Avian Infectious Bronchitis Virus: Solutions and Tools

more than ten years Zoetis Spain make monitor Analysis of strains present in the Spanish poultry industry by molecular biology techniques.

he Molecular Biology Research Program as follows:

• bird sampling dry swab.
• 10 swabs per set Maximum quantity per unit/batch, to be processed in pool form.
• Tracheal swab and sewers they are the most usuallyalthough they can also be taken from the choanal nares, cecal tonsils, and kidneys.
  • exist longevity bird Preferred if there are no respiratory symptoms and no egg production issues sewer routebecause the virus is excreted at this level for several weeks, while in the trachea it drops significantly after 7 days.
  • For broilers with respiratory symptoms, the tracheal level is preferred.. If monitored routinely, it is usually done at the cloacal level at the end of its productive life.
• Each swab can be used to sample 1, 2 or 3 birds, thus expanding the sample set.
• Sent to molecular diagnostic laboratory.

along with RNA extraction Present in the swab pool, the first Coronavirus RT-PCR for detection The presence any coronavirus.

• In samples where the presence of BIA virus was detected, qRT-PCR was then performed 11 primers/probes Parallel specificity testing of 11 genomes (Massachusetts, D274, 793B, D1466, Italy02, Arkansas, QX, Israel Variant2, Q1, IB80 and D181), which allows Detecting variants across different genotypes present in the same sample at the same time.

When we compare this technology to Sanger sequencing, Multiplex PCR allow Detect the different strains present rather than just the primary specimen within the same sample, allowing us to obtain a more complete picture of each case.

Depending on the situation, additional steps may sometimes be required Sequencing studies.

To do this, use Sanger sequencing of a 500-base pair fragment of the gene encoding spike protein S1.

• The resulting sequences were subjected to phylogenetic analysis based on comparison with the following sequences: Known vaccines and field strains.

Situations in which Sanger sequencing may be necessary or of interest are:

• When a sample is positive in the first aCoV RT-PCR but negative in 11 primers/probes. In these cases, it may be suspected that a new variant exists that escapes detection by primers/probes from a different genome included, or that the variant has changed such that it escapes detection by the technology.
• When the CT value (from English cycle threshold, represents the number of cycles a sequencer must perform before a virus is detected) The results of aCoV RT-PCR did not correlate well with the qRT-PCR results of 11 specific primers/probes.

For example, when a BIA virus is detected with a CT value of 20 and a virus from the QX genome is subsequently detected with a CT value of 30, this difference in CT values ​​indicates that there is a large number of viruses that were not detected by multiplex PCR.

• For example, this situation is Strain type-V1397 Primers/probes for strains D1466 belonging to the same GII-1 genotype cannot be detected Because they have changed, meaning they cannot be detected this way.

Zoetis Spain has been provided to poultry veterinariana web page with an interactive map containing all historical results obtained as a result Process large numbers of samples Per year.

• These results come from samples from customers across Spain, both from batches of birds suspected of BIA and from samples obtained through routine monitoring.

Navigation allowed test result From 2017 to present, it can be carried out Filter results by strain type, geographic region and bird type (broilers, layers and breeders).

• The database is Regular updates throughout the year.

Below we can see an example Filter results for the past 3 years (2021 to the first half of 2023) and graphics generated via the IB Maps website.

Layers of pressure from 2021 to 2023: In this chart we can see the high positivity rate of QX and 793B strains, as well as the emergence of new strains IB80 and V1397 Laying hens. (figure 2)

Breeding Strains 2021 to 2023: In this figure we can see the strains detected reproduction QX and 793B are present in 2021 and 2022, but there is an increase in IB80 and V1397 type strains. (image 3)

2021 to 2023 Broiler Lines: A large amount of QX strain can be observed, followed by 793B strain, followed by Mass strain, followed by D181 strain and Italy02 strain. (Figure 4).

Broiler chicken strains by region from 2021 to 2023: In areas with the following situations Higher broiler production (Andalusia, Catalonia, Castilla-La Mancha, Castile and León and the Autonomous Community of Valencia), The QX strain dominates the field. (Figure 5).

By providing this tool to veterinarians, Zoetis helps disseminate knowledge on the epidemiology of BIA for better control through vaccination programs.

Commercial vaccines (both live and inactivated) available on the Spanish market include:

For long-lived poultry (layers and breeders), different combinations of different live vaccine strains are used, followed by an inactivated vaccine that may contain one or two IAB strains.

• Based on molecular biology studies showing that QX field strains persist, particularly in long-lived birds, inclusion of this vaccine in vaccination programs is strongly recommended.

As new strains emerge, GII-1 genotype (Type V1397), GII-2 (D181) and GVIII-1 (PA/1220/98, which has a very high similarity to the IB80 strain, although the latter has not yet been officially accepted by the new classification),

• It is recommended, especially for birds of high economic value, to maximize immune response profile Produced by birds using different commercially available strains (live and inactivated),
• so that Birds can identify different virus variants as widely as possibleas demonstrated in various published works (Blue, 2023; Carranza, 2023).

In broiler chickens, The main pathogenic strain is QX type strainone option to consider is to use Mass-type strains with QX-type strains.

• In addition to preventing its live counterpart, it has also been shown to provide Excellent protection Against type 793B strain (DeWitt, 2022).

For long-lived birds, especially in areas at high risk for BI, it is recommended to use inactivated vaccines to obtain greater protection against BI and, in general, to use more vaccine strains to achieve broad and heterologous results. “De Wit, the more the merrier” when vaccinating layers and breeders against IB, Poultry.com, 2012.