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- Open Access
Zika virus can be venereally transmitted between Aedes aegypti mosquitoes
- Stéphanie Silva Campos1,
- Rosilainy Surubi Fernandes1,
- Alexandre Araujo Cunha dos Santos2,
- Rafaella Moraes de Miranda1,
- Erich Loza Telleria3,
- Anielly Ferreira-de-Brito1,
- Marcia Gonçalves de Castro1,
- Anna-Bella Failloux4,
- Myrna C. Bonaldo2 and
- Ricardo Lourenço-de-Oliveira1Email authorView ORCID ID profile
© The Author(s). 2017
Received: 5 September 2017
Accepted: 20 November 2017
Published: 15 December 2017
Alternative transmission routes have been described for Zika virus (ZIKV). Here, we assessed for the first time the venereal transmission of ZIKV between Aedes aegypti under laboratory conditions.
Orally-infected mosquito females were able to transmit the virus to males venereally, and males inoculated intrathoracically were capable of infecting females during mating. The genome of venereally-transmitted virus recovered from males was identical to that of ZIKV ingested by mated females.
We conclude that venereal transmission between Aedes mosquitoes might contribute to Zika virus maintenance in nature.
Zika virus (ZIKV, Flavivirus, Flaviviridae) is an arbovirus that has undergone a rapid spread in the Pacific region and across tropical America since 2015, causing a severe pandemic in 2015–2016 [1–3]. Moreover, microcephaly and other congenital neurological malformations and disorders were associated with ZIKV infections worldwide, which have made this virus currently one of the most significant public health issues. ZIKV transmission to people is primarily through the bite of an infected Aedes mosquitoes, mainly Aedes aegypti [1, 4]. However, the description of other modes of transmission, like inter-human contamination, may also explain ZIKV emergence, its efficient spread and maintenance in nature [5–8]. Moreover, inter-mosquito transmission through the vertical route is also likely to play a role. Therefore, we experimentally demonstrated that ZIKV could be venereally transmitted between Ae. aegypti, a phenomenon that could help in perpetuating ZIKV in nature.
Infection rates in Aedes aegypti females orally challenged with ZIKV and males contaminated by the venereal route
Sex ratio female: male (insemination rate)a
Female orally challenged
Male venereal transmission
Infection rates in Aedes aegypti males inoculated intrathoracically with ZIKV-RioU1 and female contaminated by the venereal route. Mosquitoes were let to copulate for 30 h devoid of any food source at a sex ratio of: 1 male: 2 females (81:162)
Days after intrathoracic inoculation of males
Male inoculated intrathoracically
Female venereal transmission
Male Aedes mosquitoes have been found naturally infected with ZIKV in Africa  and South America , providing evidence that inter-mosquito contamination occurs in nature and this phenomenon may play some role in virus maintenance and viral evolution . Being non-hematophagous, male mosquitoes may acquire an arbovirus infection through the vertical route. Nevertheless, the venereal transmission has also been experimentally demonstrated for several pairings insect-arbovirus [15–17], including other flaviviruses such as Japanese encephalitis, dengue and St Louis encephalitis viruses [18–20]. We demonstrated that ZIKV could be venereally transmitted between Ae. aegypti of two geographically-distant populations. Males obtained the infection from females and vice versa. Moreover, the genome of the virus transmitted by the venereal route was identical to those orally absolved as well as infecting females, suggesting that no expressive genetic changes occur in the viral genome during the venereal transmission. The efficiency of the venereal transmission route may be greater than expected. The variation in insemination and infection rates in orally-challenged females suggest that not all of them had sexual contact with males, especially in the groups brought into contact for only 30 h. The higher rate of venereal transmission from infected females to males (33%) was detected in the group of mosquitoes in which contact time was 5 days and insemination rate was of 100%, that is, all females had sexual contact with males. Considering that one male could have inseminated more than one female in such a group , it is possible that not all males had sexual contact with infected females, reducing the chance of venereal transmission. These data altogether may explain the large variation in male IRs.
Several factors have been proposed to explain the silent endemic/enzootic maintenance of ZIKV in Africa and Asia as well as the recent fast spread of this virus in the West Hemisphere, but they remain poorly understood. Although the main mode of maintenance of ZIKV in nature is supposed to be the primate-mosquito-primate transmission cycle, evidence of inter-vertebrate (congenital, perinatal, sexual, occupational and others) [1, 5–7] and inter-invertebrate contamination routes (vertical and venereal)  may help in explaining the high capacity of ZIKV to be transmitted and spread.
We conclude that together with other modes of transmission, the venereal route in Aedes mosquitoes might contribute to ZIKV virus maintenance in nature.
The authors thank Iule de Souza Bonelly, Keli Antunes Barbosa da Silva, Lidiane M. S. Raphael, Bruno Felix Pimentel Vianna and Maria Ignêz Bersot for technical support. To Luciano Moreira and Marli T. Cordeiro for providing virus isolated from Northeast Brazil.
This work was supported by the European Union’s Horizon 2020 research and innovation programme (ZIKAlliance grant 734,548), CAPES-COFECUB Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (grant 799/14), Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (grants E-26/102.351/2013 and E-26/201.335/2016), Conselho Nacional Desenvolvimento Científico e Tecnológico (grant 309,577/2013-6) and National Institut of Health (grant 1UO1 AI115595-01). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Availability of data and materials
The data used in the present study are available from the corresponding author upon reasonable request.
SSC and RSF carried out mosquito rearing and experimental infections. SSC and ELT performed mosquito intrathoracic inoculation. SSC, RSF, RMM, MGC and AFB tested mosquito samples by molecular methods. AACS and MCB produced the viral stocks and sequenced and analyzed the whole virus genomes. MCB and ABF participated in producing reagents for mosquito experiments and helped to prepare the text. RLO and SSC conceived the study and analyzed data. RLO wrote the manuscript. All authors read and approved the final manuscript.
This study was approved by the Institutional Ethics Committee on Animal Use (CEUA-IOC license LW-34/14) at the Instituto Oswaldo Cruz.
Consent for publication
The authors declare that they have no competing interests.
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