A virus that infects pigs in China appears in humans in Brazil

A virus infecting the worm Ascaris suum in the intestine of pigs in China was discovered in Brazil. It has been discovered in the feces of a child with gastroenteritis and has been described by scientists from various Brazilian and American institutions. An article about it has been published in the journal Virus Genes.

This investigation does not conclude that the virus in question – called WLPRV / human / BRA / TO-34/201 – arrived in Brazil from China with a person who ate infected pork. Or that this virus has been the cause of gastroenteritis.

"We badyzed a stool sample from a child with diarrhea whose pathogen had not been identified and we found a virus that had not been sequenced until Only once, in China, but it is too early to say that the virus has arrived in Brazil from China.As we have described, it is possible – and it is very likely – that over time, it is also found in other places, and maybe that will establish a propagation sequence, but for now we do not know if the virus has come from China, all we have are two similar genomic sequences, "said study coordinator Ester Cerdeira Sabino, director of the Institute of Tropical Medicine (IMT) in São Paulo, Brazil. , and professor in the Department of Infectious Diseases of the Faculty of Medicine of the University of São Paulo.

This study received support from FAPESP as part of the projects entitled "Study of the evolution of animal strains of rotavirus that infect humans" and "Metagenomic viral dengue, Chikungunya and Zika: follow , explain and ensure spatio-temporal transmission and distribution in Brazil. "

According to Antonio Charlys da Costa, a postdoctoral researcher, there is an enormous amount of active viruses in the world that have not yet been described.

Pig farm. (Photo: UCM)

"Given the number of eukaryotic beings on Earth, it is estimated that there are about 87 million viruses to describe.Today, the International Committee on Viral Taxonomy (ICTV) recognizes 4,404 species of virus in eukaryotes, which means that more than 99.99% of viruses are still unknown or have not been clbadified.Although this is only an estimate, we estimate that this percentage is valid because of the great viral diversity that we have found in the sequenced samples so far, "said Da Costa, IMT's postdoctoral fellow with a FAPESP grant. [19659002]

One of the objectives of Da Costa's research is to identify and sequence viruses that have not yet been described. The epidemiological study – which includes the distribution of viruses, frequency of occurrence in the population, badociated diseases, etc. – is a little later.

"We therefore studied human faecal specimens collected during episodes of gastroenteritis for which no pathogenic agent had been identified.We found countless agents present and we We now describe these results.The methodology used is viral metagenomics, which allows the identification of any infectious agent.This does not mean that the agents found are responsible for gastroenteritis, but this mapping allows us to establish correlation with the goal of future studies, "explained Cerdeira Sabino.

The viruses being investigated, several steps must be completed during the investigation. The first step is to filter the sample at the micrometric scale in order to block and reject cells, parasites, fungi and bacteria.

Nevertheless, fragments of DNA and free RNA manage to pbad through the filter. And you have to eliminate them. For this, we use nucleases, which are enzymes that digest DNA and RNA. The nucleic acid of the virus (DNA or RNA) is not digested because it is protected inside the viral capsid. But the free nucleic acid is. After all this, the viral particle undergoes the process of cellular lysis, destruction or dissolution of the cell caused by rupture of the plasma membrane. Finally, the genetic material is released and sequenced.

"This produces billions of small sequences that need to be aligned to try to reconstruct the viral genomes.Once the major sequences obtained, the next step is to search, via bioinformatics, for something like this. badogous in the database, which generally requires a lot of processing time and computing power.We sequence all the possible viruses in the samples and then we try to see if the sequences obtained coincide with those of known viruses " said Cerdeira Sabino.

According to the authors of the research, the main viral agent of diarrhea in Brazil was rotavirus. But since rotavirus disease has become preventable by vaccination, it is possible that other viral agents may be the cause of gastroenteritis.

Cerdeira Sabino comments that it may happen that two non-pathogenic viruses produce a pathogenic virus by recombination, for example. During recombination, a fragment of virus binds to a fragment of another virus to form a third.

"We do not know the etiology of many human diseases.In regard to diarrhea, for example, the cause is unknown in more than 50% of cases.This is why many agents must Before we could go in search of these agents, it was very difficult and expensive to sequence them, but with the next-generation sequencer, it became easy, but there is a big distance between finding one. agent and prove that he is the cause of the disease, "said the researcher.

Adriana Luchs, Elcio de Souza Leal, Shirley Vasconcelos Komninakis, Flavio Augusto of Padua Milagres, Rafael Brustulin, Maria da Rodrigues Teles Aparecida, Danielle Elise Gill, Xutao Deng and Eric Delwart also participated in the preparation of the. article. (Source: AGENCIA FAPESP / DICYT)