title: Italian field survey reveals a high diffusion of avian metapneumovirus subtype B in layers and weaknesses in the vaccination strategy applied.
abstract: The current information on the 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 epidemiologic picture of aMPV presence in layer flocks in Italy, a survey was performed on 19 flocks of pullets and layers based on longitudinal studies or sporadic samplings. aMPV was detected by reverse transcription (RT)-PCR, and blood samples were collected for serology by aMPV ELISA. Occurrences of respiratory signs and a drop in egg production were recorded. Possible involvement of infectious bronchitis (IB) and egg drop syndrome (EDS) viruses that could have caused loss of egg production we ruled out for IB virus by RT-PCR, and EDS virus was ruled out by hemagglutination-inhibition (HI). Only subtype B of aMPV was found in both pullet and layer farms. Surveys of pullets showed that most groups became infected prior to the onset of lay without showing clear respiratory signs. At the point of lay, these groups were serologically positive to aMPV. In two layer flocks, egg drops were observed and could be strongly linked to the presence of aMPV infection. Results were correlated with aMPV vaccination programs applied to the birds in three flocks on the same farm. Only a vaccination program which included two live and one killed vaccines gave complete protection from aMPV infection to the birds, while a single live vaccine application was not efficacious. The current study gives an inside view of field aMPV diffusion in Italy and its control in layers.
authors: Department of Animal Medicine, Production and Health, University of Padua, Viale dell'Università, 16, 35020 Legnaro (PD), Italy.
authors: Mattia
authors: M
authors: Cecchinato
authors: Caterina
authors: C
authors: Lupini
authors: Enrico
authors: E
authors: Ricchizzi
authors: Marco
authors: M
authors: Falchieri
authors: Amelio
authors: A
authors: Meini
authors: Richard C
authors: RC
authors: Jones
authors: Elena
authors: E
authors: Catelli
mesh_terms: D000257:Adenoviridae Infections / Q000175:diagnosis / Q000453:epidemiology / Q000662:veterinary; D000818:Animals; D046808:Atadenovirus / Q000302:isolation & purification; D002645:Chickens; D018352:Coronavirus Infections / Q000175:diagnosis / Q000453:epidemiology / Q000662:veterinary; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005260:Female; D006385:Hemagglutination Inhibition Tests / Q000662:veterinary; D001351:Infectious bronchitis virus / Q000302:isolation & purification; D007558:Italy / Q000453:epidemiology; D008137:Longitudinal Studies; D029121:Metapneumovirus / Q000145:classification / Q000302:isolation & purification*; D018184:Paramyxoviridae Infections / Q000453:epidemiology / Q000517:prevention & control / Q000662:veterinary*; D011201:Poultry Diseases / Q000453:epidemiology* / Q000517:prevention & control* / Q000821:virology; D012098:Reproduction; D012141:Respiratory Tract Infections / Q000453:epidemiology / Q000517:prevention & control / Q000821:virology; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D012698:Serologic Tests / Q000662:veterinary; D014611:Vaccination / Q000379:methods* / Q000662:veterinary