Phylogeny and evolution of infectious bursal disease virus circulating in Turkish broiler flocks.

The emergence of new infectious bursal disease virus (IBDV) variants can threaten poultry health and production all over the world causing significant economic losses. Therefore, this study was performed to determine IBDV molecular epidemilogy, VP2 gene variation, and corresponding pathological lesions in IBDV infected chickens in Turkey. For this, 1855 bursa of Fabricius samples were collected from 371 vaccinated broiler flocks. Atrophia and haemorrhages were seen in the bursa Fabricius of very virulent IBDV (vvIBDV) infected chickens. Partial VP2 gene was sequenced and phylogenetic, recombination, and evolutionary analyses were performed. 1548 (83.5%) out of 1855 of bursa of Fabricius samples were IBDV positive and 1525 of those could be sequenced. The recombination analysis did not detect occurrence of any recombination event among the Turkish strains. Among 1525 sequenced samples, 1380 of them were found to be classical strains. Among 1380 classical strains, 1317 were similar to IBDV 2512, 11 to Faragher 52/70, 40 to 228 E, and 12 to Lukert strain. Out of 1525 reverse transcriptase ploymerase chain reaction positive samples, 144 of them were found to be similar to vvIBDV-VP2 gene reported to GenBank previously. The phylogenetic tree performed on a broad sequence dataset demonstrated grouping of vvIBDV Turkish strains in three different clusters, including sequences collected also from Iraq and Kuwait (Cluster 1), Indian (Cluster 2), and a distinct Turkish-only cluster (Cluster 3). The evolutionary rate estimation on branches/clades including Turkish strain mirrored the expected one for RNA viruses and no significant differences were found among different considered branches. In conclusion, results of this study indicate that vvIBDV strains similar to those circulating in various countries in the Middle East are present and undergoing evolution in chickens from Turkish broiler flocks. This point needs to be taken into account in planning adequate control strategies.

Application of different laboratory techniques to monitor the behaviour of a Mycoplasma synoviae vaccine (MS-H) in broiler breeders.

BACKGROUND: Mycoplasma synoviae (MS) is a major poultry pathogen which causes severe economic losses in all the productive sectors. The prevalence of MS in European countries has increased in the last few years, leading to greater attention to the available methods to prevent its spread. The main strategy currently applied for its containment is the development and maintenance of MS-free breeder flocks. A live MS vaccine (MS-H) obtained by mutagenizing an Australian field strain has recently been introduced in Italy. The aim of the present study was to evaluate the vaccine behaviour in broiler breeder groups at different production stages and the effectiveness of the available laboratory tests in discriminating the MS-H from a field strain. RESULTS: The vaccine diffused extensively through the population, shown by the wide serological response (over 80% of positive samples in RSA and 85% in ELISA), the high serological titres, the positivity of all the tracheal samples collected during the production phase by MS PCR and the positivity by cultivation from tracheal swabs at the end-point (55 weeks after vaccination). In contrast, only one swab from a sternal bursa was positive in MS PCR, while all the joint and oviduct samples were negative. There was no evidence of vertical transmission. Different genotyping techniques were used to achieve a clear classification of the MS positive samples. The vlhA and the obg gene analysis showed that most of the strains were homologous with the vaccine, but some ambiguous samples were further investigated with the multi locus sequence typing (MLST) scheme which confirmed the homology. CONCLUSIONS: The development of a multi-technique approach to monitor vaccinated avian flocks, based both on serological and biomolecular methods, is advised as well as the use of effective genotyping techniques to analyse the MS strains circulating in high densely populated poultry areas.

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.

Genome sequence analysis of a distinctive Italian infectious bursal disease virus.

In a recent study, an emerging infectious bursal disease virus (IBDV) genotype (ITA) was detected in IBDV-live vaccinated broilers without clinical signs of infectious bursal disease (IBD). VP2 sequence analysis showed that strains of the ITA genotype clustered separately from vaccine strains and from other IBDV reference strains, either classic or very virulent. In order to obtain a more exhaustive molecular characterization of the IBDV ITA genotype and speculate on its origin, genome sequencing of the field isolate IBDV/Italy/1829/2011, previously assigned to the ITA genotype, was performed, and the sequences obtained were compared to the currently available corresponding sequences. In addition, phylogenetic and recombination analyses were performed. Interestingly, multiple amino acid (AA) sequence alignments revealed that the IBDV/Italy/1829/2011 strain shared several AA residues with very virulent IBDV strains as well as some virulence markers, especially in the VP1 protein. Nevertheless, sequence analysis demonstrated the presence of several residues typical of IBDV strains at a low degree of virulence in the IBDV/Italy/1829/2011 strain. Although homologous recombination and reassortant phenomena may occur naturally among different IBDV strains, no evidence of those events was found in the genome of the IBDV/Italy/1829/2011 strain, which was confirmed to be a genetically distinctive IBDV genotype.

A novel variant of the infectious bronchitis virus resulting from recombination events in Italy and Spain.

Infectious bronchitis is considered to be one of the most devastating diseases in poultry. Control of its spread is typically attempted through biosecurity measures and extensive vaccination. However, the remarkable genetic and antigenic variability of the virus, which originate from both mutations and recombination events, represents an unsolved challenge for this disease. The present study reports on the emergence and spread of recombinant clusters detected in Italy and Spain between 2012 and 2014. A total of 36 Spanish and Italian infectious bronchitis virus (IBV) field strains were investigated and genetically characterized using phylogenetic, molecular, recombination and selection pressure analyses of the complete S1 gene. Based on the partial S1 sequencing, 27 IBV strains originating from Spain and nine from Italy were initially classified as being closely related to the Guandong/Xindadi (XDN) genotype. Phylogenetic analysis of the complete S1 gene revealed that the XDN strains formed a homogeneous clade with the Spanish IBV isolates within the QX genotype, whereas there was higher variability within the Italian strains. Recombination analysis determined that these strains belonged to four groups, which originated from independent recombination events between the QX and 793B IBV genotypes. Our data support the hypothesis of two different scenarios: firstly, in Spain, the large and homogeneous clade probably originated from a single offspring of the recombinant founder, which became dominant and spread throughout the country. Secondly, the nine Italian recombinants, which are characterized by three different recombination patterns, probably represent less fitted strains, because they were less viable with respect to their recombinant parents.

Gamma and Deltacoronaviruses in quail and pheasants from Northern Italy1.

In view of the restricted knowledge on the diversity of coronaviruses in poultry other than chicken, this study aimed to investigate the genetic diversity of coronaviruses in quail, pheasant, and partridge from two regions of Northern Italy. To this end, pools of tracheal and cloacal swabs from European quail (Coturnix Coturnix) and intestinal tract from pheasants (Phasianus Colchicus) and partridge (Perdix Perdix) flocks, with or without enteric signs, were collected during 2015. Avian coronavirus (Gammacoronavirus) was detected in quail not vaccinated against Infectious Bronchitis Virus (IBV) and in pheasants vaccinated with an IBV Massachusetts serotype. Based on DNA sequences for the gene encoding the S protein, the avian coronaviruses detected in the quail and pheasant are related to the IBV 793B and Massachusetts types, respectively. However, RNA-dependent RNA polymerase (RdRp) analyses showed the susceptibility of quail also to Deltacoronaviruses, suggesting that quail and pheasant avian coronaviruses share spike genes identical to chicken IBV spike genes and quail might host Deltacoronavirus.

Gammacoronavirus and Deltacoronavirus in Quail.

This paper expands on a previous report about coronaviruses in quail. After surveillance carried out in 2009 and 2010, some farmers started vaccinating quail with the Massachusetts avian infectious bronchitis virus serotype. The samples for this study were collected in 2013 from São Paulo state in southeastern Brazil. Pools of trachea, lungs, reproductive tract, kidneys, and enteric contents from quail and laying hens kept in the same farms and from quail-only farms as well as from both healthy birds and those showing infectious bronchitis-like symptoms were sampled in this study. The samples were screened using nested RT-PCR targeting the 3'-untranslated region of the Gammacoronavirus genus. Based on the DNA sequence for the RNA-dependent RNA polymerase (RdRp) gene, the strains isolated from quail clustered within either the Gammacoronavirus or Deltacoronavirus genus, and sequences from both genera were found in one quail sample. The phylogeny based on the partial S1 subunit sequence showed that the gammacoronaviruses detected in quail and layers belonged to the Brazil type. These results suggest that quail are susceptible to Gammacoronavirus and Deltacoronavirus viruses and indicate that the Massachusetts vaccination was not controlling IBV in quail or chickens.

Technological quality, mineral profile, and sensory attributes of broiler chicken breasts affected by White Striping and Wooden Breast myopathies.

The aim of the research was to study the impact of white striping and wooden breast myopathies on the technological quality, mineral, and sensory profile of poultry meat. With this purpose, a total of 138 breasts were selected for a control group with normal breasts (N), a group of breasts characterised by white striping (WS) myopathy, and a group of breasts having both white striping and wooden breast myopathies (WSWB). Data revealed that the simultaneous presence of the two myopathies, with respect to the WS lesion individually considered, had a further detrimental effect on pH (6.04 vs. 5.96; P < 0.05), yellowness (11.4 vs. 10.3; P < 0.01), cooking losses (30.4 vs. 27.6%; P < 0.05), toughness instrumental values (22.8 vs. 20.0 N; P < 0.01), and perception (6.22 vs. 5.56; P < 0.01). In addition, mineral contents suggest that a defective ions regulation is also present in white striping and wooden breast myopathies.

Impact of coccidiosis control program and feeding plan on white striping prevalence and severity degree on broiler breast fillets evaluated at three growing ages.

This study investigated the impact of 2 coccidiosis control systems (vaccine vs anticoccidial) and 2 feeding plans (standard energy vs low energy content, the latter supplemented with threonine and enzymes in the second half of the production cycle) on white striping (WS) prevalence and severity in chicken broiler breasts at commercial slaughter age (51 d). The age of lesion onset was also investigated with the sacrifice of 80 chicks at 12, and 80 chicks at 25 d of age. Seven hundred and twenty ROSS 708 strain male chicks were divided into 4 groups: a non-vaccinated group fed with standard diet (CONTROL); two groups vaccinated against coccidiosis but fed either a standard diet (VACC) or a low-energy diet supplemented with threonine and enzymes (VACC-LE plus); and a fourth group fed a standard diet containing anticoccidial additive except during the finishing period (COX). After live performance, yields, and fillet pH were measured, the breasts were weighed and scored as level 0 (no WS), level 1 (moderate WS), and level 2 (severe WS) at each of the 3 ages; data were covariate for slaughter weight. The results suggest an ameliorative effect of coccidiosis control systems when compared to the control group in terms of live weight, breast yield, and whole breast weight, with heavier fillets characterized by higher pH values. WS appeared at 25 d of age with an average prevalence of 11.5% and with lesions of moderate severity. There were no statistically significant differences due to the experimental treatment at this age. At commercial slaughter age, total average prevalence was 96%, with COX birds showing higher level 2 prevalence (77.6%). This could be related to the higher slaughter weight reached by the COX group (P<0.001) and the treatment effect (P<0.01) that probably adds to the effect of live weight. Diet had no effect on overall live performance of VACC-LE plus chickens, which were similar to those of the VACC group.

Subpopulations in aMPV vaccines are unlikely to be the only cause of reversion to virulence.

Avian metapneumovirus (aMPV) infects respiratory and reproductive tracts of domestic poultry, often involving secondary infections, and leads to serious economic losses in most parts of the world. While in general disease is effectively controlled by live vaccines, reversion to virulence of those vaccines has been demonstrated on several occasions. Consensus sequence mutations involved in the process have been identified in more than one instance. In one previous subtype A aMPV candidate vaccine study, small subpopulations were implicated. In the current study, the presence of subpopulations in a subtype B vaccine was investigated by deep sequencing. Of the 19 positions where vaccine (strain VCO3/50) and progenitor (strain VCO3/60616) consensus sequences differed, subpopulations were found to have sequence matching progenitor sequence in 4 positions. However none of these mutations occurred in a virulent revertant of that vaccine, thereby demonstrating that the majority progenitor virus population had not survived the attenuation process, hence was not obviously involved in any return to virulence. However within the vaccine, a single nucleotide variation was found which agreed with consensus sequence of a derived virulent revertant virus, hence this and other undetected, potentially virulent subpopulations, can be involved in reversion. Much deeper sequencing of progenitor, vaccine and revertant may clarify whether problematic virulent subpopulations are present and therefore whether these need to be routinely removed during aMPV vaccine preparation prior to registration and release.

A sensitive, reproducible, and economic real-time reverse transcription PCR detecting avian metapneumovirus subtypes A and B.

Use of real-time PCR is increasing in the diagnosis of infectious disease due to its sensitivity, specificity, and speed of detection. These characteristics make it particularly suited for the diagnosis of viral infections, like avian metapneumovirus (AMPV), for which effective control benefits from continuously updated knowledge of the epidemiological situation. Other real-time reverse transcription (RT)-PCRs have been published based on highly specific fluorescent dye-labeled probes, but they have high initial cost, complex validation, and a marked susceptibility to the genetic variability of their target sequence. With this in mind, we developed and validated a SYBR Green I-based quantitative RT-PCR for the detection of the two most prevalent AMPV subtypes (i.e., subtypes A and B). The assay demonstrated an analytical sensitivity comparable with that of a previously published real-time RT-PCR and the ability to detect RNA equivalent to approximately 0.5 infectious doses for both A and B subtypes. The high efficiency and linearity between viral titer and crossing point displayed for both subtypes make it suited for viral quantification. Optimization of reaction conditions and the implementation of melting curve analysis guaranteed the high specificity of the assay. The stable melting temperature difference between the two subtypes indicated the possibility of subtyping through melting temperature analysis. These characteristics make our assay a sensitive, specific, and rapid tool, enabling contemporaneous detection, quantification, and discrimination of AMPV subtype A and B.

An outbreak of blindness due to retinopathy in nine flocks of guinea fowl.

Blindness was observed in 10- to 14-day-old guinea fowl. The incidence ranged from 25% to 80% in nine flocks within a total population of 110,000 guinea fowls. Clinical signs of blindness in birds included aimless wandering, failure to find feed and water, lateral recumbency, loss of weight, and increased mortality. The birds lacked papillary reflexes to light, and there were no gross lesions in the eyes. Histologically there was degeneration and disorganization of photoreceptors in the retina. The guinea fowl came from three different breeder sources but all of the birds were given the same feed. The condition was not observed in the subsequent flocks that came from the same breeder sources but that were given different feed. Based on these observations, toxicity of an unknown ingredient in the feed is suspected as the cause of blindness in the guinea fowl.

Reversion to virulence of a subtype B avian metapneumovirus vaccine: is it time for regulators to require availability of vaccine progenitors?

Empirically derived live avian metapneumovirus (AMPV) vaccines developed during the late 80s and early 90s have generally performed well in controlling turkey rhinotracheitis. Nonetheless, unstable attenuation was previously demonstrated in an AMPV subtype A vaccine. Until now this had not been investigated in subtype B vaccines due to lack of any similar availability of a vaccine progenitor or its sequence. The publication of the full genome sequence for the VCO3 vaccine progenitor facilitated a conclusive investigation of two AMPVs isolated from poults on a farm which had been vaccinated with VCO3 derived vaccine. Full genome sequencing of the isolates and their comparison to sequences of the vaccine and its progenitor, confirmed their vaccine origin. After determining the absence of extraneous infectious agents, one of these virus isolates was inoculated into 1-day-old turkeys in disease secure isolators and shown to cause disease with a severity similar to that caused by virulent field virus. This suggests that instability in live AMPV vaccines may be generalized and highlights the need for availability of vaccine progenitor sequences for the field assessment of all live viral vaccines.

Epidemiology and control of low pathogenicity avian influenza infections in rural poultry in Italy.

We analyzed the involvement of the rural poultry sector in outbreaks of low pathogenicity avian influenza (AI) in Italy in 2007-2009 and discuss possible measures for improving monitoring and control. A description of how the rural poultry sector is organized also is provided. Data were obtained by the AI surveillance system established in the areas affected by the outbreaks. The surveillance activities identified two H7N3 epidemics, in 2007 and 2009, both of which mainly involved the rural sector, yet these activities did not allow for the prompt eradication of the disease. Additional strategies could be adopted to avoid the persistence of AI within the rural sector, based on the regulation and control of poultry holdings at the top of the production chain.

West Nile virus circulation in Veneto region in 2008-2009.

West Nile virus (WNV) was detected in Italy, in late summer 2008 in horses and birds in the Po valley. As a consequence, an intense WNV surveillance was implemented in that area involving Emilia-Romagna, Veneto and Lombardy. This paper presents the results of the September 2008-November 2009 surveillance on equines, mosquitoes, wild birds, dogs and cattle in Veneto. WNV was detected in equines and dogs, and, to a lesser extent in cattle and wild birds. Simultaneous circulation of Usutu virus was detected by testing wild birds found dead. Usutu virus but not WNV was also found in mosquitoes monitored during 2009. Equine practices monitoring allowed the definition of an area of WNV circulation and the 2008-2009 westward and northward spread of the infection. Although a relatively low number of human cases and a low virus circulation in vectors and birds detected in Veneto region could be considered favourable conditions for a limited risk of human exposure, it remains difficult to predict the possible evolution of the epidemiological situation.

Low pathogenicity avian influenza in Italy during 2007 and 2008: epidemiology and control.

Since 1999, the Italian poultry production system has experienced several outbreaks of avian influenza (AI), mainly located in northeastern Italy. This paper describes the low pathogenicity (LP) AI outbreaks detected during the surveillance activities implemented in 2007-08. From May to October 2007, ten rural and hobby poultry farms were infected by an LPAI virus of the H7N3 subtype. In August-October 2007, the H7N3 LPAI virus was introduced into the industrial poultry sector with the involvement of six meat turkey farms. Phylogenetic analysis of the hemagglutinin gene indicated that all but one of the H7N3 virus strains had a high level of homology (98.7%-99.8%). Furthermore, in August 2007, an LPAI H5N2 virus was identified in a free-range geese and duck breeder flock. The hemagglutinin and neuraminidase genes showed a high level of homology (99.8% and 99.9%, respectively) with H5N2 LPAI viruses isolated from mallards in July 2007 in the same area, suggesting a possible introduction from the wild reservoir. All the birds (in total 129,386) on the infected poultry farms were culled. The prompt implementation of AI control measures, including the enforcement of a targeted emergency vaccination plan, allowed the rapid eradication of infection. In 2008, three LPAI viruses (two H7N1 and one H5N1) were identified in dealer/rural farms. The surveillance activity implemented in this area allowed the prompt detection of LPAI viruses of the H5 and H7 subtypes in the rural sector, which, as observed in the 2007 epidemic, might be the source of infection for industrial poultry.

The effects of control measures on the economic burden associated with epidemics of avian influenza in Italy.

In 1999, Italy experienced a devastating epidemic of high-pathogenicity avian influenza (HPAI) caused by an H7N1 virus subtype. After this epidemic, a ministerial decree was passed to implement control measures for low-pathogenicity avian influenza (LPAI) due to H5 and H7 subtypes. We investigated whether these control measures have decreased the public expenditure associated with epidemics of LPAI and HPAI by comparing the direct and consequential losses of the 1999 epidemic to the losses associated with successive epidemics. The estimated total economic burden of the epidemics was about euro650 million (euro217 million in direct losses and euro433 million in consequential losses). The 1999 epidemic accounted for most of these losses (euro507 million: euro112 million in direct losses and euro395 million in consequential losses), whereas the total economic burden for the 5 successive LPAI was euro143 million (euro105 million in direct losses and euro38 million in consequential losses). These results demonstrate that the implementation of a coordinated set of disease-control measures, which included both emergency and prophylactic vaccination, was able to reduce the overall costs associated with avian influenza epidemics. The results also show that the application of adequate LPAI control measures may limit the risk of emergence of an HPAI virus in an area with a high poultry density, allowing the complete disruption of the poultry market and its huge associated costs to be avoided.

In vitro antiviral activity of chestnut and quebracho woods extracts against avian reovirus and metapneumovirus.

Field evidences have suggested that a natural extract, containing tannins, could be effective against poultry enteric viral infections. Moreover previous studies have shown that vegetable tannins can have antiviral activity against human viruses. Based on this knowledge three different Chestnut (Castanea spp.) wood extracts and one Quebracho (Schinopsis spp.) wood extract, all containing tannins and currently used in the animal feed industry, were tested for in vitro antiviral activity against avian reovirus (ARV) and avian metapneumovirus (AMPV). The MTT assay was used to evaluate the 50% cytotoxic compounds concentration (CC(50)) on Vero cells. The antiviral properties were tested before and after the adsorption of the viruses to Vero cells. Antiviral activities were expressed as IC(50) (concentration required to inhibit 50% of viral cytopathic effect). CC(50)s of tested compounds were > 200 microg/ml. All compounds had an extracellular antiviral effect against both ARV and AMPV with IC(50) values ranging from 25 to 66 microg/ml. Quebracho extract had also evident intracellular anti-ARV activity (IC(50) 24 microg/ml). These preliminary results suggest that the examined vegetable extracts might be good candidates in the control of some avian virus infections. Nevertheless further in vivo experiments are required to confirm these findings.

Use of vaccination in avian influenza control and eradication.

Vaccination against avian influenza (AI) infections caused by viruses of the H5 and H7 subtypes has been used in several occasions in recent years with the general objective of controlling and in some cases eradicating the disease. To contain AI infections effectively, vaccination should only be used as part of a comprehensive control strategy that also includes biosecurity, quarantine, surveillance, education, and elimination of infected and at-risk poultry. Although properly used, potent AI vaccines can prevent disease and death, increase resistance to infection, reduce virus replication and shedding, and reduce viral transmission, they cannot completely prevent AI virus replication. A wide variety of vaccines against AI has been developed and tested in experimental conditions, but only inactivated whole AI virus vaccines and recombinant H5-AI vaccines have been licensed and widely used in various countries. AI vaccination programmes should be adapted to local conditions to guarantee efficacy and sustainability. In particular, vaccination programmes should be modulated in diverse situations according to the virus strain involved, the characteristics of the poultry producing sector, the capacity of the veterinary infrastructure, and the availability of adequate resources. Based on the eco-epidemiological situation in the affected region/area/compartment and the assessment of the risk of AI introduction, different vaccination strategies could be implemented to control AI: (i) routine vaccination performed in endemic areas; (ii) emergency vaccination in the face of an epidemic; and (iii) preventative vaccination carried out whenever a high risk of virus incursion is identified.