Abstract
The VecTest antigen-capture assay for West Nile virus was performed on oral and tissue swabs from dead birds in New York State from April 2003 through July 2004. Results were compared with those from real-time reverse transcriptase-polymerase chain reaction of kidney or brain. Oral VecTest sensitivity is adequate for surveillance in American Crows (Corvus brachyrhynchos) (87%), Blue Jays (Cyanocitta cristata) (80%), and House Sparrows (Passer domesticus) (76%). Oral VecTest performed well for small samples of American Kestrels (Falco sparverius), Northern Cardinals (Cardinalis cardinalis), Common Grackles (Quiscalus quiscula), and House Finches (Carpodacus mexicanus). Poor sensitivity occurred in most raptors, Mourning Doves (Zenaida macroura), Fish Crows (Corvus ossifragus), and American Robins (Turdus migratorius). Specificity was excellent (98%), except for false-positive results that occurred mostly in Gray Catbirds (Dumatella carolinensis), Green Herons (Butorides virescens), and tests of blood and tissues. Feather pulp and kidney may be useful for VecTest assays in corvids.
Highlights
After West Nile virus (WNV) was discovered in birds, horses, and humans in New York State in 1999 [1], the New York State Department of Health established a surveillance system to follow seasonal and geographic trends in WNV activity [2]
The Wildlife Pathology Unit necropsies priority birds and collects tissues, which are sent to the health department’s Arbovirus Laboratory, where they are tested for WNV RNA by real-time reverse transcriptase–polymerase chain reaction (RT-PCR) [3]
Poor VecTest sensitivity was recorded in small numbers of Mourning Doves (Zenaida macroura) (0/6), American Robins (Turdus migratorius) (3/16), and Fish Crows (Corvus ossifragus) (2/10)
Summary
In the dead bird testing program, birds are reported by the public and submitted (largely through county health departments) to the Wildlife Pathology Unit of the New York State Department of Environmental Conservation. The Wildlife Pathology Unit necropsies priority birds and collects tissues, which are sent to the health department’s Arbovirus Laboratory, where they are tested for WNV RNA by real-time reverse transcriptase–polymerase chain reaction (RT-PCR) [3]. Since WNV was detected in New York in 1999, the Wildlife Pathology Unit and the Arbovirus Laboratory have processed >19,000 specimens as part of the surveillance program. The elapsed time between the initial reporting of a dead bird and posting of the RT-PCR results on the surveillance system’s Health Information Network, an Internet-based data and information tracking system [4], can be as long as 3 weeks. We explored use of the VecTest with swabs from the cloaca, feather pulp, and internal tissues to determine whether use of other antigen sources might improve the sensitivity of the test
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