The ecology of eastern equine encephalitis virus in wildlife and mosquitoes in Minnesota

Background/Question/Methods

The disease dynamics of multihost pathogens are challenging to understand; this lack of understanding presents obstacles for disease control. This notion holds especially true for the complex cycles of vector-borne diseases with myriad insect vectors. Eastern equine encephalitis virus (EEEV) is a mosquito-borne zoonotic virus that is prevalent in North America. The primary transmission cycle involves mosquitoes and wild birds as reservoir hosts; infection has been documented in horses, humans and wildlife species. The aim of this interdisciplinary correlative study was to examine mosquito vectors of EEEV in relation to prevalence levels found in moose and elk that were sampled as part of the Minnesota Department of Natural Resources’ wildlife health surveillance efforts. Adult mosquitoes were sampled weekly during the summer of 2012 from 6 regions in northern Minnesota. In each region, one trapping site was in an area with high moose or elk EEE seroprevalence (‘hot’ site), while another was in a matching low seroprevalence area (‘cold’ site). Specimens were identified to species by light microscopy and taxonomic key.

Results/Conclusions

Out of 54,319 mosquitoes consisting of 29 different species, only 79 Culiseta melanura, the enzootic amplifying vector, were found. However, C. melanura occurred at 11 of the 12 of the trapping sites, with the exception of one ‘cold’ site located in the Northeast. Both Aedes sticticus and Aedes vexans were more abundant in high seroprevalence trapping locations. EEEV has been detected from Aedes vexans in previous studies and the species is a competent vector. Mosquito species are currently being tested for EEEV by RT-PCR. After testing, if infection prevalence is sufficient, regression methods will be employed to determine which factor, or combination of factors: mosquito species, region, or time is the most predictive of wildlife exposure status. This study will provide us with additional information on potential EEE vectors in northern Minnesota and shed light on disease dynamics in complex multihost communities.