Vector Competence of Aedes aegypti and Aedes polynesiensis Populations from French Polynesia for Chikungunya Virus

Abstract

BackgroundFrom October 2014 to March 2015, French Polynesia experienced for the first time a chikungunya outbreak. Two Aedes mosquitoes may have contributed to chikungunya virus (CHIKV) transmission in French Polynesia: the worldwide distributed Ae. aegypti and the Polynesian islands-endemic Ae. polynesiensis mosquito.MethodsTo investigate the vector competence of French Polynesian populations of Ae. aegypti and Ae. polynesiensis for CHIKV, mosquitoes were exposed per os at viral titers of 7 logs tissue culture infectious dose 50%. At 2, 6, 9, 14 and 21 days post-infection (dpi), saliva was collected from each mosquito and inoculated onto C6/36 mosquito cells to check for the presence of CHIKV infectious particles. Legs and body (thorax and abdomen) of each mosquito were also collected at the different dpi and submitted separately to viral RNA extraction and CHIKV real-time RT-PCR.ResultsCHIKV infection rate, dissemination and transmission efficiencies ranged from 7–90%, 18–78% and 5–53% respectively for Ae. aegypti and from 39–41%, 3–17% and 0–14% respectively for Ae. polynesiensis, depending on the dpi. Infectious saliva was found as early as 2 dpi for Ae. aegypti and from 6 dpi for Ae. polynesiensis. Our laboratory results confirm that the French Polynesian population of Ae. aegypti is highly competent for CHIKV and they provide clear evidence for Ae. polynesiensis to act as an efficient CHIKV vector.ConclusionAs supported by our findings, the presence of two CHIKV competent vectors in French Polynesia certainly contributed to enabling this virus to quickly disseminate from the urban/peri-urban areas colonized by Ae. aegypti to the most remote atolls where Ae. polynesiensis is predominating. Ae. polynesiensis was probably involved in the recent chikungunya outbreaks in Samoa and the Cook Islands. Moreover, this vector may contribute to the risk for CHIKV to emerge in other Polynesian islands like Fiji, and more particularly Wallis where there is no Ae. aegypti.

Molecular determinants of arbovirus transmission by mosquitoes

“…Transmission rates of CHIKV by Ae. aegypti mostly range between 40-60% with exceptions to some virus-vector strain combinations that report low transmission rates [31,32,275]. These findings confirm that vector competence is highly variable and dependent on the specific combination of viral strain and mosquito population.…”

“…aegypti and Ae. albopictus mosquitoes [31][32][33]. Initially, the urban transmission of CHIKV was mainly caused by Ae.…”

“…However, a causal relationship between ZIKV infection in pregnant women and subsequent birth malformations, such as microcephaly, have now been confirmed [50,58,59]. The main vector for ZIKV transmission is the Aedes aegypti mosquito [32,54,250,251], while Ae. albopictus [54,56,252], Ae.…”

“…For example, at 28 °C CHIKV has a relatively short EIP of 6-8 days in Ae. aegypti [519], and in some individual mosquitoes, virus can already be detected in the saliva at 2 days post infection (dpi) [31,32]. ZIKV has a substantially longer EIP at 28 °C in Ae.…”

A comparative analysis of Chikungunya and Zika transmission

“…Case identification and counting has been an issue for epidemiological surveillance since symptoms caused by ZIKV and CHIKV infection are most of the times mild and not specific. Finally, both diseases can be transmitted by the same mosquitoes of the Aedes genus [8,9]. The most common vector, Ae.…”