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Host preference and arboviral encephalitis transmission in the Eastern USA.
Unnasch, Thomas*,1, Cupp, Eddie2, Hill, Geoff2, Katholi, Charles1, Hassan, Hassan1, Apperson, Charles 3, Savage, Harry4, 1 University of Alabama at Birmingham, Birmingham, AL, USA2 Auburn University, Auburn, AL, USA3 North Carolina State, Raleigh, NC, USA4 Centers for Disease Control and Prevention, Fort Collins, CO, USA
ABSTRACT- Arthropod-borne encephalomyelitis viruses, including West Nile (WNV) and Eastern Equine encephalomyelitis (EEE) virus represent a significant and growing public health threats in the United States. These viruses are primarily infections of the endemic avifauna and are maintained in an enzootic cycle by mosquitoes that feed primarily on birds. The viruses escape this enzootic cycle to infect mammals through the activity of bridge vectors with catholic feeding patterns. It is likely that an important variable in viral amplification and escape from the enzootic cycle is the degree of contact of the avian host and its mosquito vector. To investigate this, bloodfed mosquitoes from confirmed EEE vectors were collected from a site in the Tuskagee National Forest during an EEE outbreak in 2001. The bloodmeals were identified to the species level and the proportion of bloodmeal derived from each species compared to the overall composition of the avifauna at the study site. EEE vector mosquitoes were found to demonstrate a marked preference for certain bird species, and that this preference was not determined by the overall density or biomass of the avian species present at the site. In particular, a single species, the Brown-headed Cowbird, was significantly over-represented in the bloodmeals, with over 40% of the bloodmeals having been derived from this species. Taken together, the data suggested that the vector mosquitoes were targeting young of the year and species that inhabited the fringes of the study site. A similar host preference pattern was demonstrated in vectors for WNV collected in three states during the WNV outbreak of 2001. Taken together, these data suggest that forest fragmentation and increases in the populations of the Brown-headed Cowbird may result in an increase the potential for the development of outbreaks of encephalomyelitis viruses, and in particular EEE.
Key words: bloodmeal, encephalomyelitis, avain