Health ministry tackles dengue, Zika in Nha Trang

Khanh
Hoa (VNA) – The Ministry of Health will release 1 million to 1.4
million of Wolbachia-infected mosquitoes in four wards in , the
central province of Khanh Hoa in an effort to reduce the number of incidences
of dengue fever and infections.

About 56,000 people live
in the wards, which include Vinh Phuoc, Vinh Tho, Vinh Truong and Phuoc Long.

Wolbachia is a bacterium that exists in up to 60 percent of different species
of insects, but not in the dengue and Zika-carrying mosquito Aedes aegypti.

Scientists have transferred Wolbachia from the fruit fly to Aedes aegypti
mosquitoes to reduce the ability of mosquitoes to transmit dengue and Zika
viruses.

After the initial release of several weeks, mosquitoes with a Wolbachia
bacterium are expected to mate with wild mosquitoes without Wolbachia.

When male mosquitoes with the Wolbachia bacterium mate with female mosquitoes,
the females develop eggs, but they won’t hatch. If the females already carry
Wolbachia, all the offspring will have Wolbachia.

When female mosquitoes with the Wolbachia bacterium mate with males without
Wolbachia, all her offspring will have Wolbachia.

As the bacteria are passed on from generation to generation and over time, the
percentage of mosquitoes carrying Wolbachia grows until it remains high without
any need for further release.

After three months of releasing , the number of
the mosquitoes at the four localities is expected to reach 70 percent of the
total mosquito population.

In March last year, the World Health Organisation recommended pilot deployments
of the Eliminate Dengue Programme approach, which introduces Wolbachia into
mosquito populations to prevent transmission of Aedes aegyot- transmitted viruses as an alternative to mosquito population
suppression.

Le Tan Phung, deputy head of Khanh Hoa province’s Department of Health, said
the provincial People’s Committee has not yet decided the time to release the
Wolbachia-infected mosquitoes in the four wards.

The committee is now instructing agencies to collect opinions about the release
to people in the wards.

The first trial site for release of Wolbachia-infected mosquitoes was on Tri
Nguyen Island in Khanh Hoa province in 2013 under the Eliminate Dengue Vietnam programme, monitored by the Ministry of Health. The release was completed in
2014.

Around 100 percent of the mosquitoes in the area are now carrying Wolbachia,
according to a press release published on the website of the Eliminate Dengue Vietnam
programme.

Thanks to the programme, only one person was infected with on the
island in 2015. As of the end of last year, there were no cases of dengue
fever, but cases still occurred in Nha Trang.

The programme is conducted by Australia’s Monash University under the
sponsorship of the Foundation for the National Institutes of Health through the
Bill & Melinda Gates Foundation’s Grand Challenges in Global Health
Initiative.

Begun in 2005, the programme has been carried out in Australia, Brazil, China,
Indonesia and Vietnam.

Research published in Scientific Reports journal in July 2016 showed more
evidence that Wolbachia blocked transmission of the Zika virus.

The research was conducted by scientists from the University of
Wisconsin-Madison and the Universidad de Antioquia.

“We found that mosquitoes carrying Wolbachia were less likely to become
infected with Zika virus after feeding on viral blood, and those that were
infected were not able to transmit the virus through their saliva,” said Jorge
Osorio, professor at the University of Wisconsin, one of the authors of the
report.

In the Eliminate Dengue Vietnam programme, 23,682 Aedes aegypti mosquitoes were collected and stored in
Nha Trang from March 2015 to May 2016.

Of these, 56 tested positive for Zika virus and 29 positive for dengue virus.

As of November last year, the province had recorded two patients positive for
Zika virus and 4,454 patients infected with dengue fever.

Nha Trang city and Ninh Hoa town had the highest number of dengue fever
patients.-VNA