Abstract
BackgroundA number of mosquito-borne viruses such as dengue virus (DENV), Usutu virus (USUV), West Nile virus (WNV) are autochthonously transmitted in Europe and six invasive mosquito species have been detected in this temperate region. This has increased the risk for the emergence of further mosquito-borne diseases. However, there is a paucity of information on whether European populations of invasive mosquito species are competent to transmit arboviruses. In this study, the susceptibility of Aedes albopictus originating from Spain and a laboratory-adapted colony of Aedes aegypti, was assessed for infection with, and transmission of Zika virus (ZIKV). Vertical transmission in both species was also assessed.MethodsAedes albopictus colonised from eggs collected in Spain and an existing colony of Ae. aegypti were fed infectious blood meals containing ZIKV (Polynesian strain) at 1.6 × 107 PFU/ml. Blood-fed mosquitoes were separated and maintained at 20 °C or 25 °C. Legs, saliva and bodies were sampled from specimens at 7, 14 and 21 days post-infection (dpi) in order to determine infection, dissemination and transmission rates. All samples were analysed by real-time RT-PCR using primers targeting the ZIKV NS1 gene.ResultsAt 14 dpi and 21 dpi, ZIKV RNA was detected in the bodies of both species at both temperatures. However, live virus only was detected in the saliva of Ae. aegypti at 25 °C with a transmission rate of 44%. No evidence for virus expectoration was obtained for Ae. albopictus under any condition. Notably, ZIKV RNA was not detectable in the saliva of Ae. aegypti at 20 °C after 21 days. No vertical transmission of ZIKV was detected in this study.ConclusionsExperimental infection of Ae. albopictus colonized from Spain with ZIKV did not result in expectoration of virus in saliva in contrast to results for Ae. aegypti. No evidence of vertical transmission of virus was observed in this study. This suggests that this strain of Ae. albopictus is not competent for ZIKV transmission under the conditions tested.
Highlights
A number of mosquito-borne viruses such as dengue virus (DENV), Usutu virus (USUV), West Nile virus (WNV) are autochthonously transmitted in Europe and six invasive mosquito species have been detected in this temperate region
This is not directly reflected by the results in vector competence studies in the literature, with some studies showing that Ae. albopictus can be an efficient vector of Zika virus (ZIKV), especially at higher temperatures, with the species being able to vertically transmit the virus to their progeny [8]
Due to the potential public health risk of ZIKV being introduced into Spain and other countries in Europe [19], this study has evaluated the vector competence of a Spanish population of Ae. albopictus for the Asian genotype of ZIKV at two temperatures
Summary
A number of mosquito-borne viruses such as dengue virus (DENV), Usutu virus (USUV), West Nile virus (WNV) are autochthonously transmitted in Europe and six invasive mosquito species have been detected in this temperate region. This has increased the risk for the emergence of further mosquito-borne diseases. Epidemiological investigations of the recent outbreak in Brazil and earlier outbreaks in Asia and Polynesia has linked ZIKV infection to clinical manifestations such as neonatal microcephaly and increased neurological disorders such as the Guillain-Barré Syndrome [5] This prompted the World Health Organization (WHO) to declare the ZIKV epidemic a Public Health Emergency of International Concern in 2016 [6, 7]. In addition to ZIKV, Ae. aegypti and Ae. albopictus can transmit many other arboviruses such as DENV, chikungunya virus (CHIKV), Mayaro virus (MAYV), yellow fever virus (YFV) and WNV [9–11]
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