WBVR research shows that a daily mortality rate of 0.3% is a reliable indicator of possible infection. The research institute also found that a 9% or more decrease in daily egg production could also indicate a possible outbreak.

"A daily mortality rate of over 0.3% - after the first week of life at the farm - could be an excellent indicator for broiler ducks," said WBVR epidemiologist Armin Elbers. "A decrease in the daily food and water intake of more than 7 grams or 14 ml respectively are also accurate indicators of avian influenza infection."

Available data for breeding ducks is limited. The mortality in three flocks of breeding ducks in Germany was very limited after an infection, said Elbers, but the British flock showed rapid mortality.

"Applying the threshold value of 0.3% mortality is recommended for all breeding and reproduction ducks," said Elbers. "A decrease in egg production of over 9% is also a very effective indicator of a bird flu outbreak in breeding and laying ducks."

The results of the study were published in Pathogens.