Estimating the risk of arbovirus transmission in Southern Europe using vector competence data

Abstract

Arboviral diseases such as chikungunya, dengue, and Zika viruses have been threatening the European countries since the introduction in 1979 of the major vector Aedes albopictus. In 2017, more than three hundred of CHIKV autochthonous cases were reported in Italy, highlighting the urgent need for a risk assessment of arboviral diseases in European countries. In this study, the vector competence for three major arboviruses were analyzed in eight Ae. albopictus populations from Europe. Here we show that Southern European Ae. albopictus were susceptible to CHIKV, DENV-1 and ZIKV with the highest vector competence for CHIKV. Based on vector competence data and vector distribution, a prediction risk map for CHIKV was generated stressing the fear of CHIKV and to a lesser extent, of other arboviruses for Europe, calling us for new public health strategies.

Figure 1

Infection rate, dissemination and transmission efficiencies of each Southern European Ae. albopictus population for CHIKV (a–c), DENV-1 (d–f), and ZIKV (g–i). Mosquitoes challenged an infectious blood meal were analyzed for infection, dissemination, and transmission at 7, 14 days post-infection (dpi) for CHIKV; 7, 14, and 21 dpi for DENV-1 and ZIKV. Infection rate (IR) refers to the proportion of mosquitoes with infected body among engorged mosquitoes. Dissemination efficiency (DE) corresponds to the proportion of mosquitoes with infected head among mosquitoes examined. Transmission efficiency (TE) represents the proportion of mosquitoes with infectious saliva among mosquitoes examined. AAF: Faliro, Greece; AAT: Tivat, Montenegro; AAM, Mirogoj, Croatia; AAV: Velika, Croatia; AAA: Arogno, Switzerland; AAE: Tenero, Switzerland; AA9: Cesena9, Italy; AA4: Cesena3 + 4, Italy; AAC: Canton, China. Error bars represent the 95% confidence intervals.

Figure 2

CHIKV dissemination (a) and transmission (b) models according to viral load and mosquito population. The solid lines show the probability of a successful viral transition from body to head (dissemination) or head to salivary glands (transmission) as a function of the viral load in the initial compartment (dissemination: body; transmission: head). The grey envelopes present 95% confidence intervals.

Figure 3

Probabilities of Ae. albopictus-mediated CHIKV transmission in Southern Europe. The colors correspond to probabilities: lower (blue) or higher (red) than the median probability across the whole map (white). Probabilities were derived using an inverse distance-weighting spatial model as described in the methods. Blue dots correspond to sampling locations while red labeled dots highlight places where a CHIKV outbreak has been reported in a recent past. This map uses data published by Kraemer et al. as well as modeled vector competence (see methods) and was generated with R v3.5.2 (packages raster v3.0.7 and gstat v2.0.3).