Five-year surveillance of West Nile and Eastern equine encephalitis viruses in southeastern Virginia.
* The area is characterized by both urban and wetland ecologies.
* It is the home of the Great Dismal Swamp, migratory and permanent bird sanctuaries, and the largest U.S. naval base.
* The wetlands provide an ideal place for mosquito breeding.
* The bird sanctuaries provide an abundance of hosts for the mosquitoes to feed upon.
* The large Navy installation may be an attractive target for bioterrorism.
* Easter equine encephalitis (EEE) is classified as a select agent for bioterrorism.
* Mosquito pools were monitored to determine the occurrence of West Nile virus (WNV) and EEE in the environment.
* Only one WNV-infected mosquito pool was detected in 2001, in September.
* Peak WNV activity occurred in August in 2003 and 2004 and in October in 2002.
* Peak EEE activity was observed in July in three years--2001, 2003, and 2004.
* In 2004, the EEE activity extended into November.
* Overall, Culiseta (Cs.) melanura and Culex (Cx.) pipiens were the primary vectors for EEE and WNV.
* The bridge vectors Cx. salinarius, Aedes vexans, and Anopheles crucians also contributed to arboviral activity.
* In 2004, WNV infection in Cx. pipiens reached the level of infection in Cs. melanura.
* This finding may indicate a shift in vector preference or availability.
* Or it may be attributable to more consistent use of gravid traps for Cx. pipiens.
* But since Cx. pipiens is a potential bridge vector, this shift might increase the risk of epizootic transmission in future seasons.
* Chicken sera were also collected.
* Chickens are well suited to serve as sentinel birds.
* They exhibit a transient viremia that stimulates the production of IgM antibodies against both WNV and EEE.
* The authors calculated the seroconversion rate by dividing the number of IgM-reactive chickens by the total number of chickens tested.
* Both WNV and EEE activity in sentinel chickens peaked in 2003 and declined in 2004.
* The seroconversion percentage in 2004 was, however, greater than the percentages in 2000 through 2002.
* The dramatic increase in the virus activity over the study period could be a result of increased precipitation in 2003 and 2004.
* Or it could be an indication of a permanent increase in the distribution of the viruses in southeastern Virginia.
* The mounting evidence that arboviruses persist in their vertebrate hosts during the winter would suggest the latter.
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|Publication:||Journal of Environmental Health|
|Date:||May 1, 2006|
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