Coarse particles and insects – which can be infected with bird flu or other pathogens – can enter the vents of poultry farms with the air. This has emerged from research by Wageningen Bioveterinary Research (WBVR), part of Wageningen University & Research, and Utrecht University on the transport of possible carriers of the bird flu virus through an air vent. “Even though we did not find an avian influenza virus in our research, we advise poultry farmers to take additional steps to minimize the potential risks of this route of introduction via the snorkel,” says Armin Elbers, researcher of the WBVR. More research is needed to map out the effectiveness of the various measures.
Poultry can become infected with the avian influenza virus through direct or indirect contact with faeces or other secretions of infected wild birds or other infected poultry. The applicable confinement obligation prevents direct contact between kept poultry and infected wild birds or an infected environment. It is not clear how, despite the biosecurity measures taken by the poultry farmer and the confinement obligation, the poultry still become infected in some cases. Various introduction paths are conceivable; one is by air through the air intake of poultry houses.
Commissioned by the Ministry of Agriculture, Nature and Food Safety, the Wageningen Bioveterinary Research (WBVR) in Lelystad, in collaboration with Utrecht University (Faculty of Veterinary Medicine and Institute for Risk Assessment Science/IRAS), studied the transport of possible carriers of the virus through the vent of a poultry farm.
Remarks
On a recently infected broiler and layer farm, after culling and several rounds of cleaning and disinfection, WBVR placed a vent hood over the inlet valve to 18 vents per house. A fine mesh net is also attached to it (see photo). The ventilation was managed as if poultry were present. The fine-mesh net collected wild bird feathers, plant material, cobwebs, plastics, wool, and manure.
Additionally, WBVR has installed a camera monitoring system. This recorded wild birds visiting the area around the barn.
Results
The content of the fine mesh nets was collected every 5 days in both poultry farms in the period January-March 2022 for a total of 25 days. Even the fine mesh nets were cleaned with a duster. Incoming material, duster and trapped insects were tested for influenza virus, Campylobacter and Salmonella. The insects were also tested for Schmallenberg, West Nile and Usutu viruses.
The researchers found small amounts of material in the networks. This ranged from small pieces of plant and/or crop material, bits of plastic and paper, to wool and cobweb. No wild bird feathers or droppings were observed. Cobwebs and plant matter were observed the most: averaging 1 to 2 cobwebs or plant matter per air intake per 5-day collection period. However, the variation in the amount of material entering through the various vents was considerable. During an occasional storm with high winds, large quantities of material can enter the house through vents on the windward side.
No viruses detected
All material samples tested were PCR negative for influenza virus and Salmonella. The bugs tested negative for Schmallenberg, West Nile and Usutu viruses. Evidence of the introduction of Campylobacter through the snorkel has been found. The area at a short distance (up to 10 m) from the poultry houses was regularly frequented by wild birds: blackbird, carrion crow, black backed gull, oystercatcher and mallard.
Continuation
Research indicates that coarse particles and insects – which may be contaminated with HPAIv or other pathogens – can enter poultry vents with air. “It is therefore wise to limit this potential route of introduction,” says WBVR researcher Armin Elbers. However, more research is needed to figure out how to do this correctly. “The use of windbreak netting can help limit this path of introduction,” predicts Elbers. He knows a company that installed a windbreak some years ago after a bird flu infection. “That company has now been infected again, so it is likely that this was via the air supplied via the vent. The windbreak net is therefore not a panacea”. According to Elbers, a good alternative is to use an automated laser. “With the laser you make the area around the chicken coop unattractive for wild birds to visit.”
Additional line of defense
Piet Faber, propagator in Nijerberkoop (FR) and chairman of the LTO/NOP-NVP propagation steering group, has long recommended the installation of windbreak nets in particular. “With the windbreak net, the feathers can be stopped and contamination can be prevented. As poultry farmers, we have organized the entrance to the door well. We have not yet set up anything to prevent the entrance through the ventilation. I see this as a “additional line of defense. This year’s outbreaks also show that companies don’t just get infected from the air.
The researchers published their findings in the scientific paper ‘Monitoring wind-borne particulate matter entering poultry houses through the vent: risk of highly pathogenic avian influenza virus and other pathogensin Pathogens journal.
