Recommendations have been published by university researchers for the reduction of the disease risks posed to public health by intensive pig and poultry farms that are situated in close proximity to each other, known as mixed pig/poultry farms.
This research was conducted between the University of Winchester and Griffith University, with a focus on mixed pig/poultry farms in the UK.
Avian and swine influenzas are of the most concerning due to several factors, including the numerous type A influenza virus subtypes hosted in these animals, as type A is the most widespread.
Other factors include the vast numbers of farmed pigs and poultry, how farmed poultry and pigs are kept, the presence of both domesticated and wild birds and swine, and the close proximity of farmed pigs and poultry to humans.
Many species of natural avian influenza hosts are migratory species, which facilitates the international spread of AIVs (avian influenza viruses).
Pigs are natural hosts for several influenza viruses, though of fewer types than birds.
The world saw its largest highly pathogenic H5N1 avian influenza outbreak in 2022, causing the culling or death of over 130m domesticated birds globally, and at least 50,000 wild birds in the UK alone.
It has now reached 81 countries and five continents, after spreading into Antarctica in October 2023.
The following eight factors account for the higher risk of viral infection among domesticated mammals:
- High population numbers among farmed pigs, farmed chickens, and humans;
- How the vast majority of farmed pigs and chickens are kept;
- How the vast majority of farmed pigs and chickens are bred;
- Close proximity of farmed pigs and chickens to humans (staff);
- The globalized and international nature of industrialized intensive animal farming (IIAF);
- The high land/resource requirements of IIAF disrupting ecosystems and increasing proximity to wild animals;
- The locations of IIAF operations;
- Misperceptions of low risks to and posed by farmed animals.
Biosecurity practices alone are proving insufficient at lowering the risk of zoonotic disease to a manageable level, as demonstrated by indoor systems with good biosecurity that are still acquiring influenzas.
Recommendations
The university researchers strongly discourage granting any planning applications for new or expanding industrialized intensive animal farms in the UK, especially poultry and pig farms or a mix thereof, and especially in areas with high-existing concentrations of intensive animal farms.
Instead, they recommend that efforts should concentrate on supporting arable agriculture (or transitions toward this), and on de-intensifying remaining animal farms.
As a recommended first step, stocking densities should be lowered to around five meat chickens/m2 (11 kg/m2) and to one pig/1.5 m2 (assuming a 100kg pig).
These recommendations, according to the researchers, are essential for minimizing stress and safeguarding immune system health, and therefore, essential for minimizing zoonoses risks.
They include the reduction of “clusters of operations” (IIAF farms that are in close proximity) to reduce transmission risks, as dust particles can carry viruses and be wind-carried between farms.
There are also calls in the research for improved breeding practices, away from a focus on maximizing productivity, and toward lowered susceptibility to infection, and optimal overall health and welfare.
