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Zika virus was detected in dead monkeys found in Brazil, near São José do Rio Preto, in the state of São Paulo, and Belo Horizonte, in Minas Gerais. The animals had been slaughtered or beaten to death by locals who thought they had yellow fever. In fact, the monkeys did not carry this disease, but an infection with the Zika virus made them sick and made them more vulnerable to human attacks.
"The discovery shows that there is a potential for Zika to establish a sylvatic transmission cycle [involving wild animals] in Brazil, as is already happening in the case of yellow fever. If the wild cycle is confirmed, the epidemiology of Zika changes completely, because it means that there is a natural reservoir from which the virus can re-infect the human population much more frequently, "said Maurício Lacerda Nogueira, senior research scientist study funded by the São Paulo Research Foundation – FAPESP, Nogueira is a professor at the São José do Rio Preto School of Medicine (FAMERP) and chairs the Brazilian Society of Virology (SBV).
The Zika virus has been detected in monkeys accustomed to human presence in the state of Ceará a few years ago, but this is the first discovery in the wild since the beginning of the year. epidemic. An article on the study signed by Nogueira and researchers affiliated with several other institutions has just been published in Scientific reports, an online journal owned by Springer Nature.
"During the yellow fever epidemic, we realized that there were many dead monkeys, not killed by the disease, but by people fearing contagion.The monkeys had been shot, reddened or bitten by When they were healthy, these primates – mainly marmosets (Callithrix sp.) and capuchins (Sapajus sp.) – are very difficult to capture, "said Nogueira. "So we concluded that, if they were killed relatively easily, it was probably because they were sick, not yellow fever, lethal to monkeys, but of another a disease that did not kill them but made them weak and vulnerable. "
The researchers analyzed the dead monkeys and found that they had been infected with the Zika virus in São José do Rio Preto and Belo Horizonte. Sequencing of the entire genome showed that the virus was very similar to the type that infects humans. In addition, during the same week, researchers collected mosquitoes infected with Zika at the same locations where dead monkeys were found.
"We did the study by experimentally infecting live monkeys with Zika," Nogueira said. "Inoculation with the virus caused viremia [presence of the virus in the blood]. The monkeys presented behavioral changes, confirming our initial hypothesis that the infection made them more likely to be captured and killed. "
Yellow fever cycle
A natural and experimental infection of the monkeys by Zika shows that these animals can be vertebrate hosts, contributing to the transmission and circulation of the virus in tropical urban environments. According to the article we just published, however, "further studies are needed to understand the role they can play in maintaining the urban cycle of the Zika virus and how they can be a channel." for the establishment of an enzootic environment. " [nonhuman] transmission cycle in tropical Latin America ".
"As has shown yellow fever, epizootics [occurring at the same time in many animals in the same geographic area] will always be a source of epidemics in humans, even after possible control and eradication of the urban transmission cycle through the development of effective countermeasures such as vaccines and antivirals. Policymakers, public health officials and vaccine designers should be aware of this, "said Nikos Vasilakis, professor at the UTMB's Center for Tropical Diseases and one of the leading authors of the vaccine. 39; article that has just been published.
The Zika virus first appeared in monkeys in Africa. From time to time, he left the jungle and infected human populations. It finally spread to Asia, where it circulated only among humans. Apparently, it has retained this property with respect to the Americas, suggesting a cycle similar to that of the dengue virus.
The new discovery, however, suggests the possibility of a different epidemiology, closer to that of yellow fever. If this epidemiology is confirmed, it means that the fight against Zika will be much more difficult than expected.
"Our observations will have important implications for our understanding of the ecology and transmission of Zika in the Americas," said Vasilakis. "While it is one of the first steps in establishing a cycle of enzootic transmission in non-human primates and New World arboreal mosquitoes, The implications are enormous because it is impossible to eradicate this cycle of transmission. "
Vasilakis emphasized the importance of funding for the study received from FAPESP and the US National Institutes of Health (NIH), which "recognize the importance of the subject at an early stage" and support the research which is also an example of the "long and continuous establishment of a collaboration between the UTMB and FAMERP groups."
The study was funded by the São Paulo Research Foundation – FAPESP via a thematic project coordinated by Nogueira and the Zika virus research network in São Paulo (Rede Zika). The first author of the article, Ana Carolina Bernardes Terzian, conducts postdoctoral research at FAMERP with a FAPESP scholarship.
Researchers from FAMERP in Brazil, the Federal University of Minas Gerais (UFMG), the Adolfo Lutz Institute, the University of São Paulo (USP), the University of State of São Paulo (UNESP) and the National Institute of Science and Technology Dengue also participated in the study, as well as researchers from the medical branch of & # Paulo Paulo. University of Texas (UTMB) in the United States.
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