Avian mortality surveillance for West Nile virus in Colorado.

We tested 1,549 avian carcasses of 104 species to identify targets for West Nile virus (WNV) surveillance in Colorado, determine species affected by WNV, compare virus isolation versus RNA detection applied to hearts and oral swabs from carcasses, and compare the VecTest WNV Antigen Assay (VecTest) to standard assays. Forty-two species tested positive. From June to September 2003, 86% of corvids, 34% of non-corvid passerines, and 37% of raptors tested positive. We developed the Target Species Index, which identified American crows as the most important avian indicator species. However, testing multiple species maximizes detection, which may be important early and late in the transmission season. This index may benefit surveillance for other zoonotic pathogens, such as highly pathogenic avian influenza H5N1 virus. VecTest using oral swabs was most sensitive for American crow, black-billed magpie, house finch, house sparrow, and American kestrel. Wildlife rehabilitation centers should be recruited to enhance WNV surveillance.

West Nile virus survey of birds and mosquitoes in the Dominican Republic.

We report West Nile virus (WNV) activity from a new area on Hispaniola, in the vicinity of Monte Cristi National Park in northwest Dominican Republic. Specific anti-WNV antibodies were detected in 12 of 58 (21%) resident birds sampled in March 2003, representing six species in the orders Cuculiformes (cuckoos), Strigiformes (owls), and Passeriformes (song birds). This seroprevalence is the highest reported from any site in the Caribbean Basin. Virus was not detected in any mosquitoes or tissues from bird specimens. Testing of 20 sick or dead birds was negative for WNV. Undetermined flavivirus antibodies were detected in four resident birds at Monte Cristi, as well as in five resident birds at Sierra de Baoruco National Park in southwest Dominican Republic. These data suggest that an unidentified flavivirus, as well as WNV, is active in the Dominican Republic.

Sentinel pigeon surveillance for West Nile virus by using lard-can traps at differing elevations and canopy cover classes.

Sentinel pigeons, Columba livia, were installed in lard-can traps at heights of 1.5 m and 7.6-9.1 m within differing canopy cover classes in New York City. Adult mosquitoes were collected weekly from July to October 2002, as were serum samples from each pigeon. Culex pipiens L. and Culex restuans Theobald comprised 97% of mosquitoes collected and were most numerous in canopy-level, forested traps. The West Nile virus (family Flaviviridae, genus Flavivirus, WNV) seroconversion rate was significantly greater for pigeons in canopy-level traps, although seroconversions occurred concurrently with human cases in the city and were of little prognostic value to public health agencies. Our results indicate that sentinel pigeons were most effective for monitoring enzootic transmission of WNV when placed in single-sentinel caging 7.6-9.1 m above ground level.

Alligators as West Nile virus amplifiers.

Recent evidence suggests that American alligators (Alligator mississippiensis) may be capable of transmitting West Nile virus (WNV) to other alligators. We experimentally exposed 24 juvenile alligators to WNV parenterally or orally. All became infected, and all but three sustained viremia titers >5.0 log10 PFU/mL (a threshold considered infectious for Culex quinquefasciatus mosquitoes) for 1 to 8 days. Noninoculated tankmates also became infected. The viremia profiles and multiple routes of infection suggest alligators may play an important role in WNV transmission in areas with high population densities of juvenile alligators.