Avian metapneumovirus excretion in vaccinated and non-vaccinated specified pathogen free laying chickens

Abstract

Vaccinated and non-vaccinated specified pathogen-free White Leghorn laying chickens were challenged at peak of lay by the intravenous or oculonasal route with a virulent avian metapneumovirus (aMPV) subtype B chicken strain. Severe clinical signs and a drop in egg production were induced in the non-vaccinated intravenously challenged birds whereas the vaccinates were not affected. Live virus excretion was demonstrated in the faeces and respiratory tract of non-vaccinated hens for up to 7 days post intravenous challenge. After oculonasal challenge, virus excretion could only be demonstrated in the respiratory tract for up to 5 days. No live virus excretion was found in either the faeces or the respiratory tract of vaccinated birds. Concurrent with live virus isolation, the presence of viral RNA was demonstrated by single reverse transcription-polymerase chain reaction (RT-PCR). Nested RT-PCR was more sensitive and viral RNA could be detected in non-vaccinated birds up to 28 days post either intravenous or oculonasal challenge, at which time the experiment was terminated. Viral RNA was detected for up to 12 days in vaccinated birds. This is the first study investigating excretion of aMPV and viral RNA in vaccinated and non-vaccinated laying hens challenged under experimental conditions. The results are of importance with regard to the persistence of aMPV and the appropriate diagnostic detection method in laying birds.

Hatchability, serology and virus excretion followingin ovovaccination of chickens with an avian metapneumovirus vaccine

“…A possible explanation for this could be the low titre of vaccine that was used. Using the progenitor virus of this attenuated virus re-isolation after intravenous challenge of laying chickens was also restricted up to 5 days after infection (Hess et al, 2004). This is in agreement with earlier findings that the time period for isolating metapneumoviruses from chickens is restricted to the first 5 days post infection (Khehra & Jones, 1999).…”

“…The re-isolation of the vaccine virus in tracheal organ cultures was carried out as described recently (Hess et al ., 2004). Each sample was given two blind passages at intervals of 3 to 4 days.…”

“…The whole process of RNA isolation, cDNA description and PCR was performed as described recently using an RNA extraction kit (Qiagen, Hilden, Germany) (Hess et al ., 2004).…”

Protection Conferred by a Live Avian Metapneumovirus Vaccine when Co-Administered with Live La Sota Newcastle Disease Vaccine in Chicks

“…In addition, no aMPV was isolated from the aMPV-vaccinated groups even though one of six chicks in the VG/GA:aMPV was positive for aMPV by RT-PCR. However, the detection of aMPV genome in the absence of viable virus isolation has been reported before (Hess et al, 2004;. Thus, it appears that simultaneous application of live aMPV and NDV La Sota vaccines in chicks already primed with NDV VG/GA showed no adverse effects in conferring protection against aMPV challenge.…”

APLICAÇÃO DA TÉCNICA DE RT-PCR PARA Metapneumovírus aviário (aMPV)

“…Em frangos de corte o genoma viral já foi detectado até 28 dias PI em suabes clocais (HESS et al, 2004). Banet-Noach et al (2009) e Cecchinato et al (2010 evidenciaram a presença do aMPV em plantéis de frango de corte vacinado e atribuem essa infecção por um subtipo ainda não incluído em vacinas, ou por uma possível reversão da virulência (CATELLI et al, 2006) ou devido a alta variabilidade genética entre as amostras circulantes a campo (BANET-NOACH et al, 2009;CATELLI et al, 2010).…”