The chance that a poultry farm will become infected with the bird flu virus via the air inlet is negligible. Research by Wageningen Bioveterinary Research shows this.
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There are noises from poultry farmers that bird flu may be entering their farms through the air intake. They infer this from the fact that poultry that has died from bird flu are regularly located near the air inlet. In addition, there are indications from previous experience that the bird flu virus can be transferred via the air from farm to farm if it is produced in large quantities by large numbers of infected chickens in a house.
That is why it has been investigated whether there is a risk that the avian flu virus from wild birds can enter the barn through the air inlet, says Armin Elbers, project leader of the research and senior epidemiologist working at Wageningen Bioveterinary Research.
No connection
To begin with, the fact that poultry that is out of action due to bird flu are near the air inlet does not appear to be a reason to demonstrate a link between air inlet and contamination. After all, it usually takes more than a week after the infection before the poultry dies from bird flu.
The infected animals will not have remained near the air inlet all week. It is likely that sick animals move towards the air inlet because they have breathing problems and there is more fresh air close to the air inlet.
Manure does not evaporate
More importantly, the research by Wageningen Bioveterinary Research shows that the risk of transmitting the highly pathogenic bird flu virus from infected wild birds through the air is negligible. To this end, the research institute carried out field research with manure from wild water birds in the risk period from October to March. According to Elbers, the chance that the manure will evaporate during this period is extremely unlikely.
The moisture content of the fresh manure is between 75 and 85 percent and the manure should then dry out to 10 percent moisture. In view of the climatic conditions in this period, where it is often wet with low temperatures and hardly any solar radiation, that has not happened. The moisture content of the manure remains between 70 and 90 percent. The chance that the bird flu virus with volatile manure particles will blow into the barn is therefore estimated to be negligible.
Aerosols
The chance is also small via aerosols that infected birds cough out or spit out, according to Wageningen Bioveterinary Research. Short distance transmission, i.e. 10 to 40 centimeters, is possible. But the chance that poultry will actually become infected as a result is small because the dose is too low. Over longer distances, the chance is much smaller.
Incidentally, this is not to be confused with the risk of bird flu spreading from an infected poultry stock. An enormous amount of virus is released in a short time, which can then end up at a nearby company via the ventilation air.
No windbreak mesh needed
The chance of contamination from poultry manure or aerosols from wild birds via the air inlet is therefore small. The use of windbreak mesh or air filtering to prevent this is therefore not necessary. It is still being investigated whether there may be a risk by running off manure from wild birds flying directly from the roof into the air inlet.
It is clear that the introduction of bird flu mainly comes from other risk sources. Direct introduction of manure from wild (water) birds from the farmyard via footwear, clothing, materials or litter is a risk that must be excluded by good biosecurity. The virus can also enter the stable on the legs or fur of vermin. In addition, manure on the range of poultry is a risk. It is therefore important to keep wild birds out of the range, and it is certainly important to prevent pools in which wild birds swim and fatten.
Infected feathers
Another risk factor is the feathers of wild birds infected with highly pathogenic avian flu. The virus remains infectious for at least 34 days at 4 degrees Celsius and much longer at lower temperatures. Feathers from infected wild birds could be released when scavengers feed on carcasses and possibly be transported by wind to the environment and possibly through the air intake of poultry houses. There is no data on this, but it is a theoretical possibility.
As a precautionary measure, it seems important to remove carcasses of dead (water) birds that may be infected with bird flu from the natural environment as soon as possible after death, because they could be the source of loose feathers.
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