Wild bird distribution a good predictor of avian influenza outbreaks on poultry farms

Schreuder studied the environmental factors of 26 outbreaks of highly pathogenic avian influenza in Dutch poultry farms and compared them with factors around 104 non-infected control farms. Using machine learning, the researcher analysed predictive indicators for avian influenza outbreaks. The density of wild birds proved to be the best predictive indicator; 19 of the 20 highest scoring indicators were related to wild birds. Of these, 17 were waterfowl and two were birds of prey. In addition to wild birds, one landscape feature, agricultural use, also contributed to the prediction of avian influenza on poultry farms.

Mallard duck

Of the waterfowl, the mallard duck proved to be the most important contributor to the risk prediction, followed by the mute swan, brent goose, and wigeons. "Previously, landscape features such as open water were mainly considered predictive factors. Landscape features play a role in the presence of wild birds and the numbers in which they occur in a particular place. My research shows that the presence and numbers of wild birds are better indicators for predicting an outbreak of avian influenza on poultry farms than landscape features alone," Schreuder explains.

Prioritisation

"Despite the limited number of avian influenza cases analysed, 26 in total, the model appears to provide an accurate prediction of the risk of an outbreak," said researcher Schreuder. She believes that these analyses and the resulting avian influenza risk map are good tools for prioritising avian influenza monitoring. This knowledge also contributes to the targeted use of preventive measures to avoid the spread of avian influenza on farms. “The maps can also help determine where poultry farms would be best located to minimise the risk of an avian influenza outbreak."

Distribution

According to Schreuder's model, the presence and numbers of the mallard duck and the mute swan are of the greatest importance, followed by some goose species. "Highly pathogenic virus variants have been found in many of these waterfowl in several recent avian influenza outbreaks, as well as in some other species from the list of best predicting bird species," says the researcher. The study does not clarify the role of these birds in transmitting the avian influenza virus to poultry farms. "Further research into these bird species could provide new leads for this."