Molecular Similarly Between Infectious Bronchitis Viruses and Common Vaccines

Abstract

Saja Sameer Abbood* and Balqees Hassan Ali

Infectious bronchitis is an acute extremely infectious respiratory illness caused by the avian gamma-corona virus. Infection with infectious bronchitis virus predisposes the bird to subsequent bacterial infection, worsening the situation. Infection causes severe morbidity and variable mortality in broilers, as well as a significant decrease in layer production of eggs. Samples were collected from clinical cases submitted for necropsy at local veterinary clinics.This study was conducted to detect the molecular similarity in S1 gene sequence between field viruses and commonly used vaccines. In order to compare the sequences of field viruses with vaccinal viruses, two vaccines are chosen based on their popularity in veterinary clinics. These are MA5 strain and H120 strain.  Molecular identification was done by using polymerase chain reaction (PCR) which was employed using primers target the S1 gene. Four positive field cases and two vaccine samples were sent to sequencing. The results of sequence alignment showed that vaccine viruses differ by more than 30% when compared to sequences of all the field viruses. The difference between genetic sequence leads to vaccine failure due to difference in the antigenic molecules on the spike protein of IBV.