Brazil: Zika in House Mosquitos Requires 'Radical Change'

crofsblogs.typepad.com - g1.globo.com - July 24, 2016

Transmission of Zika by house mosquito requires 'radical change' in control measures

Biologist Constância Ayres, of Fiocruz Pernambuco, has made an unprecedented discovery that has the potential to provide a leap in scientists' knowledge of the Zika virus, and radically change the Brazilian strategy of preventing it.

Ayres succeeded in finding for the first time, mosquitoes carrying the virus in nature.

On Thursday, Fiocruz officially announced that the mosquito Culex quinquefasciatus, known as muriçoca or house mosquito, can also transmit the virus that causes microcephaly and malformations in babies.

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Zika transmission by common stilt requires 'radical change' in control measures

Scientists at Fiocruz Pernambuco met for the first time this type of mosquitoes carrying the Zika in nature - now analyze how effective it is in its transmission among humans.

Biologist Constance Ayres, of Fiocruz Pernambuco, made an unprecedented discovery that has the potential to provide a leap in the knowledge of the scientists on the Zika virus, and radically change the Brazilian strategy of prevention of it.

Ayres succeeded in finding for the first time, mosquitoes carrying the virus in nature.

On Thursday, Fiocruz officially announced that the mosquito Culex quinquefasciatus, known as muriçoca or house mosquito, can also transmit the virus that causes microcephaly and malformations in babies.

Until then, scientists believed that the mosquito Aedes aegypti was the main virus vector in Brazil. Now, according to Ayres, scientists need to determine which of the two species is the most important in Zika epidemic in Brazil.

During the announcement, Fiocruz said, until it understands the importance of mosquito in the epidemic, Zika control policy will remain focused on Aedes aegypti.

But depending on the results, it would take a "radical change" in the current current strategy of epidemic control, says the researcher.

"There are Culex control strategies in Brazil. This will have to change radically," he says.

In an interview with BBC Brazil, Ayres clarified the doubts about the progress of research and the implications of his discovery.

1. As determined that the mosquito can transmit Zika virus?

The research analyzed 500 mosquitoes captured in the Metropolitan Region of Recife. They were obtained at places where there were reports of Zika, according Ayres, to increase the possibility of finding the virus in the environment.

The mosquitoes were divided into 80 groups and the virus was found in three of them. In two of these groups according to Fiocruz, the mosquitoes were not fed. This shows "that the virus was widespread in the insect body and not (it was contracted) in a recent power in an infected host."

In the laboratory, the Ayres team fed the mosquitoes with a mixture of blood and viruses, to understand how Zika replicates in insects.

Then, researchers investigated the gut and salivary glands of mosquitoes. If the mosquito vector would not be his bowel block the growth of the virus within the body.

But if the virus could replicate, he would reach the salivary gland of Culex and could be transmitted to humans during the bite.

Thus, Ayres team confirmed that the Culex can carry the virus in your body. Saliva samples of infected mosquitoes were analyzed and contained similar amounts of virus found in the saliva of Aedes aegypti.

According to Ayres, another discovery of Fiocruz Pernambuco gives strength to the hypothesis: a research group realized that the geographical distribution of filariasis (elephantiasis) and Zika virus in Recife is very similar.

In Recife, the Culex quinquefasciatus is the only mosquito that transmits the parasite that causes elephantiasis. "We are the only endemic area of ​​Brazil for this disease," explains the biologist.

"About 85% of mothers who had babies with microcephaly because of Zika are in very poor areas without basic sanitation, which occurs more filariasis. This may explain the participation of Culex in the transmission of Zika and support our hypothesis. "

"Aedes aegypti, on the other hand, is more distributed in the city. We see that dengue is a disease and democratic, is not only in poor areas," he says.

2. The mosquito can also be tranmissão vector of dengue and chikungunya?

According to Fiocruz, the research has prioritized the Zika virus because of disease epidemic in Brazil and its connection with microcephaly.

Despite the chikungunya epidemic, which also affects mainly states in the Northeast, it is not known if this disease can also be transmitted by Culex.

Ayres said that the dengue virus has been found in mosquitoes collected in the field but still not confirmed whether it can be your vector.

3. If the mosquito is the main transmitter, which would be the impact of this discovery?

For Ayres, it would mean the need to change the current control strategy Zika epidemic, completely focused on the control of Aedes aegypti population.

"There are Culex control strategies in Brazil. This will have to change radically, and this is why the authorities require caution and more evidence. It is natural to be so," he says.

The mosquito has different habits of Aedes aegypti. It is most active at night, for example, which would make important protection with repellents and long clothing also at this time, especially for pregnant women.

He also prefers to lay its eggs in extremely polluted places such as sewers, drains and channels, which, according to the researcher, would make the sanitation measures further "urgent" to prevent new cases of Zika and microcephaly in more precarious neighborhoods.

"The sanitation will not eradicate the mosquito, but it will help in its population control. The reorganization measures help to keep the mosquitoes at a level where we no big epidemic, only sporadic cases of the disease."

4. What are the next steps of the research?

According to Ayres, his team now investigate what exactly is the vectorial capacity of the Culex, that is, how efficient it is to carry and transmit the virus.

"We know that the natural infection rate of Culex is similar to Aedes aegypti, but it involves other biological mosquito in nature: the size of its population, the longevity of these species, the number of bites that give the man, prefer to feed on human blood or not, "he says.

"Once we have this information, we can know which of the two species is more important in the transmission of Zika."

According to the biologist, the population of mosquito in Recife is 20 times greater than that of Aedes aegypti. But despite this advantage population of Culex, Aedes bites more often a person to feed.

It is necessary to understand, for example, chopping repeatedly makes the most competent vector Aedes transmission.

The Pernambuco team is also investigating the possibility of a female mosquito to transmit the virus to their offspring even eggs.

"We collect the eggs of infected mosquitoes, the larvae hatched, let it grow until they become adults and freeze the material. We will review it," said Ayres.

"If we can detect Zika, it means they contracted the virus mother. This has epidemiological importance, because it is a way to keep the virus in nature. He could remain in the environment without necessarily having to go through human."

In the disease transmission cycle as Zika, Aedes aegypti bites a sick person is infected and carries the virus to others. It does not transmit Zika, as far as is known, their eggs.

5. The discovery of Culex as Zika vector is of concern to other countries?

According to the biologist, Culex quinquefasciatus is present in all urban areas of tropical, subtropical and temperate regions - cooler weather, as the countries of northern Europe, Canada and Australia. But the Aedes aegypti is restricted to tropical and subtropical regions.

It clarifies, however, that show the ability to transmit Culex Zika in Brazil does not mean that it would occur, for example, in the United States.

"There is a possibility, but each population should be investigated, mainly because the Culex quinquefasciatus, which is what we have in Brazil is part of a species complex," he says.

"In the United States there are other sub-forms of this species of mosquito. And we do not know if the vector competence of all species are the same."

* Collaborated Gabriela Belem, Recife for BBC Brazil

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