email received from Chris Ashton February 27
The two questions below are in response to the message from Kyprianou sent 24.2.06: NEWSDESK http://mobile.alertnet.org/thenews/newsdesk/L24672359.htm which was circulated on 24 Feb 2006 16:20:31 GMTRPT-"Learn to live with bird flu," says EU health chief
(i) Is vaccination only 80% effective?ANSWERS
(ii) Fred Landeg says that a vaccinated bird might become infected and then act as a 'silent' emitter of virus. Is that true?
BIRD FLU VACCINES ARE MORE EFFECTIVE THAT DEFRA WANTS YOU TO KNOW
1. IT DEPENDS ON HOW YOU INTERPRET THE FIGURES
These figures are often given in case of an emergency vaccination, that is, AFTER an outbreak.
First of all: the infection is already present. Birds which are already infected with HPAI and LPAI may not respond as well to the vaccine as birds which are ‘clean’. It is these already infected birds which can become silent carriers.
Secondly: 80% is after the first inoculation. And time for the second inoculation is not available because of the panic etc.
Thirdly: In a documented case in Hong Kong, vaccination gave 100% protection (see the synopsis from Avian Pathology below)
Fourthly: Hong Kong continues successfully to run vaccinated poultry units in an area where AI is endemic in wild species, and surrounding countries.
And let’s face it, if the European authorities had had the guts to introduce the vaccination programme long before the threat was actually here, we would not be in this position.
Avian Pathology August 2004 33 (4) , 405-412, T M Ellis et al
Vaccination of chickens against H5N1 avian influenza in the face of an outbreak interrupts virus transmission [in Hong Kong]
‘A field evaluation trial using . . . an inactivated avian influenza Type A H5N2 virus . . . .on chicken farms was commenced on April 2002 in the district where the last four farm outbreaks of H5N1 had occurred, and evaluation continued until March 2003. The evaluation trial showed that acceptable flock H5 antibody responses were generated by the vaccine and vaccinated chickens were protected from high-dose laboratory challenge with H5N1 HPAI viruses from the February to April 2002 outbreaks. . . .’
Taking the Farm 2 shed 2 investigation [the only shed of birds which lived through this investigation because intervention had been early enough]:
‘By the time the affected chickens were detected . . . these batches were already 13 to 17 Days post-vaccination and there was only limited disease in these sheds over a 2 day period [days 25 – 26.1.03]’
After that period, the table of results (page 408) shows that from the 27.1.03 until 7.2.03, all samples tested for the H5N1 virus were negative.
‘Prior to marketing of the first batch of chickens from this farm, virus culture testing of cloacal swabs collected from 60 randomly sampled chickens and swabs of 100 randomly collected fresh faecal droppings from the cage trays were shown to be negative for H5N1 viruses. Subsequently no H5N1 virus was detected . . . from 60 randomly sampled cloacal swabs from the next seven batches of market aged chickens from this farm. H5N1 antibody titre greater than 16 was detected . . . in all chickens from shed 2 . . . at 30 to 33 days post vaccination.’
‘One of the concerns in the use of vaccine to control HPAI in poultry farms is the possibility that while vaccine may protect from disease, asymptomatic virus circulation may continue, resulting in spread of infection to other farms. The monitoring and surveillance on these three chicken farms showed that the use of this killed H5N2 vaccine in the face of H5N1 virus challenge was able to protect chickens from disease and interrupt virus transmission. The protective effect of vaccine became apparent AFTER DAY 18 POST VACCINATION’.
As the article points out, eradication of HPAI was the goal of the control programme. Hong Kong has achieved that in its commercial poultry, despite infection in the wild bird population, and daily movement of poultry from the mainland. All poultry produced for consumption in the region is vaccinated. Commercial units in the UK do not want to make use of vaccination because it affects marketing the product: note the refusal of Japan to accept vaccinated chicken from Europe, and Hong Kong refusing products from France today!
Vaccines for other diseases are not 100% efficient. However, if poultry are not vaccinated, each disease out break will cause the virus to be shed in huge quantities. Each disease cycle also gives the opportunity for the virus to change. We are going to have to live with AI. It will not be wiped out in the short term. More flexible strategies are needed to manage the situation.
2. SO, WHAT IF THE VACCINE IS NOT 100% EFFECTIVE?
In the field, a vaccinated bird MIGHT, IF CHALLENGED, become a silent carrier. This presupposes that the wild bird population is therefore carrying the disease. Therefore there is a risk in the environment anyway. If the domesticated birds are not protected, the risk of disease outbreak and viral shedding and further infection of the wild population is therefore greater in non-protected flocks. DO WE WANT TO CULL HUGE NUMBERS OF BIRDS WHICH, IN THE MEANTIME, RELEASE HUGE AMOUNTS OF VIRUS INTO THE ENVIRONMENT AND INFECT THE WILD BIRD POPULATION, OR DO WE USE COMMON SENSE AND MODERN TECHNOLOGY TO MONITOR VACCINATED BIRDS? Points which follow: .
H5N2 vaccine has been used in Hong Kong to control avian influenza for years. Monitoring and the use of sentinel birds establishes its efficacy. Cases of H5N1 infection have been in only smuggled birds and wild birds. They have even held regular wet markets, though this is recognized as a hazard. This is a pretty good record because the disease has become endemic since 1996. The disease is well recorded in wild birds.
Monitoring in the UK is going to be expensive, but it will have to take place anyway. Culling of potential sporadic outbreaks, disposal of infected waste, interruption of businesses and transport will be a lot more expensive than monitoring a controlled situation. Surely we have the technology to do this if they can be successful in Hong Kong and Vietnam?
DEFRA already monitors both wild birds and domesticated birds anyway, so it could monitor vaccinated birds.
The current situation is a bird-flu pandemic for birds. Conditions have changed since the 1990s. There are more people, more domesticated birds, more transport of birds and bird products, more birds eaten (increase in broiler industry), more travel. No wonder we have problems. Transmission rates are faster. This situation needs a new, more flexible policy.
DEFRA is stuck with the cull policy of the past. It is insufficient. The 1992 AI case is cited as a good example of control by cull. It was. However, the 'outbreak' took place IN a shed. It was alleged to be a mutation within the shed, therefore the virus never escaped into the environment--hardly a working model for success in a much more complex situation.
DEFRA has only really listened to big business. At the meeting in January, DEFRA took the response of the businesses as a mandate to carry on with the policy that ‘DEFRA does not expect vaccination to play a part in its control strategy'. The numbers of people involved in the industry are relatively small. The first commercial EU outbreak of the H5N1 disease has been in intensively reared poultry. The industry should take note of this.
The numbers of people involved with birds on a small scale has been underestimated; half a million has been cited. Although the amount of business per person is small, the total trade linked to cage and aviary birds, pets, garden birds and pure breeds is large, probably larger than the free range egg industry. The impact on such trade was not fully explored in DEFRA's impact assessment. I doubt if the people who drew up the assessment had any idea of the linkages and the scale of the activities. This has become evident in meetings with DEFRA where the types of birds kept, and conditions which they need, are clearly not initially known and not well understood. Nor do the organisers have a clear idea of how to contact stakeholders.
Vaccination of pet birds would prevent people from dumping their pets. Cases of caged birds on rubbish tips, parrots worth thousands of pounds being discarded, have already been cited. Monitoring of vaccinated pet birds would not be difficult.
Vaccination offers an incentive for ALL BIRD KEEPERS TO REGISTER THEIR BIRDS. At the moment, DEFRA is perceived as the agency to cull birds. SO, WHY REGISTER?
There is concern from rural businesses that the effect of control zones and surveillance zones would have an adverse impact on business and tourism in the same way as happened in FMD. Local papers are increasingly re-publishing FMD data as a comparison with the current situation with AI. The national papers have also become more vociferous about the lack of vaccination for birds. This will become even more apparent now that Holland and France are to vaccinate. How pleased France must be with its vaccination policy!
The UK, through DEFRA, has to produce a report on our Farm Animal Genetic Resources. This is an EU and an FAO requirement. FMD resulted in the loss of a significant part of the gene pool in cloven-hoofed rare breeds. Is the same thing to happen again with poultry and waterfowl? Derogation of pure breeds is no protection for them without additional protection of vaccination. Most of these pure breeds are kept free range. They, most of all, need the protection of vaccination
'Bringing the birds in doors' is totally impractical in many cases. Does anyone realistically think that this a solution once wild birds are infected? ONLY IF WE GET RID OF BIRDS ON SMALLHOLDINGS ALL TOGETHER. IS THAT WHAT IS WANTED?
DEFRA'S non-vaccination policy currently lacks drive, imagination and flexibility. It lacks the resources to manage an outbreak which might get out of control. We do not know what will happen. We do know that there are currently insufficient vaccine in place to manage outbreaks and conserve our pure breeds. As we can see in Europe tonight, with the suspected case in Switzerland, outbreaks can be sporadic and quite unpredictable.
Wake up DEFRA! Admit that wild birds fly; pochard fly round Europe; swallows migrate from Africa; the disease is airborne by the birds; people smuggle birds; your cull policy alone may not work. As I said in an earlier published article, will you stop at the 8-9 million deaths for FMD, or go the 28 million bird deaths notched up in Holland in 2003?
Chris Ashton 27.2.03