SINGAPORE (Reuters) – From the high balcony of a public housing block in Singapore, an environmental official confirms his mosquito launcher, the latest control authorities have set out to combat a record outbreak of tropical disease dengue.
With the click of a button and a whirl of a fan, a hatch opens and 150 male mosquitoes are raised with labs, looking for a female mate with whom they can mate but not reproduce.
The dengue virus, which in rare cases can be fatal, is transmitted and spread to humans by infected mosquitoes.
But specially bred mosquitoes from Singapore carry a bacterium that prevents eggs from hatching, and “compete with the wild type”, leading to “a slow reduction in the mosquito population,” said Ng Lee Ching, the official head of Wolbachia project, named after the bacteria.
Some areas with high mosquito populations have seen up to 90% declines with this technique, they added.
Singapore – a small Southeast Asian island nation of 5.7 million people – has registered more than 26,000 dengue cases this year, surpassing the previous annual record of about 22,000 in 2013 with four months left.
Twenty people have died this year from the disease, which can cause extreme fever leading to internal blood and shock. By comparison, only 27 people have died from the coronavirus in the city-state from more than 56,000 infections.
A new strain of the disease, combined with unforgivably wet weather and coronavirus shots that left buildings and other mosquito breeding grounds undisturbed, are all seen as factors behind the outbreak of dengue.
That has put the bag on traditional deterrents such as fogging, fining people for anti-mosquito rules, such as leaving plant pots full of stagnant water, and using new techniques such as the Wolbachia project.
In government laboratories, scientists breed the bacterial mosquitoes in rows of pallets – separating the male babies for release in high-risk dengue areas.
For every person living in those areas, a maximum of six Wolbachia mosquitoes are released each week, the environmental bureau said.
Wolbachia mosquitoes cannot transmit diseases like dengue, and only female mosquitoes bite humans.
If male Wolbachia mosquitoes mate with females that do not carry the bacteria, none of the resulting eggs will hatch.
The strategy is successful in Australia, but some experts say it may have its limits in dense urban areas such as Singapore.
“You have to flood the island with these mosquitoes, and people are getting annoyed,” said Paul Tambyah, senior consultant at the National University Hospital of Singapore.
‘They will not grab the mosquito and examine it and see if it is a male or female. They will sweep them away, and that kind of defeats the purpose, ‘he said.
Written by John Geddie; Edited by Gerry Doyle
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