Avian Communal Roosts as Amplification Foci for West Nile Virus in Urban Areas in Northeastern United States

Abstract

West Nile virus (WNV) perpetuates in an enzootic transmission cycle involving Culex mosquitoes and virus-competent avian hosts. In the northeastern United States, the enzootic vectors, Cx. pipiens and Cx. restuans, feed preferentially on American robins (Turdus migratorius), suggesting a key role for this bird species in the WNV transmission cycle. We examined the role of American robin communal roosts as virus amplification foci in greater New Haven, Connecticut. Robin communal roosts were located by radio tracking. After mid-August, when most robins were using the roosts, Cx. pipiens and Cx. restuans fed often on robins and were significantly more infected with WNV at communal roosts than at non-roosting sites. We also identified 6.4% human-derived blood meals in Aedes vexans in communal roosts. Our results indicate that communal roosts act as late-season amplification foci facilitating transmission to humans because of high infection rates, high abundance, and feeding patterns of enzootic and bridge vectors.

Supersuppression: Reservoir Competency and Timing of Mosquito Host Shifts Combine to Reduce Spillover of West Nile Virus

“…In addition, the Park: Water microhabitat type, which had the highest probability of seropositive birds, also had the highest WNV amplification fraction (80%) from American robins, with less than 6% of amplification from northern cardinals and song sparrows combined. Taken together, these results suggest that the absence of American robins, which have been considered "superspreaders" of WNV elsewhere, 13,14,37,45 combined with WNV amplification arising predominantly from northern cardinals and song sparrows, may be responsible for diminished WNV transmission in the urban forest patch microhabitats.…”

“…Located near the southern end of the Atlantic flyway in the continental United States, Atlanta provides stopover habitat for large numbers of migrating birds in both spring and fall and supports a substantial and diverse summer breeding bird population. 12 Because its climate and latitude differ from other major urban centers with the same vector species previously studied for WNV transmission such as Chicago, IL, 11 Washington, DC, 13 New Haven, CT, 14 and New Orleans, 15 our study objective was to test whether the unique extrinsic conditions in Atlanta translate into different WNV transmission dynamics among the vertebrate hosts.…”

A Multi-Year Study of Mosquito Feeding Patterns on Avian Hosts in a Southeastern Focus of Eastern Equine Encephalitis Virus

“…8 For example, temporal and spatial patterns of American robin ( Turdus migratorius ) abundance have been associated with variability of the rate of human cases of West Nile virus (WNV) and prevalence of WNV in mosquito populations. 6,9 Such patterns have been attributed to a higher rate of feeding on American robins by foraging mosquitoes relative to other avian species, 10 which leads to a higher probability of infection of robins, potentially causing robins to function as a superspreader of the virus. 3 Studies of avian host use by mosquitoes are vital components to elucidating the ecology of arbovirus transmission.…”

“…To date, however, such studies have been largely restricted to potential vectors of WNV. [3][4][5][6][7] The extent to which observations from studies of WNV can be applied to other mosquito-borne pathogen systems for which birds serve as reservoir hosts is uncertain, because these pathogens vary in the ecological factors that influence transmission. 11 The ecology of the transmission dynamics of eastern equine encephalitis virus (EEEV) is distinct from that of WNV.…”

“…1 Recent research has emphasized that some bird species are overused relative to their local availability by vector mosquitoes as blood-meal sources [2][3][4][5][6][7] and that overuse of certain avian species could influence the transmission of pathogens. 8 For example, temporal and spatial patterns of American robin ( Turdus migratorius ) abundance have been associated with variability of the rate of human cases of West Nile virus (WNV) and prevalence of WNV in mosquito populations.…”