Dengue virus (DENV) and Zika virus (ZIKV) belong to the same viral family, the Flaviviridae. They cause recurring threats to the public health systems of tropical countries such as Brazil. The primary Brazilian vector of both viruses is the mosquito Aedes aegypti. After the mosquito ingests a blood meal from an infected person, the viruses infect and replicate in the midgut, disseminate to secondary tissues and reach the salivary gland (SG), where they are ready to be transmitted to a vertebrate host. It is thought that the intrinsic discrepancies among mosquitoes could affect their ability to deal with viral infections. This study confirms that the DENV and ZIKV infection patterns of nine Ae. aegypti field populations found in geographically separate health districts of an endemic Brazilian city vary. We analyzed the infection rate, disseminated infection, vector competence, and viral load through quantitative PCR. Mosquitoes were challenged using the membrane-feeding assay technique and were tested seven and fourteen days post-infection (early and late infection phases, respectively). The infection responses varied among the Ae. aegypti populations for both flaviviruses in the two infection phases. There was no similarity between DENV and ZIKV vector competencies or viral loads. According to the results of our study, the risk of viral transmission overtime after infection either increases or remains unaltered in ZIKV infected vectors. However, the risk may increase, decrease, or remain unaltered in DENV-infected vectors depending on the mosquito population. For both flaviviruses, the viral load persisted in the body even until the late infection phase. In contrast to DENV, the ZIKV accumulated in the SG over time in all the mosquito populations. These findings are novel and may help direct the development of control strategies to fight dengue and Zika outbreaks in endemic regions, and provide a warning about the importance of understanding mosquito responses to arboviral infections.
Background Aedes aegypti is a highly competent vector in the transmission of arboviruses, such as chikungunya, dengue, Zika and yellow fever, and causes single and coinfections in the populations of tropical countries. Methods The infection rate, viral abundance, vector competence, disseminated infection and survival rate were recorded after single and multiple infections of the vector with 15 combinations of chikungunya, dengue, Zika and yellow fever arboviruses. Results Infection rates were 100% in all single and multiple infection experiments, except in one triple coinfection that presented a rate of 50%. The vector competence and disseminated infection rate varied from 100% (in single and quadruple infections) to 40% (in dual and triple infections). The dual and triple coinfections altered the vector competence and/or viral abundance of at least one of the arboviruses. The highest viral abundances were detected for a single infection with chikungunya. The viral abundances in quadruple infections were similar when compared to each respective single infection. A decrease in survival rates was observed in a few combinations. Conclusions Ae. aegypti was able to host all single and multiple arboviral coinfections. The interference of the chikungunya virus suggests that distinct arbovirus families may have a significant role in complex coinfections.
Zika virus (ZIKV) is transmitted to humans by the infectious bite of mosquitoes such as Aedes aegypti. In a city, the population control of mosquitoes is carried out according to alerts generated by different districts via the analysis of the mosquito index. However, we do not know whether, besides mosquito abundance, the susceptibility of mosquitoes could also diverge among districts and thus impact the dissemination and transmission of arboviruses. After a viremic blood meal, the virus must infect the midgut, disseminate to tissues, and reach the salivary gland to be transmitted to a vertebrate host. This study evaluated the patterns of ZIKV infection in the Ae. aegypti field populations of a city. The disseminated infection rate, viral transmission rate, and transmission efficiency were measured using quantitative PCR at 14 days post-infection. The results showed that all Ae. aegypti populations had individuals susceptible to ZIKV infection and able to transmit the virus. The infection parameters showed that the geographical area of origin of the Ae. aegypti influences its vector competence for ZIKV transmission.
Zika virus (ZIKV) is transmitted to humans by the infectious bite of mosquitoes like Aedes aegypti. After a viremic blood meal, the virus must infect the midgut, disseminate to tissues, and reach the salivary gland to be transmitted to a vertebrate host. Many factors influence the mosquito’s ability to become infected and transmit viruses, such as the mosquito’s genetic diversity, intrinsic antiviral barriers, and midgut microbiota. This study evaluated the patterns of ZIKV infection in Ae. aegypti field populations of a city. The infection rate, disseminated infection rate, viral transmission rate, and transmission efficiency were measured by quantitative PCR at 14 days post-infection. The results showed that all Ae. aegypti populations had individuals susceptible to ZIKV infection and able to transmit the virus. The infection parameters showed the city’s geographical area of origin of the Ae. aegypti influences their vector competence for ZIKV transmission.
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