Methylome Analysis in Chickens Immunized with Infectious Laryngotracheitis Vaccine.

In this study we investigated the methylome of chickens immunized with Infectious laryngotracheitis (ILT) vaccine derived from chicken embryos. Methyl-CpG binding domain protein-enriched genome sequencing (MBD-Seq) method was employed in the detection of the 1,155 differentially methylated regions (DMRs) across the entire genome. After validation, we ascertained the genomic DMRs distribution and annotated them regarding genes, transcription start sites (TSS) and CpG islands. We found that global DNA methylation decreased in vaccinated birds, presenting 704 hypomethylated and 451 hypermethylated DMRs, respectively. Additionally, we performed an enrichment analysis detecting gene networks, in which cancer and RNA post-transcriptional modification appeared in the first place, followed by humoral immune response, immunological disease and inflammatory disease. The top four identified canonical pathways were EIF2 signaling, regulation of EIF4 and p70S6K signaling, axonal guidance signaling and mTOR signaling, providing new insight regarding the mechanisms of ILT etiology. Lastly, the association between DNA methylation and differentially expressed genes was examined, and detected negative correlation in seventeen of the eighteen genes.

Transcriptome analysis reveals an activation of major histocompatibility complex 1 and 2 pathways in chicken trachea immunized with infectious laryngotracheitis virus vaccine.

Infectious laryngotracheitis is an acute, contagious, upper respiratory disease of chickens caused by gallid herpes virus 1. Due to mortality rates that can reach up to 70% depending on the virulence of the virus, the disease is of great economic importance to the poultry industry. In this study, 15-d-old specific pathogen-free White Leghorn chickens were used to perform transcriptome analysis of chicken trachea immunized with infectious laryngotracheitis virus vaccine. Myosin and several collagen-related genes were downregulated in the immunized group, suggesting that normal function and structure may be compromised. In addition, we identified some cytokine receptors and several immune genes, such as Granzyme A (GZMA), CD4 molecule (CD4), CD8a molecule (CD8A), and CD8b molecule (CD8B), that were upregulated upon vaccination. The gene ontology analysis shows that genes included in the biological process cluster were related to antigen processing and presentation, positive regulation of immune system processes, T cell selection, and positive regulation of T cell activation. In conclusion, chicken embryo origin vaccine activation of the major histocompatibility complex 1 and 2 pathways provides insight for evaluation and design of infectious laryngotracheitis vaccines.

Molecular epidemiology of infectious laryngotracheitis: a review.

Infectious laryngotracheitis (ILT) is an economically important respiratory disease of poultry that affects the poultry industry worldwide. The disease is caused by gallid herpesvirus I (GaHV-1), a member of the genus Iltovirus, family Herpesviridae, subfamily Alphaherpesvirinae. The current incidence of the disease is heavily influenced by live attenuated vaccines, which have been used extensively since their introduction in the mid-twentieth century. The capability of current live attenuated vaccine viruses to revert to virulence and spread from bird to bird has shaped the molecular epidemiology of ILT. Because of the antigenic homogeneity among GaHV-1 strains, differentiation of strains has been achieved by targeting genomic differences between outbreak-related isolates and vaccine strains. Numerous genes and genomic regions have been utilized in the development of DNA-based diagnostic assays to differentiate outbreak-related isolates from vaccine strains in countries where ILT outbreaks have occurred. More recently, full genome sequences have allowed determination of the origin of some of the outbreak-related isolates circulating in some poultry production countries. Overall, molecular typing data collected worldwide have identified live attenuated vaccine-related isolates as the primary source for outbreaks of the disease.

Prevalence and differentiation of diseases in Maryland backyard flocks.

Several epidemiologic surveillance studies have implicated backyard flocks as a reservoir for poultry diseases; however, much debate still exists over the risk these small flocks pose. To evaluate this concern, the prevalence of Newcastle disease (ND), infectious laryngotracheitis (ILT), Mycoplasma gallisepticum (MG), and Salmonella was determined in 39 Maryland backyard flocks. Serum, tracheal, and cloacal swabs were randomly collected from 262 birds throughout nine counties in Maryland. Through PCR and ELISA analysis, disease prevalence and seroprevalence were determined in flocks, respectively, for the following: ND (0%, 23%); ILT (26%, 77%); MG (3%, 13%); and Salmonella (0%, not done). Vaccine status could not be accurately confirmed. Premise positives were further differentiated and identified by partial nucleotide sequencing. Screening of the 10 ILT premise positives showed that most were live attenuated vaccines: eight matched a tissue culture origin vaccine, one matched a chicken embryo origin (CEO) vaccine, and one was CEO related. The single MG-positive flock, also positive for the CEO-related sequence, was identified as the infectious S6 strain. The prevalence rates for these economically important poultry diseases ranged from none to relatively low, with the vast majority of sampled flocks presenting no clinical signs.

Avian influenza seroprevalence and biosecurity risk factors in Maryland backyard poultry: a cross-sectional study.

Major implications on a country's economy, food source, and public health. With recent concern over the highly pathogenic avian influenza outbreaks around the world, government agencies are carefully monitoring and inspecting live bird markets, commercial flocks, and migratory bird populations. However, there remains limited surveillance of non-commercial poultry. Therefore, a cross-sectional study was conducted in backyard poultry flocks using a convenience sampling method across three regions of Maryland from July 2011 to August 2011. The objective of this study was to develop a better understanding of the ecology and epidemiology of avian influenza by investigating the prevalence and seroprevalence in this potentially vulnerable population and by evaluating biosecurity risk factors associated with positive findings. Serum, tracheal, and cloacal swabs were randomly collected from 262 birds among 39 registered premises. Analysis indicated bird and flock seroprevalence as 4.2% (11/262) and 23.1% (9/39), respectively. Based on RT-qPCR analysis, none of the samples were found to be positive for AI RNA and evidence of AI hemagglutinin subtypes H5, H7, or H9 were not detected. Although no statistically significant biosecurity associations were identified (p≤0.05), AI seroprevalence was positively associated with exposure to waterfowl, pest control, and location. AI seropositive flocks exposed to waterfowl were 3.14 times as likely to be AI seropositive than those not exposed (p = 0.15). AI seropositive flocks that did not use pest control were 2.5 times as likely to be AI seropositive compared to those that did and AI seropositive flocks located in the Northern region of Maryland were 2.8 times as likely to be AI seropositive than those that were located elsewhere.

Evaluation of Maryland backyard flocks and biosecurity practices.

Domesticated poultry are susceptible to infectious and zoonotic diseases and can serve as a transmission source to other bird and human populations. In recent years, the number of noncommercial poultry has been on the rise in the United States. To evaluate potential risks of this growing population, a descriptive epidemiologic survey was conducted among Maryland backyard flocks. Owner and flock demographics were characterized as well as management practices such as husbandry, human-to-bird interaction, bird exposure risks, poultry health status, and biosecurity. Data from the 41 returned questionnaires indicated a median flock size of 38 birds (range, 3-901). Chickens accounted for 86.5% of the reported birds overall. Just over half of the owners (51.2%) kept chickens only, with the remaining backyard flocks consisting of chickens, other gallinaceous species, waterfowl, or a combination. Of flocks with multiple species, 70.0% of owners did not keep them separate. Almost two thirds of owners (61.0%) had kept poultry for < or = 5 yr, with 44.0% of all flocks on free range. Over the past 2 yr, predation was the highest cause of specific mortality (57.1%) followed by disease (30.2%), unknown (8.7%), and injury (4.0%), and over half of owners (56.1%) reported signs of disease in their flock within the last 6 mo. Biosecurity practices were highly variable among flocks. Data from this study identified gaps in the disease prevention and biosecurity practices of backyard flocks. These results can be useful in developing educational extension and outreach programs as well as policies, in efforts to further mitigate the spread of diseases.

The development and validation of a geographic information system database for the poultry industry on the Delmarva Peninsula.

A geographic information system (GIS) database of the poultry industry on the Delmarva Peninsula was developed through a cooperative agreement between the Delmarva Poultry Industry, Inc., and the Virginia-Maryland Regional College of Veterinary Medicine. The purpose of this database was to facilitate disease surveillance and assist in managing the response to outbreaks and other emergencies. Two methods of data collection were employed and are described in this paper. The first method was to visit each poultry farm and collect the latitude and longitude coordinates with a handheld global positioning system unit. The second method used property ownership information, aerial photographs, and a GIS to determine the latitude and longitude of each poultry farm. There was no significant difference between the two methods in the accuracy of the results, but there was a large difference in the amount of time and money necessary to obtain the data. These findings indicate that whereas there are many ways to obtain accurate data for a GIS database, other factors may influence which method is chosen. A subset of farms contained within the database was visited to assess the accuracy of the locations contained within the database. Of the 240 farms visited for validation, 212 showed evidence of a functioning or previously functioning poultry operation. The corresponding error rate was 11%. This demonstrates the need to assure that the database is kept up to date to ensure that attrition among poultry growers is recorded. Several potential factors that might contribute to sources of error are discussed.

A survey of biosecurity practices as risk factors affecting broiler performance on the Delmarva Peninsula.

A 10-page questionnaire on biosecurity practices was mailed to 187 growers on the Delmarva Peninsula in October 2000. The growers were selected by three broiler integrators on the basis of flock performance and were classified as cases (bottom 10% performers) and controls (top 10% performers). After two mailings, 71 growers (38%) responded to the survey, of which 47 (66.2%) represented good performers and 24 (33.8%) represented poor performers. Univariate and multivariate statistical analyses revealed that increased frequency of sanitizing water lines was statistically significantly associated with good flock performance (P = 0.0449). The presence of wild birds inside poultry houses during grow-out showed a slightly statistically significant association with poor flock performance (P = 0.0633).