by A recent study published in the journal PNAS has warned about the potential risks of large-scale pig farming, which may lead to the emergence and transmission of novel zoonotic pathogens. The researchers utilized various methods such as molecular dating, comparative genomic analysis, and phylogeography to investigate how the rearing of pigs can contribute to the development of new strains of infectious diseases, some of which have the potential to infect humans.
The global expansion of livestock rearing, driven by the increasing demand for food and agricultural labor, has resulted in a significant rise in the number of livestock populations. This, in turn, has led to intensive farming practices characterized by low genetic diversity and high-density livestock. With the widespread transportation of animals, these conditions provide a favorable environment for the outbreak of pathogens that can not only affect other livestock populations but also wild animals.
This combination of intensive farming, lack of genetic diversity, and long-distance transport can potentially promote the emergence of novel zoonotic pathogens. Pathogens that were previously associated only with reared animals can mutate and jump to new hosts, posing risks to both human and animal populations. One example highlighted in the study is Streptococcus suis, a bacterium commonly found in the upper respiratory tract of pigs. Over time, intensive pig farming has caused this bacterium to become more pathogenic, leading to widespread disease in pig populations. Moreover, mutations in the bacterium have allowed it to infect humans, causing serious illnesses such as meningitis, arthritis, endocarditis, and septicemia.
To understand the link between intensive pig rearing and the emergence of novel strains of Streptococcus suis, the researchers conducted a population genomic analysis. They collected bacterial samples from pigs and wild boars across different regions and also obtained infected blood samples from humans and pigs with Streptococcus suis disease. Through genomic sequencing and analyzing the obtained data, they aimed to identify the emergence, spread, and diversification of pathogenic lineages of the bacterium.
The study found that the rearing of porcine populations has increased significantly over the past two centuries, with the most significant rise occurring in the latter half of the 20th century. This has corresponded with the gradual emergence of more than 10 highly pathogenic lineages of Streptococcus suis. The high density of pigs in intensive farming systems, along with the use of antibiotics, has led to the development of antibiotic-resistant strains, posing challenges for disease control.
Further analysis of samples from Spain revealed that both reared pigs and wild boars carry genetically diverse strains of Streptococcus suis, indicating a long-standing association between the bacterium and its host. However, genetic dating analysis showed that the six most common pathogenic strains emerged during the 19th and 20th centuries, aligning with the period of increased pig rearing.
In conclusion, the study highlights the potential risks associated with intensive pig farming, including the emergence of novel zoonotic pathogens. The findings underscore the importance of implementing measures to ensure the health and safety of both animals and humans in livestock rearing systems. By addressing issues such as genetic diversity, animal welfare, and disease control, it may be possible to mitigate the risks associated with intensive farming practices and prevent the emergence of dangerous pathogens.
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1. Source: Coherent Market Insights, Public sources, Desk research
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