Isolation and Molecular Characterization of Avian metapneumovirus

A study was undertaken to isolate and characterize avian metapneumovirus (aMPV) causing swollen head syndrome in chickens. Out of 21 oropharyngeal swab samples collected, only one sample from eight weeks old commercial layers was positive for aMPV N gene specific RT-PCR. The positive sample was inoculated in vero cells and isolated after four blind passages. The virus was identified by Agar gel precipitation test with reference aMPV hyperimmune serum. Further it was confirmed by N gene specific RT-PCR. Molecular subtyping based on G gene specific RT PCR revealed that the isolate belong to aMPV subtype A. The isolate was shown to have a homology of 96.4 per cent with the European isolate (#8544) and 89.7 to 100 per cent with other isolates of Europe, South Korea and Brazil (SHS/BR/669/03). Seroprevalence study of 1745 serum samples collected from 69 flocks using ELISA revealed that 925 samples from 48 flocks (69.56 %) were positive for aMPV antibodies with a GMT of 3513±114. The inactivated mineral oil adjuvant vaccine prepared from the isolate induced effective seroconversion after booster vaccination.