Avian Diseases最新文献

About 35% of all broiler flocks in the United States receive an anticoccidial vaccine, but it is not possible to easily differentiate Eimeria vaccine strains from Eimeria field isolates. Being able to do that would allow using vaccines in a more targeted way. The objective of this study was to collect Eimeria maxima isolates from broiler flocks that received anticoccidial feed additives and flocks that had been vaccinated against coccidia and then test them with a multilocus sequencing typing (MLST) scheme developed for this study. Fecal samples were obtained from commercial broiler flocks in Alabama and Tennessee. Oocyst counts in samples tended to be lower in flocks receiving anticoccidial feed additives and higher in vaccinated flocks. Selected samples were screened for presence of E. maxima by quantitative PCR, and Eimeria spp. composition was investigated by next-generation amplicon sequencing (NGAS) in 37 E. maxima positive samples. Other detected Eimeria spp. besides E. maxima were Eimeria acervulina in 35 samples, Eimeria praecox in 23 samples, Eimeria mitis or Eimeria mivati in 17 samples, and Eimeria necatrix or Eimeria tenella in 10 samples. Six partial E. maxima genes (dnaJ domain containing protein, 70-kDa heat shock protein, prolyl endopeptidase, regulator of chromosome condensation domain containing protein, serine carboxypeptidase, and vacuolar proton-translocating ATPase subunit) of 46 samples were sequenced. The MLST scheme was able to differentiate two vaccines from each other. Three of 17 samples from vaccinated flocks differed from the vaccine used in the flock, while 16 of 29 samples from unvaccinated flocks differed from the vaccine. However, there was also a large number of low-quality, ambiguous chromatograms and negative PCRs for the selected genes. If and when more advanced, possibly next-generation sequencing-based methods will be developed, the genes should be considered as targets.

The advent of turkey herpesvirus (HVT) vector vaccine technology (vHVT) has made a huge improvement in the prevention and control of several poultry diseases. The objective of this study was to compare, under experimental conditions, the protection conferred by different vaccination programs based on an HVT double-insert (infectious bursal disease {IBD] and Newcastle disease [ND]) vector vaccine (vHVT-IBD-ND) and an HVT single-insert (vHVT-ND) vector vaccine followed by a vaccination with a live ND vaccine at Day 1 only or at Days 1 and 14. Commercial broilers were vaccinated by the recombinant ND virus vaccines subcutaneously at 1 day old, in the hatchery, and challenged at 30 days of age using the Moroccan ND virus velogenic viscerotropic JEL strain. The results showed that the tested vaccine induced 95% to 100% clinical protection against mortality and clinical signs. The humoral immune response to vaccination was detected from 3 wk of age using enzyme-linked immunosorbent assay and hemagglutination inhibition tests. ND challenge virus shedding was significantly reduced in the vaccinated birds as compared to controls. Significant reduction of the cloacal shedding suggests that the vHVT-IBD-ND vaccine stimulates actively the immunity against the tested ND challenge virus. No significant differences were found between the vaccination programs based on vHVT-IBD-ND or on vHVT-ND.

The ban of effective feed additives and therapeutics in the European Union and in other parts of the world led to a dramatic increase of histomonosis in turkeys. Despite the impact of the disease on the health and welfare of poultry, many questions remain open regarding the epidemiology of the pathogen. In this study, we retrospectively monitored a farm with recurring cases of histomonosis to identify possible routes of pathogen introduction and predisposing factors that may influence the disease development. We included 32 consecutive turkey flocks, which were fattened between 2007 and 2021 on the same farm under the same management and housing conditions. During this period, Histomonas meleagridis was detected in eight flocks of toms and four flocks of hens with a high variability in disease development. Outbreaks in toms led to significantly (P ≤ 0.05) higher mortality rates (5.3%-98.3%) than in hens (2.6%-6.1%). Most of the outbreaks (9/12) were diagnosed between June and September with a peak in August, suggesting a possible impact of higher temperatures either on the host or on the pathogen and pathogen-transmitting vectors. Further investigation is necessary to determine why hens might cope better with histomonosis than toms. Continuous flock and hygiene management is important to prevent an introduction of the causative pathogen and to control potential vectors.

Avian reovirus variants (ARVs) are important pathogens currently causing losses in poultry production. These variants escape protection elicited by conventional vaccines, i.e., S1133, 2408, and 1733 in chickens. Historically, ARVs have been classified according to their antigenic type and relative pathogenicity. Due to the virus variability, antigenic testing is difficult and laboratory specific, while pathotyping is costly and complex. Current molecular classification methods focus only on one gene, and genomic changes within this gene are not predictive of changes in antigenicity and pathogenicity. This review focuses on existing literature on reovirus antigenicity, pathogenicity, and molecular assessments as an aid to provide insights on how to predict antigenic and pathogenic phenotypes based on genomic information and future focus on development of new and comprehensive classification systems.

The Reoviridae family represents the largest family of double-stranded RNA viruses, and members have been isolated from a wide range of mammals, birds, reptiles, fishes, insects, and plants. Orthoreoviruses, one of the 15 recognized genera in the Reoviridae family, can infect humans and nearly all mammals and birds. Genomic characterization of reoviruses has not been adopted on a large scale because of the complexity of obtaining sequences for all 10 segments. In this study, we develop a time-efficient and practical method to enrich reovirus sequencing reads from isolates that allows for full-genome recovery using a single-primer amplification method coupled with next-generation sequencing. We refer to this protocol as reovirus-single-primer amplification (R-SPA). Our results demonstrate that most of the genes are covered with at least 500 reads per base space. Furthermore, R-SPA covers both the 5' and 3' ends of each reovirus genes. In summary, this study presents a universal and fast amplification protocol that yields sufficient double-stranded cDNA and facilitates and expedites the whole-genome sequencing of reoviruses.

Avian reovirus (ARV) is highly disseminated in commercial Brazilian poultry farms, causing arthritis/tenosynovitis, runting-stunting syndrome, and malabsorption syndrome in different meat- and egg-type birds (breeders, broilers, grillers, and layers). In Brazil, ARV infection was first described in broilers in the 1970s but was not considered an important poultry health problem for decades. A more concerning outcome of field infections has been observed in recent years, including condemnations at slaughterhouses because of the unsightly appearance of chicken body parts, mainly the legs. Analyses of the performance of poultry flocks have further evidenced economic losses to farms. Genetic and antigenic characterization of ARV field strains from Brazil demonstrated a high diversity of lineages circulating in the entire country, including four of the five main phylogenetic groups previously described (I, II, III, and V). It is still unclear if all of them are associated with different diseases affecting flocks' performance in Brazilian poultry. ARV infections have been controlled in Brazilian poultry farms by immunization of breeders and young chicks with classical commercial live vaccine strains (S1133, 1733, 2408, and 2177) used elsewhere in the Western Hemisphere. However, genetic and antigenic variations of the field isolates have prevented adequate protection against associated diseases, so killed autogenous vaccines are being produced from isolates obtained on specific farms. In conclusion, ARV field variants are continuously challenging poultry farming in Brazil. Epidemiological surveillance combined with molecular biological analyses from the field samples, as well as the development of vaccine strains directed toward the ARV circulating variants, are necessary to control this economically important poultry pathogen.

Avian reovirus (ARV) has been determined to be the etiologic agent of viral arthritis/tenosynovitis. In Israel, meat-type chickens, including broilers and breeders, are the most affected. Severe disease symptoms can appear in broiler flocks at a very young age because of early exposure and vertical transmission, causing significant welfare problems. Jewish laws define birds with inflamed, damaged, or torn gastrocnemius and digital flexor tendons as religious condemnations (non-kosher), resulting in severe economic losses for the poultry industry. Vaccination of breeders is a strategy to control the disease by reducing vertical transmission and providing maternal-derived antibodies to the progeny. This review describes Israel's ARV variants and the various vaccines developed over the years. Identification of co-circulating variants triggered the development of multivalent autogenous inactivated vaccines. However, the genotype-matched vaccines failed to provide protection, resulting in an increased prevalence of Cluster II ARV (classified as genotyping cluster 5 in the ARV common world classification). Since 2014, ARV Cluster II has been dominant in Israel. In 2015, the dominant variant s7585 tropism changed the virus pathogenesis and affected broilers with severe clinical signs between 12 and 15 days of age. A new vaccine approach developed in Israel used controlled exposure of the breeding flock to virulent ARV at the age when they are resistant to infection. This approach significantly reduced clinical field cases and reovirus isolations of breeding and broiler flocks between 2020 and 2022.

Escherichia coli (E. coli) is a commensal bacteria found in the gastrointestinal tract of poultry; however, some strains are pathogenic and can cause a wide range of diseases. In addition, some strains of pathogenic E. coli can survive in the litter between flocks, making litter management critical for reducing E. coli-associated infections. Biochar (BC) is a porous, carbonaceous material that may be a beneficial litter amendment to reduce moisture and microbial loads. The objectives of this study were to evaluate the effects of pine BC, miscanthus BC, and Poultry Litter Treatment (PLT) on E. coli, total aerobic bacteria populations, and bacterial communities when added to used broiler litter. Pine and miscanthus BC were mixed into poultry litter at inclusion rates of 5%, 10%, 20%, 25%, and 30% w/w. PLT was surface applied at a rate of 0.73 kg/m². Baseline E. coli and aerobics were measured after a 48-hr litter incubation period and just prior to adding litter treatments. Escherichia coli and aerobics were enumerated 2 and 7 days after adding treatments. Overall, pine BC at 30% had the lowest E. coli and aerobic counts (5.98 and 6.44 log ₁₀ colony-forming units [CFU]/g, respectively); however, they were not significantly different from the control (P ≤ 0.05). At day 2, 30% pine BC inclusion rate treatment resulted in a significant reduction in E. coli and aerobic bacteria counts compared to the control. Miscanthus BC application did not result in significant reductions in E. coli or aerobic bacteria at days 2 or 7. PLT had the highest E. coli (7.07 log ₁₀ CFU/g) and aerobic counts (7.21 log ₁₀ CFU/g) overall. Bacterial community analysis revealed that the alpha and beta diversity between pine BC- and PLT-treated litter were significantly different. However, neither BC type significantly impacted bacterial diversity when compared to the control. Differences in E. coli and aerobic counts between BC types may be attributed to variations in feedstock physiochemical properties.

Viral arthritis/tenosynovitis, a disease caused by avian reovirus (ARV), leads to great economic losses for the chicken industry worldwide. Since autumn 2011, the poultry industries in the United States and Canada have sustained significant economic losses in the progeny of broiler breeders vaccinated with classic strains of ARV. Vaccination failure has been caused by field challenge with variant ARVs. The variant field ARVs are refractory to the immunity stimulated by classic vaccines and have become the prevalent challenge in the field. Because all genotypes described in the literature have been reported to be circulating in Canada, genotyping of circulating ARVs is paramount for the selection of appropriate isolates, representative of the field challenge, for use in autogenous vaccines. In this review, the history of ARVs and the current situation in Canada are discussed. On the basis of recent field data, inadequate measures commonly used in the field are discussed, and successful vaccination strategies are recommended.