La Crosse Virus in Southwestern Virginia: Role of Exotic Mosquito Species and Effect of Virus Infection on Feeding
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In laboratory studies of oviposition preference, only Ae. japonicus demonstrated a preference when presented with preexisting eggs. They deposited more eggs in cups containing either conspecifics or Ae. albopictus. The presence of 1st instar larvae Ae. albopictus larvae deterred oviposition by Ae. triseriatus and Ae. japonicus. Ae. japonicus and Ae. triseriatus preferred cups containing larval rearing water (LRW) of conspecifics and Ae. albopictus. Aedes albopictus preferred LRW regardless of species compared to control cups. Field experiments with fresh egg papers and preexisting eggs did not show significant differences, although the unequal population densities of species in the study area confounded the analysis. More work is needed to elucidate the interaction among these species and its effect on oviposition in the field.
Blood-feeding experiments showed that LAC virus-infected Ae. triseriatus and Ae. albopictus imbibed significantly less blood compared to uninfected mosquitoes. Because blood meal size affects the subsequent inhibition of host seeking, experiments were done to ascertain the effect of virus infection on refeeding. Significantly more infected Ae. triseriatus mosquitoes refed but there was no effect on the refeeding rate of Ae. albopictus. Thus, the detrimental effect of virus infection, i.e., reduction in blood meal size, may lead to increased host exposure by Ae. triseriatus, enhancing horizontal transmission.
Collecting adult mosquitoes was more efficient to detect virus in field populations than the collection of eggs. Maximum likelihood estimation-infection rates (MLE-IR) were calculated using bias-corrected maximum likelihood estimation. Adult collections yielded significantly more positive pools compared with egg collections. Virus was isolated from pools from Ae. canadensis, Ae. triseriatus, and Ae. albopictus. These results are comparable to other studies.
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