Abstract
BackgroundVector-borne diseases are a major public health concern and cause significant morbidity and mortality. Zika virus (ZIKV) is the etiologic agent of a massive outbreak in the Americas that originated in Brazil in 2015 and shows a strong association with congenital ZIKV syndrome in newborns. Cache Valley virus (CVV) is a bunyavirus that causes mild to severe illness in humans and ruminants. In this study, we investigated the vector competence of Virginia mosquitoes for ZIKV and CVV to explore their abilities to contribute to potential outbreaks.MethodsTo determine vector competence, mosquitoes were fed a blood meal comprised of defibrinated sheep blood and virus. The presence of midgut or salivary gland barriers to ZIKV infection were determined by intrathoracic inoculation vs oral infection. After 14-days post-exposure, individual mosquitoes were separated into bodies, legs and wings, and saliva expectorant. Virus presence was detected by plaque assay to determine midgut infection, dissemination, and transmission rates.ResultsTransmission rates for Ae. albopictus orally infected (24%) and intrathoracically inoculated (63%) with ZIKV was similar to Ae. aegypti (48% and 71%, respectively). Transmission rates of ZIKV in Ae. japonicus were low, and showed evidence of a midgut infection barrier demonstrated by low midgut infection and dissemination rates from oral infection (3%), but increased transmission rates after intrathoracic inoculation (19%). Aedes triseriatus was unable to transmit ZIKV following oral infection or intrathoracic inoculation. CVV transmission was dose-dependent where mosquitoes fed high titer (ht) virus blood meals developed higher rates of midgut infection, dissemination, and transmission compared to low titer (lt) virus blood meals. CVV was detected in the saliva of Ae. albopictus (ht: 68%, lt: 24%), Ae. triseriatus (ht: 52%, lt: 7%), Ae. japonicus (ht: 22%, lt: 0%) and Ae. aegypti (ht: 10%; lt: 7%). Culex pipiens and Cx. restuans were not competent for ZIKV or CVV.ConclusionsThis laboratory transmission study provided further understanding of potential ZIKV and CVV transmission cycles with Aedes mosquitoes from Virginia. The ability for these mosquitoes to transmit ZIKV and CVV make them a public health concern and suggest targeted control programs by mosquito and vector abatement districts.
Highlights
Vector-borne diseases are a major public health concern and cause significant morbidity and mortality
We investigated the vector competence of Virginia mosquitoes common in urban and suburban environments for Zika virus (ZIKV) and Cache Valley virus (CVV) to explore their abilities to contribute to potential outbreaks and help inform local mosquito control strategies
Vector competence for ZIKV following oral infection There was a significant difference among infection (χ2 = 58.73, df = 5, P < 0.05), dissemination
Summary
Vector-borne diseases are a major public health concern and cause significant morbidity and mortality. ZIKV is transmitted primarily by urban and sylvatic Aedes mosquitoes, with Ae. aegypti serving as the main vector for human infection outside of Africa [8,9,10]. This emerging mosquito-borne virus has caused epidemics throughout Africa, Asia, the Pacific Islands and the Americas [11, 12]. Recent studies have shown that some Aedes, Culex and Coquillettidia mosquitoes from temperate regions of North America were not competent for ZIKV [13, 14], but this is a small representation of the species and strain diversity of mosquitoes that are found in the USA
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