Vaccination of Poultry Against Influenza.

The complexity of influenza A virus (IAV) infections in avian hosts leads to equally complex scenarios for the vaccination of poultry. Vaccination against avian influenza strains can be used to prevent infections from sources with a single strain of IAV. It has been used as a part of outbreak control strategies as well as a way to maintain production for both low and high pathogenicity outbreaks. Unlike other viral pathogens of birds, avian influenza vaccination when used against highly pathogenic avian influenza virus, is tied to international trade and thus is not freely available for use without specific permission.

Vacunación de aves comerciales contra la influenza aviar. La complejidad de las infecciones por el virus de la influenza A en las aves hospedadoras conduce a escenarios igualmente complejos para la vacunación en la avicultura. La vacunación contra cepas de influenza aviar se puede utilizar para prevenir infecciones provenientes de fuentes con una sola cepa del virus de influenza. Se ha utilizado como parte de las estrategias de control de brotes, así como como una forma de mantener la producción tanto en brotes de baja como de alta patogenicidad. A diferencia de otros patógenos virales de las aves, la vacunación contra la influenza aviar, cuando se usa contra el virus de la influenza aviar altamente patógeno, está vinculada al comercio internacional y por lo tanto, no está disponible para su uso sin un permiso específico.

Refining the definition of the avian pathogenic Escherichia coli (APEC) pathotype through inclusion of high-risk clonal groups.

Colibacillosis in poultry is a unique disease manifestation of Escherichia coli in the animal world, as one of the primary routes of entry is via the respiratory tract of birds. Because of this, a novel extraintestinal pathogenic E. coli (ExPEC) subpathotype coined avian pathogenic E. coli (or APEC) has been described. Like other ExPEC, this pathotype has been challenging to clearly define, and in the case of APEC, its role as an opportunistic pathogen has further complicated these challenges. Using 3,479 temporally matched genomes of poultry-source isolates, we show that the APEC plasmid, previously considered a defining trait of APEC, is highly prevalent in clinical isolates from diseased turkeys. However, the plasmid is also quite prevalent among cecal E. coli isolates from healthy birds, including both turkeys and broilers. In contrast, we identify distinct differences in clonal backgrounds of turkey clinical versus cecal strains, with a subset of sequence types (STs) dominating the clinical landscape (ST23, ST117, ST131, ST355, and ST428), which are rare within the cecal landscape. Because the same clinical STs have also dominated the broiler landscape, we performed lethality assays using strains from dominant STs from clinical or cecal landscapes in embryonated turkey and chicken eggs. We show that, irrespective of plasmid carriage, dominant clinical STs are significantly more virulent than dominant cecal STs. We present a revised APEC screening tool that incorporates APEC plasmid carriage plus markers for dominant clinical STs. This revised APEC pathotyping tool improves the ability to identify high-risk APEC clones within poultry production systems, and identifies STs of interest for mitigation targets.

Genomic Landscape of Ornithobacterium rhinotracheale in Commercial Turkey Production in the United States.

Ornithobacterium rhinotracheale is a causative agent of respiratory tract infections in avian hosts worldwide but is a particular problem for commercial turkey production. Little is known about the ecologic and evolutionary dynamics of O. rhinotracheale, which makes prevention and control of this pathogen a challenge. The purpose of this study was to gain insight into the genetic relationships between O. rhinotracheale populations through comparative genomics of clinical isolates from different U.S. turkey producers. O. rhinotracheale clinical isolates were collected from four major U.S. turkey producers and several independent turkey growers from the upper Midwest and Southeast, and whole-genome sequencing was performed. Genomes were compared phylogenetically using single nucleotide polymorphism (SNP)-based analysis, and then assembly and annotations were performed to identify genes encoding putative virulence factors and antimicrobial resistance determinants. A pangenome approach was also used to establish a core set of genes consistently present in O. rhinotracheale and to highlight differences in gene content between phylogenetic clades. A total of 1,457 nonrecombinant SNPs were identified from 157 O. rhinotracheale genomes, and four distinct phylogenetic clades were identified. Isolates clustered by company on the phylogenetic tree, however, and each company had isolates in multiple clades with similar collection dates, indicating that there are multiple O. rhinotracheale strains circulating within each of the companies examined. Additionally, several antimicrobial resistance proteins, putative virulence factors, and the pOR1 plasmid were associated with particular clades and multilocus sequence types, which may explain why the same strains seem to have persisted in the same turkey operations for decades.IMPORTANCE The whole-genome approach enhances our understanding of evolutionary relationships between clinical Ornithobacterium rhinotracheale isolates from different commercial turkey producers and allows for identification of genes associated with virulence, antimicrobial resistance, or mobile genetic elements that are often excluded using traditional typing methods. Additionally, differentiating O. rhinotracheale isolates at the whole-genome level may provide insight into selection of the most appropriate autogenous vaccine strain, or groups of strains, for a given population of clinical isolates.

Environmental Sampling for Influenza A Viruses in Turkey Barns.

We have examined a variety of sampling strategies for detecting pathogens in turkey flocks undergoing infections with low pathogenicity avian influenza virus (LPAIV). We found that viral RNA was widely distributed in the barn environment of turkey flocks undergoing an active LPAIV infection and was in both water and drinker biofilm samples. Viral RNA was concentrated in drinker biofilm and sediment and was detectable using real-time reverse-transcription polymerase chain reaction (RRT-PCR) and by virus isolation. Drinker biofilm sample results correlated with concurrently collected oropharyngeal (OP) sample results from flocks on a farm with LPAI in which the two sampling strategies were directly compared. To evaluate the utility of biofilm sampling for the detection of highly pathogenic avian influenza virus (HPAIV), biofilm and OP swabs from mortality pools were collected daily from negative turkey flocks on an HPAI-positive premise. The biofilm swabs were positive 1-2 days prior to positives appearing in the OP sample pools. The drinker biofilm sampling strategy overcame the difficulty of finding a subclinical infectious bird in a population by collecting material from a large number of individuals and testing a sample in which a positive signal persists for several days to weeks. The sampling method is convenient for use in turkey barns and has been reliably used in both active and passive surveillance programs for LPAIV and HPAIV using RRT-PCR.

Muestreo ambiental para el virus de influenza A en casetas de pavos. Se han examinado una variedad de estrategias de muestreo para detectar patógenos en parvadas de pavos que sufren infecciones con el virus de la influenza aviar de baja patogenicidad (con las siglas en inglés LPAIV). Se encontró que el ARN viral se distribuyó ampliamente en el ambiente de las casetas con parvadas de pavos con infección activa por el virus de la influenza aviar de baja patogenicidad y se determinó tanto en muestras de agua como en muestras de la biopelícula de bebederos. El ARN viral se concentró en la biopelícula y en el sedimento de bebederos y se detectó mediante transcripción reversa y reacción en cadena de la polimerasa en tiempo real (RRT-PCR) y mediante el aislamiento del virus. Los resultados de la muestra de la biopelícula del bebedero se correlacionaron con los resultados de la muestra orofaríngea (OP) colectada de forma simultánea de parvadas en una granja con influenza aviar de baja patogenicidad en las que se compararon directamente las dos estrategias de muestreo. Para evaluar la utilidad del muestreo de la biopelícula para la detección del virus de la influenza aviar altamente patógena (HPAIV), se recolectaron diariamente biopelículas e hisopos orofaríngeos de grupos de mortalidad de parvadas de pavos negativas en una granja positiva para la influenza aviar de alta patogenicidad. Los hisopos de biopelículas fueron positivos de uno a dos días antes de que aparecieran resultados positivos en las muestras orofaríngeas agrupadas. La estrategia de muestreo de la biopelícula del bebedero eliminó la dificultad de encontrar un ave infectada subclínicamente en una población al recolectar material de un gran número de individuos y analizar una muestra en la que persiste una señal positiva durante varios días o semanas. El método de muestreo es adecuado para su uso en casetas de pavos y se ha utilizado de manera confiable en los programas de vigilancia activa y pasiva para el virus de influenza aviar tanto de baja como de alta patogenicidad utilizando transcripción reversa y reacción en cadena de la polimerasa en tiempo real.

Establishing Monitored Premises Status for Continuity of Business Permits During an HPAI Outbreak.

Recent experiences with avian influenza outbreaks in poultry in the United States have tested biosecurity protocols and outbreak management strategies. During an outbreak, regulatory officials managing the emergency response need to make timely decisions in order to achieve disease control and eradication goals while simultaneously decreasing the unintended consequences of the response. To move susceptible animals or animal products out of a disease Control Area via a secure food supply continuity of business (COB) permit without the risk of expanding a disease outbreak, premises must be designated as Monitored Premises (MP) by regulatory officials. The experience of and lessons learned from the 2014 to 2015 highly pathogenic avian influenza (HPAI) outbreak have resulted in defined criteria necessary to establish MP status during an HPAI outbreak and highlighted the need for a clear method to determine that those criteria have been met. Establishing MP status is different from an epidemiologic investigation, though they both require analyses of how avian influenza virus may enter poultry premises and can take significant staff time. MP status of premises seeking to move animals or animal products must be continuously re-evaluated as Infected Premises status, and resulting epidemiologic contacts, can rapidly change during an outbreak. We present here a questionnaire to establish MP status, designed to be initially completed by industry representatives in an attempt to streamline processes and conserve resources. During an outbreak, the MP status questionnaire is an essential risk-based management tool used to establish premises status, as part of operationalizing permitted movement to support COB.

A noncytolytic α toxin recombinant protein protects turkeys against Clostridium septicum challenge.

Clostridium septicum and its associated cytolytic α toxin, along with several other clostridial species, has been implicated as the causative agent of gangrenous dermatitis. A recombinant noncytolytic C. septicum α toxin (NCAT) peptide was developed for use as a vaccine and demonstrated to be safe at concentrations as high as 1 mg/ml. NCAT, used as a purified antigen, partially purified antigen, or in combination with native antigens, was compared to salt-fractionated α toxin combined with denatured C septicum bacteria (native) in a vaccination trial. Three-day-old poults were placed into one of five groups and received two, 0.2-ml vaccinations 5 wk apart. Subcutaneous challenge with 3.2 x 10(7) log phase C. septicum resulted in 78% to 95% of the vaccinated birds surviving challenge compared to 48% of sham-injected controls. By ELISA analysis on NCAT-coated plates, birds receiving vaccines containing the recombinant NCAT peptide showed significantly higher blood serum antibody concentrations than did birds receiving vaccines containing native antigens or alum controls. Additionally, high levels of maternally transferred antibodies reactive to NCAT-purified antigens found in the pre-immune sera from naive 3-day-old poults suggest that the tertiary structure of the NCAT peptide has a high homology to the native protein structure. In conclusion, our study showed that the use of a vaccine comprised of a noncytolytic recombinant α toxin peptide antigen provided clinical protection equal to the use of vaccines formulated with inactivated native proteins at a reduced overall cost.

The occurrence of enteric viruses in Light Turkey Syndrome.

Two studies were conducted to determine the role of enteric viruses in Light Turkey Syndrome (LTS), which is characterized by lower weight in market age turkeys than their standard breed character. In the surveillance study, we selected four LTS and two non-LTS turkey flocks in Minnesota and collected faecal samples at 2, 3, 5 and 8-weeks of age. Astrovirus, rotavirus, and reovirus were detected alone or in various combinations in both LTS and non-LTS flocks. No coronavirus was detected in LTS flocks and no corona- or reovirus was detected in non-LTS flocks. In the second study, 2-week-old turkey poults were divided into two groups; Group A (challenged) was inoculated orally with 10% pooled faecal suspension from LTS flocks and group B (control) was inoculated with phosphate buffered saline (PBS). Clinical signs of depression, huddling, and lack of uniform size were observed in the challenged group but not in the control group. diarrhoea was observed in both groups but was more severe in the challenged group than in the control group. Birds in the challenged group shed astrovirus, rotavirus and reovirus, while the control group shed only astrovirus. Virus shedding in both groups was observed for up to nine weeks of age. Significantly lower body weights were seen in the challenged group starting at seven weeks of age and lasting until 20 weeks of age. These findings suggest that viral enteritis at an early age may set up conditions for the development of LTS in adult turkeys.

Vaccination of turkeys with Clostridium septicum bacterin-toxoid: evaluation of protection against clostridial dermatitis.

Clostridial dermatitis is an acute disease causing high mortality in turkeys. Both Clostridium septicum and Clostridium pefringens have been isolated from these cases; however, reports from several diagnostic laboratories indicate an increased isolation rate of C septicum compared with C. perfringens from cases of clostridial dermatitis in recent years. Previous studies suggested C. septicum was more potent than C. perfringens in causing clostridial dermatitis in turkeys. The objective of this study was to develop and evaluate the use of a C. septicum bacterin-toxoid to control clostridial dermatitis in turkeys. A C. septicum bacterin-toxoid was prepared and was initially tested in 6-wk-old commercial turkeys under laboratory conditions for its safety and efficacy. Subsequently, the bacterin-toxoid was evaluated for use in commercial turkey farms with a consistent history of clostridial dermatitis. Birds in the field were vaccinated subcutaneously once at 6 wk of age with C. septicum bacterin-toxoid, and then mortality in both vaccinated and unvaccinated groups was recorded and compared. Blood samples from birds in both groups were examined using ELISA to detect antibody response to the C. septicum toxoid. The C. septicum bacterin-toxoid was found to be safe and to elicit antibodies against the toxoid. In vaccinated commercial turkeys, control of clostridial dermatitis was achieved via antibiotic use and clostridial dermatitis mortality was significantly reduced compared with that of birds in the unvaccinated group. The C. septicum bacterin-toxoid seems to be a valuable tool for the turkey industry to reduce losses due to clostridial dermatitis.