Over half of the ducks vaccinated against avian influenza in France are still not fully protected against the virus.
A model from France’s agency for human and animal health, Anses, indicates that only 40-45% of ducks achieve full protection from a complete vaccination scheme. The remaining ducks are either partially protected or have waning immunity, largely due to the challenges of ongoing vaccination processes.
Research from Anses shows that the protection levels in ducks older than 10 weeks decline over time. In response, foie gras ducks, which generally are reared for around 16 weeks, are administered a third vaccine dose to enhance their immunity.
Mandatory Vaccination for Ducks
In an unprecedented step, France mandated vaccination for all ducks on farms with more than 250 birds in October 2023. This decision followed severe avian influenza outbreaks in recent winters.
By March 31, 2024, a total of 51 million vaccine doses were administered, covering over 95% of ducks on the affected farms. Most of these ducks received two doses: the initial dose at 10 days of age followed by a second dose approximately 20 days later, a protocol that has been consistently applied in subsequent vaccination drives.
Assessing Campaign Effectiveness
The effectiveness of these extensive and costly vaccination campaigns has been evaluated using a model developed by Anses. This model utilizes data collected in the field by the state’s directorate-general for agriculture.
“By understanding the percentages of livestock holdings that are fully or partially protected, we can estimate the overall level of protection in the duck population. Adhering to the vaccination protocols laid out by the production sectors is vital to optimizing that protection,” said Morgane Salines, a scientific expert in epidemiology, health, and welfare at Anses.
Mitigating Avian Influenza Spread
Béatrice Grasland, head of avian virology and immunology, emphasizes, “Vaccination doesn’t stop infection by the virus but can effectively limit clinical signs and reduce the virus excretion by infected animals, which ultimately helps to slow the spread within farms and to other holdings.”
The developed model also explores innovative vaccination scenarios that have yet to be implemented. One such approach considered is forgoing vaccinations during periods of lower risk for avian influenza to cut down on costs for both the government and poultry sector. However, Anses has deemed this the impractical route; without summer vaccination, immunity would develop too slowly, leaving ducks vulnerable during peak infection seasons in autumn and winter.
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