August 1, 2020


European pig holdings reservoir for novel influenza viruses, study finds



A new study has found that European pig holdings are reservoirs for an increasing number of diverse influenza viruses, some of which can be transmitted to humans and may have pre-pandemic potential.


The study, published on July27 in the scientific journal Cell Host & Microbe, investigated more than 18,000 individual samples from almost 2,500 European pig holdings affected by respiratory diseases, according to a press release by the Friedrich-Loeffler-Institut (FLI) which, together with the Freiburg University Medical Centre in Germany, coordinated the study.


The study noted that pigs are ideal mixing vessels for the replication and reassortment of influenza viruses originating from humans, pigs or birds. It showed that the causative agent (biological pathogen) of the latest human influenza pandemic influenza A(H1N1)/2009, which was introduced into European pig populations in 2009, led to the rapidly growing repertoire of novel virus variants in pigs.


Moreover, the study found that some virus variants have zoonotic potential, or potential for transmission to humans.


Other viruses proved to be resistant to an important component of the human antiviral defence: "Some of the swine influenza viruses have already crossed an important immune defence barrier for transmission to humans. This considerably increases the risk", said Prof. Martin Schwemmle of the Freiburg University Medical Centre.


The study investigated pig holdings in Germany and 16 other European and found that in more than half of them, there were influenza virus infections all year round. Four influenza virus strains with different geographical distribution were predominant, and novel virus variants increasingly emerged from these four strains.


The study said that up-to-date knowledge of the infection situation leading to improved control strategies, and the optimisation of vaccines for pigs against influenza viruses can significantly contribute to increased animal welfare and reduced economic losses in pig production.


At the same time, a decrease in influenza virus prevalence in pig holdings would reduce the risk of human exposure to potentially zoonotic influenza viruses from this reservoir. 


The research project was funded by CEVA Tiergesundheit GmbH.