The recently introduced Aedes albopictus in Tunisia has the potential to transmit chikungunya, dengue and Zika viruses

Abstract

The mosquito Aedes albopictus was detected for the first time in Tunisia in 2018. With its establishment in the capital city of Tunis, local health authorities fear the introduction of new human arboviral diseases, like what happened in Europe with unexpected local cases of chikungunya, dengue and Zika. Even though this mosquito is competent to transmit the arboviruses mentioned above, the transmission level will vary depending on the couple, mosquito population and virus genotype. Here, we assessed the vector competence of Ae. albopictus Tunisia by experimental infections with chikungunya (CHIKV), dengue (DENV), and Zika (ZIKV) viruses. We found that Ae. albopictus Tunisia was highly competent for CHIKV (transmission efficiency of 25% at 21 post-infection) and to a lesser extent, for ZIKV (8.7%) and DENV (8.3%). Virus was detected in mosquito saliva at day 3 (CHIKV), day 10 (ZIKV) and day 21 (DENV) post-infection. These results suggest that the risk of emergence of chikungunya is the highest imposing a more sustained surveillance to limit Ae. albopictus populations in densely populated urban dwellings and at the entry points of travelers returning from CHIKV-endemic regions.

Fig 1

CHIKV infection, dissemination, transmission (A) and viral loads in abdomen, head/thorax and saliva (B-F) in Aedes albopictus Tunisia at different days post-infection (3, 7, 10, 14 and 21). Mosquitoes were infected with a blood meal at a titer of 10⁷ ffu/mL and at each day post-infection, mosquitoes were processed to estimate the viral load in abdomen, head/thorax and saliva by titration on cells. On top of the bars are the numbers of mosquitoes tested (A). Means are represented by horizontal bars (B-F). ns, non-significant, **p ≤ 0.01, ***p ≤ 0.001, ****p ≤ 0.0001.

Fig 2

DENV infection, dissemination, transmission (A) and viral loads in abdomen, head/thorax and saliva (B-F) in Aedes albopictus Tunisia at different days post-infection (3, 7, 10, 14 and 21). Mosquitoes were infected with a blood meal at a titer of 10⁷ pfu/mL and processed as described in Fig 1. On top of the bars are the numbers of mosquitoes tested (A). Means are represented by horizontal bars (B-F). ns, non-significant, *p < 0.05.

Fig 3

ZIKV infection, dissemination, transmission (A) and viral loads in abdomen, head/thorax and saliva (B-F) in Aedes albopictus Tunisia at different days post-infection (3, 7, 10, 14 and 21). Mosquitoes were infected with a blood meal at a titer of 10⁷ pfu/mL and processed as described in Fig 1. On top of the bars are the numbers of mosquitoes tested (A). Means are represented by horizontal bars (B-E). ns, non-significant, *p < 0.05.

Fig 4

Viral loads in abdomen according to mosquito dissemination and transmission status: CHIKV (A-E), DENV (F-J) and ZIKV (K-N). Abdomen were homogenized and supernatants were titrated on cells. Means are represented by horizontal bars. ns, non-significant, *p < 0.05.

Fig 5

Viral loads in head/thorax according to mosquito transmission status: CHIKV (A-E), DENV (F-J) and ZIKV (K-N). Head/thorax were homogenized and supernatants were titrated on cells. Means are represented by horizontal bars. ns, non-significant, *p < 0.05, Mann-Whitney test.

Fig 6

Infection, dissemination, transmission (A) and viral loads in abdomen, head/thorax and saliva (B-D) in Aedes albopictus La Réunion, 14 days after infection with CHIKV, DENV and ZIKV. Mosquitoes were infected with a blood meal at a titer of 10⁷ ffu/mL and at 14 days post-infection, mosquitoes were processed to estimate the viral load in abdomen, head/thorax and saliva by titration on cells. Means are represented by horizontal bars. ns, non-significant, **p ≤ 0.01, Kruskal-Wallis test.

Fig 7. Comparison between Aedes albopictus Tunisia and Aedes albopictus La Réunion for viral loads in abdomen, head/thorax and saliva 14 days after infection with CHIKV, DENV, and ZIKV.

Means are represented by horizontal bars. ***p ≤ 0.001, Mann-Whitney test.