Mammography test sets: reading location and prior images do not affect group performance.

AIM: To examine how the location where reading takes place and the availability of prior images can affect performance in breast test-set reading. MATERIALS AND METHODS: Under optimized viewing conditions, 10 expert screen readers each interpreted a reader-specific set of images containing 200 mammographic cases. Readers, randomly divided into two groups read images under one of two pairs of conditions: clinical read with prior images and laboratory read with prior images; laboratory read with prior images and laboratory read without prior images. Region-of-interest (ROI) figure-of-merit (FOM) was analysed using JAFROC software. Breast side-specific sensitivity and specificity were tested using Wilcoxon matched-pairs signed rank tests. Agreement between pairs of readings was measured using Kendall's coefficient of concordance. RESULTS: Group performances between test-set readings demonstrated similar ROI FOMs, sensitivity and specificity median values, and acceptable levels of agreement between pairs of readings were shown (W = 0.75-0.79, p < 0.001) for both pairs of reading conditions. On an individual reader level, two readers demonstrated significant decreases (p < 0.05) in ROI FOMs when prior images were unavailable. Reading location had an inconsistent impact on individual performance. CONCLUSION: Reading location and availability of prior images did not significantly alter group performance.

Assessing reader performance in radiology, an imperfect science: lessons from breast screening.

The purpose of this article is to review the limitations associated with current methods of assessing reader accuracy in mammography screening programmes. Clinical audit is commonly used as a quality-assurance tool to monitor the performance of screen readers; however, a number of the metrics employed, such as recall rate as a surrogate for specificity, do not always accurately measure the intended clinical feature. Alternatively, standardized screening test sets, which benefit from ease of application, immediacy of results, and quicker assessment of quality improvement plans, suffer from experimental confounders, thus questioning the relevance of these laboratory-type screening test sets to clinical performance. Four key factors that impact on the external validity of screening test sets were identified: the nature and extent of scrutiny of one's action, the artificiality of the environment, the over-simplification of responses, and prevalence of abnormality. The impact of these factors on radiological and other contexts is discussed, and although it is important to acknowledge the benefit of standardized screening test sets, issues relating to the relevance of test sets to clinical activities remain. The degree of correlation between performance based on real-life clinical audit and performances at screen read test sets must be better understood and specific causal agents for any lack of correlation identified.

Reversion to subgroup J avian leukosis virus viremia in seroconverted adult meat-type chickens exposed to chronic stress by adrenocorticotrophin treatment.

Chickens infected with subgroup J avian leukosis virus (ALV J) early in posthatch life develop viremia followed by a neutralizing antibody (Nab) response that may or may not be able to clear the viremia. Occasionally, chickens that do clear viremia by developing an efficient Nab response revert to viremia, and the factors responsible for this reversion are not clear. In this study, it was hypothesized that stress can cause seroconverted viremia-free chickens to revert to viremia. Adult (52-wk-old) male commercial meat-type chickens that were exposed to ALV J at hatch and had since cleared viremia and remained viremia-free for up to 40 wk, when subjected to chronic stress (for 14 days) induced by porcine adrenocorticotrophin (ACTH), reverted to viremia and cloacal shedding (2/6 [33%]). However, chickens that were contact-exposed to ALV J at 32 wk of age and had seroconverted failed to revert to viremia when subjected to similar chronic stress. Stress did not increase the susceptibility of adult meat-type chickens to ALV J infection by contact exposure. The lack of statistical significance due to the small sample size is a limitation of this study. However, in general, the results suggest that treatment of chickens with ACTH can cause reversion of viremia and cloacal shedding in ALV J-seroconverted adult male chickens that had been exposed to the virus at hatch, but not in chickens that were contact-exposed at 32 wk of age. The results warrant further studies with greater sample size to examine the role of stress in ALV J epidemiology.

Subgroup J avian leukosis virus neutralizing antibody escape variants contribute to viral persistence in meat-type chickens.

We have previously demonstrated a high incidence of chickens with persistent viremia even in the presence of neutralizing antibodies (V+A+) against the inoculated parental virus in commercial meat-type chickens inoculated at hatch with subgroup J avian leukosis virus (ALV J) field isolates. In this study, we used an ALV J molecular clone, ADOL pR5-4, to determine the role of neutralizing antibody (NAb) escape mutants in maintaining a high incidence of viral persistence, namely, V+A+ infection profile in commercial meat-type chickens. Chickens were housed as a flock in a pen or housed in isolation in solitary Horsfall-Bauer units for testing for NAb escape variants. The emergence of NAb escape variants was evaluated by sequential autologous virus neutralization (VN) (between virus and antibody from the same sampling period) and heterologous VN (between virus and antibody from preceding and succeeding sampling periods). Sequential virus isolates and corresponding antisera from 18 chickens were examined by VN matrix. In all chickens, autologous virus isolates were not neutralized by corresponding antisera. However, some of these resilient autologous virus isolates were neutralized by antibodies from subsequent sampling intervals. Nucleotide sequence analysis of consecutive isolates from three individually housed chickens with V+A+ infection profile revealed distinct changes within the envelope region, suggesting viral evolution to escape the host immune response. These results demonstrate that the emergence of antibody escape variants in commercial meat-type chickens contributes to ALV J persistence.

Experimental inoculation of wild turkeys (Meleagris gallopavo) with Mycobacterium bovis.

Although avian species are known to be susceptible to infection with Mycobacterium spp. organisms, much remains unknown about the susceptibility of birds to infection with M. bovis. The objective of this current study was to determine if wild turkeys (Meleagris gallopavo) can be infected with M. bovis when inoculated by the oral or intratracheal route. Six turkeys were orally inoculated and another six were inoculated via the trachea with a high dose of M. bovis, 1 x 10(5) CFU/ml. Six turkeys were sham-inoculated controls. Two turkeys from each treatment group were sacrificed on days 30, 60, and 90 postinoculation. There were no gross or microscopic lesions consistent with mycobacteriosis in the 23 inoculated turkeys over the 90-day duration of this study. Fecal cultures were also consistently negative for M. bovis when sampled before inoculation and on days 1, 30, and 60 postinoculation. Two intratracheally inoculated turkeys were positive for M. bovis in visceral tissues at 30 days postinoculation. However, this finding was only indicative of passive persistence of mycobacteria in the tissues and not of infection, as there were no attendant lesions or clinical compromise to support infection. Thus, it can be concluded that young wild turkeys are resistant to infection with M. bovis and, therefore, pose minimal threat as reservoir or spillover hosts for this organism.

Effects of T-2 Toxin on Turkey Herpesvirus-Induced Vaccinal Immunity Against Marek's Disease.

T-2 toxin, a very potent immunotoxic Type A trichothecene, is a secondary metabolite produced primarily by Fusarium spp., which grows on cereal grains and can lead to contaminated livestock feed. Repeated exposure to T-2 toxin has been shown to cause immunosuppression and decrease the resistance of exposed animals to a variety of infectious diseases; however, the effects of T-2 toxin on Marek's disease (MD) vaccinal immunity have not been reported. Four trials were conducted to determine the effects of T-2 toxin on vaccinal immunity against MD. Day-old, white leghorn chicks of Avian Disease and Oncology Laboratory line 15I5 × 71 were treated daily for 7 days via crop gavage with T-2 toxin at a sublethal dose of 1.25 mg/kg body weight. Treated and untreated chicks were also vaccinated with turkey herpesvirus (HVT) at hatch and were challenged with the JM strain of MD virus (MDV) at 8 days of age. Chickens were tested for HVT viremia at 1 wk postvaccination immediately before challenge, and for HVT and MDV viremia at 3 wk postchallenge. Chickens were observed for the development of MD lesions and mortality within 8 wk of age. T-2 toxin significantly reduced body weight and titers of HVT viremia within 7 days after hatch. T-2 toxin shortened the incubation period for the development of MD lesions and mortality, but only in unvaccinated chickens. The percent MD protection in T-2-toxin-treated, HVT-vaccinated chickens ranged from 82% to 96% and was comparable to that in HVT-vaccinated untreated control chickens (89%-100%). The data suggest that exposure of chickens to sublethal doses of T-2 toxin for 7 consecutive days after hatch may influence the development of 1) HVT viremia; and 2) MD lesions and mortality, but only in unvaccinated chickens.

Lockjaw syndrome in cockatiels associated with sinusitis.

Two cases where multiple juvenile cockatiels exhibited inappetance, depression, upper respiratory signs, and "lockjaw" are described. Symptoms progressed over several weeks until all birds died, in spite of antibacterial therapy. Seven affected birds from each case were submitted for diagnostic evaluation. Microscopically, all birds had necrotizing rhinitis and sinusitis, as well as myositis, perineuritis and osteomyelitis affecting the jaw muscles and cranial bones. Multiple bacterial agents were isolated from the lungs and sinuses in both cases. Juvenile cockatiels appear to be particularly susceptible to temporomandibulitis, temporomandibular joint rigidity, or "lockjaw". Once chronic inflammation and fibrosis develop, it appears unlikely that jaw mobility can be restored.

Development and application of an immunohistochemical staining technique to detect avian polyomaviral antigen in tissue sections.

An immunohistochemical staining technique was developed to detect polyomaviral antigens of budgerigar fledgling disease in formalin-fixed tissue sections. This technique used an indirect avidin-biotin, alkaline phosphatase labeling system with a mixture of monoclonal antibodies developed against the virus major capsid protein. The staining technique was applied retrospectively to 24 avian accessions which were originally diagnosed as budgerigar fledgling disease or avian polyomavirus infection based on microscopic findings including typical intranuclear inclusions. Immunohistochemical staining resulted in positive reactions in some tissues from 17 of 24 cases. The tissues most frequently containing typical intranuclear inclusions or positive immunohistochemical staining were the spleen, liver, and kidney. Neither of the 2 nonpsittacine cases was positive immunohistochemically. This technique may be used wither as a rapid test on routinely processed diagnostic samples to confirm the presence of avian polyomavirus or for pathogenesis research studies.

Conium maculatum (poison hemlock) toxicosis in a flock of range turkeys.

Five 20-week-old tom turkeys from a flock of range turkeys were presented for examination; the flock had a history of salivation, tremors, paralysis, and increased mortality. Necropsy revealed numerous seeds identified as seeds from Conium maculatum (poison hemlock) within the crop, proventriculus, and gizzard. Histopathologic alterations were limited to catarrhal enteritis. Clinical signs of Conium maculatum toxicosis abated after the turkeys were removed from their range, which was infested with poison hemlock.

Observations of experimentally induced quail bronchitis.

Quail bronchitis was experimentally reproduced in captive-reared bobwhite quails (Colinus virginianus). Quails were inoculated with 10(6) mean tissue culture infective doses of quail bronchitis virus at 1,3,6, or 9 weeks of age by the intratracheal, intraperitoneal, or subcutaneous route. Clinical signs were minimal, but occasionally birds were ruffled, exhibited open-mouthed breathing, and developed "snicks." Mortality rates of quails inoculated at 1 or 3 weeks ranged from 7% to 87%. Quails inoculated at 6 or 9 weeks of age had mortality rates from 0% to 20%. Mean body weights of survivors that had been inoculated at 3 or 6 weeks were significantly less than those of controls (P less than 0.05). No significant differences in body weight were detected between quails inoculated at 1 or 9 weeks and their uninoculated controls. Antibodies to group I adenovirus were detected by agar gel precipitation in 87.5% of birds that survived infection.

Further characterization of an avian adenovirus associated with inclusion body hepatitis in bobwhite quails.

An adenovirus (isolate 1452) associated with inclusion body hepatitis of bobwhite quails (Colinus virginianus) was characterized as a group I, serotype 1 avian adenovirus and was indistinguishable from quail bronchitis virus. Bobwhite quails were inoculated via the intratracheal or intraperitoneal route with 10(6) mean tissue-culture infective dose of isolate 1452 at 1, 3, 6, or 9 weeks of age. Lesions produced by either route of inoculation were similar to those of quail bronchitis and included necrotizing tracheitis, proliferative and necrotizing bronchitis and pneumonia, and multifocal necrotizing hepatitis, necrotizing splenitis with or without hyperplasia of splenic macrophages, and lymphoid necrosis and atrophy of the bursa of Fabricius. Basophilic intranuclear viral inclusions were present in respiratory mucosal epithelium, hepatocytes and occasionally bile duct epithelium, and the mucosal epithelium overlying follicles of the bursa. Results indicate that isolate 1452 is a field isolate of quail bronchitis virus and that inclusion body hepatitis of bobwhite quails is a manifestation of quail bronchitis.

Evaluation of a commercial quail pox vaccine (Bio-Pox Q) for the control of "variant" fowl poxvirus infections.

Groups of 3-week-old specific pathogen-free chickens immunized with a commercial live-virus quail pox vaccine (Bio-Pox Q) were not protected against challenge with "variant" poxviruses isolated from chickens that were previously vaccinated with commercial fowl pox vaccine. The percentages of vaccinated chickens resistant to challenge with each of the five variant field isolates were 0%, 20%, 0%, 20%, and 10%, respectively. However, when immunity engendered by the variant field isolates was challenged with the commercial quail pox vaccine virus, 80%, 70%, 80%, 50%, and 60% of the vaccinates, respectively, were protected. Results from cross-immunity studies indicate that the commercial quail pox vaccine does share some immunologic relationship with these variant poxvirus field isolates, but not enough to be used in the control of some outbreaks of pox caused by variant poxviruses.

Comparative toxicity of coniine, an alkaloid of Conium maculatum (poison hemlock), in chickens, quails, and turkeys.

Coniine, an alkaloid of Conium maculatum (poison hemlock), was administered by gavage to immature chickens, quails, and turkeys at 0, 25, 50, and 100 mg/kg body weight. At 25 mg coniine/kg body weight, clinical signs were observed only in quails (2/10) and consisted of excitement, depression, hypermetria, seizures, opisthotonos, and flaccid paralysis. Chickens (9/10) and quails (8/10) dosed at 50 mg/kg body weight were affected, and several birds of each species died (2/10 and 5/10, respectively). Turkeys (7/10) were affected only when dosed at 100 mg/kg body weight, and quails (6/10), turkeys (4/10), and chickens (10/10) died at this dose. There were no gross or microscopic lesions. Coniine was detected in skeletal muscle and liver of birds dying after ingestion and was present in some survivors 7 days post-treatment.

Pathology of experimentally induced quail bronchitis.

Bobwhite quails (Colinus virginianus) were inoculated with 10(6) mean tissue-culture infective dose of quail bronchitis virus at 1, 3, 6, or 9 weeks of age by intratracheal, intraperitoneal, or subcutaneous routes. Quails developed necrotizing tracheitis, proliferative and necrotizing bronchitis and pneumonia; multifocal necrotizing hepatitis; necrotizing splenitis, with or without hyperplasia of splenic mononuclear phagocytes; bursal lymphoid necrosis; and bursal atrophy. Lesions were more extensive and severe in quails inoculated at 1 or 3 weeks of age than in older quails. Large intranuclear inclusions, characteristic of adenovirus infection, were identified in trachea, lung, liver, and bursa of Fabricius. This is the first report of the histopathology of experimentally induced quail bronchitis.

Pathogenesis of marble spleen disease in bursectomized and non-bursectomized ring-necked pheasants following oral inoculation with cell-culture-propagated virus.

Seventy-two 13-week-old ring-necked pheasants were inoculated orally with 5.0 x 10(2) tissue-culture infective dose (TCID) of cell-culture-propagated marble spleen disease virus. Inoculated birds exhibited neither mortality nor clinical disease. Gross and histologic lesions were typical of marble spleen disease. The mean splenic weight was significantly (P less than 0.02) higher in inoculated birds than in controls between 6 and 10 days postinoculation (PI). The histologic splenic lesions, which consisted of reticuloendothelial cell hyperplasia, intranuclear inclusions within reticuloendothelial cells, and lymphoid depletion, were most prominent between 6 and 10 days PI. In a second experiment, 1-day-old pheasants were chemically bursectomized by dosing birds with 1.2 mg cyclophosphamide on 3 consecutive days. At 7 weeks of age, 54 bursectomized birds were inoculated orally with 5.0 x 10(2) TCID of marble spleen disease virus. Gross and histologic lesions were detected in one of the inoculated pheasants, but the mean splenic weight was not significantly different from control birds at any time PI. These results are evidence of the role of the bursa of Fabricius in the pathogenesis of marble spleen disease.

Experimental infection of bobwhite quail with Indiana C adenovirus.

Bobwhite quails (Colinus virginianus) were inoculated intratracheally, intraperitoneally, or subcutaneously with Indiana C adenovirus at 1, 3, 6, or 9 weeks of age. Mortality rates were 33-100% in quails inoculated at 1 or 3 weeks of age and 0-10% in quails inoculated at 6 or 9 weeks of age. Gross and histologic lesions included necrotizing tracheitis and bronchitis with pneumonia, necrotizing hepatitis and splenitis, and lymphoid depletion of the bursa of Fabricius; these were consistent with quail bronchitis. Indiana C is highly pathogenic in bobwhite quails and cannot be recommended as a vaccine to prevent quail bronchitis.

Evaluation of a commercial modified live virus fowl pox vaccine for the control of "variant" fowl poxvirus infections.

Three-week-old specific-pathogen-free chickens were vaccinated with either a commercial modified live virus fowl pox vaccine or five "variant" poxvirus field isolates. Immunity engendered by the commercial modified vaccine or field isolates was challenged with either the variant isolates or commercial modified vaccine virus. The commercial modified vaccine did not adequately protect vaccinates against challenge with the variant isolates. The percentages of vaccinated chickens protected following challenge with each of the variant isolates were 70%, 20%, 30%, 20%, and 25%. However, when the isolates were applied as vaccines, 100% of the vaccinates were protected against challenge from the modified vaccine virus. Furthermore, the variant poxvirus isolates offered excellent protection from challenge with homologous variant isolates. The modified live virus vaccine was expected to offer significant protection against challenge from the variant pox isolates, but in this experiment it did not. The variant isolates tested may be good vaccine candidates to prevent the vaccine breaks currently encountered in previously pox-vaccinated flocks.

Serological characteristics of a membrane glycoprotein gp82 of Marek's disease virus.

Marek's disease virus (MDV) is a cell-associated herpesvirus of gallinaceous fowl. Glycoproteins of herpesviruses have been reported to be important in stimulating humoral and cell-mediated immune responses against viral infection. At least eight glycoproteins of MDV have been identified, and glycoprotein B (gB) has been reported to produce protective immunity. In addition to glycoproteins, other cell membrane proteins may also be important for engendering immunity. In an attempt to determine whether the protein is involved in immune responses, we developed three monoclonal antibodies (Mabs) and rabbit polyclonal antibodies specific for MDV membrane protein gp82. Three Mabs (Mab2.1, 3.7, and 5.7) were produced by using TrpEgp82 fusion protein as the immunogen that was expressed by recombinant pATH expression vector pATHgp82 in Escherichia coli. Indirect immunofluorescence assay (IFA), immunoprecipitation, and Western blot analysis were used to determine the characteristics of gp82. All of the Mabs reacted with gp82 protein irrespective of its conformation. The gp82 protein was predominantly anchored on the surface membrane of a chicken embryo fibroblast (CEF) infected with serotype 1 MDV (MDV-1). There was no detectable immunofluorescence staining in the cytoplasm or nucleus in the MDV-1-infected CEFs. These results indicate that gp82 is a membrane protein. The distribution pattern of immunofluorescence staining of gp82 varies between CEFs infected with the low passage MDV-1 isolate Md11, and those infected with a high passage derivative, Md11/75c. In SB-1 (Serotype 2 MDV [MDV-2]) and Turkey herpesvirus (HVT) (serotype 3 MDV [MDV-3]) infected CEFs, gp82 was not detected by immunoprecipitation, Western blot, or IFA using both monoclonal and polyclonal antibodies. These results suggest that gp82 in serotype 2 or 3 has a modified epitope, or that the gene is permanently repressed.

The influence of age on the response of ring-necked pheasants to infection with marble spleen disease virus.

Ring-necked pheasants that were negative for maternal antibody against type II avian adenoviruses were orally inoculated with 5.0 x 10(2) tissues-culture-infective doses of marble spleen disease (MSD) virus at 1-week intervals through 6 weeks of age, and at 9 and 13 weeks of age. Groups of four virus-inoculated birds and two control birds were necropsied at 4, 6, 8, and 10 days postinoculation, and the spleens were evaluated for gross and microscopic lesions. No lesions consistent with MSD were present in birds inoculated at 1, 2, 3, or 4 weeks of age. A single bird in the group inoculated at 5 weeks of age had gross and microscopic lesions of MSD. Five birds in the group inoculated at 6 weeks of age had lesions of MSD. The patterns of lesion development in the 6-week-old birds were similar to those produced in the 9- and 13-week-old birds inoculated with MSD virus. The reason for the lack of gross or microscopic lesion development during the first 4 weeks of life is unknown.

The pathogenesis of quail bronchitis.

To determine the fate of virus and characterize the development of lesions, 1-week-old bobwhite quails (Colinus virginianus) were inoculated intratracheally with 10(6) mean tissue-culture-infective doses of quail bronchitis virus. Quails were killed and necropsied sequentially at 2, 4, 8, 16, and 24 hours postinoculation (PI) and on days 2-10 PI. Virus was first isolated from the lung as early as 2 hours PI, from cecal tonsils and bursa of Fabricius 4 hours PI, and from spleen and liver 8 hours PI. Tissue virus titers were highest on days 4 to 6 PI, corresponding with the severity of histologic lesions. Viral inclusions were present in tracheal mucosal epithelium by day 2 PI. On day 3 PI, tracheal epithelium was deciliated, formed an irregular luminal border, and had more frequent inclusions. On days 4 and 5 PI, tracheal epithelium was partially desquamated, but there were minimal leukocytic infiltrates. Bronchiolar epithelium underwent similar changes, but the leukocytic infiltration was more intense and included lymphocytes and heterophils. There was extension of leukocytic infiltrates into surrounding lung that was most extensive on day 3 PI. Hyperplasia of splenic macrophages was first identified on day 2 PI and peaked by day 5 PI.