An Update on Avian Influenza

H5 Highly Pathogenic Avian Influenza (HPAI), or Bird Flu, has become a global issue. The virus is now present in wild birds on six continents and the use of sanitary control measures alone may no longer be a sustainable solution to effectively contain the disease. The time has come to move away from the systematic mass culling of flocks as the main measure to control HPAI. We need to consider the use of safe and effective vaccines in combination with proper monitoring and surveillance to control this disease. Research is well on the way and Royal GD is currently carrying out field tests in laying hens. In the shadow of the global H5 outbreak, the H9N2 strain is also endemic in many countries. A new animal model has recently been developed to test vaccines against this strain.

Bird flu is a clear and present danger to biodiversity, human health and the economic sustainability of commercial poultry farming worldwide. In December 2023, the World Organisation for Animal Health (WOAH) sent out a policy brief on Avian Influenza. The brief noted that the rapidly evolving nature of avian influenza and its patterns of spread require a review of existing prevention and control strategies. To effectively contain the disease, protect the economic sustainability of the poultry sector and reduce potential pandemic risks, all available tools – including vaccination – must be reconsidered according to the WOAH.

GD is participating in experiments to test the efficacy of vaccines in collaboration with Wageningen University, Wageningen Bioveterinary Research and Utrecht University. We have already established – under experimental conditions at eight weeks post-vaccination – that these vaccines are capable of fully protecting chickens against disease and of stopping the spread of the virus to other animals completely. Moving on, we are now carrying out a controlled experiment under practical circumstances. In this small-scale field test, we will determine the vaccines’ effectiveness in laying hens and the duration of the protection acquired. The first challenge has been performed recently and all results will be available in May 2024. The second challenge, to determine the level of protection, will be done at around 23 to 25 weeks of age. Should protection still be present, we will continue this experiment for an even longer period. This kind of controlled field experiment is very important to the validation of the vaccines. The results of the tests have so far been very encouraging.

However, in order to be able to stay on top of the global outbreak of H5, we need more than testing different kinds of vaccines and carrying out scientific experiments. The epidemiology of Avian Influenza is evolving fast: the disease is gradually losing its seasonal nature and becoming endemic in wild birds. This increases the likelihood of virus evolution and spill-over to new species, posing a risk to human health as well. WOAH urges countries to be prepared for an increase in outbreaks and recommends complementary approaches, such as vaccination. However, many current international and bilateral regulations still present a major barrier to the use of vaccines.