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Most emerging infectious diseases affecting people are zoonotic – they make the leap from animals to humans. The transmission, however, is a two-way street. These zoonotic diseases can also switch from humans to other animals. Even if a disease is eradicated in humans, it can survive in animals that act as reservoirs, thus ensuring that the risk of human infection is never completely eradicated.
In an attempt to discern the risk of Zika virus contamination, a team of researchers, led by an anthropologist from Washington University in St. Louis, is investigating whether non-human primates from South America have been infected by the virus. disease. in humans in 2015. But they first needed a non-invasive way to test the virus on animals.
"These animals could be reservoirs and humans could then become infected with the virus of animal origin," said Krista Milich, badistant professor of biological anthropology of arts and sciences.
This happens in related viruses, she said. "There are feedback cycles, where humans are exposed through non-human primate reservoirs," said Milich, who, along with Benjamin Koestler, a postdoctoral fellow in molecular bioscience at the University of Texas at Austin, said led the recently published study in PLOS ONE. The researchers determined that the Zika virus can be detected with the help of faecal samples.
The virus can be found in a host of body fluids: sperm, urine, blood and saliva. Getting these samples, however, requires capturing the animals; a risky proposition for all the primates involved.
The simplest option would be to look for the virus in the feces, but only one research team said to have managed to do so, and this team did not publish its methods. "Ours continues by providing the method used so that people can follow it if they wish," said Milich.
It is not surprising that there is not yet a method for collecting the virus in the stool. Although Zika has been present in Africa and Asia since the 1940s, researchers have not looked for it in the Americas before it arrived around 2015. Once researchers started looking for the virus in the Americas, the Available tests concerned other fluids. , not faeces.
This, says Milich, is due to the fact that wildlife research is often "limited by what tests and methods have been developed for humans". And for humans, she said, "you will not ask for a stool sample if you can take a blood sample."
The team was not sure it would be possible for another reason. "RNA viruses can be brittle," said Milich, referring to viruses, such as Zika, whose genetic material is RNA, as opposed to DNA.
"That's why we were not sure we could detect it," she said. "In feces, the body breaks down things … And you have a lot more contaminants, so to be able to measure things in feces, you have to deal with those contaminants."
Before going to the field to test his methods, the team had to make sure of the accuracy of his tests. They provided blood, urine, saliva and stool samples to captive and infected squirrel monkeys, which were part of an ongoing study of the Zika virus in pregnant monkeys.
Using proven methods, the researchers tested the virus in the blood, urine and saliva. They then tested the faeces using a RT-qPCR-based test (additional information on the methods is available in the document). The results corresponded; they could detect the virus in feces, although detection time windows vary between different types of samples.
The group has now started testing samples of nature. Until now, researchers have collected several samples of nearly 50 animals. The samples come from sites as varied as the middle of the Amazon, where people are not present and where there should be no infections in Zika, said Milich, to animals that were previously kept as pets.
"We are looking for diversity," said Mr. Milich, "not only in terms of countries and species, but also with regard to the proximity of animals close to humans."
In February, the team had collected samples from Ecuador, Colombia and Brazil.
Ideally, he added, people should not keep monkeys as pets or hunt monkeys. "In fact, you are at greater risk of sharing diseases with animals when you live near them or when you come into contact with their bodily fluids, which happens when you kill them," he said. she said it's so that zoonotic diseases such as HIV have spread to humans.
"If the primates are infected with Zika, let's hope that the message will not be that these animals are terrible, we have to get rid of them," she said. "But it will be, we must respect these wild animals and not come into contact with them."
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