Virus avian infectious bronchitis (from English, IBV) is a highly contagious coronavirus that affects the upper respiratory tract of birds.
- It’s an RNA virus, essentially, Can change quickly when replicated within the host.
There are many types of IBV (and variants of these types) with little cross-reactivity. therefore, A vaccine developed to target only one virus is unlikely to provide adequate protection against another.
Initially, neutralizing antibody-based tests were used for IBV typing, but Currently, IBV types are genetically identified based on the glycoprotein sequence of the viral “spike.” (English, spike).
The genetic type of viruses circulating in the field can inform the selection of one or more commercial vaccines that can be used for their prevention and control.
this means Using vaccines homologous to circulating viruses is the best strategy to ensure success.
If a homologous vaccine does not exist, combinations of several IBV vaccine types can sometimes provide acceptable protection and achieve the goal of reducing viral replication in the field to prevent or minimize its spread.
A number of studies have been conducted to examine different combinations of IBV vaccine types against viral variants, and this information will be valuable in developing vaccine strategies. However, It is currently impossible to predict which combination of vaccine types will provide an acceptable level of protection against new variants of the virus circulating in the field.
The only way to determine whether a vaccine combination provides adequate protection is to Challenge studies were conducted with chickens.
avian infectious bronchitis
Avian infectious bronchitis is an infectious disease of the upper respiratory system that affects chickens and is distributed worldwide.
- From an economic point of view, this is a very important disease because it causes The poultry industry loses millions of dollars each year due to reduced production, seizures and deaths during processing.
- It can also lead to losses of breeder and laying hens due to infection by viral strains. Kidney damage, diarrhea, and dehydration.
- The pathogen causing the disease is avian infectious bronchitis virus (IBV). enveloped RNA viruses.Currently, the best and only strategy to control this virus is Use live attenuated and inactivated vaccines.
vaccine
usually, live vaccine They are administered to day-old chicks in hatcheries and sometimes in the field to 14-18-day-old chicks.
this inactivated vaccineIt is a mandatory injection and is used after the initial vaccination of breeders and laying hens (live virus) to extend the immunity of the flock throughout its life.
Regardless of which vaccine is used, Since different types of IBV do not produce cross-protection, it is difficult to achieve complete protection.
Additionally, live and inactivated vaccines are difficult to administer correctly, so equipment failure, improper vaccine handling, poor dosing techniques, and dose reduction can result in flocks not being adequately protected.
We vaccinate against IBV to prevent clinical symptoms of the disease, but the vaccine can also reduce the replication and spread of disease-causing viruses in the wild.
As with all positive-sense RNA viruses, IBV can change rapidly as it replicates.This is important because These changes are the source of new virus variants that can replicate and spread, even in vaccinated birds.
Monitor or monitor
this monitor (or monitor) The type of IBV transmitted in the field is critical and an important component successful control strategies.
IBV diagnosis madealmost completely passed Molecular biology technology.Viral RNA can be detected by Reverse transcription polymerase chain reaction detection (reverse transcriptase polymerase chain reaction) and Real-time RT-PCR.These tests are designed to Detects all types of IBV The S1 gene is then sequenced to determine the genetic type or perform a specific type of real-time RT-PCR test.
Determining the types of IBV circulating in the field is critical for selecting effective vaccines and designing appropriate vaccine strategies to control the virus.
The high rate of genetic modification that this virus undergoes contributes to the spread of many different types (variants) in the field.
The type of virus is determined by the spike protein on the surface of the virus. This means that different types of viruses have different proteins in their spikes.
this Antigenic diversity Viral variants (virus variants) occur when mutations, insertions, deletions and recombination occur in the gene encoding the spike protein.
This could result in the presence of significantly different spike proteins on the surface of the virus, creating genetically and antigenically new IBVs.
When the virus is free to replicate and spread to unexposed or partially protected birds, mutations accumulate, and mutations that lead to a fitness advantage persist.
If the spike gene mutates, the result could be a new type of IBV for which a vaccine may or may not be effective.
There are many different IBV variants around the world. In the United States, the major viruses circulating in commercial poultry are:
Arkansas and Massachusetts types have also been isolated, but these are usually associated with vaccine viruses.
We try to control IBV through vaccination, and in order to develop effective vaccination strategies it is necessary to understand the types of viruses circulating in the area and the types of viruses we wish to control. Due to the above circumstances, It is important to have surveillance programs in place to understand existing mutations of the virus so that the vaccines used can be updated.
Lack of protection or partial protection against viruses in the wild is common due to poor cross-protection of the vaccines used or due to incorrect vaccination techniques. Actually, Vaccination is critical, and incorrect administration is a common cause of IBV vaccine failure.
- Vaccination equipment must be working properly
- The full dose must be taken
- Vaccines must be prepared according to the manufacturer’s instructions
- Vaccines should be kept refrigerated
Improper use of vaccines may result in severe reactions due to transfer of virus from vaccinated to unvaccinated birds, which may also result in the vaccine virus reverting to a more virulent form.
he control The prevention and treatment of avian infectious bronchitis is mainly through Application of live attenuated and inactivated vaccinesbut it is Good protection is difficult to achieve due to lack of cross-protection between different types of viruses.
Adequate and regular monitoring of the virus present on site is an important component of an IBV control plan.For more information about Avian Infectious Bronchitis Virus, we invite you to read the full article here.