Vaccine failures in poultry

Vaccination seeks to generate a protective immune response against a disease. Therefore, a vaccine failure occurs when a disease appears despite birds have been previously vaccinated.

There are many factors involved in the efficacy of the vaccination, which are related to the vaccine, the pathogen, and the animals.

1.1.FACTORS LINKED TO THE VACCINE

Poor management of the vaccination strategy, including an unproper storage and preservation, a wrong type of vaccine or technique of administration, and/or the use of a vaccine strain that differs from the field strain when there is no cross immunity.

1.2.FACTORS LINKED TO THE PATHOGEN

There are some pathogens, like infectious bronchitis virus (IBV), that have a great mutation and recombination capacity, and their genetic variability may make vaccines lose their effectivity. There are other cases where infective pressure is high enough to exceed the defensive capacity of the immune system despite the animals have been properly vaccinated.

1.3.FACTORS LINKED TO THE ANIMAL

The administration of a vaccine in the first weeks of life may interfere with maternal immunity, which might neutralize live vaccines and reduce their efficacy.

Another factor of great importance is the immune status of the animal. Immunosuppressed animals will not develop a good response to vaccination and will not achieve a proper immunity. Immunosuppression is a common finding in commercial farming and may be related to many factors, like productive stress, management, environmental and nutritional conditions, and especially to immunosuppressive diseases.

Immunosuppressive diseases, like infectious bronchitis and Gumboro disease, are ubiquitous in Asia and have a great impact in the poultry industry of the region because they reduce vaccine efficacy, favour the outbreak of secondary diseases, and negatively affect the productivity of the farms.

The economic losses caused by vaccine failures are difficult to be assessed due to the multiple factors to be considered. First one is the investment in useless vaccine and, secondly, productive losses including the direct effect of immunosuppressive diseases and indirect losses because of the outbreaks caused by secondary diseases, together with the overall mortality increase.

Vaccines generate humoral immune response based on the production of antibodies and vaccine efficacy is usually assessed by measuring the antibody titres obtained against a specific disease. The most common technique to evaluate antibody levels are the serologic tests, such as ELISA.

Assessment of the level of protection of the animals is done by evaluating the presence of antibodies prior and after the vaccination. Postvaccination evaluation is recommended to be done more than 21 days after the vaccination. The higher growth in antibody production, the better protection of the animal. Evaluation in pullets can be done later to assess antibody persistence during the laying period.

First, the key for prevention is to identify the factors implied in the vaccine failure to apply measures to reduce the risk.

Regarding vaccine election against a specific disease, it is basic to be informed to make the correct choice and know the types of vaccines available and administration methods and which is the aim of the vaccination, considering the age of the animal and management conditions of the farm.

Manufacturer and professional recommendations should always be followed and trained and experienced personnel is fundamental for a polished technique. In addition, veterinarians should always consider the vaccination plan of breeders to prepare the plan for broiler chicken and avoid neutralisation of the vaccine by material antibodies.

There are other factors that are more difficult to be controlled and it is strongly recommended to combine vaccination with additional support tools, such as immunostimulant pronutrients, to reduce the risk of vaccine failures.

5. ALQUERNAT IMMUPLUS TO IMPROVE VACCINE EFFICACY  

Alquernat Immuplus is a natural solution based on immunostimulant pronutrients. This product is demonstrated to be a positive tool to reduce the risk of vaccine failures in commercial farming and improve immunity obtained with vaccination, especially for immunosuppressive diseases.

Immunostimulant pronutrients are active molecules of plant extracts capable of enhancing, physiologically, the cellular and humoral immune response of birds through a proved metagenetic mechanism of action, increasing the synthesis of specific functional proteins related to the immune system.

Several trials have been performed in commercial farms assessing the effect of Alquernat Immuplus when combined with vaccination against the most common diseases present in the vaccination plans in the poultry industry.

The use of Alquernat Immuplus administered 5 days prior and after vaccination in 14000 pullets (chart below) caused an average increase in the antibody titres of 51% against Newcastle disease (NDV), of 57% against Gumboro disease (IBD) and of 50% against infectious bronchitis (IBV), reducing the risk of vaccine failure compared to two control groups with same number of animals which were not using any immune booster.

 Another trial made in broiler chickens (56200 birds) showed an increase of antibody titres against Newcastle disease of 36% when receiving Alquernat Immuplus, compared to a control group (131480 birds).  Furthermore, improvement in the immunity of the animals was also visible as a reduction of general mortality (-16%). Such results are related to higher economic benefits of the farm and corroborates that Alquernat Immuplus is a profitable investment for farmers.

Vaccination plans are imperative in the poultry industry to prevent major diseases present in commercial farming. Vaccine failures are often related to immunosuppression caused by productive stress and immunosuppressive diseases. Thus, it is essential to maximize the effectiveness of vaccination by complementing vaccination with supportive tools.

Alquernat Immuplus optimizes the function of the immune system and improves the immune response when combined with vaccination, increasing the production of antibodies in birds (demonstrated increase over 50% in the antibody levels of pullets against NDV, IBD and IBV), as well as reducing the general mortality of the batch by 15% in the case of broiler chickens.

Therefore, the use of such natural active molecules together with vaccination is one of the most helpful strategies to reduce the risk of vaccine failures.