By Anthony Boadle

BRASILIA (Reuters) - A genetically modified mosquito has helped reduce the proliferation of mosquitoes spreading Zika and other dangerous viruses in Brazil, its developers said on Tuesday.

The self-limiting strain of the Aedes aegypti mosquito was developed by Oxitec, the UK-subsidiary of U.S. synthetic biology company Intrexon. The male mosquitoes are modified so their offspring will die before reaching adulthood and being able to reproduce.

Oxitec, which produces the mosquitoes in Campinas, announced it will build a second facility in nearby Piracicaba, Sao Paulo state, following strong results there in controlling the population of the Aedes vector that also carries the dengue virus.

Zika virus, first detected in Africa in the 1940's, was unknown in the Americas until last year when it appeared in northeastern Brazil. The virus has quickly spread through Latin America.

Brazilian health authorities have linked the Zika outbreak to a surge in the number of babies born with unusually small heads, a damaging neurological condition called microcephaly.

The U.S. Centers for Disease Control and Prevention issued a travel advisory last week warning pregnant women to avoid 14 countries and territories in the Caribbean and Latin America affected by the virus.

With Brazil's rainy season underway, authorities are scrambling to fight the seasonal surge in mosquito populations.

Two weeks ahead of Carnival celebrations, a highlight of Brazil's tourism calendar, officials want to stem international concern about the virus. They also want to reassure travelers who plan to attend the opening ceremonies of the 2016 Olympics in Rio de Janeiro.

There is no vaccine or treatment for Zika, which causes mild fever and rash.

Oxitec said its proprietary OX513A mosquito succeeded in reducing wild larvae of the Aedes mosquito by 82 percent in a neighborhood of Piracicaba, where 25 million of the transgenic insects were released between April and November. Authorities reported a big drop in dengue cases in the area.

Story continues

"This is a powerful and versatile tool that can dramatically reduce the levels of infestation, which is the core of Brazil's prevention strategy right now," said Oxitec business development director in Brazil, Glen Slade.

The transgenic mosquito know as OX513A was approved by Brazil's National Technical Commission for Biosafety (CTNBio), but needs authorization from health surveillance regulator Anvisa to move to commercial production.

Oxitec began as a spin-off from Oxford University and was acquired in September by Intrexon, which has provided resources to invest in an expansion to fight the mosquito causing Brazil's public health emergency, Slade said.





(Reporting by Anthony Boadle; Editing by David Gregorio)