IBV genotypes & pathotypes

IBV genotypes & pathotypes

infectious bronchitis virus (IBV) a Gammacoronavirus of the family Coronaviridae, is 120 nm in diameter with crown-like spikes of 20 nm length. IBV possesses a single-stranded, positive-sense RNA of about 27.6 kb in length, The genome contains 13 open reading frames (ORF) that code for 25 proteins. The key protein containing neutralization epitopes is the spike protein  (S) that is post-translationally cleaved into two subunits, S1 and S2. The S1 is responsible for the attachment of the virus to the cellular membrane and plays a major role in tissue tropism, induction of protective immunity, virus neutralization, and serotype specificity The S1 gene sequencing is the most widely used method for classifying IBV isolates into genotypes, there are 8 genotypes (GI to GVIII) and 37 lineages.

 

 

Some lineages are widely distributed, especially those used for vaccination such as GI-1 (Massachusetts, H120 and Connecticut), GI-13 (793/B), GI-9 (Arkansas), GI-19 (QXIBV) and GI-23 (EGY Var 1 & EGY Var 2).

Some lineages have been found to be geographically confined to certain countries such as Middle East (GI-23), Asia (GI-7, -15, -18, -22, -24 and GVI-1), North America (GI-8, -9, -17, -20, -25, -27 and GIV-1), South America (GI-11), Europe (GI-21 and GII-1), Africa (GI-26), Australia and New Zealand (GI-5, -6, -10, GIII-1 and GV-1).

 

IBV pathotypes can vary greatly among strains, and clinical symptoms caused by infection can be diverse due to various chicken breeds, environmental circumstances and immunity levels. Although IBV demonstrates clear tropism by producing lesions in the respiratory system, kidney, reproductive system, and alimentary tract, the viral pathotypes observed in field outbreaks are usually more complicated due to co-infections with other pathogens.

So we have to use Protectotype method for vaccine evaluation and using a vaccine has strains that matching with the genotype and the pathotypes which we have in the field region.

Article Reference :

Tags :
Share This :

Request an Appointment