Abstract
Zika is a mosquito-borne disease associated with neurological disorders that causes an on-going pandemic. The first outbreak was recorded in Micronesia in 2007, then in French Polynesia in 2014 from which it spread to South America in 2015 and ignited a widespread epidemic. Interestingly, Zika outbreaks in Asia remained of moderate intensity although the virus is circulating. To understand these epidemiological variations, we investigated the entomological determinants of ZIKV transmission in Asia. We used oral infection of mosquitoes collected in Singapore to identify the vector species, to quantify the blood infection threshold and to compare transmissibility between an Asian ZIKV strain (H/PF13) and an American strain collected in Brazil (BE H 815744). We have confirmed the vector status of Aedes aegypti and determined that 103 pfu/ml of blood is sufficient to infect mosquitoes. We showed that only the American strain was present in the saliva 3 days post-infection, and that this strain had a 30–40% higher rate of saliva infection in Ae. aegypti from 3 to 14 days post-infection than the Asian strain. Our data suggests that American strains are more efficiently transmitted than Asian strains, which raises concerns about the introduction of American strains in Asia.
Highlights
ZIKA virus (ZIKV) is a newly emerging mosquito-borne virus that belongs to the Flavivirus genus of the Flaviviridae family
Working with mosquito colonies collected in Singapore, we confirmed that Ae. aegypti mosquitoes are more susceptible to ZIKV infection than Ae. albopictus and ruled out Cx. quinquefasciatus as an efficient vector for ZIKV transmission
We showed that Ae. aegypti is extremely susceptible to ZIKV infection by determining the blood infection threshold
Summary
ZIKA virus (ZIKV) is a newly emerging mosquito-borne virus that belongs to the Flavivirus genus of the Flaviviridae family. ZIKV is present on the African and Asian continents but has not resulted in large outbreaks, despite the presence of permissive mosquito vectors and favorable ecological conditions for transmission. ZIKV has been reported to infect Culex quinquefasciatus[21], this is highly controversial[22,23,24] and may depend upon the origin of the mosquito colony and the virus strain. There is no clear evidence to explain the relatively low prevalence of ZIKV infection in Southeast Asia, nor why there have been no large ZIKV outbreaks in Asia similar to those seen in South and Central America. Working with mosquito colonies collected in Singapore, we confirmed that Ae. aegypti mosquitoes are more susceptible to ZIKV infection than Ae. albopictus and ruled out Cx. quinquefasciatus as an efficient vector for ZIKV transmission. We found that a ZIKV strain from Brazil (BE H 815744) had higher transmissibility than a strain originating from the Asian lineage (H/PF13) in Ae. aegypti
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