Millions of poultry slaughtered in France. The poultry industry believes it is facing “the most serious health crisis in its history” with avian flu which is spreading in farms. At the same time, African swine fever (ASF) arrived at French borders, particularly in Germany and Italy, raising fears of economic repercussions for breeders.
However, these two phenomena “have nothing to do”, according to Jean-Luc Guérin, professor of avian pathology at the National Veterinary School of Toulouse (ENVT) and Laboratory Director at INRAE, contacted by L’Express. The latter also believes that the responsibility for the spread of these viruses cannot be attributed solely to intensive farming because each “segment” of the farming sectors, from the smallest to the largest, can play a role. Maintenance.
L’Express: Are the spreads of avian flu and African swine fever in Europe linked?
Jean-Luc Guerin: Each situation must be seen separately: avian influenza is not comparable to ASF. Swine fever has been spreading in Europe for years, even decades, and unlike avian influenza, the disease spreads slowly, in particular because of the reservoir species: wild boars versus birds. Influenza affects migratory birds that can travel up to 1,000 kilometers a day, which is obviously not the case with wild boar. Moreover, the avian influenza virus evolves much faster than the ASF agent. Finally, ASF essentially constitutes an economic risk, whereas influenza is a global health concern, due to a risk of evolution towards viruses capable of infecting humans.
Can we attribute the responsibility for the development of these viruses to intensive farming?
This epidemic of ASF which is spreading in Europe is observed more in small farms which are in contact with wild boars. The outbreak detected at the German border concerns, for example, a farm with 35 pigs. Overall, there is a clear excess risk associated with small farms raising pigs outdoors.
With regard to avian influenza, the situation is more mixed. It is difficult to point out this or that segment, each of which can play a role in the introduction or the spread of the virus. Open-air farms generally present more risk of initial introduction from wildlife, especially when they are located near wetlands, with waterfowl all around, and this without much impact of their size. However, we thought that sheltering the animals in buildings in confinement would provide strong protection, but we must recognize that the effectiveness of this measure has proven to be disappointing due to the exceptional contagiousness of the virus which currently circulating in Europe. Moreover, the organization in a sector, with connections, animal transport, and especially the grouping of farms in high-density areas, increases the risk of spreading the virus despite the efforts made by professionals and the regulations put in place. in place. The spread of the virus is so violent and the virus so contagious that these measures, relevant in principle, are no longer sufficient.
And globally?
Today, the dynamics concerning avian influenza are as follows: the initial crucible of viral emergence is located first in Southeast Asia, the viruses continue to evolve there and circulate towards Europe and beyond. beyond via the migration corridors. On a global scale, the number of poultry is experiencing very strong growth, particularly in Asia. Increased density of poultry populations in areas where influenza viruses are emerging may be a risk factor for the spread of the virus. So Asian farming models could play a role, knowing that there is, in China as elsewhere, a very wide variety of farming models, including many small farms that are difficult to monitor.
If we think on a global scale, there is therefore a conjunction of actors, some more at risk of being infected by wildlife, others more at risk of spreading the virus to other farms. It is the juxtaposition of these actors, on the same territory, which can create a problem. Scientifically, it is therefore simplistic to specifically incriminate “intensive” breeding. By way of illustration, in France, traditionally it is not the intensive farms of the Great West that were the most affected, but rather those of the South West, with a model of smaller farms and access to outdoor runs.
How to guard against the risk of spread?
The challenge is to increase the resilience of farms, because the virus is much more virulent today and exceeds our control capacities through surveillance and biosecurity. It has also reached the large farms of Pays-de-la-Loire, when we thought these farms were better equipped to resist. Today, the higher the breeding density in a territory, the more difficult it is to control the risk of spread. This raises the question of a readjustment of the location of farms in the territory, but this proposal is easier said than done.
It is also necessary to readjust biosecurity and surveillance measures in high-risk areas: this is a very important concept which is proving to be even more decisive this year. We are facing a huge risk of spread for farms that are located a few kilometers from each other: it is a paradigm shift in relation to knowledge about influenza, on an international scale. The virus has evolved, including since last year’s crisis and it will continue to evolve, that’s for sure.
Can we fear a new pandemic, like that caused by Covid-19, which would start from a farm?
The emergence of pandemic viruses have multiple and still poorly understood origins. The risk of a virus crossing the barrier between animals and humans depends on many factors: for example, the modification of the habitat of wild animal populations, which leads to more frequent contact between humans and animal, or the growth of domestic animal populations, which is an element of viral amplification. It is the combination of factors which, taken together, can mechanically increase the risk of emergence.
In the short term, the avian influenza virus currently circulating in Europe does not present pandemic potential. Nevertheless, it is to prevent any risk of long-term genetic evolution that very strict slaughter measures are applied, in order to prevent the virus from multiplying on millions of poultry and, in passing, evolving into viruses more dangerous for humans.