Immune dysfunction following infection with chicken anemia agent and infectious bursal disease virus. II. Alterations of in vitro lymphoproliferation and in vivo immune responses.

To determine the functional impact of alterations in lymphocyte concentrations and ratios following infection with chicken anemia agent (CAA) alone or in combination with infectious bursal disease virus (IBDV) on the immune system of young chickens, in vitro lymphoproliferation assays and in vivo responses to vaccination with several common viral agents were assessed at various time intervals post-inoculation (PI). Concanavalin A (Con A), phytohemagglutinin (PHA) and pokeweed mitogen (PWM) stimulation of splenic lymphocytes (SPL) collected from control birds could not be detected until 10-14 days PI. Infection with CAA was characterized by significantly higher PWM stimulation of SPL at 17 days PI and significantly lower PWM stimulation of peripheral blood lymphocytes (PBL) at 14 days PI, compared with uninfected controls. Concanavalin A and PWM stimulation of SPL was significantly increased in birds inoculated with IBDV alone. Lymphocytes harvested from birds inoculated simultaneously with CAA and IBDV had significantly lower responses. Effects on humoral and cell-mediated immunity following CAA and/or IBDV were determined by evaluating vaccination responses to Newcastle disease virus (NDV), fowl pox virus (FPV) and infectious laryngotracheitis virus (ILTV) during the acute phase of CAA infection (2 weeks PI). Vaccination of birds 2 weeks following CAA infection at 1 day of age resulted in decreased protection against NDV (85.7%) and ILTV (7.1%) challenge compared with protection rates in control birds (100% and 53.3% respectively). Infectious bursal disease virus infection was associated with decreased protection against NDV (60%) only. Concomitant infection at 1 day of age resulted in a greater reduction in NDV challenge protection (33.3%), slightly decreased FPV protection (87.5%), increased numbers of persistent FPV vaccination lesions and increased protection against ILTV challenge (71.4%). Vaccination of birds 2 weeks following CAA infection at 2 weeks of age resulted in slightly decreased NDV humoral antibody, development of persistent FPV vaccination lesions (17%) and increased immunity to ILTV challenge compared with control birds (83.3% vs. 66.7%). Chickens inoculated with IBDV alone displayed a more severe depression in NDV antibody titers and only a slight decrease in ILTV protection. Vaccination following concomitant infection at 2 weeks of age resulted in a higher percentage of FPV persistent vaccination lesions (39%) and greatly enhanced immunity to ILTV challenge (100%).     

Immune function in pheasants experimentally infected with marble spleen disease virus.

Two experiments were conducted to evaluate the effect of marble spleen disease virus (MSDV) infection on the immune response of pheasants. In the first, 15 ring-necked pheasants were inoculated orally with cell-culture-propagated MSDV and 15 received saline (controls). On days 7, 21, and 35 postinoculation (PI), all birds received sheep erythrocytes intravenously. Hemagglutination titers to sheep erythrocytes were determined for serum samples collected weekly for 6 weeks. The virus-inoculated group had significantly (P less than 0.05) lower hemagglutination titers than the control group. In the second experiment, 30 pheasants were allotted into two groups as above. Whole blood was collected from each bird weekly for 5 weeks. The blood was cultured in microtiter plates with or without optimum concentrations of concanavalin A. Five of 10 MSDV-inoculated pheasants had significantly depressed T lymphocyte transformation on either day 7 or day 14 PI. Overall, the depression of T lymphocyte transformation was transient and mild.     

Immune dysfunction following infection with chicken anemia agent and infectious bursal disease virus. I. Kinetic alterations of avian lymphocyte subpopulations.

The potential effect of chicken anemia agent (CAA) alone or in combination with infectious bursal disease virus (IBDV) on the immune system of young chickens was determined by measuring alterations in hematocrit values, lymphoid organ-to-body weight ratios and lymphoid cell concentrations at 4, 7, 10, 14, 17, 21, 28 and 42 days post-inoculation (PI). Lymphocyte subpopulations were identified and counted by flow cytometry using cell suspensions stained with monoclonal antibodies (Mabs) for panlymphocytes (K55), cytotoxic T-cells (CTLA3), T-helper cells (CT3), Ia-expressing cells (P2M11) and macrophages (P7). Chicken anemia agent induced a substantial but transient decrease in hematocrit value, thymus-to-body weight ratio and bursa-to-body weight ratio between 7 and 21 days PI corresponding to a generalized lymphocytopenia in the thymus, bursa and spleen. However, cytotoxic T-cell, T-helper cell and Ia-expressing cell concentrations increased in the bone marrow of birds inoculated with CAA alone or in combination with IBDV during the same time period. T-helper-to-cytotoxic T-cell ratios increased in the thymus and spleen during severe lymphocytopenia, indicating a selective decrease in cytotoxic T-cells. T-helper-to-cytotoxic T-cells ratios increased in the bone marrow, indicating a selective increase in T-helper cell concentrations. The increase in Ia-expressing cells in the bone marrow may be a reflection of increased number of activated T-cells which express Ia antigen. Infectious bursal disease virus alone induced a persistent depression of Ia-expressing cells in the bursa and the spleen and no measurable change in the bone marrow lymphocyte subpopulations. Chickens inoculated simultaneously with CAA and IBDV experienced clinical signs observed in chickens inoculated with each virus separately with a prolonged acute phase prior to recovery or mortality.     

The effects of age, route of exposure, and coinfection with infectious bursal disease virus on the pathogenicity and transmissibility of chicken anemia agent (CAA)

Specific-pathogen-free (SPF) chickens were inoculated with several different concentrations of chicken anemia agent (CAA) by the intra-abdominal, intratracheal, or oral routes. Based on lowered hematocrit values, the birds were most susceptible to CAA introduced by the intra-abdominal route. When SPF chickens were infected with infectious bursal disease virus (IBDV) at 1 day of age, they remained susceptible to CAA up to at least 21 days, whereas birds inoculated with CAA alone were susceptible only at 1 day of age. Infectious bursal disease virus introduced at 1 day of age also increased the susceptibility of birds to contact infection with CAA and resulted in increased mortality rates in CAA inoculates. The response of SPF birds to CAA infection varied following exposure at 1 day of age to two different strains of IBDV (STC and Variant-E). Chicken anemia agent contacts and inoculates infected with the Variant-E strain were affected 1 week earlier by CAA than by STC inoculates, as evidenced by depressed hematocrits. However, the total number of birds affected was similar for both the Variant-E and STC-inoculated chickens. Commercial broiler chickens inoculated at 1, 7, 10, and 14 days of age by non-parenteral routes with CAA or a combination of CAA and IBDV had mean hematocrits that were lower than controls. Several CAA-inoculated birds were considered anemic, with hematocrit values of 25 or less, while uninoculated birds remained within normal ranges.     

Pathogenicity and antigenicity of avian nephritis isolates.

The G-4260, IR-N, M-6, and M-8 strains of avian nephritis virus (ANV) were inoculated orally into 1-day-old specific-pathogen-free chicks of the line PDL-1 for pathological and serological study. Five of 15 chicks inoculated with the G-4260 strain died with visceral urate depositions. One of 15 chicks each inoculated with the M-6 and M-8 strains died with nephrosis and visceral urate deposition, respectively. No chicks inoculated with the IR-N strain died. Mean body weights of ANV-inoculated chicks, except for the IR-N-inoculated chicks, at 14 days postinoculation (PI) were significantly lower than those of control chicks (P less than 0.01). However, interstitial nephritis was observed in all ANV-inoculated birds that were histopathologically examined at 14 days PI. In the serological study, the G-4260 and IR-N strains were classified as the same serotype, and the M-6 and M-8 strains were classified as a different serotype from the G-4260 and IR-N strains. These results indicate that there at least two serotypes of ANV and its strains differ in pathogenicity.     

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.     

Viral and bacterial agents associated with experimental transmission of infectious proventriculitis of broiler chickens.

Proventriculitis of broilers can be reproduced by oral inoculation of day-old chicks with a proventricular homogenate from affected 3-wk-old broilers. The objective of the following studies was to isolate from this homogenate viral and bacterial isolates that could produce proventriculitis. A monoclonal antibody to infectious bursal disease virus (IBDV) was used to precipitate virus from the homogenate. A primary chicken digestive tract cell culture system was also used to isolate virus from a 0.2-microm filtrate of the homogenate, and a bacterium was also isolated from the homogenate. In trial 1, day-old birds were orally inoculated with either proventriculus homogenate or monoclonal antibody immunoprecipitated IBDV (MAB-IBDV). At 4, 7, 14, and 21 days postinfection (PI), 12 birds from each treatment group were subjected to necropsy. In trial 2, day-old birds were orally inoculated with either infectious proventriculus homogenate, suspect virus isolated in cell culture and propagated in embryo livers and spleens, or a bacterial isolate. Twelve birds from each treatment were subjected to necropsy at days 7, 14, 21, and 28 PI. In trial 3, treatments were maintained in negative pressure isolation chambers, and an additional treatment included virus plus bacterial isolate. Twenty-four birds from each treatment were subjected to necropsy at day 21 PI. In trial 1, infectious homogenate decreased body weight and relative gizzard weights at 4, 7, 14, and 21 days PI. Proventriculus relative weight was increased at days 7, 14, and 21 PI, and proventriculus lesion scores were increased at days 14 and 21 PI. Bursa/spleen weight ratios were decreased at day 14, and feed conversion was increased at days 4 and 21. The MAB-IBDV treatment decreased proventriculus and gizzard relative weights at day 4 PI, increased proventriculus lesion scores and bursa/spleen weight ratios at day 14, and decreased heterophil/lymphocyte ratios at day 21. In trial 2, all infected birds had significantly higher mean relative proventriculus weights at 21 days PI and had higher 4-wk mean proventriculus scores as compared with both control groups. In trial 3, birds treated with homogenate and birds treated with both suspect virus and the bacterial isolate had significantly higher proventriculus lesion scores; higher relative weights of proventriculus, gizzard, liver, and heart; lower body weights; and lower relative bursa weights compared with the saline control group. These studies suggest that infectious proventriculitis has a complex etiology involving both viral and bacterial infection.     

Viral replication and lesions in BALB/c mice experimentally inoculated with porcine circovirus isolated from a pig with postweaning multisystemic wasting disease

Eight-week-old BALB/c mice were either sham inoculated (control mice) or were inoculated intraperitoneally (IP) and intranasally (IN) with a single (sPCV mice) or multiple (mPCV mice) doses of porcine circovirus 2 (PCV2). Four control mice and 4 sPCV mice were sacrificed 7, 14, 28, and 42 days postinoculation (PI). All 4 mPCV mice were sacrificed 42 days PI. In addition, 7-day and 14-day pregnant BALB/c mice were either sham inoculated (control mice) or were inoculated IP and IN with a single dose of PCV2. Newborn mice were euthanatized 1, 8, and 15 days after birth. Necropsies were performed on all euthanatized mice and tissues were collected for histopathology, electron microscopy, in situ hybridization, and polymerase chain reaction (PCR). PCV2 replicated in 8-week-old BALB/c mice that were inoculated with PCV2 and caused fetal infection when inoculated into pregnant BALB/c mice at 7 days and 14 days of gestation. PCV was detected by in situ hybridization and PCR in sPCV mice on days 7, 14, 28, and 42 PI; in mPCV mice on day 42 PI; and in newborn mice from mothers inoculated with PCV at 7 days and 14 days of gestation at 1, 8, and 15 days after birth, but not in control mice. No clinical signs or gross lesions were found in sPCV or mPCV mice during the study. Microscopic lesions in sPCV mice and mPCV mice were characterized by expansion of germinal centers in lymphoid organs with large numbers of histiocytic cells and lymphoblasts, apoptosis of histiocytic cells in germinal centers, and mild lymphoid depletion of the paracortex. PCV nucleic acid was detected in the nuclei and cytoplasm of histiocytes and apoptotic cells in germinal centers in lymphoid tissues as well as in the nuclei of hepatocytes in the liver, in the nuclei of renal tubular epithelial cells, and in the cytoplasm of single lymphocytes in the thymus. Congenitally infected mice only had PCV nucleic acid detected in putative Kupffer cells in livers.     

Pathology of avian adenovirus serotypes in the presence of Escherichia coli in infectious-bursal-disease-virus-infected specific-pathogen-free chickens

Ten strains of adenovirus representing 10 serotypes were administered intratracheally to 3-week-old specific-pathogen-free chickens, which also received 2.5 X 10(5) colony-forming units of a pathogenic Escherichia coli intranasally. Those birds had been inoculated by eye drop at 1 day of age with a virulent infectious bursal disease virus (IBDV). Controls consisted of groups of chickens inoculated with: (a) IBDV and E. coli, (b) IBDV only, (c) E. coli only, and (d) no virus or E. coli. Gross pulmonary alterations at 5 days postinoculation (PI) included congestion and consolidation of one or both lungs of a chick inoculated with adenovirus serotype Ind-C and another inoculated with A-2. Histopathologic alterations in the lungs were those of multifocal interstitial and occasionally diffuse pneumonia. All 10 adenovirus serotypes elicited multifocal or diffuse pneumonia and bronchiolitis in one or more of the five birds per group necropsied at 5 days PI. T-8 and A-2 serotypes induced marked to serve diffuse pneumonia within 5 days; Ind-C, Stein, Tipton, 75-1A, B-3, and X-11 incited a mild diffuse pneumonia. In all groups, the pneumonic lesions were more severe 5 days PI than 12 days PI. Tracheitis was incited by Ind-C, Stein, T-8, and A-2 at 5 days PI; the lesions were minimal to marked in severity. None of the four control groups exhibited gross or histopathologic alterations except the two IBDV-infected groups, which exhibited bursal change.     

Immune profile of infectious bursal disease. III. Effect of infectious bursal disease virus on the lymphocyte responses to phytomitogens and on mixed lymphocyte reaction of chickens

A whole-blood-culture technique was used to sequentially evaluated peripheral blood lymphocyte responses to phytohemagglutinin (PHA) and concanavalin A (Con A) of normal chickens and chickens infected at 1 day or 3 weeks of age with infectious bursal disease virus (IBDV). This method had numerous advantages over the more conventional techniques. A comparative study was made on the percentage of inhibition of responses of peripheral blood lymphocytes to PHA and Con A of 1-day- and 3-week-old IBDV-infected chickens. In both groups, there was a minimum inhibition between 3 and 4 weeks postinfection (PI) and a maximum inhibition at 6 weeks PI. A one-way mixed lymphocyte reaction (MLR) was performed using mitomycin-C-treated cells as stimulator cells obtained from chickens of genetically different strains. Lymphocytes from the experimental birds (control, 1-day-infected, and 3-week-infected groups) were used as the responder cells. The results showed that MLR response of the IBDV-infected chickens was significantly reduced compared with those of the uninfected controls. The degree of lowered response was much more severe in chickens infected at 1 day of age than in those infected at 3 weeks of age.     

A model of avian mycobacteriosis: clinical and histopathologic findings in Japanese quail (Coturnix coturnix japonica) intravenously inoculated with Mycobacterium avium

Mycobacterial infections are an important cause of morbidity and mortality in birds and a considerable diagnostic challenge until the disease is advanced. In order to develop more clinically useful antemortem tests, a biological model was created that replicated naturally occurring disease. Japanese quail (Coturnix coturnix japonica; n = 8) were inoculated intravenously with Mycobacterium avium. Two additional birds served as uninoculated controls. Mean survival time of the inoculated birds was 68 +/- 13 days postinoculation (PI). Seven of the eight inoculated birds died naturally. Clinical and postmortem abnormalities in inoculated birds were characteristic of naturally occurring mycobacteriosis. Abnormal clinical findings included decreased activity, feather erection, and sudden death. Mean body weight and packed cell volume declined and mean total white blood cells (primarily heterophils, bands, and monocytes) increased from 28 days PI onward. Similar to birds that are naturally infected with mycobacteriosis, the inoculated birds were thin and had severe hepatosplenomegaly on postmortem examination. All eight birds had lesions in the liver, spleen, intestine, lung, gonads, and serosa. Less commonly affected tissues included bone marrow, thymus, gizzard, heart, pancreas, and brain. Lesions were invariably severe in the liver and spleen. These gross postmortem findings were consistent with natural infections of avian mycobacteriosis. Mycobacterium avium was isolated from the liver, spleen, and intestine of all inoculated birds. Both control birds remained disease free and culture negative. This inoculation protocol is a reliable and practical means of inducing avian mycobacteriosis for further study.     

酵母诱导表达鸡IFN-α抗IBDV效果及其对信号分子PI3K和NF-κB的影响

试验旨在研究酵母表达鸡IFN-α抗传染性法氏囊病病毒（IBDV）的效果及对其淋巴细胞信号分子PI3K和NF-κB p65的影响。将40只10日龄非免疫雏鸡随机分为IFN-α组和空白对照组,持续注射给药3 d后,于第3次给药后第1天开始每天心脏采血,持续3 d,并于最后一次采血后对雏鸡进行攻毒,在攻毒后开始每天心脏采血,连续3 d。通过MTT法检测淋巴增殖活性情况,ELISA测定不同时间段淋巴细胞中PI3K的水平、细胞中总NF-κB p65、细胞核中NF-κB p65蛋白表达含量及IBDV抗原量。结果显示,与对照组相比,攻毒前,IFN-α对淋巴增殖活性、细胞中PI3K和NF-κB p65的表达具有极显著地促进作用（P<0.01）;与攻毒前相比,攻毒后第1和2天IFN-α组淋巴增殖活性、细胞中PI3K和NF-κB p65的表达极显著增加（P<0.01）,IFN-α对IBDV-Ag具有极显著地抑制效果（P<0.01）。这些结果表明,IFN-α可通过增加PI3K激活NF-κB信号通路以增强机体免疫反应,并对IBDV-Ag有显著的抑制作用,本试验为IFN-α免疫增强和抗病毒作用的研究提供科学依据。     

Comparative immunopathogenesis of mild,intermediate, and virulent strains of classic infectious bursal disease virus

Differences in the immunopathogenesis of several strains of infectious bursal disease virus (IBDV) were compared. The strains included a virulent virus (IBDV-IM) and three vaccine viruses that included an intermediate vaccine virus (IBDV-B2) and two mild vaccine viruses (IBDV-Lukert and IBDV-BVM). The most significant differences were found in the systemic effects of these strains. In comparison with other strains, IBDV-IM antigen was detectable for up to 8 days postinfection (PI) in lymphoid tissues that included spleen and cecal tonsils, whereas only a few IBDV-B2- and IBDV-Lukert- and no IBDV-BVM-inoculated birds had detectable IBDV antigen in these tissues. IBDV-IM induced systemic circulating nitrite levels in over 86% of the birds at days 2 and 3 PI. IBDV-IM suppressed most vigorously the splenic mitogenic response on days 3-8 PI. Among the three vaccine strains, IBDV-B2 was the most virulent of the three, inducing a significant suppression of the mitogenic response (P < 0.05) and the most vigorous lesions in the bursa of Fabricius with the highest possible lesion score of 4 at 3 days PI (P < 0.05). IBDV-BVM was the mildest strain, not inducing any detectable lesions in lymphoid tissue at the tested time points. Whereas all IBDV-BVM-inoculated and 67% and 33% of the IBDV-Lukert- and IBDV-B2-inoculated birds, respectively, had detectable IBDV antigen in the bursa at 4 days postchallenge, none of the IBDV-IM-inoculated birds was positive for IBDV by immunohistochemistry. IBDV-IM induced the highest enzyme-linked immunosorbent assay (ELISA) antibody levels detected at days 8-29 PI (P < 0.05) and the best protection against challenge virus replication in comparison with IBDV-B2 and IBDV-Lukert. Only one of five IBDV-BVM-inoculated birds developed anti-IBDV ELISA antibodies at 29 days PI, and none of the birds was protected against IBDV challenge. We speculate that better protection with more virulent strains was due to more systemic antigenic stimulation on the basis of higher replication of IBDV in extrabursal lymphoid tissues. Interestingly, IBDV-IM did not differ from IBDV-B2 and IBDV-Lukert in its ability to induce T cell accumulation in the bursa at 8 days PI and local interferon-gamma induction from days 2 to 5 PI. These results suggested that the local T cell events in the bursa alone may not be indicative of a rapid and protective immune response.     

Effects of live attenuated and killed Salmonella vaccine on T-lymphocyte mediated immunity in laying hens

The impact of live and killed Salmonella vaccines on cell-mediated immunity (CMI) was investigated in 18- and 32-week-old White Leghorn chickens, by assessing splenic lymphocyte proliferation, expression of IL-2 mRNA in concanavalin A (Con A) stimulated cells and flow cytometric analysis of cell subpopulations. Con A and Salmonella enteritidis (SE) flagella induced proliferation of splenocytes were enhanced in the 18- and 32-week-old chickens treated with live vaccine, compared to the corresponding control chickens. Among the killed vaccine treated birds, Con A-mediated response was higher in the 18-week-old chickens compared to the corresponding control birds. Increased proliferation was accompanied by increased CD4 and reduced CD8 and gammadelta T-lymphocytes in the 18-week-old live vaccine treated chickens. Relative expression of IL-2 mRNA in Con A-stimulated splenocytes from 18-week-old birds was not affected by vaccine treatment. Overall, live vaccine was more effective in increasing the lymphocyte proliferation to Con A as well as SE antigen. This enhanced CMI may prove beneficial in protecting chickens against SE infection.     

Experimental transmission of turkey viral hepatitis to day-old poults and identification of associated viral particles resembling picornaviruses.

Turkey viral hepatitis (TVH) was experimentally reproduced in two experiments in 1-day-old poults. In the first experiment, an infectious inoculum was prepared from filtered yolk materials harvested from dead embryonating chicken eggs (ECE) previously inoculated with suspensions of liver and pancreas tissues collected from TVH-affected birds in commercial turkey flocks. One-day-old poults given a yolk-sac inoculation or oral gavage with this preparation developed lesions in the liver and pancreas characteristic of TVH at 20 days postinoculation (PI) in 60% and 14% of the experimentally infected birds, respectively. With the identical inoculum, embryo mortality occurred at 8 and 10 days PI in embryonating turkey eggs (ETE) inoculated into the yolk sac. In the second experiment, an infectious inoculum was prepared from filtered yolk materials from dead ETE harvested in the first experiment. One-day-old poults given a yolk-sac inoculation with this filtered yolk material developed lesions in the liver and pancreas within 5 days PI. At 20 days PI, 67% of the experimentally infected birds had similar lesions. With the inoculum given to these poults, embryo mortality occurred at 6, 8, and 10 days PI in ETE inoculated into the yolk sac. Virus particles 26-28 nm in diameter with icosahedral morphology typical of picornaviruses were identified by EM in the yolk sacs of ETE that died in both experiments, and inoculated ETE that died following passage of filtered suspensions of pancreatic tissues collected from affected birds in the first experiment.     

Studies on orthoreoviruses isolated from young turkeys. II. Virus distribution in organs and serological response of poults inoculated orally

Day-old specific-antibody-negative turkey poults were inoculated orally with cloned turkey reovirus isolate 81-68. Virus reisolations from 11 different tissues revealed widespread distribution at 3, 5, and 7 days postinoculation (PI). Virus was isolated from the intestines until 21 days PI. Virus was isolated from tendons until day 7 PI and again at day 28 PI. Reovirus serum-neutralization antibodies appeared as early as 7 days PI. All inoculated birds showed positive VN serum titers (greater than or equal to 1:20) by day 21 PI. No reovirus was isolated from control poults, and they remained antibody-negative during the entire experiment.     

Chicken anemia agent in the United States: isolation of the virus and detection of antibody in broiler breeder flocks

Chicken anemia agent (CAA) was isolated from broiler chickens in Texas with a blue wing or anemia dermatitis-like syndrome. Specific-pathogen-free chicks inoculated with field material developed anemia, and CAA was isolated in MDCC-MSB1 cells from bone marrow and lymphoid tissue from inoculated chicks. One isolate, designated EF88/78/276, was further characterized. Infectivity of EF88/78/276 was resistant to treatment with chloroform and with heat at 70 C for 5 minutes. EF88/78/276 was indistinguishable from the Cux-1 and Gifu-1 isolates of CAA by cross-neutralization tests. Almost all 1-day-old susceptible chicks inoculated intramuscularly with EF88/78/276 developed anemia, but contact-infected chicks did not. Antibody to CAA was detected in broiler breeder flocks from Texas, the Delmarva peninsula, and Alabama.     

Experimental inoculation of pigeons (Columba livia) with Mycobacterium bovis

The purpose of this pilot study was to determine if pigeons (Columba livia) are susceptible to infection with Mycobacterium bovis by either oral or intratracheal inoculation and to assess their possible role in the lateral transmission of bovine tuberculosis. Six pigeons were orally inoculated with 1.3 x 10(5) colony-forming units of M. bovis, six pigeons were intratracheally inoculated with the same dose, and six pigeons served as noninoculated controls. The study continued for 90 days postinoculation (PI), with groups of birds necropsied at 30-day intervals, and fecal samples and tissues were collected for mycobacterial culture. Two pigeons, one intratracheally inoculated and one orally inoculated, shed M. bovis in their feces at 1 day PI, and one intratracheally inoculated bird shed M. bovis in its feces 60 days PI. Whereas no illness or weight loss was present during the course of the study, 2 of 12 inoculated birds exhibited microscopic lesions of mycobacteriosis, and the organism was isolated from tissues of three inoculated birds. Pigeons are susceptible to infection with M. bovis after high dose inoculation and can shed the organism in their feces for up to 60 days PI; intratracheally inoculated birds appear more likely to become active fecal shedders of M. bovis. Although these were high dose inoculations under experimental conditions, pigeons may potentially play a role in the lateral transmission of bovine tuberculosis between infected and uninfected mammalian hosts.     

Quantitative measures of disease in broiler breeder chicks of different major histocompatibility complex genotypes after challenge with infectious bursal disease virus

Criteria for evaluating genetic differences in resistance and susceptibility to infectious bursal disease (IBD) within a commercial broiler breeder line of chickens were compared. Line A broiler breeder chickens were challenged with graded doses of Animal and Plant Health Inspection Service (APHIS) strain IBD virus (IBDV) and evaluated at 2 time points, 3 days postinoculation (PI) and 10 days PI. Measures obtained at both time points included bursa to body weight, bursa histology, bursa lymphocyte count, and percentage of T cells in the bursa. Furthermore, viral load in the bursa was determined 3 days PI and anti-IBDV antibody titers, 10 days PI. A dose of 50 50% embryo infective dose caused IBD in about half the line A birds at the 10-day time point, and this dose was chosen for further studies. The data were analyzed for correlation among the various measures. Comparison of the 3-day- and 10-day-PI bursa lymphocyte counts indicated that birds challenged with low doses of virus suffered lymphocyte depletion at the 3-day time point, but many or all (depending on the dose) recovered by the 10-day time point. With a viral dose that caused bursal atrophy in about half the birds by 10 days PI, families segregating for 2 major histocompatibility complex (MHC) haplotypes were compared in terms of resistance to IBD. Results indicated that there was no difference among the 3 MHC genotypes in incidence of IBD by any of the disease measures.