# Effective mortality thresholds for reporting suspicion of highly pathogenic avian influenza in mule ducks

## TL;DR

The study identifies effective mortality thresholds for detecting avian influenza in mule ducks, improving disease surveillance and response.

## Contribution

The study introduces specific mortality thresholds for early detection of avian influenza in mule ducks, filling a policy-relevant knowledge gap.

## Key findings

- An eightfold increase in mortality over two days correctly classified all validation flocks.
- A fixed threshold of 0.25% daily mortality achieved perfect sensitivity and good specificity.
- The findings can inform HPAI surveillance policies for non-vaccinated mule ducks.

## Abstract

Effective mortality thresholds are critical for timely reporting and management of highly pathogenic avian influenza. Using standard modelling techniques, we evaluated the performance of different mortality thresholds in mule duck flocks. Using an eightfold increase of the mortality for two consecutive days compared to the average mortality the previous week led to a perfect classification of all flocks used for validation (12 affected and 18 non-affected flocks). A fixed daily threshold of 0.25% showed a perfect sensitivity and a good specificity (3 false positives/18). Our results fill a knowledge gap and can inform HPAI surveillance policy in non-vaccinated mule ducks.

The online version contains supplementary material available at 10.1186/s13567-025-01525-9.