Dengue-1 virus and vector competence of Aedes aegypti (Diptera: Culicidae) populations from New Caledonia

Abstract

Background: Dengue virus (DENV) is the arbovirus with the highest incidence in New Caledonia and in the South Pacific region. In 2012-2014, a major DENV-1 outbreak occurred in New Caledonia. The only known vector of DENV in New Caledonia is Aedes aegypti but no study has yet evaluated the competence of New Caledonia Ae. aegypti populations to transmit DENV. This study compared the ability of field-collected Ae. aegypti from different locations in New Caledonia to transmit the DENV-1 responsible for the 2012-2014 outbreak. This study also aimed to compare the New Caledonia results with the vector competence of Ae. aegypti from French Polynesia as these two French countries have close links, including arbovirus circulation.

Methods: Three wild Ae. aegypti populations were collected in New Caledonia and one in French Polynesia. Female mosquitoes were orally exposed to DENV-1 (10⁶ FFU/ml). Mosquito bodies (thorax and abdomen), heads and saliva were analyzed to measure infection, dissemination, transmission rates and transmission efficiency, at 7, 14 and 21 days post-infection (dpi), respectively.

Results: DENV-1 infection rates were heterogeneous, but dissemination rates were high and homogenous among the three Ae. aegypti populations from New Caledonia. Despite this high DENV-1 dissemination rate, the transmission rate, and therefore the transmission efficiency, observed were low. Aedes aegypti population from New Caledonia was less susceptible to infection and had lower ability to transmit DENV-1 than Ae. aegypti populations from French Polynesia.

Conclusion: This study suggests that even if susceptible to infection, the New Caledonian Ae. aegypti populations were moderately competent vectors for DENV-1 strain from the 2012-2014 outbreak. These results strongly suggest that other factors might have contributed to the spread of this DENV-1 strain in New Caledonia and in the Pacific region.

Keywords: Aedes aegypti; Dengue virus (DENV); New Caledonia; Pacific region; Vector competence.

Fig. 1

Map showing Ae. aegypti sampling sites in New Caledonia, 2015. The three sample sites are represented by red dots. Breeding sites are indicated in parentheses

Fig. 2

DENV vector competence results for NC mosquitoes (7, 14 and 21 dpi). DENV-1 infection rates (a), dissemination rates (b), transmission rates (c) and transmission efficiencies (d). Error bars represent 95% confidence intervals. Numbers of mosquitoes tested in each condition are indicated above each barplot. Significant differences are indicated by asterisks (*P < 0.05; **P < 0.01; ***P < 0.001)

Fig. 3

Comparison between Ae. aegypti population from Nouméa (NC) and Papeete (FP) (21 dpi). Comparison of DENV-1 infection rates (a), dissemination rates (b), transmission rates (c) and transmission efficiencies (d). Error bars represent 95% confidence intervals. Numbers of mosquitoes tested are indicated above each barplot. Significant differences are indicated by asterisks (*P < 0.05; **P < 0.01; ***P < 0.001)