Mosquito culprit found for Brazil chikungunya epidemic

fiocruz_20160301_rodrigo_mexas_e_raquel_portugal_aedes hembra
Female Aedes aegypti mosquito Copyright: Fundación Oswaldo Cruz

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  • Brazilian scientists find Aedes aegypti mosquito infected with African genotype of chikungunya
  • Research is first to find mosquito infected with strain in Brazil and the Americas
  • Discovery hints at on-going epidemic

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Brazilian scientists have identified the first Aedes aegypti mosquito infected with the chikungunya virus in the country, a discovery that confirms the species is a carrier for the disease and reinforces suspicions of its involvement in an epidemic in the Northeast Region in 2015-2016.
The infected mosquito was found within a batch of mixed species collected in the city of Aracaju as part of a research project undertaken by a Sao Paulo-based Zika network which is supported by Brazil’s research foundation FAPESP.
The batch contained 50 A. aegypti mosquitoes, 194 Culex quinquefasciatus and two specimens each of A. scapularis and A. Taeniorhynchus mosquitoes.
After sequencing the virus genome, the scientists confirmed that a female A. aegypti mosquito was a carrier of the East-Central-South Africa (ECSA) genotype of chikungunya.

“Knowing for certain which vector is involved in an epidemic is something that directly impacts on control measures, because protocols are specific to each mosquito species.”

Margareth Capurro

André Luis Costa-da-Silva, lead author of the study, which was published in the journal PLoS Neglected Tropical Diseases, explained that although a single specimen may seem insignificant, finding an infected female among 50 mosquitoes suggests “a high viral circulation and an indication of an on-going epidemic”.
Prior to this finding, there was only one report of an A. aegypti mosquito infected by the Asian genotype of the chikungunya virus in Latin America and the Caribbean, through research done in Mexico. However, viruses from both the Asian and African cell lines had already infected patients in Brazil according to Costa-da-Silva, a post-doctoral student of the Institute of Biomedical Sciences (ICB) at Sao Paulo University.
More than 265,000 probable human cases of chikungunya disease had been reported in Brazil up to December 2016, according to the Ministry of Health, and 40,000 cases were suspected in 2015. But no mosquito infected with the virus had been detected until now.
The research team collected mosquitoes in February 2016 in six areas of Aracaju, a city in northeastern Brazil where thousands of people had reported high fever and body pains — symptoms characteristic of arthropod-borne diseases.
A total of 248 mosquitoes were caught alive, frozen, and then sent to ICB in Sao Paulo to test for infection with dengue, Zika or chikungunya.
No mosquitoes other than the single female A. aegypti were found to be infected with any of the viruses.
One possible reason for finding just one infected mosquito, according to the researchers, is that the epidemic had already peaked by the time the mosquitoes were collected.
“Knowing for certain which vector is involved in an epidemic is something that directly impacts on control measures, because protocols are specific to each mosquito species,” says Margareth Capurro, a professor at ICB.

Capurro also expressed disappointment that almost all public funding for Zika-related research is linked to development of vaccines and diagnostic methods. “There is no investment in pilot programmes for mosquito control,” she pointed out.
The next step for the research team will be to collect mosquitoes and conduct a similar analysis in Southeastern Brazil, this time focusing on Zika detection.
Taken from a newsletter by FAPESP, a SciDev.Net donor, edited by SciDev.Net’s Latin America and the Caribbean desk.
This piece was originally published by SciDev.Net’s Latin America and Caribbean desk.