A Research Blog

mosquito

In 2016, the Zika virus dominated all other public health concerns. It was an epidemic in South America and threatened to become one in Asia. Zika is a flavivirus that is mainly spread by the bite of an infected Aedes mosquito. Symptoms range from mild fever to body aches, while an infection during pregnancy could cause foetal brain defects, such as microcephaly.

This year Zika isn’t the hot topic that it was, but it remains a research priority and health concern.

Recently, Assistant Professor Julien Pompon and his team, from the Emerging Infectious Diseases Programme at Duke-NUS Medical School (Duke-NUS), published research that identified the main carrier for an Asian Zika virus strain and compared different Zika virus strains. This work increases our understanding of the virus transmission.

Asst Prof Pompon compared the susceptibility of Aedes aegypti, Aedes albopictus and Culex quinquefasciatus to an Asian Zika virus strain (H/PF13). The mosquitoes from these species were orally fed infected blood and, at seven days post infection, were examined to determine their infection rate and genome copies of the virus. High infection rates and genome copies indicate that the mosquito is more susceptible to picking up and transmitting a virus.

Infection rates and genome copies of Culex quinquefasciatus were significantly lower than that found in Aedes aegypti and Aedes albopictus. While infection rates in Aedes albopictus were not different from Aedes aegypti, the number of genome copies of the virus in Aedes albopictus was far lower than that in Aedes aegypti. These results suggest that Aedes aegypti mosquitoes are the main carrier of this Asian Zika virus strain in Singapore and suggest the same for Southeast Asia. The Duke-NUS team also found that a very low blood titre threshold was required to infect Aedes aegypti mosquitoes.

To compare how efficiently Zika virus strains from America (BE H 815744) and Asia (H/PF13) were transmitted, Asst Prof Pompon and his team orally infected Aedes aegypti mosquitoes with both strains. They then measured genome copies at day 3, 7, 10 and 14, post-infection. In the mosquitoes, the American Zika virus strain showed a higher infection rate at each time point. Similarly, in mosquito saliva, the American strain was present earlier and had a higher infection rate than that of the Asian strain. These results show that the Zika virus strain from the Americas is more efficiently transmitted than the Asian strain by Aedes aegypti mosquitoes.

“While Zika has been present in Asia for decades, it has not become a major epidemic unlike what happened in Brazil last year. In light of our results, we should monitor the genotypes of the Zika virus strains in Singapore so that we are aware if different virus strains were to be imported here,” shared Asst Prof Pompon.

“The next step is to determine how the American strain of the Zika virus manages to increase transmission efficiency. This will add to our knowledge about the characteristics of the virus, and improve our preparedness for an epidemic in Singapore.”

The study was published in Scientific Reports on 27 April 2017 and was supported by the Duke-NUS Signature Research Programme, with funding from the Singapore Ministry of Health.

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