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Five-year surveillance of West Nile and Eastern equine encephalitis viruses in southeastern Virginia.

* An enhanced arbovirus and mosquito surveillance program began in southeastern Virginia in 2000.

* 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
Geographic Code:1U5VA
Date:May 1, 2006
Words:387
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