Five-year surveillance of West Nile and Eastern equine encephalitis viruses in southeastern Virginia.* An enhanced arbovirus arbovirus Any of a large group of viruses that develop in arthropods (chiefly mosquitoes and ticks). The name derives from “arthropod-borne virus.” The spheroidal virus particle is encased in a fatty membrane and contains RNA; it causes no apparent harm to the 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 Great Dismal Swamp See 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 EEE eastern equine encephalomyelitis. EEE eastern equine encephalomyelitis. ) is classified as a select agent for bioterrorism. * Mosquito pools were monitored to determine the occurrence of West Nile virus West Nile virus, microorganism and the infection resulting from it, which typically produces no symptoms or a flulike condition. The virus is a flavivirus and is related to a number of viruses that cause encephalitis. (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 Anopheles: see mosquito. 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 gravid /grav·id/ (grav´id) pregnant. grav·id adj. Carrying eggs or developing young. gra·vid traps for Cx. pipiens. * But since Cx. pipiens is a potential bridge vector, this shift might increase the risk of epizootic ep·i·zo·ot·ic adj. Affecting a large number of animals at the same time within a particular region or geographic area. Used of a disease. ep 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 arboviruses (ar´bōvī´r  sz),n. persist in their vertebrate hosts during the winter would suggest the latter. |
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