Scientists unravel the mystery behind the death of pigeons in São Paulo

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In 2019, days before a weather event that turned day into night in the city of São Paulo, dozens of pigeons began mysteriously dropping dead. The birds had some injuries, neurological symptoms and were found already lifeless or almost dead near the Zoonosis Control Center in São Paulo.

A multicentric team of researchers found that, despite the proximity of the dates, the deaths were not related to the pollution generated by fires in the Amazon. They were, in fact, the effect of an avian paramyxovirus type 1 – also known as Newcastle disease virus.

The virus, with a genotype called VI.2.1.2, is usually lethal to pigeons. Also known as pigeon paramyxovirus (PPMV), this agent rarely infects people and, when it does, it is through close contact with sick animals.

“We discovered that it was a virus that had been circulating silently in Brazil since 2014. Based on the molecular data, we noticed that it was the same PPMV that had been identified in Porto Alegre five years earlier. And there are about 1,100 kilometers between the two cities. This fact demonstrates the potential of this pathogen to spread without being noticed”, says Luciano Matsumiya Thomazelli, researcher at the Laboratory of Clinical and Molecular Virology at the Institute of Biomedical Sciences at the University of São Paulo (USP) and first author of the article, published in Viruses magazine.

Since 2005, the laboratory has had a team that goes into the field to carry out epidemiological surveillance research in different regions of Brazil. The activity is carried out within the scope of the Virus Genetic Diversity Network (VGDN), coordinated by USP professor Edison Luiz Durigon and financed by the São Paulo Research Foundation (Fapesp).

Currently, the group is part of the National Network for the Surveillance of Viruses in Wild Animals (PREVIR), promoted by the Ministry of Science, Technology and Innovations (MCTI) through the National Council for Scientific and Technological Development (CNPq).

pigeon death

Newcastle disease virus normally causes disease in chickens, but not in pigeons. According to the researchers, however, with the genotype VI.2.1.2, the opposite occurs.

“It is endemic in the pigeon population worldwide, causing neurological symptoms and high mortality. There are frequent reports of cases in Asia, Europe and North America. Despite this being the second record in Brazil, This is no cause for alarm, as this genotype does not pose a major risk to humans. or for poultry farming”, says Helena Ferreira, professor at USP’s School of Animal Science and Food Engineering in Pirassununga, member of the PREVIR-MCTI network and research coordinator.

Scientists point out that monitoring has been shown to be extremely important for controlling epidemics, outbreaks and for warning about the emergence of new diseases.

“Obvious and active surveillance throughout the country is essential to identify and control pigeon populations not only near farms, but also in urban areas. Monitoring the Newcastle disease virus is also important from an economic point of view, as Brazil is the largest exporter of chicken meat in the world”, says Thomazelli.

team work

To unravel the mysterious disease that afflicted pigeons in the capital, it was necessary to activate a wide network of researchers. First, the São Paulo State Surveillance and Zoonoses Center identified the death of the birds and called the Official Veterinary Service.

“At first it was thought that the cause could be a bacterium, but no pathogenic species was identified. They sent samples to the ICB-USP and to the Federal Laboratory of Agricultural Defense. There they performed the characterization, which is the recommended standard for notifiable viruses as they affect domestic birds. It was up to our laboratory, in Pirassununga, to carry out the analysis of the viral genome”, says Helena.

The researcher also performed analyzes to identify tissue injuries. “We sequenced the complete genome of this virus, which we identified as VI.2.1.2. This allows us to do a more in-depth investigation, compare with outbreaks in other parts of the world and also follow the evolution of the pathogen here in the country,” she says.

According to Helena, the knowledge acquired in the analysis can help predict how the virus will behave from now on. Genomic analysis showed that the virus found in São Paulo and Rio Grande do Sul (in 2014) clusters with samples from Africa.

“Other cases need to be identified in order to be able to propose the classification of the genotype that has been circulating in Brazil, which is relatively different from the African one. It is very important to do this type of monitoring. In this specific case, this genotype cannot infect domestic birds [galinhas] efficiently and, when infected, the chicken does not transmit the virus to others with which it lives”, he says.

According to the expert, studies suggest that this genotype can adapt in chickens after a few passages and cause disease in poultry as well. “Even so, it is not considered very dangerous for commercial birds”, she reinforces.

Source: CNN Brasil

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