The current West Nile virus (WNV) epidemic/epizootic in the United States is exhibiting unprecedented avian mortality, equine disease, involvement of many vertebrate and vector species, and non-vector transmission. Perennial outbreaks in the Northeast point toward the local establishment of natural foci rather than reintroduction by migrating birds. However, we know very little with regard to endemic/enzootic WNV transmission dynamics or if non-vector transmission manifests itself under field conditions. Host behavior likely plays a role in determining local transmission patterns particularly for directly transmitted diseases. The crow's complex social relationships lend themselves to indolent transmission studies. Our specific hypothesis is that non-vector transmission, crow movement and secondary transmission cycles play an important role in the local transmission, amplification and persistence of WNV. We have an exclusive opportunity to test our hypothesis by enlisting a well-studied and marked American crow (Conus brachyrhynchos) population. First, behavioral risk factors, e.g., contact with sick birds, infectious feces and carcasses, hypothesized to play a role in the risk of WNV transmission among crows will be collated in an ambidirectional epidemiology study to determine if non-vector transmission is manifested in the field. Second, we will document the movement of crow families with marked individuals and known family members by sightings, radio-tagging, and nighttime observations using infrared cameras and determine whether mosquito infection and human risk is enhanced on home territories as a result of crow movement. And third, we will determine the involvement of non-Culex mosquitoes to test the notion that when abundant these species play a role in secondary transmission cycles. This is an important piece of detective work involving a Category B agent that will have valuable implications for public health policies relating to mosquito control, arboviral encephalitis prevention and risks associated with non-vector transmission.
| DeCarlo, C H; Clark, A B; McGowan, K J et al. (2011) Factors associated with the risk of West Nile virus among crows in New York State. Zoonoses Public Health 58:270-5 |
| Townsend, Andrea K; Clark, Anne B; McGowan, Kevin J et al. (2009) Reproductive partitioning and the assumptions of reproductive skew models in the cooperatively breeding American crow. Anim Behav 77:503-512 |
