The La Crosse virus (LACV) is an emerging pathogen in the Appalachian region of the United States. The virus maintains a complex natural cycle through horizontal transmission with sciurid rodents and Aedes mosquitoes in Virginia. Transovarial transmission also occurs in this host-parasite system and has evolved for the virus to persist through winter. The virus perpetuates in diapause induced embryos and infects naive rodents the following spring. As global temperatures rise, it is imperative we evaluate how the virus and its vectors overwinter. We conducted experiments to evaluate and determine the diapause induction, or prediapause stage, in Aedes japonicus japonicus, and the ecophysiology and low temperature biology of how LACV affects Aedes triseriatus and Aedes albopictus embryos at low temperatures. We found that the prediapause stage of Ae. j. japonicus is the maternal stage, the developing adult female that lays diapause eggs. This more closely resembles Ae. albopictus and not Ae. triseriatus. As measured in the field and laboratory, LACV has a clear negative effect on the ability of Ae. triseriatus and Ae. albopictus to survive the winter. There was no major effect of LACV infection on the ability of these two species to enter diapause or their critical photoperiods, but there was a significant negative effect of LACV infection on survivorship of embryos that were placed in their natural habitat and in their susceptibility to low temperatures. LACV infection had a more significant negative effect on Ae. albopictus than on Ae. triseriatus and suggests that Ae. albopictus is a subordinate vector relative to Ae. triseriatus in the maintenance of the virus over the winter season. Our findings highlight the need for the increased surveillance of LACV as temperatures continue to rise due to climate change. / PHD / In Virginia, mosquitoes may transmit the La Crosse virus (LACV) that can cause swelling of the brain in humans. This virus infects mosquitoes which is then transmitted to chipmunks. When a mosquito bites an infected chipmunk and then bites a human, the virus be transmitted to the human. Adult female mosquitoes can also pass the virus on to their developing offspring, which is the way it is maintained throughout the winter. Certain infected mosquitoes will spend the winter as eggs and the mosquitoes that hatch carry the virus and can infect chipmunks the following spring. The experiments conducted here looked at how one mosquito that can spread the LACV begins the process to survive the winter. We also did experiments to look at how the virus affects two other mosquito’s ability to begin the same process and then if they can survive the winter and cold temperatures while infected. We found that the Asian Bush Mosquito enters diapause in a different way than we suspected by the female mosquito sensing shorter days at the end of the summer; at this point she will then lay eggs that survive the winter. We discovered that viral infection will hurt the chances of the Asian Tiger Mosquito and Eastern Tree-hole Mosquito to survive the winter. We also found that virus-infected mosquitoes cannot survive temperatures as lower than those that are not infected. This means that the risk of the virus to humans can be greater as temperatures rise due to global warming.

No description available.