Saturday 24 August, 2019

Watch: Brazilian researchers develop new mosquito trap

Photo: iStock/Getty images.

Photo: iStock/Getty images.

Zika, chikungunya, dengue and yellow fever all have in common that they can be transmitted by the female of the Aedes Aegypti mosquito.

Although a tropical mosquito, some predict that global warming is expected to expand its habitat to Europe and North America by the end of the century.

 

In Rio de Janeiro and other cities, public health clinics receive a large number of patients afflicted by these diseases.

Yellow fever was eradicated through vaccination.

However dengue fever registered a seven-fold increase in the first semester of 2019 with 1.1 million suspected cases and 388 deaths, a 163% increase compared to the same period last year.

Zika is at a much lower level than in the epidemic of 2015 and 2016, with 7530 suspected cases and two deaths.

"Dengue, Chikungunya and Zika, they are three arbovirus diseases. A fourth one is arriving but in principle it's those three" says Dr. Garcia Vergara, are the diseases more frequent in this clinic.

Dr. Garcia Vergara checks all patients for joint symptoms which could reveal the feared chikungunya, a crippling disease causing extreme joint pain that can last for months and impede work.

For health professionals here, there is little hope these diseases will subside.

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"That mosquito has many ways to hide and reproduce. As long as the mosquito focal points are not neutralised within the ecosystem, it will continue to exist" said Dr. Garcia Vergara.

Cases of dengue fever and other mosquito-borne diseases are seen here on a daily basis.

"Brazil and Rio de Janeiro try to control the Aedes Aegypti. Controlling mosquito populations is not an easy task as they reproduce even on water inside a soda cap" says Cristina Lemos, Rio's superintendent of public health surveillance.

At Rio de Janeiro's Federal University, a professor of dentistry took up the task to find ways to prevent the Aedes mosquito from reaching his then small newborn child.

Ivo Carlos Correa uses many kinds of light in his work and he thought maybe light could provide the answer.

After some research in medical journals, he found a study about the light sensitivity of the female of the Aedes Aegypti mosquito - and he decided to manufacture a trap using the right combination of lights.

"This a graph showing the spectrum of the light sensibility of the female of the Aedes Aegypti mosquito, transmitter of the arbovirus diseases.

"The peak of the sensibility is on the green and a little 450, 455 in yellow" says Professor Ivo Carlos Correa.

But first he had to run tests to see if these light frequencies would be efficient attractors of the Aedes Aegypti.

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At the Chemistry department of the same university, Professor Monica Ferreira Moreira is used to breeding mosquitoes for testing the effects of different substances on their biology.

A large numbers of mosquitoes were bred for the tests from larvae and placed into a special compartment where the experimental traps were tested.

Different colours of LED lights were used in the experiment. Green, blue and yellow were the main colours used in the tests.

The lights were tested on batches of 20 female mosquitoes at a time.

"Three experiments using the lesser intensity, three with medium intensity and three with strongest intensity using all the colours, yellow, blue and green. The results were very distinct in which the green catches nineteen mosquitoes the blue light catches 14 or 15 and the blue light a little more, 15 or 16."

Once the results were ready, Professor Ivo Correa proceeded to mount 20 experimental traps which were also tested at the chemistry lab.

The group applied for a world patent which has been accepted and is negotiating with local industries for the production.

At his home, Dr. Correa shows the commercially-available traps using blue and ultraviolet he bought for comparing the results with his invention.

"This is a trap that attracts all kinds of insects, like this other one and this one too.

So these are not specific traps, they can attract bees, flies, stink bugs, all kinds of insects besides the Aedes" said Professor Correa.

He himself uses the trap at home where his concerns with children's health stimulated his research.

"I cannot conceive of these children getting chikungunya, zika or even dengue, haemorrhagic dengue. We are very afraid" says Dr Correa's wife.

The trap has also been tested in neighbourhoods with high rates of arbovirus infestations.

At the home of Maria Guiomar Lopes, her mother contracted the feared chikungunya fever as did many in the neighbourhood.

Lopes is also a professor at the faculty of dentistry and is satisfied with the results using the trap invented by his colleagues.

"I didn't get chikungunya. My father didn't either but my mother and my daughter and many of the neighbours here in the street had it. I didn't get it and I think it's effective" says Lopes about the trap.

Many of her neighbours here are expecting the beginning of commercial production of the provisionally named Zika Trap to prevent the spread of these diseases while the Aedes Aegypti mosquito still resists efforts for its eradication.

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