Vector and virus interactions: La Crosse encephalitis virus and the mosquito vector Aedes (stegomyia) albopictus
Date
2008
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Abstract
La Crosse encephalitis continues to be an important cause of pediatric arboviral encephalitis in the United States. Since 1985, the invasive mosquito vector, Aedes albopictus, has spread across the country and into La Crosse virus endemic regions. As an aggressive, daytime feeder, this vector has the potential to change the epidemiology of La Crosse encephalitis. This study investigated 4 components of the La Crosse virus- Ae. albopictus system: (1) time course of disseminated and filial infection rates (FIR) among recently colonized field strains, (2) anatomic basis of ovarian infection during the 1st gonotrophic cycle, (3) mitochondrial DNA (mtDNA) variation among geographically dispersed populations in the U.S., and (4) development of transovarially susceptible and refractory strains of Ae. albopictus. All geographic strains tested are susceptible to La Crosse virus oral infection and capable of transovarial transmission (TOT). No regional or geographic patterns emerged with respect to dissemination or TOT. 1st gonotrophic cycle vertical transmission was observed at low levels, with an FIR averaging 1%. 2nd gonotrophic cycle FIR averaged approximately 10% and was significantly lower than that of the natural vector, Ae. triseriatus. La Crosse virus antigen (Ag) was detected in ovaries by Day 2 after oral infection and prior to detection in head tissues. Ag was not detected in follicles through Day 7, suggesting vertical transmission. Examination of variation in the ND5 mtDNA marker revealed high levels of homogeneity among U.S. Ae. albopictus populations. Only 2 haplotypes were observed from 16 geographically dispersed states, including Hawaii. Such broad homogeneity could be due to multiple factors, including founder effects and cytoplasmic incompatibility. Ae. albopictus responded poorly to selection based on FIR for the development of susceptible and refractory strains. This study supports prior literature suggesting Ae. Albopictus may be an important secondary vector of La Crosse virus.
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Aedes albopictus
La Crosse virus
medical entomology
mosquitoes
transovarial transmission
vector biology
organismal biology
microbiology
public health
virology