Zika virus threshold determines transmission by European Aedes albopictus mosquitoes

Abstract

Since its emergence in Yap Island in 2007, Zika virus (ZIKV) has affected all continents except Europe. Despite the hundreds of cases imported to European countries from ZIKV-infested regions, no local cases have been reported in localities where the ZIKV-competent mosquito Aedes albopictus is well established. Here we analysed the vector competence of European Aedes (aegypti and albopictus) mosquitoes to different genotypes of ZIKV. We demonstrate that Ae. albopictus from France was less susceptible to the Asian ZIKV than to the African ZIKV. Critically we show that effective crossing of anatomical barriers (midgut and salivary glands) after an infectious blood meal depends on a viral load threshold to trigger: (i) viral dissemination from the midgut to infect mosquito internal organs and (ii) viral transmission from the saliva to infect a vertebrate host. A viral load in body ≥4800 viral copies triggered dissemination and ≥12,000 viral copies set out transmission. Only 27.3% and 18.2% of Ae. albopictus Montpellier mosquitoes meet respectively these two criteria. Collectively, these compelling results stress the poor ability of Ae. albopictus to sustain a local transmission of ZIKV in Europe and provide a promising tool to evaluate the risk of ZIKV transmission in future outbreaks.

Different populations of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) from Central Africa are susceptible to Zika virus infection

“…The results of these experiments indicate that ZIKV could be transmitted during blood feeding. Our analysis showed high infection, dissemination, and transmission rates in both species which is in agreement with previous experiments using ZIKV from the African lineage [36][37][38][39]. Disseminated infection and transmission rates varied significantly according to Ae.…”

Evidence of Zika virus horizontal and vertical transmission in Aedes albopictus from Spain but not infectious virus in saliva of the progeny

“…vittatus, Aedes vexans [1], Aedes polynesiensis [20] and Ae. Albopictus [21][22][23][24][25]. The Asian tiger mosquito species, Ae.…”

“…It has been experimentally demonstrated that Mediterranean Ae. albopictus mosquitoes are competent vectors for ZIKV [22,25,29,30]. However, differences in vector competence (VC) among Ae.…”

Vector-Borne Transmission of the Zika Virus Asian Genotype in Europe

“…This was unexpected since previous vector competence studies found that both "Asian" and "American" strains belonging to the Asian genotype of ZIKV were poorly transmitted by French Ae. albopictus [2]. We propose several hypotheses that may allow reconciling these experimental and epidemiological findings.…”

“…This question is of specific importance since recent vector competence studies suggested that Ae. albopictus from France can transmit more efficiently the African genotype of ZIKV than the Asian genotype [2]. The latter includes both viruses that have been circulating in Asia for decades (as far as is known without causing large epidemics), and viruses that circulated during the recent important outbreaks in the Americas (mostly Latin America and the Caribbean) [3,4].…”