A Retrospective Study of Transmissible Viral Proventriculitis in Broiler Chickens in California: 2000-18.

Transmissible viral proventriculitis (TVP) is a disease of chickens, mostly in broilers of 2-8 wk of age. Chicken proventricular necrosis virus (CPNV), a birnavirus, is the etiologic agent. Characteristic gross lesions are enlargement, atony, and pallor of the proventriculus. Cases diagnosed in California between 2000 and 2018 (n = 477), originating from 93 different farms representing all major companies in the region, were analyzed. Frequency of cases varied widely between years, with no recognizable seasonality. The flocks were between 6 and 61 days of age; the average age was 34.0 days, and the median age was 35 days. In 166 cases, between 6.3% and 100% of the submitted birds had gross lesions in the proventriculus. The most common findings were enlarged or dilated proventriculi, thickened walls, and pale or mottled serosal appearance. Histopathologically, inflammation of the glands was the most frequent finding. Other lesions included necrosis, hyperplasia, or both conditions of the glandular epithelium; dilated glands; and occasionally fibrin deposition, fibrosis, and hemorrhages. Twenty-three proventriculi from six cases were tested by immunohistochemistry for the presence of CPNV antigen; 21 stained positive. In 209 cases, birds also had lesions in the bursa fabricii attributed to infectious bursal disease, but with no significant difference in the mean percentage of birds with gross lesions in the proventriculus between cases with or without lesions in the bursa fabricii. The results show that TVP is a common disease of broiler flocks in California and confirms that CPNV is the likely causative agent.

Partial Molecular Characterization and Pathogenicity Study of an Avian Reovirus Causing Tenosynovitis in Commercial Broilers.

This study describes the molecular characterization of avian reoviruses (ARVs) isolated during an outbreak in commercial chickens between 2015 and 2016. In addition, a pathogenicity study of a selected ARV strain isolated from a field case of viral tenosynovitis in commercial broiler chickens was performed. On the basis of phylogenetic analysis of a 1088-bp fragment of the ARV S1 gene, the investigated sequences were differentiated into five distinct genotypic clusters (GCs), namely GC1, GC2, GC3, GC4, and GC6. Specific-pathogen-free (SPF) and commercial broiler chickens were challenged with the GC1 genetic type MK247011, at 14 days of age via the interdigital toe web. No significant effects in body weight gain and feed conversion were detected in both chicken types. The Δ interdigital web thickness was most severe at 4 days postchallenge (DPC) in both the SPF and broiler subgroups. The inflammation in SPF birds was slightly more severe compared with broilers. Neither mortality nor clinical signs occurred in the infected groups for the duration of the experiment, despite the presence of significant microscopic lesions in challenged birds. Microscopic changes of tenosynovitis became evident at 3 DPC, with the highest incidence and severity detected at 14 and 21 DPC, respectively. Seroconversion against ARV occurred 3 wk postchallenge, and the microscopic lesions detected in tendon and heart sections were highly compatible with those described in the field. Increased severity of tenosynovitis and epicarditis lesions were noted in the ARV-challenged groups compared with the control groups. Although SPF and broiler chickens showed comparable responses to the challenge with an ARV genetic variant, detected lesions were subclinical, denoting the limitations of our challenge approach. The age selected in this experiment possibly influenced the course of the infection. Data from this study highlight the genotypic diversity of isolates in California, and the outcome of the pathogenicity study can be used as a basis to improve protocols for pathogenicity studies to characterize ARV variants causing clinical disease in the field.

Caracterización molecular parcial y estudio de patogenicidad de un reovirus aviar que causa tenosinovitis en pollos de engorde comerciales. Este estudio describe la caracterización molecular de reovirus aviares (ARV) aislados durante un brote en pollos comerciales entre los años 2015 y 2016. Además, se realizó un estudio de patogenicidad de una cepa de reovirus seleccionada que fue aislada de un caso de campo de tenosinovitis viral en pollos de engorde comerciales. Con base en el análisis filogenético de un fragmento de 1088 pb del gene S1 de reovirus, las secuencias investigadas se diferenciaron en cinco grupos genotípicos distintos (GCs), denominados, GC1, GC2, GC3, GC4 y GC6. Aves libres de patógenos específicos (SPF) y pollos de engorde comerciales se desafiaron con el tipo genético GC1 MK247011 a los 14 días de edad a través de la membrana interdigital. No se detectaron efectos significativos en el aumento de peso corporal ni en la conversión de alimento en ambos tipos de aves. El grosor de la banda interdigital diferencial fue más severa a los cuatro días posteriores al desafío en las aves libres de patógenos específicos y en los pollos de engorde. La inflamación en las aves libres de patógenos específicos fue ligeramente más severa en comparación con los pollos de engorde. No se presentó mortalidad ni signos clínicos en los grupos infectados durante la duración del experimento, a pesar de la presencia de lesiones microscópicas significativas en las aves desafiadas. Los cambios microscópicos de la tenosinovitis se hicieron evidentes a los tres días postinoculación, con la mayor incidencia y severidad detectadas a los 14 y 21días postinoculación, respectivamente. La seroconversión para reovirus ocurrió tres semanas después del desafío, y las lesiones microscópicas detectadas en secciones de tendón y corazón fueron altamente compatibles con las descritas en el campo. El aumento en la severidad de las lesiones de tenosinovitis y epicarditis se observó en los grupos expuestos a reovirus aviar en comparación con los grupos de control. Aunque las aves libres de patógenos específicos y los pollos de engorde mostraron respuestas comparables ante el desafío con una variante genética de reovirus, las lesiones detectadas fueron subclínicas, lo que denota las limitaciones de nuestro enfoque de desafío. La edad seleccionada en este experimento posiblemente influyó en el curso de la infección. Los datos de este estudio resaltan la diversidad genotípica de los aislamientos en California y el resultado del estudio de patogenicidad se puede usar como base para mejorar los protocolos de los estudios de patogenicidad para caracterizar las variantes de reovirus que causan enfermedades clínicas en el campo.

Characterization of an Outbreak of Infectious Coryza (Avibacterium paragallinarum) in Commercial Chickens in Central California.

In 2017, the Turlock branch of the California Animal Health & Food Safety laboratory system received a significant increase in infectious coryza (IC) necropsy cases, with a total of 54 submissions originating from commercial broilers (n = 40), commercial layers (n = 11), and backyard chickens (n = 3). Layer flocks positive for IC were distributed within the adjacent counties of Merced and Stanislaus, while broiler flocks were concentrated within Merced County. The backyard flocks were located in Alameda and Sacramento counties. The clinical and pathologic presentation was consistent with IC, although septicemic lesions were also noticed. Avibacterium paragallinarum was isolated and identified by PCR from the respiratory tract as well as from extrarespiratory sites. Polymicrobial infections involving other viral (infectious bronchitis virus, infectious bursal disease virus) and bacterial (Mycoplasma spp., Escherichia coli, Ornithobacterium rhinotracheale, Gallibacterium anatis biovar haemolytica) agents were commonly reported. Thirteen selected Av. paragallinarum isolates were successfully characterized as serovar C (Page scheme) and serovar C2 (Kume scheme). They shared a unique enterobacterial repetitive intergenic consensus (ERIC) PCR, differing from the four reference strains, and showed consistent high minimum inhibitory concentration values for tetracycline, suggesting a common origin from a single clone. Based on these results, high biosecurity standards and proper immunization of susceptible, multi-age flocks should always be implemented and adjusted as needed. The importance of backyard flocks should not be underestimated due to their unique epidemiologic role.

Caracterización de un brote de coriza infecciosa (Avibacterium paragallinarum) en pollos comerciales en la parte central de California. En el año 2017, la sede en Turlock del Sistema de Laboratorios de Salud Animal y Seguridad Alimentaria de California recibió un aumento significativo en el número de casos de necropsia por coriza infecciosa, con un total de 54 casos, incluyendo casos provenientes de pollos de engorde comerciales (n = 40), gallinas de postura comerciales (n = 11) y aves de traspatio (n = 3). Las parvadas de gallinas de postura positivas para coriza infecciosa se distribuyeron en los condados adyacentes de Merced y Stanislaus, mientras que las parvadas de pollos de engorde se concentraron en el condado de Merced. Las parvadas de traspatio estaban ubicadas en los condados de Alameda y Sacramento. La presentación clínica y patológica fue consistente con coriza infecciosa, aunque también se observaron lesiones septicémicas. Se aisló Avibacterium paragallinarum y se identificó mediante PCR en el tracto respiratorio y también de sitios extrarespiratorios. Las infecciones polimicrobianas relacionadas con otros virus (virus de la bronquitis infecciosa, virus de la enfermedad infecciosa de la bolsa) y bacterias (Mycoplasma spp., Escherichia coli, Ornithobacterium rhinotracheale, Gallibacterium anatis biovar haemolytica) fueron reportadas comúnmente. Trece aislamientos seleccionados de A. paragalinarum se caracterizaron con éxito como serovar C (esquema de Page) y serovar C2 (esquema de Kume). Estos aislamientos Compartieron por PCR un consenso intergénico repetitivo enterobacterial (ERIC) único, que difiere de las cuatro cepas de referencia y mostraron valores constantes de concentración mínima inhibitoria alta para tetraciclina, lo que sugiere un origen común de un solo clon. Con base en estos resultados, siempre se deben implementar y ajustar estándares de bioseguridad altos y la inmunización adecuada de parvadas susceptibles de edades múltiples, según sea necesario. La importancia de las parvadas de traspatio no debe subestimarse debido a su función epidemiológica especial.

Otitis and meningoencephalitis associated with infectious coryza ( Avibacterium paragallinarum) in commercial broiler chickens.

Infectious coryza, caused by Avibacterium paragallinarum, is an acute respiratory disease of poultry that can result in substantial morbidity, mortality, and economic losses. In March 2017, the Turlock branch of the California Animal Health and Food Safety laboratory system encountered an unusual clinical and pathologic presentation of infectious coryza in 6 live, 29-d-old, commercial broiler chickens that were submitted for diagnostic investigation. Antemortem evaluation revealed severe neurologic signs, including disorientation, torticollis, and opisthotonos. Swollen head-like syndrome and sinusitis were also present. Histologically, severe sinusitis, cranial osteomyelitis, otitis media and interna, and meningoencephalitis were noted, explaining the clinical signs described. A. paragallinarum was readily isolated from the upper and lower respiratory tract, brain, and cranial bones. Infectious bronchitis virus (IBV) was also detected by PCR, and IBV was isolated in embryonated chicken eggs. Based on sequencing analysis, the IBV appeared 99% homologous to strain CA1737. A synergistic effect between A. paragallinarum and IBV, resulting in exacerbation of clinical signs and increased mortality, may have occurred in this case. A. paragallinarum should be considered among the possible causes of neurologic signs in chickens. Appropriate media should be used for bacterial isolation, and the role of additional contributing factors and/or complicating agents should be investigated in cases of infectious coryza.

Serologic Surveillance of Wild and Pen-reared Ring-necked Pheasants ( Phasianus colchicus) as a Method of Understanding Disease Reservoirs.

We investigated exposure to infectious diseases in wild ( n=33) and pen-reared ( n=12) Ring-necked Pheasants ( Phasianus colchicus) in the Central Valley of California, US during 2014 and 2015. Serologic tests were positive for antibodies against hemorrhagic enteritis, infectious bursal disease, and Newcastle disease viruses in both wild and pen-reared pheasants.

Evolution of avian encephalomyelitis virus during embryo-adaptation.

Wild-type avian encephalomyelitis virus (AEV) causes neurological signs in young chicks but no disease in pullets after oral or intracutaneous infection. However, if the virus gets embryo-adapted by serial passaging in chicken embryos, it will cause AE after intracutaneous infection in chickens of all ages. Recently, several cases of AE in layer pullets occurring shortly after intracutaneous vaccination were described. The present investigation was initiated to determine if vaccines that had inadvertently been embryo-adapted were responsible for these outbreaks. Virus isolation was done from two vaccines and one field sample. One of the vaccines had been used in one of the flocks before the outbreak. After the first passage, regardless of the inoculum, no embryo was paralyzed, indicating that the vaccines and the field isolate were not embryo-adapted. After seven passages all three strains were fully embryo-adapted causing typical lesions in the embryos. Viral load as determined by RT-qPCR remained constant during the passages. Partial sequences of the VP2 gene of vaccines, the field sample and four other field isolates were nearly identical and highly similar to published sequences from all over the world; only sequences originating from non-vaccinated birds were clearly set apart. Analysis of whole genomes identified two single nucleotide polymorphisms (SNPs) that distinguished wild-type and embryo-adapted strains. Sanger sequencing brains and nerves of the five field isolates and of the first, third and fifth passages of the isolates showed that the mutations indicating embryo-adaptation were first observed in the fifth passage.

A Serosurvey of Greater Sage-Grouse ( Centrocercus urophasianus ) in Nevada, USA.

To better understand the potential avian diseases in Greater Sage-grouse ( Centrocercus urophasianus ) in the Great Basin in Nevada, US, we collected 31 blood samples March-April 2014 and tested for antibodies to eight viruses and two bacteria. Specifically, sera were tested for antibodies to avian leukosis virus type A, B, and J (ALV-A, ALV-B, and ALV-J, respectively), infectious bursal disease virus, infectious bronchitis virus, reticuloendothelial virus, avian influenza virus (AIV), West Nile virus, Pasteurella multocida (PM), and Salmonella enterica serovar Pullorum. Serum antibodies against ALV-A and -B (1/31, 3%), ALV-J (5/31, 16%), PM (1/31, 3%), and AIV (2/31, 6%) were detected by enzyme-linked immunosorbent assay (ELISA). While ELISA tests used have only been validated in domestic poultry, the serologic data should be used as a potential indicator of the range of bacterial and viral infectious agents that can infect the Greater Sage-grouse.

Descriptive survey and Salmonella surveillance of pastured poultry layer farms in California.

While pasture-raised poultry comprises a small portion of the commercial poultry industry in North America, these alternative rearing systems have become increasingly popular. As such, it is critical to improve our understanding of husbandry practices and prevalence of zoonotic and epizoonotic diseases in these systems. This research reviews the results of a survey sent to 82 commercial pastured poultry farms in California. While the survey response was low (13.4%), it was enhanced by detailed in-person interviews and farm visits. In addition, we conducted drag swabs for Salmonella Enteritidis. On average, farms utilized 12.3% of their total farmland for pastured poultry operations, which often coexisted with other livestock (45%), touch crops (27%), and non-touch crops (45%). While the mean (44.6 sq. ft./hen) and median (22.2 sq. ft./hen) pasture stocking densities were within auditing guidelines, the mean (1.2 sq. ft./hen) and median (0.5 sq. ft./hen) coop stocking densities were below the pending USDA (2016) guidelines recommended in 7 CFR Part 205. Drag swab results showed the presence of Salmonella Enteritidis (SE) in the environment of one of the 11 farms (9.1%). In addition, Salmonella Pullorum (SP) whole blood agglutination tests were used to understand the prevalence of Salmonella spp. in laying hens within the studied farms. Results showed the presence of antibodies in flocks at six of the seven non-SE vaccinated farms, with a mean on-farm prevalence of 25.6% in laying hens. Logistic regression was used to determine risk factors for Group D Salmonella exposure in non-vaccinated flocks, using the SP blood agglutination data as the dependent variable and the survey questions as the independent variables. Statistically significant (P < 0.05) risk factors included exposed wire floors and flock size. These results improve our understanding of Salmonella prevalence and husbandry practices on commercial pastured poultry farms in California.

Vegetative Valvular Endocarditis and Hepatitis Associated with Helcococcus ovis in a 7-year-old White Leghorn Rooster.

Helcococcus ovis is a slow-growing, pyridoxal-dependent, Gram-positive coccus belonging to the Peptostreptococcaceae family. Bacteria belonging to the genus Helcococcus are considered normal inhabitants of keratinized epithelium in humans; however, several reports support their role as pathogens in humans and several animal species. This case report describes the identification of H. ovis in a white leghorn rooster with valvular vegetative endocarditis and hepatitis. In February 2017 one dead, 7-yr-old, white leghorn rooster was submitted to the California Animal Health and Food Safety Turlock laboratory for diagnostic testing. Postmortem and microscopic examination revealed vegetative endocarditis and aortic thrombosis associated with large numbers of Gram-positive cocci. Myocarditis and extensive necrotic hepatitis were also noticed. Helcococcus ovis was isolated in large numbers from the aortic endothelium and confirmed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Bacterial colonies become evident 48 hr postincubation and exhibited a satellite growth around Escherichia coli on blood agar plates. A similar relationship has been described between Helcococcus spp. and Staphylococcus aureus. The primary site of infection in this chicken was not determined. To our understanding this is the first report of H. ovis infection in an avian species. The fastidious nature and nutritional requirements of Helcococcus spp. must be considered in order to allow proper identification and avoid misdiagnosis. Further studies are needed to define pathogenesis, virulence factors, and predisposing conditions associated with this microorganism.

Avian Encephalomyelitis in Layer Pullets Associated with Vaccination.

Avian encephalomyelitis (AE) was diagnosed in three flocks of leghorn layer pullets following AE vaccination. Ages of the birds were 11, 12, and 14 wk. The submissions came from three different companies located in two geographic areas of the Central Valley of California. The clinical signs included birds down on their legs, unilateral recumbency or sitting on their hocks, lethargy, reluctance to move, dehydration, unevenness in size, low weight, tremors of the head in a few birds, and mildly to moderately elevated mortality. The flocks had been vaccinated against fowl pox and AE with a combined product in the wing-web 2 wk prior to the onset of AE clinical signs. Histopathologic examination revealed lesions consistent with AE, including lymphocytic perivascular infiltration and neuronal central chromatolysis in the brain and spinal cord, as well as gliosis in the cerebellar molecular layer. The AE virus was detected by reverse-transcriptase PCR in the brain homogenate from three cases and peripheral nerves in one case. Additionally, the AE virus was isolated in specific-pathogen-free (SPF) embryonated eggs from brain tissue pool samples. Other avian viral infections capable of causing encephalitis, including avian paramyxoviruses, avian influenza virus (AIV), West Nile virus (WNV), eastern equine encephalitis virus (EEEV), and western equine encephalitis virus (WEEV), were ruled out by attempting virus isolation and molecular procedures.

Yersinia pseudotuberculosis in Eurasian Collared Doves (Streptopelia decaocto) and Retrospective Study of Avian Yersiniosis at the California Animal Health and Food Safety Laboratory System (1990-2015).

In February 2015, two Eurasian collared doves (Streptopelia decaocto) were submitted dead to the California Animal Health and Food Safety (CAHFS) Laboratory, Turlock branch, from a private aviary experiencing sudden, high mortality (4/9) in adult doves. In both doves, the gross and histologic lesions were indicative of acute, fatal septicemia. Grossly, there were numerous pale yellow foci, 1 to 2 mm in diameter, in the liver and spleen. Microscopically, these foci were composed of acute severe multifocal coagulative necrosis of hepatocytes and splenic pulp with infiltration of heterophils mixed with fibrin and dense colonies of gram-negative bacteria. Yersinia pseudotuberculosis was isolated from the lung, liver, spleen, heart, ovary, kidney, and trachea. The organism was susceptible to most antibiotics it was tested against, except erythromycin. Based on a retrospective study of necropsy submissions to CAHFS between 1990 and 2015, there were 77 avian case submissions of Y. pseudotuberculosis. There were 75/77 cases identified from a wide range of captive avian species from both zoo and private facilities and 2/77 cases from two backyard turkeys submitted from one premise. The largest number of cases originated from psittacine species (31/77). The lesions most commonly described were hepatitis (63/77), splenitis (49/77), pneumonia (30/77), nephritis (16/77), and enteritis (12/77). From 1990 to 2015, there was an average of three cases of avian pseudotuberculosis per year at CAHFS. Although there were no cases diagnosed in 1993 and 1994, in all other years, there were between one and eight cases of Y. pseudotuberculosis detected from avian diagnostic submissions.

Diagnosis and Control of a LPAI H5N8 Outbreak in a Japanese Quail (Coturnix coturnix japonica) Commercial Flock in the Central Valley of California.

In April 2014 an outbreak of low pathogenic avian influenza H5N8 North American genetic lineage was diagnosed in a commercial quail operation in Stanislaus County, California. Sudden increase in mortality prompted the submission of 20 Japanese quail hens (Coturnix c. japonica) to the California Animal Health and Food Safety Laboratory, Turlock Branch. Oropharyngeal and cloacal swabs tested positive for influenza A virus H5N8 by real-time reverse transcription-polymerase chain reaction. The virus was subsequently isolated. In vivo assay and sequencing of the hemagglutinin protein cleavage site classified the virus as a North American genetic lineage of low pathogenicity for chickens. Following the diagnosis, a rapid and coordinated response took place to contain the outbreak. The affected premise was depopulated, cleaned, and disinfected. Three areas from the affected premises-a 3 kilometer (km) radius (High Risk Zone), a 3-10 km area (Buffer Zone), and a 10-20 km (Surveillance Zone)-were established for avian influenza testing of commercial and noncommercial poultry operations. Surveillance testing and rapid control measures were successful in the control and eradication of the outbreak and revealed no area of spread of the virus from the index flock. This report describes the history, diagnosis, surveillance, and control measures applied to manage this outbreak.

Historical, spatial, temporal, and time-space epidemiology of very virulent infectious bursal disease in California: a retrospective study 2008-2011.

In December of 2008 very virulent infectious bursal disease virus (vvIBDV) was identified in a commercial flock in northern California. Since then several other backyard and commercial facilities in California have had flocks affected by the same strain and other unique (previously unseen) strains of IBDV. Previous to this incident, very virulent infectious bursal disease (vvIBD) had never been identified in North America. Following the initial outbreak in 2008, California became the first state to undertake a voluntary surveillance effort to try to determine the geographical prevalence of vvIBD based on sequencing of a portion of the segment A region of the vvIBDV genome. To date we have complete geographical information on approximately 500 separate accessions representing approximately 1500 birds from over 200 commercial (-85% of the facilities) and backyard facilities (-15% of the facilities) throughout the state. Sequencing of targeted regions of both the segment A and segment B regions of the genome has revealed three distinct types of IBDV in California chickens. One type is genetically and in pathogenically consistent with vvIBDV. The second and third types only have a segment A region consistent with vvIBDV. Geographic information system mapping coupled with spatial-temporal cluster analysis identified significant spatial and time-space clustering; however, no temporal clustering was noted. The lack of temporal clustering coupled with negative vvIBDV results in tested avian wildlife implies that avian wildlife in California do not currently appear to play a significant role in vvIBDV transmission. In the voluntary surveillance that was done in the Central Valley of California, which has a high density of commercial poultry, no positive farms were found when 142 of 504 farms were sampled. Given this level of sampling, the confidence (probability) of detecting an affected commercial flock was calculated to be between 28% and 81% depending on whether one or five hypothetically affected farms were affected.

Parasitic ventriculitis caused by Hadjelia truncata in California rock pigeons (Columba livia).

Severe ventriculitis and emaciation caused by the infestation of the nematode Hadjelia truncata occurred in meat-type breeder rock pigeons (Columba livia) in southern and central California. Hadjelia truncata can infest several species of birds, although it has only been reported as pathogenic in pigeons. The factors that contribute to H. truncata pathogenicity are not known. The gross and microscopic pathology caused by the infestation of H. truncata in the ventriculus of pigeons and its morphological identification are presented.

Epidemiology and effect on production parameters of an outbreak of inclusion body hepatitis in broilers.

In 2007, an inclusion body hepatitis (IBH) outbreak affected several broiler farms in Mississippi. Results of logistic regression analyses showed significant associations between IBH occurrence and high enzyme-linked immunosorbent assay geometric mean titers for infectious bursal disease virus. However, there was no association between IBH occurrence and chicken infectious anemia virus status. Results of linear regression model analyses showed significant associations between IBH occurrence with average weight and with cost deviation. Broiler meat production cost was $0.0058/kg more expensive to produce when IBH occurred. Although feed conversion was higher with IBH occurrence, the association was not significant. IBH onset in the first farms affected occurred between 19 and 30 days of age, whereas in the last farms affected, IBH onset occurred as early as 10 days.

The diagnosis of very virulent infectious bursal disease in California pullets.

This report documents the occurrence of a very virulent infectious bursal disease virus (vvIBDV) in Northern California commercial brown pullets. Diagnosis was made from multiple accessions from two neighboring and epidemiologically related ranches submitted to the California Animal Health and Food Safety (CAHFS) laboratory. Pullets, 11 and 14 wk of age from ranch A (rA) and ranch B (rB) respectively, were submitted from infectious bursal disease virus vaccinated flocks experiencing a drastic increase in mortality. The December 2008 outbreak resulted in 26% and 34% mortality on rA and rB respectively. Gross and histologic lesions characteristic of acute vvIBDV were observed. Gross lesions included edematous bursas, hemorrhages at the junction of the proventriculus and gizzard as well as hemorrhages on skeletal muscles. Microscopic lesions included severe lymphoid necrosis and inflammation in edematous bursas, lymphoid necrosis in thymus, spleen, Peyer's patches and cecal tonsils. Diagnosis of vvIBDV was confirmed by molecular characterization of the IBDV from bursas as well as viral pathogenicity in specific-pathogen-free birds. RT-PCR and nucleotide sequencing of the hypervariable region of the VP2 (vVP2) gene segment of the IBDV genome was performed on rA, rB and embryo passaged rA virions.The amino acids compatible with vvIBDV isolates: 222(Ala), 242(Ile), 256(Ile), 294(Ile) and 299(Ser) were reported from both ranches. In addition, nucleotide sequencing of a fragment of the VP1 gene demonstrated the viruses have the segment B genotype associated with highly pathogenic vvIBDV. Inocula of 10(5.5) 50% egg infective dose of vvIBDV virus from rA and rB were introduced orally into two groups (g1 and g2 respectively) of 4 wk 2-day-old SPF leghorns. At 4 days postinoculation, there was 100% (22/22) morbidity in g1 and g2; 91% (20/22) mortality in g1; 100% (22/22) mortality for g2; 0% (0/20) morbidity and 0% (0/ 20) mortality was reported in the control group. This is the first occurrence of vvIBDV reported from birds in the United States.