RIO DE JANEIRO — Brazilian researchers said Tuesday they have concluded that the common Culex mosquito is not transmitting Zika, the rapidly spreading virus that has been linked to severe birth defects.
Rio de Janeiro’s Fiocruz institute said the Culex quinquefasciatus mosquito has not played a role in the Zika epidemic that has hit Brazil over the last year.
Culex is 20 times more common than the Aedes aegypti mosquito, which is the main spreader of Zika. The Aedes also transmits dengue fever and chikungunya.
For the study, researchers gathered several hundred mosquitoes in four areas of Rio and fed them Zika-infected blood. Only two showed an early infection 14 days later, and the virus was not detected on their heads or in their saliva.
The report came a few months after a study published in July by the same institute but by researchers in the northeastern city of Recife concluded that the Culex could transmit the virus. Scientists said then that more studies were necessary to definitively determine whether the Culex could transmit Zika.
One possibility for the discrepancy in the two studies is that Culex mosquitoes in Recife may have a genetic variation that makes them different from those in Rio or elsewhere, the Fiocruz institute said.
Studies in other countries have suggested Culex may not be effective at spreading Zika.