“Expert advisory report warns of potential bird flu and swine influenza mixing vessel on mixed farms”

“Mixed farms with pigs and poultry, pig farms with an outdoor range and farms near poultry farms or in areas rich in waterfowl are a ‘potential mixing vessel’ for bird flu and swine influenza viruses. They can cause avian flu to spread to humans,” says a recent advisory report from the Dutch Association of Experts on Zoonoses.

Horror image

According to the Dutch Expert Council, it is therefore not desirable to have poultry and pigs at the same location. Although the Dutch experts are now sounding the alarm about mixed farms, the risk of that specter is currently estimated to be low. “Research has shown that pigs are particularly difficult to infect with the bird flu virus H5N1. There is a very large animal species barrier for that virus to jump over to the pig,” says Kristien Van Reeth, professor of virology at the Faculty of Veterinary Medicine at UGent. “But the scenario that the Dutch experts warn about is a situation in which the virus mutates and thus becomes more effective in pigs. The risk for this is low but not impossible because flu viruses are genetically labile. The most disturbing scenario is if a pig were to become infected with an avian flu virus and a swine flu virus at the same time. These two viruses could result in a hybrid form that can multiply and spread more easily in pigs and humans. The risk of this remains very low, but the consequences could be significant.”

Approach

To reduce the risk of contamination, the Dutch experts recommend developing an approach that could target farms with the highest risk and to give biosecurity a higher priority on pig farms. They also recommend paying more attention to proactive monitoring. In addition, everyone within the pig farm who has been exposed to the bird flu virus would be offered a test, even if they have no complaints. This could be worked out for groups such as scrapers, veterinarians and pig farmers involved in outbreaks in poultry on mixed farms.

Bird flu in pigs

Pigs are currently also usually sampled if there is an outbreak among poultry on mixed farms. HPAI virus has never been detected in pigs in Belgium. However, it is increasingly happening that the bird flu virus spreads to mammals. Since October 2021, Europe has been dealing with the largest bird flu outbreak ever. Worldwide, at least 30 different species of mammals have been infected with avian flu. From foxes, sea lions and badgers to even grizzly bears in America.