EPIDEMIOLOGY AND CONTROL OF AVIAN METAPNEUMOVIRUS INFECTION IN ITALIAN LAYERS

The current information on prevalence of avian metapneumovirus (AMPV) infection in layers is fragmentary and its true impact on egg production often remains unknown or unclear. In order to draw an epidemiological picture of AMPV spreading in layer flocks in Italy, a survey was performed on five pullet and eight layer farms, based on longitudinal studies or sporadic samplings. AMPV was detected by RT-PCR, and blood samples were collected for serology by AMPV ELISA. Where possible, occurrence of respiratory signs and drop in egg production were recorded. Only AMPV of B subtype was found in both pullet and layer farms. Surveys of pullets showed that most groups become infected prior to the onset of lay without showing clear respiratory signs. At point of lay these groups were serologically positive to AMPV. In two layer flocks, egg drops were observed and could be strongly linked in presence of AMPV infection. Results were correlated with AMPV vaccination programs applied to the birds. Only a vaccination program, including two live and one killed vaccines, was able to give complete protection from AMPV infection to the birds, while a single live vaccine application was not efficacious. The present survey provides preliminary but unique data on the epidemiology of AMPV infection in layers in Italy.