Robert Jan Molenaar DVM, FRCPath, Sjaak de Wit, DVM, PhD, dipl. ECPSV, Published by Avined
Various types of infectious bronchitis virus (IBV) can be found worldwide. According to the World Bank, it is the second most harmful virus in the poultry farming sector, after avian influenza. Since early 2017, an new IBV strain has been detected at more than 60 Dutch poultry farms with hens with clinical symptoms. Most seen were drops in egg production, eggshell abnormalities and increased mortality due to a co-infection with E. coli. Royal GD was commissioned by the poultry sector to examine this new IBV strain. Does it resemble the strains we already know?
By determining the serotype of the new IBV strain, it becomes clear whether the strain resembles to IBV strains we already now or not. A serotype is a specific subtype of a certain pathogen, in this case IBV. This is an important first step in determining the possible consequences of the new strain.
New IBV strain very different to known strains
The virus neutralisation test showed that the new IBV strain (D181) is a new serotype. While the strain is genetically and serologically most related to a known strain (D1466), it deviated too much to be classified as one of the known serotypes. As D181 was a new subtype of IBV, it was difficult to estimate the impact of the strain, and further research was conducted.
Clinical signs in experimental conditions
Further research showed that infection with the new strain (D181) in adult layers without co-infections led to a significant reduction in egg production and egg quality without respiratory symptoms. In young pullets, respiratory signs were present.
Current vaccine strains may not be effective against new IBV strain
The available vaccine strains do not produce neutralising antibodies against D181. It is therefore uncertain whether the current vaccines or vaccine combinations offer sufficient protection against the new IBV strain.
In short, the new IBV strain D181 is a new serotype, resulting in a significant decline in egg production and egg quality under experimental conditions, and the current vaccine strains may not able to induce sufficient protection against it. That is why the poultry sector has commissioned further research into this strain in 2020, which will answer the question: can some new IBV strains including D181 cause kidney damage and false layers?
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