VECTOR-BORNE DISEASES, SURVEILLANCE, PREVENTION Mosquito and Arbovirus Activity During 1997–2002 in a Wetland in Northeastern Mississippi

The species composition and population dynamics of adult mosquitoes in a wetland near Iuka, MS, were analyzed over a 6-yr period (1997Ð2002) and reverse transcription-polymerase chain reaction(PCR)detection ratesof arbovirusesdeterminedduringÞveof thoseyears.Bloodmeals of three likely vector species were identiÞed using a PCR-based method that allows identiÞcation of the host to species. Culex erraticus (Dyar & Knab) composed 51.9% of the population during the 6-yr period with 295 females collected per trap night. Eastern equine encephalomyelitis (EEE) virus was detected in six genera of mosquitoes [Coquillettidia perturbans (Walker), Culex restuans Theobald, Culex salinariusCoquillett,Culex erraticus (Dyar&Knab),Anopheles cruciansWiedemann,Anopheles quadrimaculatus Say, Aedes vexans (Meigen),Ochlerotatus triseriatus Say, and Psorophora feroxHumboldt) with positive pools occurring in 1998, 1999, and 2002. Culiseta melanura Coquillett occurred at a low level ( 1%) andwas not infected. Saint Louis encephalitis virus was detected once in a single pool ofCx. erraticus in 1998.NeitherWestNile virus norLaCrosse viruswas found.Minimum infection rates per 1000 females tested of competent vectors of EEE virus were variable and ranged from 0.14 forCx. erraticus to 40.0 forOc. triseriatus.Thirty-nine species of birds were identiÞed in the focuswith blood-engorged mosquitoes found to contain meals (n 29) from eight avian species. The majority of meals was from the great blue heron, Ardea herodias L. (n 55%), but when bird abundance data were adjusted for avian mass, the brown-headed cowbird, Molothrus ater (Boddaert); blue jay, Cyanocitta cristata (L.); and northern mockingbird, Mimus polyglottos (L.), were overrepresented as hosts.