The International Egg Commission (IEC) has produced a report looking into the advantages and disadvantages of vaccination against avian influenza.

 

Photo by Mark Bullimore

At a time when AI is seen as a growing threat to the poultry industry, both in the United Kingdom, across Europe and in other parts of the World, an expert group of the IEC has considered the possible benefits of vaccination.
The expert group points to some advantages – particularly in developing countries where vaccination can, it says, help to protect a vital source of protein.
But it says there are concerns that vaccination can lead to complacency in implementing good surveillance and bio-security measures.
And in developed countries the use of avian influenza vaccines can impact on trade, it says.

“Given the high exposure of poultry to HPAI (highly pathogenic avian influenza) circulating in wild birds in recent years, the question regarding use of vaccination to prevent HPAI in poultry has gained interest (for example in free range/organic chicken and duck/geese production in developed countries),” says the group in its report.

“However, at this moment use of vaccines against H5 and H7 HPAI may have unintended negative consequences on trade in genetic stocks and poultry products.”

’Increased resistance’

The report continued: “Under optimal conditions, vaccination will increase resistance to infection, prevent illness and death, reduce virus replication and shedding from respiratory and alimentary tracts and reduce virus transmission to birds and mammals, including humans.

“Vaccination as practiced in some developing countries with endemic HPAI allows continued food security in resource scarce situations, especially continued production of low cost high quality animal protein for human consumption at the village and household level.

“However, HPAI vaccination has been associated with complacency for implementation and maintenance of adequate surveillance and bio-security processes and has slowed the overall momentum to move to an eradication strategy.

“Moreover, as H5N1 and related viruses have become entrenched and outbreaks prolonged, field outbreaks have been reported in flocks that are well vaccinated with early classical H5 AI vaccines in Central America, China, Egypt, Hong Kong, Indonesia and Vietnam.

“These failures have been the result of failure of the vaccines (i.e. vaccine efficacy) or failure of administration to produce an immune response of the target species (i.e. vaccination effectiveness).”

Presence of AI

The expert group was chaired by Ben Dellaert, the chairman of the IEC, as well director of Ovoned, the organisation representing the Dutch egg industry.

One member of the group was Professor Ian Brown, the head of virology in the United Kingdom’s Veterinary Laboratories Agency.

Another member was Dr Alejandro Thiermann, former president of the Terrestrial Animal Health Standards Commission at the World Organisation for Animal Health (OIE), who warned at an IEC conference last year that some countries were not being open about the presence of avian influenza.

“The fact that some countries appear blank is not that they are necessarily free of the disease, but that they are not reported,” he said.

“Reporting is an obligation for each member country but, unfortunately, it is not always done.”

International rules

He said it was vital that countries followed international rules and reported outbreaks of bird flu.

Failure to report outbreaks could lead to disruption of trade, with countries shutting down imports to protect themselves, he said.

“The OIE does not have the power to enforce the implementation of standards or to punish those who don’t. The only body that can do that is the World Trade Organisation.”

He said: “We need to find a mechanism to improve transparency and find a punishment for those who don’t report and don’t apply the rules.”

Outbreaks

Last winter there were 1,629 cases of highly pathogenic H5N8 in 28 countries across Europe.

In the United Kingdom there were 13 outbreaks of H5N8, although none of them were in commercial layer flocks.

Other strains of bird flu were confirmed in other parts of the world – H5N1 in Asia and Africa, H5N6 in Asia, H7N9 in China and the United States.

In 2015 the United States lost 42 million birds in an epidemic that spread right across the country.

The IEC’s expert group says in its report that so far the main measures for dealing with the threat of avian influenza have been bio-security measures to prevent introduction of the virus, early and accurate diagnosis, adequate notification and “stamping-out of poultry on affected farms to eliminate the virus.”

But it says that over the last two decades vaccines have emerged “as an essential tool for controlling AI in poultry in some countries, especially in countries with restricted financial and human resources.”

’Proper execution’

However, it says that the success of a vaccination programme depends not only

on “technically sound and effective elements” but also on “proper execution.”

The group has listed a series of requirements necessary for a successful vaccination programme.

The list includes having a national or regional emergency vaccine bank, ensuring that only high quality (high potency) vaccines are made and used, testing the quality of the vaccine in birds vaccinated under field condition, using targeted or sector specific vaccination, ensuring individual birds have adequate numbers of vaccinations over their lifetime – usually a minimum of two vaccinations, possibly more in long-lived layers and breeders – maintaining a good bio-security programme and continually reviewing the vaccination programme to ensure it is effective.

The IEC report is entitled Avian Influenza Vaccination, Considerations and Essential Components.

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