Showing papers by "Erica Spackman published in 2007"

Movements of birds and avian influenza from Asia into Alaska.

Abstract: Asian-origin avian influenza (AI) viruses are spread in part by migratory birds. In Alaska, diverse avian hosts from Asia and the Americas overlap in a region of intercontinental avifaunal mixing. This region is hypothesized to be a zone of Asia-to-America virus transfer because birds there can mingle in waters contaminated by wild-bird–origin AI viruses. Our 7 years of AI virus surveillance among waterfowl and shorebirds in this region (1998–2004; 8,254 samples) showed remarkably low infection rates (0.06%). Our findings suggest an Arctic effect on viral ecology, caused perhaps by low ecosystem productivity and low host densities relative to available water. Combined with a synthesis of avian diversity and abundance, intercontinental host movements, and genetic analyses, our results suggest that the risk and probably the frequency of intercontinental virus transfer in this region are relatively low.

Periodic monitoring of commercial turkeys for enteric viruses indicates continuous presence of astrovirus and rotavirus on the farms

Abstract: A longitudinal survey to detect enteric viruses in intestinal contents collected from turkeys in eight commercial operations and one research facility was performed using molecular detection methods. Intestinal contents were collected from turkeys prior to placement, with each flock resampled at 2, 4, 6, 8, 10, and 12 wk of age. The samples were screened for astrovirus, rotavirus, reovirus, and turkey coronavirus (TCoV) by a reverse transcriptase and polymerase chain reaction (RT-PCR), and for groups 1 and 2 adenovirus by PCR. Rotavirus was the only virus detected prior to placement (7 of 16 samples examined). All of the commercial flocks were positive for rotavirus and astrovirus from 2 until 6 wk of age, and most were intermittently positive until 12 wk of age, when the birds were processed. Of the 96 samples collected from birds on the farms, 89.5% were positive for astrovirus, and 67.7% were positive for rotavirus. All flocks were negative for TCoV, reovirus, and group 1 adenovirus at all time points, and positive for group 2 adenovirus (hemorrhagic enteritis virus) at 6 wk of age. All the flocks monitored were considered healthy or normal by field personnel. Turkeys placed on research facilities that had been empty for months and thoroughly cleaned had higher body weights and lower feed conversion rates at 5 wk of age when compared to turkeys placed on commercial farms. Intestinal samples collected at 1, 2, and 3 wk of age from these turkeys were free of enteric viruses. This report demonstrates that astroviruses and rotaviruses may be present within a turkey flock through the life of the flock. Comparison of infected birds with one group of turkeys that were negative for enteric viruses by the methods used here suggests that astrovirus and/or rotavirus may affect production. The full impact on flock performance needs to be further determined.

A Multiplex RT-PCR Test for the Differential Identification of Turkey Astrovirus Type 1, Turkey Astrovirus Type 2, Chicken Astrovirus, Avian Nephritis Virus, and Avian Rotavirus

Abstract: Recent studies have revealed the presence of astroviruses and rotavirus in numerous poorly performing and healthy chicken and turkey flocks in the United States. The phylogenetic analysis of the sequence data produced during these studies has identified four groups of avian astroviruses circulating in the United States: turkey astrovirus types 1 and 2 (TAstV-1 and TAstV-2), avian nephritis virus (ANV), and a chicken-origin astrovirus (CAstV). As the molecular epidemiology of poultry enteric disease is poorly understood, the development of updated diagnostic assays is crucial to the continued surveillance and management of enteric disease in affected as well as healthy flocks. This report details the development of a multiplex reverse transcriptase–polymerase chain reaction (RT-PCR) assay specific for astroviruses and avian rotavirus in turkey-origin and chicken-origin samples. The assay consists of two multiplex tests, one for turkey-origin samples and one for chicken-origin samples. The turkey s...

Characterization of Low-Pathogenicity H5N1 Avian Influenza Viruses from North America

Abstract: Wild-bird surveillance in North America for avian influenza (AI) viruses with a goal of early identification of the Asian H5N1 highly pathogenic AI virus has identified at least six low-pathogenicity H5N1 AI viruses between 2004 and 2006. The hemagglutinin (HA) and neuraminidase (NA) genes from all 6 H5N1 viruses and an additional 38 North American wild-bird-origin H5 subtype and 28 N1 subtype viruses were sequenced and compared with sequences available in GenBank by phylogenetic analysis. Both HA and NA were phylogenetically distinct from those for viruses from outside of North America and from those for viruses recovered from mammals. Four of the H5N1 AI viruses were characterized as low pathogenicity by standard in vivo pathotyping tests. One of the H5N1 viruses, A/MuteSwan/MI/451072-2/06, was shown to replicate to low titers in chickens, turkeys, and ducks. However, transmission of A/MuteSwan/MI/451072-2/06 was more efficient among ducks than among chickens or turkeys based on virus shed. The 50% chicken infectious dose for A/MuteSwan/ MI/451072-2/06 and three other wild-waterfowl-origin H5 viruses were also determined and were between 10 5.3 and 10 7.5 50% egg infective doses. Finally, seven H5 viruses representing different phylogenetic clades were evaluated for their antigenic relatedness by hemagglutination inhibition assay, showing that the antigenic relatedness was largely associated with geographic origin. Overall, the data support the conclusion that North American H5 wild-bird-origin AI viruses are low-pathogenicity wild-bird-adapted viruses and are antigenically and genetically distinct from the highly pathogenic Asian H5N1 virus lineage.

An Avian Influenza Virus from Waterfowl in South America Contains Genes from North American Avian and Equine Lineages

Abstract: Apart from an outbreak in commercial poultry in Chile in 2002, there have been few reports of avian influenza in South America. However, surveillance in free-flying birds has been limited. An avian influenza virus was isolated from a Cinnamon Teal (Anas cyanoptera) in Bolivia in 2001 from samples collected for an avian influenza virus and avian paramyxovirus surveillance study. This isolate was determined to be an H7N3 virus by gene sequencing. Analysis of all eight genes revealed that five genes were most closely related to the H7N3 in Chile in 2002. Two genes were most closely related to North American wild aquatic bird virus lineages and one gene was most closely related to an equine influenza virus from South America.

Pathology and virus tissue distribution of Turkey origin reoviruses in experimentally infected Turkey poults.

Abstract: The pathogenesis of 4 isolates of turkey-origin reovirus (NC/SEP-R44/03, NC/98, TX/98, and NC/85) and 1 chicken-origin reovirus (1733) was examined by infecting specific pathogen free (SPF) poults. These turkey-origin reovirus (TRV) isolates were collected from turkey flocks experiencing poult enteritis and are genetically distinct from previously reported avian reoviruses. Microscopic examination of the tissues collected from the TRV-infected poults revealed different degrees of bursal atrophy characterized by lymphoid depletion and increased fibroplasia between the bursal follicles. To understand the relationship between virus spread and replication, and the induction of lesions, immunohistochemical staining (IHC) for viral antigen, in situ hybridization (ISH) for the detection of viral RNA, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay for the detection of apoptosis in affected tissues was performed. Both IHC and ISH revealed viral antigen and RNA in the surface epithelial cells of the bursa, in macrophages in the interstitium of the bursa and, to lesser degree, in splenic red pulp macrophages and intestinal epithelial cells. Increased apoptosis of bursal lymphocytes and macrophages was observed at 2 and 5 days postinoculation. No lesions were found in tissues from poults inoculated with the virulent chicken-origin strain, however viral antigen was detected in the bursa and the intestine. Although all TRVs studied displayed similar tissue tropism, there were substantial differences in the severity of the lesions produced. Poults inoculated with NC/SEP-R44/03 or NC/98 had moderate to severe bursal atrophy, whereas poults inoculated with TX/98 or NC/85 presented a mild to moderate bursal lymphoid depletion. The lymphoid depletion observed in the bursa appears to be the effect of an indirectly induced apoptosis and would most likely result in immune dysfunction in poults infected with TRV.

Sequence and phylogenetic analysis of the S1 genome segment of turkey-origin reoviruses.

Abstract: Based on previous reports characterizing the turkey-origin avian reovirus (TRV) σB (σ2) major outer capsid protein gene, the TRVs may represent a new group within the fusogenic orthoreoviruses. However, no sequence data from other TRV genes or genome segments has been reported. The σC protein encoded by the avian reovirus S1 genome segment is the cell attachment protein and a major antigenic determinant for avian reovirus. The chicken reovirus S1 genome segment is well characterized and is well conserved in viruses from that species. This report details the amplification, cloning and sequencing of the entire S1 genome segment from two and the entire coding sequences of the σC, p10 and p17 genes from an additional five TRVs. Sequence analysis reveals that of the three proteins encoded by the TRV S1 genome segment, σC shares at most 57% amino acid identity with σC from the chicken reovirus reference strain S1133, while the most similar p10 and p17 proteins share 72% and 61% identity, respectively, with the corresponding S1133 proteins. The most closely related mammalian reovirus, the fusogenic Nelson Bay reovirus, encodes a σC protein that shares from 25% to 28% amino acid identity with the TRV σC proteins. This report supports the earlier suggestion that the TRVs are a separate virus species within the Orthoreovirus genus, and may provide some insight into TRV host specificity and pathogenesis.

Characteristics of Diagnostic Tests Used in the 2002 Low-Pathogenicity Avian Influenza H7N2 Outbreak in Virginia

Abstract: An outbreak of low-pathogenicity avian influenza (LPAI) H7N2 occurred in 2002 in the Shenandoah Valley, a high-density poultry production region in Virginia. Infected flocks were identified through a combination of observation of clinical signs and laboratory diagnostic tests designed to detect avian influenza (AI) antibodies, virus, or H7-specific RNA. In this report, fitness for purpose of 3 virus/RNA detection assays used during the outbreak was examined: 1) antigen capture enzyme immunoassay (AC-EIA), 2) real-time reverse transcription polymerase chain reaction (RRT-PCR), and 3) virus isolation (VI). Results from testing 762 turkey and 2,216 chicken tracheal swab pooled specimens were analyzed to determine diagnostic sensitivities and specificities of these tests under field conditions using Bayesian techniques for validation of diagnostic tests in the absence of a “gold standard.” Diagnostic sensitivities (with 95% probability intervals) in turkeys of AC-EIA and RRT-PCR, in reference to VI, were 65.9...