Study shows levels of risk of epidemic or pandemic outbreak in Brazil

With its continental size and heterogeneous landscapes, Brazil is home to a huge biodiversity of animals and plants and is therefore also a haven for a significant variety of pathogens and parasites - organisms that can cause disease. A study led by researchers of the Oswaldo Cruz Institute (IOC/Fiocruz) and published in Science Advances points to recent increases in the country’s social and ecological variabilities, associated to political and economic scenarios, and raises the alarm for the propensity of this megadiversity to act as an incubator of a possible pandemic caused by zoonoses (infectious diseases that circulate among animals and which may be transmitted on to humans).

Burning area of the Pantanal biome. The removal of natural vegetation is one of the main factors that promote outbreaks of zoonoses (Photo: Fabiana Lopes Rocha)

“Based on an evaluation model that identifies different interactions between the elements we are investigating, we managed to observe more widely the processes that shape the appearance of zoonoses in each Brazilian state,” says Gisele Winck, first author of the paper and researcher of the Laboratory of Biology and Parasitology of Reservoir Wild Mammals of the IOC.

Three main risk components are the focus of the evaluation: vulnerability, exposure and coping ability. Within the main groups, the study observed more specific variables, such as the number of species of wild mammals, loss of natural vegetation, changes in land use patterns, social well-being, cities’ geographical connectivity, and economic aspects.

The results highlight deforestation and poaching as highly relevant factors for the appearance of infections both old and new. The study also shows that the entire Brazilian territory is susceptible to emergencies caused by zoonoses, with higher probability observed in areas under the influence of the Amazon rainforest.

One example is the state of Maranhão: 34% of its territory is covered by tropical rainforest and is classified as a high risk area for zoonoses outbreaks. Meanwhile, in Ceará, a neighboring state, where caatinga prevails, the risk of new diseases is low.

“The Amazon rainforest has a high diversity of wild mammals and has been suffering with a huge loss of forest coverage. Many species are being deprived of their habitat due to deforestation, creating an imbalance in the local dynamics,” explains Cecília Siliansky de Andreazzi, the last author of the article and also a researcher of the Laboratory of Biology and Parasitology of Reservoir Wild Mammals of the IOC.

Other participants of the study were specialists and researchers of the Vice-Presidency of Production and Innovation in Health for Fiocruz, of the IOC Laboratory of Compared and Environmental Virology, of Fiocruz Ceará, of the Federal University of Paraíba (UFPB), of the State University of Ceará (UECE), of the Maurício de Nassau University, of the International Union for Conservation of Nature, and of the Portuguese universities of Aveiro and Coimbra.

Risk of 'spillover'

Contagion by infections of animal origin occurs due to the phenomenon known as spillover, when pathogens that were restricted to an animal group take a leap and begin infecting other species, including humans. The expansion of human activities into regions of woods and forests, naturally inhabited by wild animals, further favors this scenario.

However, the study emphasizes that in order for a zoonoses to become an epidemic, different ecological, epidemiological and behavioral factors must be aligned, including human mobility as a relevant factor. In Brazil, the socioeconomic dependence of smaller towns from capitals and metropolis increases the epidemic potential of zoonoses, as inhabitants from the hinterlands must frequently travel to urban centers to obtain goods and services.

“Human mobility is crucial for the spreading of zoonoses, especially when it comes to infections transmitted from person to person after the jump in between species, which is the case of COVID-19. Once these pathogens reach superspreading cities, such as São Paulo and Manaus, transmission is amplified and exported to different other regions,” said Andreazzi.

Game meat is another critical pathway for disease spillover. A network analysis found a correlation between species that are illegally hunted in Brazil and pathogens that have the potential to cause serious harm to public health. As a result, 63 mammals were found to interact with 173 parasites which could cause at least 76 different diseases.

“Infection can occur in different steps: when the hunter enters the forest and is exposed to mosquitos, ticks and other pathogen vectors; during the hunting itself, when the hunter can get himself a cut or scratch that comes into contact with animal fluids; when the meat is prepared and there is direct contact with the animal’s internal organs, which are also commonly offered raw to pet dogs and cats; or when the meat is consumed, if it was not well stored or cooked”, details Winck. As hunting is still an essential activity for traditional populations that use game meat for their subsistence, specialists employ a situation approach in the paper and recommend the implementation of focal actions to ensure sanitary safety for these groups.

“This is something that requires much debate and evaluation. Only traditional populations are authorized to hunt, but hunting continues to occur out of these groups and works as an interaction factor between people and wild animals that are reservoirs to pathogens. Unfortunately, they all end up being incorrectly treated as the same thing. We must differentiate populations that depend on this activity as a source of protein from those who smuggle wild animals or hunt as a sport,” Andreazzi mentioned.

Surveillance and care

The main way to mitigate the effects of an emerging zoonoses, according to the study, is to invest in the actions of the Unified Health System (SUS). According to the paper, zoonoses can be effectively contained with the promotion of public health policies that support predictive and preventive approaches that follow the One Health concept (Unified Health, which contemplates human, animal and environmental health).

Some of the recommended actions are the implementation of effective surveillance systems integrated with the epidemiological surveillance of potential zoonoses, wider and more innovative policies that mitigate environmental degradation, control of wild animal trafficking, and new approaches for the conservation of biodiversity.

“What defines whether the appearance of a zoonoses will become a local outbreak, an epidemic or a pandemic is the way we deal with the situation. We need to think about how we can implement effective surveillance in a country as large and as diverse as ours,” said Winck.

“Brazil’s response to Covid-19” The study originated from a letter published in The Lancet in September 2020. Back then, the authors of the text mentioned setbacks in social and environmental policies in Brazil, which could contribute to the occurrence of infections caused by pathogens of animal origin. Specialists also defended the creation of an integrated surveillance system for wild diseases.

“After the letter was published, we began a deeper and more detailed reflection on the potential risk of the emergence of zoonoses in Brazil. This paper is the result of plenty of research and debating among the researchers of this group, as these are complex issues that require a search for information from various sources,” emphasized Winck.

The researcher also highlighted the multidisciplinarity of the members of the research. “Our group consists of different professionals who work in the fields of public health and of environmental conservation, which led to interesting discussions on these subjects. We are often used to working with colleagues from our own field, who think in a similar manner. With this group, the highlight was this rich and diverse environment that made it possible to explore new ideas to build the paper,” she concluded.

The article is part of the SinBiose project of the National Council for Scientific and Technological Development (CNPq). The goal of the initiative is to produce data and concepts that emphasize projects that approach current issues in biodiversity and ecosystemic services.