Avian influenza (AI), or bird flu, is a deadly disease that has a high mortality rate in wild and domesticated birds. It has been prevalent for years but, over the last 18 months, we have witnessed an escalation in occurrences due to the circulation of H5N1, an extremely virulent strain of the virus.
The Animal and Plant Health Agency (APHA) recently published a report on the role of airborne particles in highly pathogenic avian influenza (H5N1) in commercial poultry production units. The research follows the 2021 UK outbreak of avian influenza, and aimed to answer questions that had been raised about the spread of disease via airborne particles.
Observations have suggested that some strains of avian influenza may be transmitted over short distances via airborne particles. However, the risk of H5N1 spreading in this way remains unclear. APHA’s research was conducted using extensive sampling inside and outside houses including deposited dust, feathers, and other potential fomites. The data arising from this research suggests that infectious highly pathogenic avian influenza airborne particles can travel short distances (less than 10 metres) through the air.
According to the research, multiple factors influence the efficiency of airborne transmission with successful airborne transmission occurring in three stages:
- Stage 1: Generation, when airborne particles are produced that have a sufficient concentration of infectious virus.
- Stage 2: Transport, when airborne particles must move to a susceptible host whilst retaining enough concentration of an infectious virus.
- Stage 3: Infection, when the virus must contact ‘target cells’ of the host to initiate infection.
The samples taken by APHA for this research were taken from three infected premises in Norfolk.
- The first premises contained approximately 26,000 fattening ducks in two houses. The houses had natural ventilation and an overhanging roof covered by metal mesh.
- The second premises had approximately 20,500 135-day old turkeys in three houses, with mechanical ventilation and six incel vents.
- The third premises held over 300,000 broiler chickens in eight houses with mechanical ventilation and fifteen inlet vents.
The results
Four air samples were collected within 1 metre outside of the vents, and two separate air samples were collected inside the houses. During the collection of samples, the mortality rate of ducks in the first premises had increased and culling had been nearly completed. All but two air samples tested positive for vRNA (viral RNA – genome of Influenza A of eight negative-strand RNA segments). Infectious virus was isolated from both samples that were collected from inside the first and second premises. Apart from one air sample, all the others tested negative for infectious virus.
Samples were also collected from dust, water, and feathers for the study. The dust showed that only one sample tested positive for vRNA but not an infectious virus. Water samples also tested negative for vRNA. Feathers that were collected showed ¼ of samples tested positive for vRNA.
There are a limited number of studies which describe the potential risks of H5 HPAIV spreading widely and quickly within an environment. There have been no reports on HPAIV H5N1 transmitting among birds or field airborne detection. A small number of historical studies detail H5N1 (highly pathogenic influenza A) HPAIV RNA in the air and around infected premises. However, the results compare historic viruses with different transmission efficiencies. Many of those studies also failed to detect or assess an infectious virus. Historical studies can be useful to enhance further studies on the topic to a certain extent, but comparing old and new data presents challenges when obtaining different results for the role of airborne particles in highly pathogenic avian influenza H5N1 in commercial poultry production units.
There is no cure for avian influenza. Prevention is the only solution.
Whilst current data have produced negative results of infectious virus from airborne particles in highly pathogenic avian influenza H5N1 in commercial poultry production units, it does not mean that farmers should be complacent in using biosecurity for their premises. Biosecurity helps to prevent poultry sickness and saves businesses.
Livetec are leaders in biosecurity. Our Livetec Biosecurity Advisory Service is a great way to obtain an assessment of the most critical biosecurity risks on farm or a specific location (hatchery, breeder unit, processing plant). We document existing risks and identify and explain the most effective prevention measures that are practical and that can be put in place effectively to reduce risk. This service is led by specialists and is based on Livetec’s extensive knowledge backed up by the latest best practice and research.
To book a Biosecurity Advisory Service, contact us here.
