Mitigation of False Layer Syndrome Through Maternal Antibodies Against Infectious Bronchitis Virus.

The relationship between passive immunity and the development of false layer syndrome (FLS) and its associated lesions was investigated in this study by comparing the long-term reproductive effects of an infectious bronchitis virus (IBV) DMV/1639 wild-type strain and the GA08 vaccine in birds with and without maternal antibodies. There was a clear protective effect provided by maternal antibodies against both the early vaccination and challenge. It was also observed that vaccination at an early age, in the absence of maternal antibodies, can induce reproductive issues, such as reduced egg production and FLS-associated lesions (e.g., cystic oviduct and egg yolk coelomitis). This might indicate that maternal antibodies and the timing of IBV infection are more important in the generation of FLS than the IBV strain type.

Mitigación del síndrome de la falsa ponedora mediante anticuerpos maternos contra el virus de la bronquitis infecciosa. En este estudio se investigó la relación entre la inmunidad pasiva y el desarrollo del síndrome de la falsa ponedora (FLS) y sus lesiones asociadas comparando los efectos reproductivos a largo plazo de una cepa de tipo silvestre DMV/1639 del virus de la bronquitis infecciosa (IBV) y la cepa vacunal GA08, en aves con y sin anticuerpos maternos. Hubo un claro efecto protector proporcionado por los anticuerpos maternos tanto contra la vacunación temprana como contra el desafío. También se observó que la vacunación a una edad temprana, en ausencia de anticuerpos maternos, puede inducir problemas reproductivos, como una reducción de la producción de huevo y lesiones asociadas al síndrome de la falsa ponedora (p. ej., oviducto quístico y celomitis de yema de huevo). Esto podría indicar que los anticuerpos maternos y el momento de la infección por el virus de la bronquitis infecciosa son más importantes en la generación del síndrome de la falsa ponedora que el tipo de cepa del virus de la bronquitis infecciosa.

Differential Impact of Massachusetts, Canadian 4/91, and California (Cal) 1737 Genotypes of Infectious Bronchitis Virus Infection on Lymphoid Organs of Chickens.

Infectious bronchitis virus (IBV) induces severe economic losses in chicken farms due to the emergence of new variants leading to vaccine breaks. The studied IBV strains belong to Massachusetts (Mass), Canadian 4/91, and California (Cal) 1737 genotypes that are prevalent globally. This study was designed to compare the impact of these three IBV genotypes on primary and secondary lymphoid organs. For this purpose, one-week-old specific pathogen-free chickens were inoculated with Mass, Canadian 4/91, or Cal 1737 IBV variants, keeping a mock-infected control. We examined the IBV replication in primary and secondary lymphoid organs. The molecular, histopathological, and immunohistochemical examinations revealed significant differences in lesion scores and viral distribution in these immune organs. In addition, we observed B-cell depletion in the bursa of Fabricius and the spleen with a significant elevation of T cells in these organs. Further studies are required to determine the functional consequences of IBV replication in lymphoid organs.

Genetic architecture of body weight, carcass, and internal organs traits of Ghanaian local chickens.

Information on the genetic architecture of the production traits of indigenous African chicken is limited. We performed a genome-wide association study using imputed Affymetrix Axiom® 600K SNP-chip genotypes on 1,113 chickens from three agroecological zones of Ghana. After quality control, a total of 382,240 SNPs remained. Variance components and heritabilities for some growth, carcass and internal organ traits were estimated. The genetic and phenotypic correlations among these traits were also estimated. The estimated heritabilities of body weight at week 22 (BW22), average daily gain (ADG), dressed weight, breast weight, thigh weight, wing weight, drumstick weight, and neck weight were high and ranged from 0.50 to 0.69. Estimates of heritabilities for head weight, shank weight, and gizzard weight were moderate (0.31-0.35) while those of liver weight, back weight, dressing percentage, and heart weight were low (0.13-0.21). The estimated heritabilities of dressed weight, breast weight, wing weight, drumstick weight, neck weight, shank weight, and gizzard weight, corrected for BW22, were moderate (0.29-0.38), while the remaining traits had low heritability estimates (0.13-0.21). A total of 58 1-Mb SNP windows on chromosomes 1, 2, 4, 5, 6, 7, 8, 9, 13, 18, and 33 each explained more than 1% of the genetic variance for at least one of these traits. These genomic regions contained many genes previously reported to have effects on growth, carcass, and internal organ traits of chickens, including EMX2, CALCUL1, ACVR1B, CACNB1, RB1, MLNR, FOXO1, NCARPG, LCORL, LAP3, LDB2, KPNA3, and CAB39L. The moderate to high heritability estimates and high positive genetic correlations suggest that BW22, ADG, dressed weight, breast weight, thigh weight, wing weight, drumstick weight, and neck weight could be improved through selective breeding.

Comparative pathogenicity of CA1737/04 and Mass infectious bronchitis virus genotypes in laying chickens.

Infectious bronchitis virus (IBV) is a respiratory virus causing atropism in multiple body systems of chickens. Recently, the California 1737/04 (CA1737/04) IBV strain was identified as one of the circulating IBV variants among poultry operations in North America. Here, the pathogenicity and tissue tropism of CA1737/04 IBV strain in specific-pathogen-free (SPF) hens were characterized in comparison to Massachusetts (Mass) IBV. In 30 weeks-old SPF hens, Mass or CA1737/04 IBV infections were carried out, while the third group was maintained as a control group. Following infection, we evaluated clinical signs, egg production, viral shedding, serology, necropsy examination, and histopathology during a period of 19 days. Also, certain tissue affinity parameters were investigated, which involved the localization of viral antigens and the detection of viral RNA copies in designated tissues. Our findings indicate that infection with CA1737/04 or Mass IBV strain could induce significant clinical signs, reduced egg production, and anti-IBV antibodies locally in oviduct wash and systemically in serum. Both IBV strains showed detectable levels of viral RNA copies and induced pathology in respiratory, renal, enteric, and reproductive tissues. However, the CA1737/04 IBV strain had higher pathogenicity, higher tissue tropism, and higher replication in the kidney, large intestine, and different segments of the oviduct compared to the Mass IBV strain. Both IBV strains shed viral genome from the cloacal route, however, the Mass IBV infected hens shed higher IBV genome loads via the oropharyngeal route compared to CA1737/04 IBV-infected hens. Overall, the current findings could contribute to a better understanding of CA1737/04 IBV pathogenicity in laying hens.

Genomic Regions and Candidate Genes Affecting Response to Heat Stress with Newcastle Virus Infection in Commercial Layer Chicks Using Chicken 600K Single Nucleotide Polymorphism Array.

Heat stress results in significant economic losses to the poultry industry. Genetics plays an important role in chickens adapting to the warm environment. Physiological parameters such as hematochemical parameters change in response to heat stress in chickens. To explore the genetics of heat stress resilience in chickens, a genome-wide association study (GWAS) was conducted using Hy-Line Brown layer chicks subjected to either high ambient temperature or combined high temperature and Newcastle disease virus infection. Hematochemical parameters were measured during three treatment phases: acute heat stress, chronic heat stress, and chronic heat stress combined with NDV infection. Significant changes in blood parameters were recorded for 11 parameters (sodium (Na+, potassium (K+), ionized calcium (iCa2+), glucose (Glu), pH, carbon dioxide partial pressure (PCO2), oxygen partial pressure (PO2), total carbon dioxide (TCO2), bicarbonate (HCO3), base excess (BE), and oxygen saturation (sO2)) across the three treatments. The GWAS revealed 39 significant SNPs (p < 0.05) for seven parameters, located on Gallus gallus chromosomes (GGA) 1, 3, 4, 6, 11, and 12. The significant genomic regions were further investigated to examine if the genes within the regions were associated with the corresponding traits under heat stress. A candidate gene list including genes in the identified genomic regions that were also differentially expressed in chicken tissues under heat stress was generated. Understanding the correlation between genetic variants and resilience to heat stress is an important step towards improving heat tolerance in poultry.

Molecular characterization of Newcastle disease virus obtained from Mawenzi live bird market in Morogoro, Tanzania in 2020-2021.

Newcastle disease (ND) is among the most important poultry diseases worldwide. It is the major threat to poultry production in Africa and causes major economic losses for both local and commercial chickens. To date, half of ND class II genotypes have been reported in Africa (I, IV, V, VI, VII, XI, XIII, XIV, XVII, XVIII, and XXI). The information on the circulating NDV genotypes is still scarce despite the endemic nature of ND in most countries on the African continent.A total of 659 oro-cloacal swabs were collected from local chickens in Mawenzi live bird market located in Morogoro, Tanzania, between June 2020 and May 2021. Newcastle disease virus was detected by using reverse transcription real-time polymerase chain reaction (RT-qPCR) and conventional PCR followed by sequencing of PCR products. The prevalence of NDV in the surveilled live bird markets was 23.5%. Sequencing and phylogenetic analysis revealed the presence of sub-genotype VII.2. The detected sub-genotype VII.2 has phylogenetic links to Zambian NDV strains implying a Southeast dissemination of the virus, considering that it was first detected in Mozambique. This study underscores the need of active NDV surveillance to determine the distribution of this NDV genotype in the country and monitor its spread and contribution to the emergence of new ND viruses.

Infectious Bronchitis Virus California Variant CA1737 Isolated from a Commercial Layer Flock with Cystic Oviducts and Poor External Egg Quality.

False layer syndrome is a condition in which the reproductive tract of chicks is infected with infectious bronchitis virus (IBV) strains that cause permanent damage to the oviduct. These chickens subsequently develop cystic oviducts and do not lay eggs, and affected flocks fail to reach expected egg production peaks. The California Animal Health and Food Safety laboratory, Turlock Branch, received four separate case submissions from a 25-to-28-wk-old commercial ISA Brown layer flock. Birds were submitted for diagnostic evaluation due to suboptimal egg production and vent pecking. Submissions totaled 31 birds and consisted of live layers, recent mortality, and a flat of eggs. No clinical signs were observed in the submitted live birds. The most common gross findings included cystic left oviducts, signs of vent pecking, ovarian regression, and yolk coelomitis. The eggs were abnormally shaped with irregular, white, gritty deposits on the surface of the shell. Microscopically, there was atrophy of the oviducts, glandular hypoplasia, and lymphocytic salpingitis. In addition, lymphoplasmacytic tracheitis was observed, and renal tubules were dilated with multifocal areas of mineralization. IBV was identified by reverse transcription quantitative PCR from cecal tonsil tissue pools and tracheal swab pools. Sequencing of the S1 hypervariable region of IBV and whole-genome IBV sequencing were 97% homologous to the California variant CA1737/04. Definitive proof of the CA1737 strain's causing reproductive abnormalities will require challenge studies with fulfillment of Koch's postulates and evaluation of confounding and risk factors.

Reporte de caso- Virus de la bronquitis infecciosa Variante de California CA1737 aislada de una parvada comercial de ponedoras con oviductos quísticos y mala calidad externa del huevo. El síndrome de la falsa capa es una condición en la cual el tracto reproductivo de las gallinas está infectado con cepas del virus de la bronquitis infecciosa (IBV) que causan daño permanente al oviducto. Posteriormente, estas gallinas desarrollan oviductos quísticos y bajas en la postura de huevo, las parvadas afectadas no alcanzan los picos de producción de huevos esperados. El laboratorio de Salud Animal y Seguridad Alimentaria de California, con sede en Turlock, recibió cuatro casos separados de una parvada comercial de ponedoras ISA Brown de 25 a 28 semanas de edad. Las aves se enviaron para evaluación diagnóstica debido a una producción de huevos subóptima y por presencia de picoteo en las cloacas. Se recibieron un total de 31 aves y consistieron en aves de postura vivas, mortalidad reciente y además una charola de huevos. No se observaron signos clínicos en las aves vivas enviadas. Los hallazgos macroscópicos más comunes incluyeron oviductos izquierdos quísticos, signos de picoteo en las cloacas, regresión ovárica y celomitis de la yema. Los huevos tenían una forma anormal con depósitos irregulares, blancos y arenosos en la superficie de la cáscara. Microscópicamente, había atrofia de los oviductos, hipoplasia glandular y salpingitis linfocítica. Además, se observó traqueítis linfoplasmocítica y túbulos renales dilatados con áreas multifocales de mineralización. El virus de la bronquitis infecciosa se identificó mediante PCR cuantitativa de transcripción inversa a partir de grupos de tejidos de tonsilas cecales y muestras agrupadas de hisopos traqueales. La secuenciación de la región hipervariable S1 de IBV y la secuenciación de IBV del genoma completo fueron homólogas en un 97 % a la variante de California CA1737/04. La prueba definitiva de las anomalías reproductivas causantes de la cepa CA1737 requerirá estudios de desafío con el cumplimiento de los postulados de Koch y la evaluación de los factores de riesgo y de confusión.

Genetic Analyses of Response of Local Ghanaian Tanzanian Chicken Ecotypes to a Natural Challenge with Velogenic Newcastle Disease Virus.

Newcastle disease is a devastating poultry disease that often causes significant economic losses in poultry in the developing countries of Africa, Asia, as well as South and Central America. Velogenic Newcastle disease virus (NDV) outbreaks are associated with high mortalities, which can threaten household livelihoods, especially in the rural areas, and lead to loss of high-quality proteins in the form of meat and eggs, as well as household purchasing power. In this study, we exposed unvaccinated Ghanaian and Tanzanian chickens of six local ecotypes to velogenic NDV strains, measured NDV response traits, sequenced their DNA on a genotyping-by-sequencing platform, and performed variance component analyses. The collected phenotypes included: growth rates (pre- and post-exposure); lesion scores (gross lesion severity) in the trachea, proventriculus, intestine, and cecal tonsils; natural antibody levels; anti-NDV antibody levels at 7 days post exposure (dpe); tear and cloacal viral load at 2, 4, and 6 dpe; and survival time. Heritability estimates were low to moderate, ranging from 0.11 for average lesion scores to 0.36 for pre-exposure growth rate. Heritability estimates for survival time were 0.23 and 0.27 for the Tanzanian and Ghanaian ecotypes, respectively. Similar heritability estimates were observed when data were analyzed either separately or combined for the two countries. Survival time was genetically negatively correlated with lesion scores and with viral load. Results suggested that response to mesogenic or velogenic NDV of these local chicken ecotypes could be improved by selective breeding. Chickens that are more resilient to velogenic NDV can improve household livelihoods in developing countries.

Infectious Bronchitis Virus: A Comprehensive Multilocus Genomic Analysis to Compare DMV/1639 and QX Strains.

Infectious bronchitis virus (IBV) is a highly variable RNA virus that affects chickens worldwide. Due to its inherited tendency to suffer point mutations and recombination events during viral replication, emergent IBV strains have been linked to nephropathogenic and reproductive disease that are more severe than typical respiratory disease, leading, in some cases, to mortality, severe production losses, and/or unsuccessful vaccination. QX and DMV/1639 strains are examples of the above-mentioned IBV evolutionary pathway and clinical outcome. In this study, our purpose was to systematically compare whole genomes of QX and DMV strains looking at each IBV gene individually. Phylogenetic analyses and amino acid site searches were performed in datasets obtained from GenBank accounting for all IBV genes and using our own relevant sequences as a basis. The QX dataset studied is more genetically diverse than the DMV dataset, partially due to the greater epidemiological diversity within the five QX strains used as a basis compared to the four DMV strains from our study. Historically, QX strains have emerged and spread earlier than DMV strains in Europe and Asia. Consequently, there are more QX sequences deposited in GenBank than DMV strains, assisting in the identification of a larger pool of QX strains. It is likely that a similar evolutionary pattern will be observed among DMV strains as they develop and spread in North America.

Outreach Efforts to Prevent Newcastle Disease Outbreaks in Southern California.

In May 2018, an outbreak of virulent Newcastle disease (vND) affected backyard and commercial premises in Southern California. The re-occurrence of these outbreaks since the 1970s suggests that some poultry communities may not have reliable and stable resources available regarding biosecurity and disease prevention. Therefore, staff at the University of California, Davis (UCD) School of Veterinary Medicine (SVM), and the California Department of Food and Agriculture (CDFA) began organizing educational events and learning more about the gamefowl breeder community through a needs assessment exercise, during which local feedstores and neighborhoods were also visited. Focus groups were organized with breeders in various cities within the regional quarantine area, established by the CDFA during the vND outbreak. The focus groups were aimed at creating open communication networks with gamefowl breeders in the affected area, as well as to learn about their current sources of information, learning preferences, and current management practices. With the input from gamefowl breeders, as well as funding and input from the CDFA and the United States Department of Agriculture (USDA), a quality assurance program called the "Gamefowl Wellness Program" was established. Educational content was created and published through the UCD Gamefowl Wellness Program poultry health website. Additionally, with the help of the CDFA, the USDA, and pharmaceutical companies, Newcastle disease vaccines and training for their application were provided to feedstores with gamefowl breeder clientele. Nurturing trust with these poultry communities allowed us to receive the information needed to develop effective outreach strategies that could better serve them. Responding to community concerns might be a way to garner the trust necessary to prevent or at least promptly detect foreign animal disease outbreaks.

Hyperimmunized Chickens Produce Neutralizing Antibodies against SARS-CoV-2.

The novel severe acute respiratory syndrome (SARS) coronavirus, SARS-CoV-2, is responsible for the global COVID-19 pandemic. Effective interventions are urgently needed to mitigate the effects of COVID-19 and likely require multiple strategies. Egg-extracted antibody therapies are a low-cost and scalable strategy to protect at-risk individuals from SARS-CoV-2 infection. Commercial laying hens were hyperimmunized against the SARS-CoV-2 S1 protein using three different S1 recombinant proteins and three different doses. Sera and egg yolk were collected at three and six weeks after the second immunization for enzyme-linked immunosorbent assay and plaque-reduction neutralization assay to determine antigen-specific antibody titers and neutralizing antibody titers, respectively. In this study we demonstrate that hens hyperimmunized against the SARS-CoV-2 recombinant S1 and receptor binding domain (RBD) proteins produced neutralizing antibodies against SARS-CoV-2. We further demonstrate that antibody production was dependent on the dose and type of antigen administered. Our data suggests that antibodies purified from the egg yolk of hyperimmunized hens can be used as immunoprophylaxis in humans at risk of exposure to SARS-CoV-2.

Porphyrin Accumulation and Biliary Lithiasis Causing Diffusely Black Livers in Broiler Chickens.

Two 7-wk-old broiler chickens presented with uniformly black livers upon postslaughter examination, while all other organs as well as their carcasses were grossly normal. No clinical signs were reported by the field veterinarian prior to slaughter. Other broiler chickens within the same flock were unaffected. Microscopically, the liver exhibited variably sized, globoid concrements that were dark brown to green-brown and birefringent under polarized light. Ultrastructurally, concrements consisted of radially arranged electron-dense crystal spicules. Concrements were located in hepatocytes, within ecstatic bile canaliculi, or surrounded by small clusters of macrophages. Liquid chromatography assay determined the presence of protoporphyrin IX in the affected liver.Two 7-wk-old broiler chickens presented with uniformly black livers upon postslaughter examination, while all other organs as well as their carcasses were grossly normal. No clinical signs were reported by the field veterinarian prior to slaughter. Other broiler chickens within the same flock were unaffected. Microscopically, the liver exhibited variably sized, globoid concrements that were dark brown to green-brown and birefringent under polarized light. Ultrastructurally, concrements consisted of radially arranged electron-dense crystal spicules. Concrements were located in hepatocytes, within ecstatic bile canaliculi, or surrounded by small clusters of macrophages. Liquid chromatography assay determined the presence of protoporphyrin IX in the affected liver.

Testicular Atrophy and Epididymitis-Orchitis Associated with Infectious Bronchitis Virus in Broiler Breeder Roosters.

Infectious bronchitis is a respiratory disease of chickens caused by a gammacoronavirus named infectious bronchitis virus (IBV). In addition to affecting the respiratory tract, IBV may also induce urogenital infections, leading to nephropathogenic disease, false layer syndrome in laying hens, and epididymal lithiasis and epididymitis in males. Here, we report a case of decreased reproductive efficiency due to male infertility in 33- to 38-wk-old broiler breeders. At necropsy, the males presented with urates deposited on the skin around the vent and testicular asymmetry due to marked unilateral atrophy. Histopathology revealed lymphocytic epididymitis, epididymal lithiasis, and orchitis. IBV antigen was detected within collecting and efferent ducts of epididymides by immunohistochemistry. IBV strain DMV/1639 was detected by reverse transcription-quantitative PCR in pools of testes, oviducts, tracheas, cecal tonsils, and kidneys from a 37-wk-old affected flock. This report shows evidence of the role of IBV in male chicken infertility and highlights the importance of performing molecular surveillance of IBV to monitor vaccine strains and to detect emerging variants that can potentially hinder production.

Reporte de caso- Atrofia testicular y epididimitis-orquitis asociadas con el virus de la bronquitis infecciosa en gallos reproductores pesados. La bronquitis infecciosa es una enfermedad respiratoria del pollo causada por un gammacoronavirus llamado virus de la bronquitis infecciosa (con las siglas en inglés IBV). Además de afectar el tracto respiratorio, el IBV también puede inducir infecciones urogenitales, lo que conduce a enfermedad nefropatogénica, síndrome de la falsa ponedora en gallinas de postura y litiasis epididimaria y epididimitis en machos. En este reporte se describe un caso de disminución de la eficiencia reproductiva debido a la infertilidad de machos en reproductores pesados de 33 a 38 semanas de edad. En la necropsia, los machos presentaron depósitos de uratos sobre la piel alrededor de la cloaca y asimetría testicular por atrofia unilateral marcada. La histopatología reveló epididimitis linfocítica, litiasis epididimaria y orquitis. Antígenos del virus de la bronquitis infecciosa se detectaron dentro de los conductos colectores y eferentes de los epidídimos mediante inmunohistoquímica. La cepa del virus de la bronquitis DMV/1639 se detectó mediante transcripción reversa y PCR cuantitativa en muestras agrupadas de testículos, oviductos, tráqueas, tonsilas cecales y riñones de una parvada afectada de 37 semanas de edad. Este reporte muestra evidencia del papel del virus de la bronquitis infecciosa en la infertilidad de los pollos machos y destaca la importancia de realizar una vigilancia molecular de este virus para monitorear las cepas vacunales y detectar variantes emergentes que potencialmente pueden dificultar la producción.

Molecular Characterization of Variant Avian Reoviruses and Their Relationship with Antigenicity and Pathogenicity.

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.

Estudio recapitulativo- Caracterización molecular de reovirus aviares variantes y su relación con antigenicidad y patogenicidad. Las variantes del reovirus aviar (ARV) son patógenos importantes que actualmente causan pérdidas en la producción avícola. Estas variantes escapan a la protección provocada por las vacunas convencionales, que incluyen a las cepas S1133, 2408 y 1733 en pollos. Históricamente, los reovirus aviares se han clasificado según su tipo antigénico y patogenicidad relativa. Debido a la variabilidad del virus, las pruebas antigénicas son difíciles y específicas de laboratorio, mientras que la patotipificación es costosa y compleja. Los métodos de clasificación molecular actuales se enfocan solo en un gene, y los cambios genómicos dentro de este gene no predicen cambios en la antigenicidad y patogenicidad. Esta revisión se centra en la literatura existente sobre la antigenicidad, la patogenicidad y las evaluaciones moleculares de los reovirus como una ayuda para proporcionar información sobre cómo predecir los fenotipos antigénicos y patógenos en función de la información genómica y el enfoque futuro en el desarrollo de sistemas de clasificación nuevos y completos.

Molecular Biology and Pathological Process of an Infectious Bronchitis Virus with Enteric Tropism in Commercial Broilers.

Infectious bronchitis virus (IBV) induces respiratory and urogenital disease in chickens. Although IBV replicates in the gastrointestinal tract, enteric lesions are uncommon. We have reported a case of runting-stunting syndrome in commercial broilers from which an IBV variant was isolated from the intestines. The isolate, CalEnt, demonstrated an enteric tissue tropism in chicken embryos and SPF chickens experimentally. Here, we determined the full genome of CalEnt and compared it to other IBV strains, in addition to comparing the pathobiology of CalEnt and M41 in commercial broilers. Despite the high whole-genome identity to other IBV strains, CalEnt is rather unique in its nucleotide composition. The S gene phylogenetic analyses showed great similarity between CalEnt and Cal 99. Clinically, vent staining was slightly more frequent in CalEnt-infected birds than those challenged with M41. Furthermore, IBV IHC detection was more evident and the viral shedding in feces was overall higher with the CalEnt challenge compared with M41. Despite underlying intestinal lesions caused by coccidiosis and salmonellosis vaccination, microscopic lesions in CalEnt-infected chickens were more severe than in M41-infected chickens or controls, supporting the enteric tropism of CalEnt. Further studies in SPF chickens are needed to determine the pathogenesis of the virus, its molecular mechanisms for the enteric tropism, and its influence in intestinal health.

Infectious Bronchitis Virus Prevalence, Characterization, and Strain Identification in California Backyard Chickens.

Infectious bronchitis virus (IBV) causes significant losses in the poultry industry throughout the world. Here we characterize the lesions of infectious bronchitis (IB) and IBV prevalence and identify the circulating strains in small flocks in California. Backyard chickens (BYCs) submitted to the Davis (Northern California; NorCal) and San Bernardino (Southern California; SoCal) branches of the California Animal Health and Food Safety Laboratory System from January through March 2019 were included in the study. Trachea, kidney, and cecal tonsils were collected for real-time reverse transcriptase (qRT)-PCR, histology, immunohistochemistry (IHC), and sequence analysis. A total of 50 chickens out of 169 submissions tested positive for IBV by qRT-PCR. Of these, 16% (20/123) were from NorCal and 65% (30/46) from SoCal laboratory. The cecal tonsil was the most frequently positive tissue by qRT-PCR and IHC. Lymphoplasmacytic tracheitis was the most frequent histopathologic finding in 24 of 39 birds, while the kidney showed interstitial nephritis, tubular necrosis, tubular dilation, and/or gout in 14 of 43 chickens. Infectious bronchitis virus played a primary role or a synergistic effect in the mortality of chickens that succumbed to other infectious diseases. The sequences of IBV detected in 22 birds were analyzed, and 14 strains were most similar to CA1737. One strain each matched Conn46, Cal99, and ArkDPI, and the remaining five did not have a substantial match to any available reference strains. The findings in this study indicate that small flocks can be reservoirs of IBV and might facilitate evolution of new variants as well as reversion of attenuated strains to virulence.

Artículo regular­Prevalencia, caracterización e identificación de cepas del virus de la bronquitis infecciosa en pollos de traspatio de California. El virus de la bronquitis infecciosa (con las siglas en inglés IBV) causa pérdidas significativas en la industria avícola en todo el mundo. En este estudio se caracterizaron las lesiones de la bronquitis infecciosa (IB), la prevalencia del virus y se identificó a las cepas circulantes en pequeñas parvadas en California. Se incluyeron en el estudio pollos de traspatio (BYC) remitidos a las sedes en Davis (norte de California; NorCal) y San Bernardino (sur de California; SoCal) del Sistema de Laboratorios de Salud Animal y Seguridad Alimentaria de California de enero a marzo del 2019. Se recolectaron tráquea, riñón y tonsilas cecales para análisis cuantitativo en tiempo real (qRT)-PCR, histología, inmunohistoquímica (IHC) y análisis de secuencias. Un total de 50 pollos de 169 casos dieron positivo para la presencia del virus de bronquitis infecciosa por qRT-PCR. De estos, el 16% (20/123) provenían del norte de California y el 65% (30/46) del laboratorio del sur de California. Las tonsilas cecales fueron las muestras de tejidos positivos con mayor frecuencia por qRT-PCR e IHC. La traqueítis linfoplasmocítica fue el hallazgo histopatológico más frecuente en 24 de 39 aves, mientras que el riñón mostró nefritis intersticial, necrosis tubular, dilatación tubular y/o gota en 14 de 43 pollos. El virus de la bronquitis infecciosa jugó un papel principal o un efecto sinérgico en la mortalidad de los pollos que murieron por otras enfermedades infecciosas. Se analizaron las secuencias del virus de bronquitis detectadas en 22 aves y 14 cepas fueron muy similares al virus de bronquitis infecciosa CA1737. Tres virus coincidieron con Conn46, Cal99 y ArkDPI, y las cinco restantes no tenían una coincidencia sustancial con ninguna cepa de referencia disponible. Los hallazgos de este estudio indican que las pequeñas parvadas pueden ser reservorios del virus de la bronquitis infecciosa y podrían facilitar la evolución de nuevas variantes, así como la reversión de cepas atenuadas a formas virulentas.

Comparison of cellular immune responses to avian influenza virus in two genetically distinct, highly inbred chicken lines.

Low pathogenicity avian influenza causes mild disease involving the respiratory, gastrointestinal, and reproductive systems of wild and domestic birds. Avian influenza research often emphasizes the effect of the virus genetics on disease, but the influence of host genetics on resistance to infection is not well understood. The genetic determinants of enhanced resistance to influenza can be explored by using genetically distinct, highly inbred chicken lines that differ in susceptibility to influenza. In this study, we compared the mucosal cellular immune responses between the relatively resistant Fayoumi M43 chicken line and the relatively susceptible Leghorn GB2 chicken line after challenging with low pathogenicity avian influenza virus (LPAIV) H6N2. The birds were inoculated at 21 days of age with 107 50 % egg infective dose (EID50) LPAIV H6N2 via nasal and tracheal routes in two separate experiments. Clinical signs were recorded, tracheal swabs were collected to measure viral titer, and tracheas and lungs were harvested for flow cytometric analysis of macrophage, B cell, and T cell populations at 4 days post-infection (dpi) (Experiments 1 and 2) and 6 dpi (Experiment 2). Blood and tears were also collected at 7 and 14 dpi (Experiment 1) to measure antibody levels. Compared to both the non-challenged Fayoumis and the relatively susceptible Leghorn chickens, relatively resistant Fayoumi chickens challenged with LPAIV demonstrated enhanced MHC class I expression on antigen-presenting cells and increased macrophage, B cell, and T cell frequencies in the trachea, which were associated with reduced tracheal viral titers at 4 dpi. In contrast, MHC class I expression and immune cell frequencies in the trachea were not different between challenged Leghorns and non-challenged Leghorns. Furthermore, Leghorns shed higher virus titers in their trachea compared to Fayoumis. Challenged Fayoumis and Leghorns both produced AIV-specific IgY detected in the serum and tears, but AIV-specific IgA was not detected in the tears. In this study, we provide new insight into immune mechanisms of enhanced resistance to avian influenza in chickens, which may lead to improved vaccination strategies and breeding programs.

Distinct transcriptomic response to Newcastle disease virus infection during heat stress in chicken tracheal epithelial tissue.

Newcastle disease (ND) has a great impact on poultry health and welfare with its most virulent (velogenic) strain. In addition, issues exacerbated by the increase in global temperatures necessitates a greater understanding of the host immune response when facing a combination of biotic and abiotic stress factors in poultry production. Previous investigations have revealed that the host immune response is tissue-specific. The goal of this study was to identify genes and/or signaling pathways associated with immune response to NDV (Newcastle disease virus) in the trachea, an essential organ where NDV replicate after the infection, by profiling the tissue specific transcriptome response in two genetically distinct inbred chicken lines when exposed to both abiotic and biotic stressors. Fayoumis appear to be able to respond more effectively (lower viral titer, higher antibody levels, immune gene up-regulation) and earlier than Leghorns. Our results suggest NDV infection in Fayoumis appears to elicit proinflammatory processes, and pathways such as the inhibition of cell viability, cell proliferation of lymphocytes, and transactivation of RNA, more rapidly than in Leghorns. These differences in immune response converge at later timepoints which may indicate that Leghorns eventually regulate its immune response to infection. The profiling of the gene expression response in the trachea adds to our understanding of the chicken host response to NDV infection and heat stress on a whole genome level and provides potential candidate genes and signaling pathways for further investigation into the characterization of the time-specific and pathway specific responses in Fayoumis and Leghorns.

Immune Responses and B Complex Associated Resistance to Infectious Bronchitis Virus in Chickens.

Infectious bronchitis (IB) continues to be a global threat to poultry producers. The chicken major histocompatibility complex (MHC) or chicken B complex is compact, restricted to a single chromosome, and approximately 20-fold smaller than the mammalian MHC. Abundant evidence indicates that the B complex is strongly associated with resistance to various infectious agents in chickens. While an association between different B haplotypes and resistance against several bacterial and viral diseases has been established, additional work needs to be performed on the association between the B complex and resistance to IB viruses (IBV). Here, some of the available knowledge on genetic resistance to viral poultry diseases conferred by the chicken B locus is reviewed. IBV immune responses and resistance associated with differing B haplotype chicken lines are reviewed and discussed herein.

Estudio recapitulativo- Respuestas inmunitarias y resistencia asociada al complejo B contra el virus de la bronquitis infecciosa en pollos. La bronquitis infecciosa sigue siendo una amenaza mundial para los productores avícolas. El complejo mayor de histocompatibilidad (MHC) o complejo B del pollo es compacto, restringido a un solo cromosoma y aproximadamente 20 veces más pequeño que el complejo mayor de histocompatibilidad de mamíferos. Existe abundante evidencia que indica que el complejo B está fuertemente asociado con la resistencia a varios agentes infecciosos en pollos. Si bien se ha establecido una asociación entre diferentes haplotipos B y la resistencia contra varias enfermedades bacterianas y virales, es necesario realizar un trabajo adicional sobre la asociación entre el complejo B y la resistencia a los virus de bronquitis infecciosa. A continuación, se revisan algunos de los conocimientos disponibles sobre la resistencia genética a las enfermedades virales en avicultura conferidos por el locus B del pollo. Las respuestas inmunes contra el virus de la bronquitis infecciosa y la resistencia asociadas con diferentes líneas de pollo de diferentes haplotipos B se revisan y se discuten en este artículo.