Eastern Equine Eneephalomyelitis Virus in Relation to the Avian Community of a Coastal Cedar Swamp

Abstract

Eastern equine encephalomyelitis virus (EEEV) is perpetuated in eastern North America in a mosquito-wild bird maintenance cycle that involves Culiseta melanura (Coquillett) as the principal enzootic vector and passerine birds as the primary amplifying hosts. We examined the role of birds in the EEEV cycle at a site in southern New Jersey where EEEV cycles annually at high levels. Birds and mosquitoes were sampled during three epiornitics and one season of limited virus activity. We examined antibody prevalence in birds in relation to eight physical and natural history characteristics. Our goal was to compare EEEV cycling in C. melanura and the primary avian hosts better to understand the mechanisms that initiate annual epiornitics. Antibody prevalence was highest in the Blue Jay (62%), Wood Thrush (60%), and Tufted Titmouse (44%). Resident status of birds was the natural history characteristic most closely linked to participation in the EEEV cycle. Species spending the greatest amount of time at our study site (permanent residents, summer residents) had the highest antibody rates. We captured viremic birds as early as 25 May, 51 d before we first detected virus in C. melanura. We recaptured 10 after hatching year adults and one hatching year (HY) bird that seroconverted before we detected virus in C. melanura. We also found EEEV antibody in 15 HY birds up to 31 d before we isolated EEEV from C. melanura. We provide evidence that a cryptic cycle develops weeks before epiornitic cycling is detected in C. melanura by traditional laboratory techniques, indicating that the early season cycle is initiated by the recrudescence of latent virus in previously infected birds.

Migratory Birds and the Dispersal of Arboviruses in California

“…6,7 Historically in the United States, large studies along the Mississippi and Atlantic flyways failed to document the introduction of encephalitis viruses by northbound migrants. [8][9][10][11] In agreement, genetic studies have shown marked separation between North and South American strains of arboviruses, such as eastern equine encephalomyelitis (EEEV), 12 western equine encephalomyelitis (WEEV), 13,14 and St. Louis encephalitis (SLEV) 15,16 viruses, suggesting limited genetic exchange. Temporal studies in California have shown intermittent genotype change among WEEV and SLEV isolates, [17][18][19] indicating possible introduction and replacement events.…”

Molecular Epidemiology of Eastern Equine Encephalitis Virus, New York

“…One potential overwintering mechanism is latent or chronic infection of wild birds. In such a scenario, springtime viral recrudescence might reinitiate the transmission cycle each new season (21,22). However, the results of a serologic survey of wild birds in upstate New York during 1986-1990 failed to support this notion, showing no consistent evidence for the current or recent infection of after-hatch year birds with EEEV early in the transmission season (23).…”

Genetic variation among isolates of western equine encephalomyelitis virus from California.

“…Eastern equine encephalitis virus was demonstrated to survive as a persistent infection of resident birds in southern New Jersey. 26 Reeves 4 made two isolations of WEE virus from the blood of white-crowned sparrows collected in the winter in Kern County, and laboratory studies 4 demonstrated that passerine birds may become chronically infected; however, efforts to infect mosquitoes by feeding on these same birds were unsuccessful. Alternatively, virus may overwinter in the adult mosquito.…”