By Carien Kruger
Chickens on a commercial South African farm will be vaccinated against highly contagious bird flu (avian influenza) for the first time, after Astral Foods, the country’s largest broiler chicken producer, received permission to begin vaccination on one of its breeding farms.
Are all chickens vaccinated or only certain ones? Will vaccinated chickens be allowed to be sold? And should people cook chicken differently?
African Farming asked Dr. Shahn Bisschop, poultry veterinarian, CEO of Avimune and senior lecturer at the University of Pretoria’s Faculty of Veterinary Science at Onderstepoort, to explain what vaccination against the bird flu virus entails.
1 Are all chickens affected by highly contagious bird flu?
All chickens can be affected, but the current focus is on vaccinating breeding chickens because they are very valuable and it takes more than a year to replace them if they die from bird flu.
2 How long does it take for chickens to develop immunity to the disease after vaccination?
It usually takes four to six weeks to achieve full immunity. More than one vaccination is also usually needed to achieve the highest level of immunity.
3 At what age are chickens vaccinated against the bird flu virus?
The first vaccination is given to day-old chicks in hatcheries. The chickens then receive one or two booster doses while they are being raised (before they are 20 weeks old) and before they start laying eggs. Different vaccines are used for each life stage. It is possible that they will receive additional booster doses while they are in their laying phase.
4 How are chickens vaccinated against the bird flu virus?
All bird flu vaccinations are administered by injection. The first vaccinations are administered at one day old at the hatcheries. Later vaccinations are administered on the farm. At hatcheries and on farms there are teams that are specifically trained to vaccinate chickens against various diseases –just as they have been doing for years against Newcastle disease. The same techniques will be used to vaccinate against the bird flu virus. We can be sure that the vaccinations are highly effective – there are already audit processes for this.
5 Are there any risks for the teams that do the vaccination against the bird flu virus to get bird flu themselves?
There is no risk regarding the vaccines. No live bird flu vaccines are used; only dead (inactivated) viruses are used in the vaccines.
6 If it is a dead virus, how can it make the chicken build up immunity?
It is only necessary that the form of the virus is there. The chicken’s immune response will still recognise it and react to it.
7 Will a chicken that has been vaccinated subsequently test positive for bird flu?
No, but there are tests that test for antibodies. These are used to determine the chicken’s immunity.
8 Can vaccinated chickens still get bird flu?
Yes, vaccinated chickens can get the disease, but they will probably show no or very few symptoms of the disease.
9 If I were to eat broiler meat that I bought from a store shelf and that comes from a chicken that is a descendant of a vaccinated breeding chicken, could I get bird flu?
No, not at all, because no live bird flu virus is used in any vaccine. Furthermore, broiler chickens will not be vaccinated; only breeding chickens, because broiler chickens are slaughtered at around five weeks of age. If we were to vaccinate laying hens in the future, there would also be no risk of contracting bird flu by eating the eggs of such hens.
10 If I am still concerned about this, what can I do?
It is always good to cook chicken meat thoroughly, because any organisms are killed in the process.
11 What happens to the breeding chickens at the end of their productive life?
The Department of Agriculture’s protocol is very clear and strict about this: No vaccinated chickens may be sold on the live chicken market. According to the protocol, those chickens may be slaughtered at a registered abattoir. Because the meat of older chickens is much tougher than broiler chicken meat, it is not meat that one would find on a supermarket shelf.
‘Stop economic losses’
John Steenhuisen, Minister of Agriculture, described the first permit issued for vaccination as a milestone and said it was evidence of the “strong partnership between government and the poultry industry to secure national food security and protect the livelihoods of thousands of South Africans”.
He stressed that this vaccination campaign is an important step to strengthen herd immunity and prevent the devastating economic losses seen in previous outbreaks. The vaccine to be used, which targets the H5 strain of the virus, has already been approved for use in other countries that are following vaccination strategies against highly contagious bird flu.
South Africa’s vaccination campaign will start with 200 000 breeding broilers, representing about 5% of Astral Foods’ total breeding stock. The value of these chickens is estimated at R35 million.
Joylene van Wyk, Steenhuisen’s spokesperson, said in addition to Astral’s application to vaccinate, the department also received other applications, which were rejected because the producers did not meet the requirements for vaccination.
