus, 16%), and house sparrow (Passer domesticus, 11%). Antibody-positive birds were detected in nine of 11 locations, among which prevalence in chickens ranged from 0% to 100%. Seropositive chickens were detected in Georgia as well. The primary transmission cycle of WNV in the southeastern United States apparently involves Culex mosquitoes and passerine birds. Chickens are frequently infected and may serve as effective sentinels in this region.

A DNA vaccine for West Nile virus (WNV) was evaluated to determine whether its use could protect fish crows (Corvus ossifragus) from fatal WNV infection. Captured adult crows were given 0.5 mg of the DNA vaccine either orally or by intramuscular (IM) inoculation; control crows were inoculated or orally exposed to a placebo. After 6 weeks, crows were challenged subcutaneously with 105 plaque-forming units of WNV (New York 1999 strain). None of the placebo inoculated–placebo challenged birds died. While none of the 9 IM vaccine–inoculated birds died, 5 of 10 placebo-inoculated and 4 of 8 orally vaccinated birds died within 15 days after challenge. Peak viremia titers in birds with fatal WNV infection were substantially higher than those in birds that survived infection. Although oral administration of a single DNA vaccine dose failed to elicit an immune response or protect crows from WNV infection, IM administration of a single dose prevented death and was associated with reduced viremia.

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.

This HCV RDT comparison identified significant sensitivity differences, particularly using whole blood under extreme storage and testing conditions. These data support OraQuick HCV superiority and illustrate the value of RDT evaluation under simulated field conditions.