Vector competence of Virginia mosquitoes for Zika and Cache Valley viruses

Abstract

Background: Vector-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. Methods:To 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. Results:Transmission 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. Conclusions:This 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.

Aedes Albopictus and Cache Valley virus: a new threat for virus transmission in New York State

“…The high susceptibility of Ae. albopictus to CVV obtained in our results are similar to the reports of others [ 31 , 40 ]. In this study, using Ae.…”

Saliva collection via capillary method may underestimate arboviral transmission by mosquitoes

“…aegypti and CHIKV. A longer EIP was considered for the oral infection, since IT inoculation is known to reduce EIP [15,27,29,30]. The data from the oral infections supports our findings that forced salivation methods significantly underestimate transmission in this system.…”

“…This was demonstrated in three studies examining Ae. aegypti transmission rates via forced salivation, in which 0% to approximately 45% of ZIKV-exposed mosquitoes were reported to have detectable virus in saliva following a 14-day EIP [28][29][30]. Such discrepancies may be attributed to differences between mosquito and virus strains, or suggest variation in forced salivation techniques.…”

Secondary vectors of Zika Virus, a systematic review of laboratory vector competence studies

“…Starting in 2019, the rational for published studies continued with the evaluation of local species [ 62 , 65 , 67 , 68 , 70 , 71 , 73 , 76 , 77 ] but also expanded to examining the role of sylvatic species [ 64 ], clarify the role of Cx . quinquefasciatus [ 13 , 63 , 66 , 72 , 74 ], and ask more specific questions about the mechanisms of ZIKV transmission within their respective vectors [ 69 , 71 ].…”