Avian metapneumovirus causes an acute highly contagious upper respiratory tract infection primarily of turkeys and chickens. The disease can cause significant economic losses in turkey and chicken flocks, particularly when exacerbated by secondary pathogens. The purpose of this study was to determine the prevalence of avian metapneumovirus antibodies in broiler and broiler breeder flocks in Kermanshah province, west of Iran. All the flocks had not been vaccinated against avian metapneumovirus. The province were divided into four geographic areas; southwest, southeast, northwest, and northeast. Flocks in each area, and 14–15 birds in each flock, were randomly sampled. The blood samples were taken regardless of the presence of any signs of respiratory or any other clinical disease in the flocks. A total of 435 blood samples were collected from 30 commercial chicken flocks (24 broiler flocks, aged between six and eight weeks, and six broiler breeder flocks, aged between 56 and 72 weeks). The presence of antibodies against avian metapneumovirus in each serum sample was tested twice by enzyme-linked immunosorbent assay using a commercial kit which was able to determine antibodies against A, B and C subtypes of avian metapneumovirus. Out of 347 serum samples obtained from broiler chickens, 167 (48.1%) were positive to avian metapneumovirus antibodies, which represented 20 (83.3%) of 24 examined broiler flocks. Out of 88 samples obtained from broiler breeder chickens, 82 (93.2%) were positive to avian metapneumovirus antibodies, which belonged to six (100%) of examined broiler breeder flocks. Detection of anti-avian metapneumovirus antibodies among broiler breeder (100%) was higher than broiler (83.3%) flocks. A higher rate of seropositivity (83.3% of samples and 100% of broiler flocks) was observed in northwest. The results of this study may indicate the possible involvement of avian metapneumovirus in the respiratory disease we are seeing in chickens in Iran. Its prevalence has to be investigated in other parts of Iran. Future work may and should include the use of molecular methods and isolation of the virus. Isolation of avian metapneumovirus will allow the possibility of making autogenous vaccines.
Compromised T-cell immunity in turkeys may lead to an unpredictable avian metapneumovirus vaccine response and variable protection against challenge