Vaccination, a vexed issue for small poultry farmers

chicken vaccinatin against Newcastle disease in TanzaniaAll mainstream poultry diseases can be prevented with relevant vaccination at an appropriate stage in a bird's life. Here a chicken is being vaccinated against Newcastle disease in Tanzania. Vaccination is an essential part of commercial poultry production but continues to remain accessible only by big farmers due to the high cost of vaccines and limited availability

In many parts of the world, vaccination is not generally practised by small poultry farm owners and for a variety of good reasons.

Some poultry farmers, and especially those that operate an essentially closed family-run operation, with minimal on and off farm movements, may be lucky to have relatively few disease problems. Others may have diseases in their birds but unaware of its presence. Consequently, the presence of sick and unthrifty hens becomes an accepted norm.

For farmers in such situations a problem of ignorance, made worse due to on-going disease problems, continues to persist. Such diseases often do not get diagnosed by a properly qualified professional, either because of limited availability of such service or due to their services being too expensive.

Other farmers may be aware of diseases in their flocks but are unable to access vaccines,or are frustrated in their attempts to purchase them, because the appropriate vaccine only comes in multiple (500 to 1,000) dose vials suitable for large producers.

The irony is that virtually all mainstream poultry diseases seen in birds could have been prevented through the relevant vaccination at the appropriate age and stage in the bird’s life.

Poultry diseases cause widespread and heavy losses in production and profit by impacting on yield and quality of meat and eggs. Vaccination is invariably a very worthwhile and indeed critically important investment.

The decision on whether or not to vaccinate against infectious diseases largely comes down to an assessment by the poultry producer on the likelihood of his or her birds becoming exposed to the causal microbial pathogens.

A completely closed flock where new birds are never introduced and the birds never leave the farm may get away without vaccination, although disease can still be introduced by wild birds, rodents and contaminated feed and water. However, this kind of completely ‘closed’ flock situation is relatively rare and all producers are advised to vaccinate the bird especially if the owner buys birds from hatcheries, bird auctions or any other sources and introduces them into his/her existing flocks.

Practical vaccination

Poultry vaccines are generally produced in large doses per vial and especially for the convenience of commercial producers who may have tens of thousands of birds requiring vaccination at the same time. This means the small producer may have to search further afield for a supplier who is prepared to sell vaccines in relatively small quantities. However, any extra hassle in accessing vaccines should in no way deter or discourage the small poultry producer from administering vaccine to his or her birds. Some vaccines such as Marek’s vaccine are best given at the hatchery and this may be the best source of vaccine and therefore the first port of call.

Once the decision has been made to vaccinate on farm, the owner should aim and plan to vaccinate the entire flock at one time and be meticulous in following the label directions on the vaccine being used to ensure best protection and complete safety for the flock.

Marek’s disease

Marek’s disease is a severe debilitating and often terminal viral disease affecting chickens. Infected birds become emaciated with drooping wings and may develop paralysis in one or both legs. Tumours may also develop within the bird’s internal organs.

Marek’s disease is invariably a lot worse that it normally appears because only a small proportion of the birds in an infected flock may show these symptoms and die.

However, the majority of birds will have ‘unsymptomatic’ infection and although appearing outwardly normal, they will be shedding virus particles in huge quantities for the rest of their life on the farm. Only a small percentage of birds within an infected flock will show typical symptoms and die.

When a virus shedding bird is introduced onto a farm where the disease has never occurred before, high mortality rates are quickly seen. Once infected with the virus a farm is, for all practical purposes, contaminated forever. Generally speaking, broiler birds encounter fewer problems from Marek's disease than do layers, simply because they spend less time on the farm.

However, the good news for small poultry producers is that vaccination against Marek's disease is highly effective provided it is carried out in the correct way. This particular vaccination is most correctly and efficiently done at the hatchery to one day old chicks. It is, therefore, easier all round for the producer to order already vaccinated chicks from the hatchery. Otherwise, it is essential to ensure vaccination of all new birds on the day of their arrival at a farm. Marek’s vaccine will not be completely effective if a bird has already been exposed to the disease for more than a few days prior to vaccination. Marek’s vaccine is sold frozen for administration under the skin at the back of the bird’s neck. Label instructions must be followed to the letter for vaccination to be successful.

Fowl pox

Fowl Pox is caused by yet another highly infectious virus (the pox virus) affecting both chickens and turkeys. Fowl pox is strictly a disease of birds and entirely unrelated to the human illness called chicken pox.

The disease typically causes round and firmly adhering scabs on any un-feathered areas of the bird’s skin, together with fever(high temperature) and a drastic fall in feed consumption, resulting in slow growth rates and reduced egg production.

The virus is spread from bird to bird through the bites of blood-sucking insects or through wounds and scratches inflicted by birds on each other while fighting.

Though seriously debilitating and often fatal, fowl pox is easily prevented by vaccination. Vaccine is introduced directly into the skin by using a two-pronged metal needle previously dipped in the vaccine. All birds on the farm should be vaccinated at one time with yearly booster vaccinations recommended.

Newcastle disease
Newcastle disease is the most important of a wide range of respiratory diseases that cause devastating losses in both commercial flocks and village chickens.

This virus disease, which is a major constraint on the productivity and survival of village chickens, can be controlled by the use of vaccines.

Some Newcastle disease vaccines deteriorate after storage for one or two hours at room temperature, which clearly makes them unsuitable for use in village situations where the vaccine may need to be transported for hours or in some cases days at ambient temperature.

The I-2 Newcastle disease vaccine, which has been specifically developed for local or regional poultry production is more robust under higher temperature conditions. It is described as a thermostable vaccine which requires long-term storage in the refrigerator.

However, this I-2 vaccine will not deteriorate as quickly as the traditional vaccines during transportation into the field. Evaporative cooling provided by wrapping the vaccine in a damp cloth will be adequate for maintaining the viability of the vaccine during transportation to remote villages. However, if it is stored in direct sunlight or allowed to reach high temperatures, above 37°C, for more than a few hours it too will deteriorate and be unsuitable for use as a vaccine.

Infectious bronchitis (IB)

Many poultry producers have problems with Infectious Bronchitis (IB), yet another highly contagious disease of the respiratory system which is caused by a virus. Any poultry producer who buys chicks from hatcheries or other sources and adds them to the flock should definitely consider vaccinating for IB. The IB live virus vaccines are usually administered to young birds and may be given together with Newcastle disease vaccine in a combined dose. Therefore, it may be possible and clearly much easier to locate a source of Newcastle vaccine and IB vaccine at the same time.

IB live-virus vaccines are usually administered to young birds combined with the Newcastle vaccine for simultaneous administration. Unfortunately, the IB vaccine is usually produced in large quantities for commercial hatchery type applications,although the actual vaccine is relatively inexpensive even when purchased in large quantities. The live-virus vaccine is shipped in a small, insulated cooler with a gel-ice pack to maintain refrigeration. It consists of two parts, the vial of vaccine and diluent, which must be stored separately in the refrigerator (in the dark) until administering the vaccine.

When ready to administer, the entire vial of vaccine and diluent are mixed, used to vaccinate the chickens and the remaining contents disposed of. The vaccine can be given via drinking water, eye drop, or nose drop.

Infectious laryngotracheitis

Infectious laryngotracheitis is a highly infectious virus disease affecting the bird's trachea or wind pipe. Affected birds typically gasp for air and cough up blood with high mortality rates not uncommon.

The disease frequently circulates at bird auctions and shows. Any decision to vaccinate must include every single bird on the farm. Treatment is most effectively applied when the birds are one month old and yearly booster vaccines are recommended. Fast diagnosis followed by prompt vaccination should curtail the spread of this disease throughout the flock and prevent an otherwise considerable loss of birds.

Dr Terry Mabbett

Alain Charles Publishing, University House, 11-13 Lower Grosvenor Place, London, SW1W 0EX, UK
T: +44 20 7834 7676, F: +44 20 7973 0076, W: www.alaincharles.com

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