Evaluation of 793/B-like and Mass-like vaccine strain kinetics in experimental and field conditions by real-time RT-PCR quantification.

Infectious bronchitis virus (IBV) is a great economic burden both for productive losses and costs of the control strategies. Many different vaccination protocols are applied in the same region and even in consecutive cycles on the same farm in order to find the perfect balance between costs and benefits. In Northern Italy, the usual second vaccination is more and more often moved up to the chick's first d of life. The second strain administration together with the common Mass priming by spray at the hatchery allows saving money and time and reducing animal stress. The present work compared the different vaccine strains (Mass-like or B48, and 1/96) kinetics both in field conditions and in a 21-day-long experimental trial in broilers, monitoring the viral replication by upper respiratory tract swabbing and vaccine specific real time reverse transcription PCR (RT-PCR) quantification. In both field and experimental conditions, titers for all the vaccines showed an increasing trend in the first 2 wk and then a decrease, though still remaining detectable during the whole monitored period. IBV field strain and avian Metapneumovirus (aMPV) presence also was also investigated by RT-PCR and sequencing, and by multiplex real-time RT-PCR, respectively, revealing a consistency in the pathogen introduction timing at around 30 d, in correspondence with the vaccine titer's main decrease. These findings suggest the need for an accurate knowledge of live vaccine kinetics, whose replication can compete with the other pathogen one, providing additional protection to be added to what is conferred by the adaptive immune response.

First Molecular Characterization of Avian Metapneumovirus (aMPV) in Turkish Broiler Flocks.

Viral respiratory diseases, including avian metapneumovirus (aMPV), have a significant economic impact on poultry industries. The frequency and genotype diversity of aMPV in Turkish broiler flocks is not known at present. The aim of this study was to report the first molecular identification and phylogeny of aMPV, which is circulating in Turkish broiler flocks. Trachea tissue samples and tracheal swabs were collected from 110 broiler flocks distributed in different geographical regions in Turkey between March 2017 and March 2018. Detection of aMPV was confirmed with the use of universal reverse transcriptase (RT) PCR, and eight (7.2%) broiler farms were positive for aMPV. Sequence analysis of the G gene revealed the exclusive presence of subtype B viruses. Three field isolates clustered closely with a 2002 Israel isolate, indicating a potential transmission route between these two countries and through the Middle East. The remaining five field isolates were closely related to a vaccine strain, even though broiler flocks in Turkey are not routinely vaccinated against aMPV. Therefore, we speculate these five isolates could have originated from nearby vaccinated turkey farms. Additionally, the presence of some nucleotide substitutions compared to the reference vaccine sequence suggests prolonged circulation and evolution of the original vaccine virus or a vaccine subpopulation was selected under field conditions. This evidence emphasizes the need for further detailed and more systemic approaches to evaluate aMPV spread and evolution in order to design effective control strategies.

Nota de investigación- Primera caracterización molecular de metapneumovirus aviar (aMPV) en parvadas de pollo de engorde en Turquía. Las enfermedades respiratorias virales, incluido el metapneumovirus aviar (aMPV), tienen un impacto económico significativo en la industrias avícola. La diversidad de la frecuencia y el genotipo de aMPV en las parvadas de pollos de engorde en Turquía no se conocen en la actualidad. El objetivo de este estudio fue reportar la primera identificación molecular y la filogenia de un metapneumovirus aviar, que circula en parvadas de pollos de engorde turcos. Se recolectaron muestras de tejido de tráquea e hisopos traqueales de 110 parvadas de pollos de engorde distribuidas en diferentes regiones geográficas de Turquía entre marzo del 2017 y marzo del 2018. La detección de metapneumovirus aviar se confirmó con el uso de un método de universal transcriptasa reversa y PCR. Ocho (7.2%) granjas de pollos de engorde fueron positivas para metapneumovirus aviar. El análisis de secuencia del gene G reveló la presencia exclusiva de virus de subtipo B. Tres virus de campo se agruparon estrechamente con un metapneumovirus de Israel del año 2002, lo que indica una posible ruta de transmisión entre estos los dos países y el Medio Oriente. Los cinco metapneumovirus de campo restantes estaban estrechamente relacionados con una cepa de vacuna, a pesar de que las parvadas de pollos de engorde en Turquía no se vacunan rutinariamente contra metapneumovirus aviar. Por lo tanto, se especula que estos cinco metapneumovirus podrían haberse originado en granjas cercanas con pavos vacunados. Además, la presencia de algunas sustituciones de nucleótidos en comparación con la secuencia de la vacuna de referencia sugiere una circulación prolongada y la evolución del virus de la vacuna original o una subpoblación de la vacuna se seleccionó en condiciones de campo. Esta evidencia enfatiza la necesidad de enfoques más detallados y más sistémicos para evaluar la propagación y evolución de metapneumovirus aviar a fin de diseñar estrategias de control efectivas. Abbreviations: aMPV = avian metapneumovirus; cDNA = complementary DNA; F = fusion; G = attachment; RT-PCR = reverse-transcriptase PCR.