|Aedes aegypti - Credit CDC|
There are times - particularly with newly emerging infectious diseases - where we must temporarily accept `facts' before they are fully vetted. Work with assumptions that are based on similar situations and scientific plausibility, at least until real evidence can be gathered and analyzed.
And most of the time these assumptions hit pretty close to the mark. Of course, sometimes we get fooled, and we end up having to rethink matters.
A prime example - prior to 2014, Ebola had never sparked a major epidemic. Outbreaks were local, limited, and so virulent that they `quickly burned themselves out'.
And for nearly four decades, that was the accepted wisdom. Until the West African epidemic, when it wasn't anymore.
Another, more recent example, involves the Zika virus. Only last January sexual transmission of the virus was considered scientifically possible, but highly unlikely. A month later, the headlines read: CDC : Sexual Transmission Of Zika May Be More Common Than Previously Believed.
Despite the fact that these missteps are the exception, and not the rule, it is important that even the most basic assumptions be tested and proved correct.
For the Zika virus epidemic in Brazil, one very basic assumption has been that the Aedes aegypti mosquito is its most common vector.
An assumption based, in large part, on previous studies from Africa which found the African strain of virus in the Aedes mosquitoes there.
Of course, today we are dealing with a different continent, a different (Asian) strain of the virus, and a different mixture of indigenous mosquito species.
Aedes aegypti have been successfully infected with Zika in the lab, and along with Aedes albopictus, have been shown capable of transmitting the virus (see here). And last month, PAHO announced the Zika Virus had been isolated in a sampling of wild Aedes albopictus collected in Mexico.
But proof of naturally infected Brazilian Aedes aegpti mosquitoes has remained elusive . . . until now.
This (translated) press statement comes from FIOCRUZ (Fundação Oswaldo Cruz), one of the oldest and most prestigious scientific research institutes in South America,
Fiocruz identify Aedes aegypti mosquitoes naturally infected Zika virus
By: Cristiane Albuquerque (IOC / Fiocruz)
The Oswaldo Cruz Foundation (Fiocruz), an agency of the Ministry of Health, found for the first time in Brazil, mosquitoes Aedes aegypti naturally infected with Zika virus. The unprecedented identification occurred during studies of surveillance and monitoring conducted by Mosquitos Laboratory hematozoa Transmitters of the Instituto Oswaldo Cruz (IOC / Fiocruz), which has been collecting mosquitoes in places where they were identified cases of Zika in the state of Rio de Janeiro.
Until then, throughout the Americas, there was only a recent report on a set of mosquitoes Aedes albopictus naturally infected Zika virus, made by the Ministry of Health of Mexico. The discovery of the presence of virus in mosquitoes reinforces that A. aegypti to be the most common route of transmission of Zika in Brazil. Data on the finding are in the process of publication.
The mosquito capture job in the search for identification of circulating viruses is carried out in the surroundings and in the homes of patients with symptoms of Zika, through a partnership with medical Patricia Brazil, researcher at the National Institute of Infectious Diseases Evandro Chagas (INI / Fiocruz ).
Over ten months, about 1,500 adult mosquitoes of different species - including males and females - were captured by means of suction equipment and taken to the laboratory analysis. Of these, almost half were of the species A. aegypti . The diagnostic of the presence of Zika virus were performed from two methodologies: molecular analysis by RT-PCR in real time, able to identify the presence of genetic material (RNA) virus, and isolation technique viral, demonstrating that the mosquito carreava infectious viral particles.
The results showed the presence of virus in three sets of mosquitoes A. aegypti collected on Rocha Coelho neighborhoods in São João de Meriti, in the Baixada Fluminense, and Realengo, western Rio Zone. Among the mosquitoes caught, no other species was infected.
Ricardo Lourenço, factors like behavior, distribution and population density of Aedes in the Brazilian regions may have contributed to the rapid spread of Zika. "In practice, the percentage of A. aegypti infected with virus and transmitting diseases is very small. On the other hand, Aedes is a domestic mosquito, who lives next to the man , and benefits from the supply of breeding inside the houses where you can lay their eggs.
The large population of mosquitoes and the proximity to humans available to poke and get the blood needed for the reproductive process, added to the large supply of breeding which lay their eggs make the longer alive mosquito, favoring the process of infection and spread of diseases such as dengue, chikungunya and Zika, "he said.