1,721,159 research outputs found
IMPATTO DI DIFFERENTI STRATEGIE VACCINALI SULLE DINAMICHE DI POPOLAZIONE DEL GENOTIPO QX DI BRONCHITE INFETTIVA E SULLA FREQUENZA DEI FOCOLAI
No full textL’estrema variabilità e la rapida evoluzione del virus della bronchite infettiva (IBV)
hanno sempre rappresentato la sfida principale per il suo controllo a causa della limitata
cross-protezione fra i diversi ceppi. Vari studi sperimentali hanno dimostrato
un incremento nello spettro di protezione qualora gli animali siano vaccinati con più
genotipi differenti. Ciò non di meno, le condizioni e la tempistica di somministrazione
della vaccinazione in campo sono a tal punto differenti che spesso una generalizzazione
dei risultati sperimentali è quantomeno questionabile. Nel presente studio è
stato utilizzato un approccio di tipo epidemiologico-filodinamico per ricostruire la
storia demografica del principale genotipo di campo (i.e. genotipo QX) circolante
in Italia. Centonovantacinque campioni raccolti nel periodo 2012-2016 sono stati
sequenziati e analizzati. Ciò ha permesso di evidenziare come sia le dinamiche
di popolazione di questo virus che la frequenza di focolai clinici siano state particolarmente
variabili nel corso del tempo. Di particolare rilievo è risultata la forte
associazione fra questi fenomeni e i cambiamenti nelle strategie vaccinali adottate.
Ciò ha permesso di dimostrare il rapporto di causa-effetto fra la somministrazione/
sospensione del vaccino per IBV e le ripercussioni in termini di dimensione della
popolazione virale e, soprattutto, dell’occorrenza di episodi clinici indotti da IBV.
È stato quindi possibile fornire una robusta dimostrazione dell’effetto protettivo indotto
della vaccinazione nella pratica routinaria di allevamento. Inoltre, il resoconto
qui riportato evidenzia l’importanza di pianificare con rigore non solo le strategie di
controllo ma anche il loro monitoraggio e la loro valutazione, evitando di affidarsi a
pareri soggettivi ed estemporanei
Zakaźne zapalenie oskrzeli kur – epidemiologia molekularna zakażeń, sytuacja we Włoszech
No full textPorcine circovirus 3 (PCV-3) as a causal agent of disease in swine and a proposal of PCV-3 associated disease case definition
Full text linkPorcine circovirus 3 (PCV-3) was discovered in 2015 using next-generation sequencing (NGS) methods. Since then, the virus has been detected worldwide in pigs displaying several clinical–pathological outcomes as well as in healthy animals. The objective of this review is to critically discuss the evidence existing so far regarding PCV-3 as a swine pathogen. In fact, a significant number of publications claim PCV-3 as a disease causal infectious agent, but very few of them have shown strong evidence of such potential causality. The most convincing proofs of disease association are those that demonstrate a clinical picture linked to multisystemic lymphoplasmacytic to lymphohistiocytic perivascular inflammation and presence of viral nucleic acid within these lesions. Based on these evidence, individual case definitions for PCV-3-reproductive disease and PCV-3-systemic disease are proposed to standardize diagnostic criteria for PCV-3-associated diseases. However, the real frequency of these clinical–pathological conditions linked to the novel virus is unknown, and the most frequent outcome of PCV-3 infection is likely subclinical based on its worlwide distribution
Field experience on the use of a multi-species symbiotic on gut health and production parameters in broiler breeders and their progeny
No full text
Effect of genome composition and codon bias on infectious bronchitis virus evolution and adaptation to target tissues
Full text linkBackground: Infectious bronchitis virus (IBV) is one of the most relevant viruses affecting the poultry industry, and several studies have investigated the factors involved in its biological cycle and evolution. However, very few of those studies focused on the effect of genome composition and the codon bias of different IBV proteins, despite the remarkable increase in available complete genomes. In the present study, all IBV complete genomes were downloaded (n = 383), and several statistics representative of genome composition and codon bias were calculated for each protein-coding sequence, including but not limited to, the nucleotide odds ratio, relative synonymous codon usage and effective number of codons. Additionally, viral codon usage was compared to host codon usage based on a collection of highly expressed genes in IBV target and nontarget tissues. Results: The results obtained demonstrated a significant difference among structural, non-structural and accessory proteins, especially regarding dinucleotide composition, which appears under strong selective forces. In particular, some dinucleotide pairs, such as CpG, a probable target of the host innate immune response, are underrepresented in genes coding for pp1a, pp1ab, S and N. Although genome composition and dinucleotide bias appear to affect codon usage, additional selective forces may act directly on codon bias. Variability in relative synonymous codon usage and effective number of codons was found for different proteins, with structural proteins and polyproteins being more adapted to the codon bias of host target tissues. In contrast, accessory proteins had a more biased codon usage (i.e., lower number of preferred codons), which might contribute to the regulation of their expression level and timing throughout the cell cycle. Conclusions: The present study confirms the existence of selective forces acting directly on the genome and not only indirectly through phenotype selection. This evidence might help understanding IBV biology and in developing attenuated strains without affecting the protein phenotype and therefore immunogenicity
Er site in Er-implanted Si nanoclusters embedded in SiO2
No full textWe have investigated by extended x-ray absorption fine structure spectroscopy the local order around Er atoms introduced by ion implantation in substoichiometric silica films prepared by plasma enhanced chemical vapor deposition, where Si nanoclusters have been formed by different preimplantation annealing processes. The results show that Er atoms are surrounded by a first shell of O atoms and no Er-Si direct correlations are observed; moreover, while the variation of the preimplantation annealing temperature has no effect on the Er site, it is observed that the increase of the Er concentration determines an increase of both the Er first shell coordination number and the Er-O interatomic distance, becoming more similar to those of Er2O3. In the presence of an extensive phase separation between Si and SiO2 the local environment around Er plays a crucial role on the efficiency of the photoluminescence emission at 1.54 mu m, which is significantly increased when the first shell of atoms around Er is closer to that one of Er2O3
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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