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.

What is new on molecular characteristics of Avian metapneumovirus strains circulating in Europe?

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nomic losses mainly due to respiratory or reproductive problems (Cecchinato et al, 2012), often exacerbated by secondary bacterial infections (Giovanardi et al, 2014).First, aMPV isolations in Europe date back to the second half of the 1980s, when turkey rhinotracheitis (TRT) outbreaks appeared in

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“…nomic losses mainly due to respiratory or reproductive problems (Cecchinato et al, 2012), often exacerbated by secondary bacterial infections (Giovanardi et al, 2014).…”

Avian Viruses that Impact Table Egg Production

“…In China, a similar disease picture was reported in egg-laying Muscovy ducks [ 63 ]. In Italy, longitudinal studies and sporadic samplings indicated that most pullet flocks get infected with AMPV before the laying begins [ 64 ].…”

Rapid detection of subtype B avian metapneumoviruses using RT-PCR restriction endonuclease digestion indicates field circulation of vaccine-derived viruses in older turkeys

“…Four aMPV subtypes (A, B, C and D) have been recognized based on nucleotide sequence differences (Gough & Jones, 2008). Subtype B infection has become endemic in densely populated Italian poultry areas since its first detection in the late 1980s (Fabris & D'aprile, 1990;Catelli et al, 2004Catelli et al, , 2010Cecchinato et al, 2012). Live vaccines of subtype B are routinely applied to 1-day-old turkeys to prevent respiratory disease.…”