Experimental transmission of Zika virus by Aedes japonicus japonicus from southwestern Germany

Abstract

The invasive mosquito species Aedes japonicus japonicus (Ae. japonicus) is widely distributed in Central Europe and is a known vector of various arboviruses in the laboratory, including flaviviruses such as Japanese Encephalitis virus or West Nile virus. However, the vector competence of Ae. japonicus for the recently emerging Zika virus (ZIKV) has not been determined. Therefore, field-caught Ae. japonicus from Germany were orally infected with ZIKV and incubated at 21, 24, or 27 °C to evaluate the vector competence under climate conditions representative of the temperate regions (21 °C) in the species' main distribution area in Europe and of Mediterranean regions (27 °C). Aedes japonicus was susceptible to ZIKV at all temperatures, showing infection rates between 10.0% (21 °C) and 66.7% (27 °C). However, virus transmission was detected exclusively at 27 °C with a transmission rate of 14.3% and a transmission efficiency of 9.5%. Taking into account the present distribution of Ae. japonicus in the temperate regions of Central Europe, the risk of ZIKV transmission by the studied Ae. japonicus population in Central Europe has to be considered as low. Nevertheless, due to the species' vector competence for ZIKV and other mosquito-borne viruses, in combination with the possibility of further spread to Mediterranean regions, Ae. japonicus must be kept in mind as a potential vector of pathogens inside and outside of Europe.

Fig. 1

Means and 95% confidence intervals for the ZIKV infection, dissemination, and transmission rates as well as the transmission efficiency of Ae. japonicus from southwestern Germany as revealed by analyses of bodies (IR), legs (DR), and saliva (TR and TE) following challenge of mosquitoes with infectious blood meals and incubation at 21 °C (n = 30), 24 °C (n = 29), or 27 °C (n = 21) for 2 weeks. Three independent trials were performed for each temperature. *Infection rate (IR): number of ZIKV-positive mosquito bodies per number of fed females. **Dissemination rate (DR): number of mosquitoes with ZIKV-positive legs per number of ZIKV-positive mosquito bodies. ***Transmission rate (TR): number of mosquitoes with ZIKV-positive saliva per number of ZIKV-positive mosquito bodies. ****Transmission efficiency (TE): number of mosquitoes with ZIKV-positive saliva per total number of fed females