With the help of serology it is possible to follow the vaccination of your flock. At Poulpharm, we compared the ELISA titres from parent animals pre and post-vaccination. Prior to vaccination, the titre varies between 300 and 5000. This shows that the animals before vaccination have no or a very limited number of antibodies against the pathogen. After a complete vaccination the titres of the animals from increases above 12000, which indicates that the animals have created antibodies against the pathogen. A measure to follow the vaccination is by the use of the variance coefficient percentage (CV%). Prior to vaccination, the CV% is often above 60%. This indicates that there is a lot of variance between the titres and thus a limited protection against pathogen. A CV% above 60 indicates that animals have been exposed to a pathogen spreading slowly through the flock, therefore this can be an indicator for an infection that has passed. After a successful vaccination, the titres increase uniformly - the target is to have a CV% below 40%, which indicates that there is less variance in the titres. A CV% below 40% implicate that the animals are really well vaccinated against the pathogen.
Serology is a method to detect antibodies in the blood of an animal. These antibodies can be maternal antibodies deriving from the mother hen or they can derive from vaccination. They will also be found in the blood after an animal survived an infection. The presence of antibodies makes an animal immune against a certain disease.
Serological analysis and required equipment
With our lab equipment, we can detect antibodies against many diseases semi-automatedly – however, some tests still have to be run manually. For analysis, the blood is put on a coated matrix, where the antibodies can bind. Then the blood will be washed away and the antibodies stay on the plate. A substrate is then added and binds to the antibodies. It reacts with a coloring agent to make the antibodies visible to our equipment. The concentration of antibodies is measured by means of the optical density of the solution and is also called “titer”.
Application in veterinary medicine
Besides diagnostics and vaccination success assessment, serology in broiler production can be used to determine the optimal timepoint for vaccinating against Gumboro disease. For this inquiry, blood of day-old chicks has to be examined. Maternal antibodies will be very high at the time of hatch, but the levels drop as the animals become older. This makes them susceptible for the disease but enables an effective vaccination at a certain age.
A formula is used to calculate the optimal timepoint of vaccination based the serum levels at day 1. In Poulpharm, 20.000 samples for PGVS (persoonlijke Gumboro Vaccinatie Service) have been analysed since august 2018. See figure 1 for the values by season of the year. The optimal day of vaccination depends on the vaccine that is used (Hot or intermediate vaccines).
|Per 15 samples incl. sampling||Price||Price package|
|IBD||€ 79||€ 79|
|IBD + ARV||€ 99||€ 128|
|IBD + FADV + ARV||€ 119||€ 177|
|IBD + FADV + ARV + ORT||€ 139||€ 226|
|IBD + FADV + ARV + ORT + CAV||€ 159||€ 298|