Why is my vaccination programme not working?

[Mumo Munuve, Standard]

In poultry production systems, there are diseases that are too widespread or difficult to eradicate. These diseases or ailments require a routine vaccination program.

For long-living birds like commercial layers and improved ‘Kienyeji’ chickens, routine vaccinations are administered against Marek’s disease, Newcastle disease (NDV), Infectious bronchitis (IB), Infectious bursal disease (IBD or Gumboro), Salmonella, and fowl pox.

Other vaccinations can be added to the programme as local disease challenges dictate. These may include Coryza, Fowl cholera, and Mycoplasma. It is therefore reasonable to state that no single programme can be recommended for all regions.

It is advisable to periodically consult your local veterinarian to review your programme. Let’s look at factors that may derail your vaccination programme.

High field disease challenge

This can occur following the introduction of a very virulent (harmful) disease virus strain or pathogen in the local environment.

In areas with densely populated poultry farms, field infections can be brought in by contaminated workers, delivery trucks, wild birds, contaminated water, or contaminated equipment.

If the field challenge is too invasive, it can overcome the vaccine immunity and cause an outbreak even in older birds. This is one of the reasons why we recommend that new poultry farms be situated far away from other poultry operations to reduce any disease field challenge.

Presence of immunosuppressive agents

The term ‘Immunosuppression’ was once described as ‘a state of temporary or permanent dysfunction of the immune response resulting from damage to the immune system and leading to increased susceptibility to disease.’ (Dohms & Saif, 1984).

If flocks with good genetics are properly cared for by providing the right nutrition, vaccination, and environment, they will grow well and perform. However, if they are subjected to immunosuppressive agents, even in the presence of a good vaccination program, the flocks are likely to succumb to disease and experience poor production performance.

These agents include stressors (poor housing, poor diets, overcrowding, etc.), chemical toxins, mycotoxins, especially aflatoxins, bacteria, and some viruses. Of the viruses, Gumboro virus, reoviruses, chicken anaemia, and Marek’s viruses are notorious for causing vaccination failures.

Ensure that you buy chicks that have been adequately vaccinated against these viral diseases at the hatchery. Flocks should only be vaccinated under minimal stress and only when they are healthy and experiencing minimal mortality. Administer multivitamins immediately before and after every vaccination.

Inadequate vaccination programmes

The primary role of vaccination is to reduce the level of clinical disease and promote optimal performance. Commercial chickens are vaccinated using different types of vaccines at various stages of their lives, depending on the disease pressure in the geographical area, the age, and the type or strain of bird. Prescribing a light vaccination program for a flock in a high disease risk area is a recipe for problems.

The pattern of poultry diseases is constantly changing, and vaccination programs will evolve. It is not possible to adhere to a rigid recommendation, and as disease patterns change, so should the program. Always consult your local veterinarian for advice.

Poor vaccine preparation and administration

Most vaccines against diseases like Gumboro, Newcastle, and Infectious bronchitis are administered through drinking water and spray. It is important to know the amount of water your birds drink to help you plan for vaccination.

Water meters and water intake charts can help estimate the amount of water needed for vaccination. Thirty percent of the total daily intake is needed for vaccine preparation. Birds must be thirsted to ensure they are ready to drink when the vaccine water is administered.

However, excessive thirsting can cause birds to drink too much, preventing all birds from getting the required dose. Withdraw water for 30-60 minutes in hot weather and 60-90 minutes in cold weather before starting vaccination.

Administer water vaccines early in the morning or during the cool hours of the evening, and ensure there is enough drinker space per bird.

Please remember that missed birds can occur during the vaccination process. During water vaccinations, it is estimated that only 80 per  of the birds will consume the vaccine water. Underdosing of vaccines, poor vaccine administration, and use of expired products can all lead to vaccination failures.

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