Showing papers in "Avian Diseases in 1983"

Evaluation of the heterophil/lymphocyte ratio as a measure of stress in chickens.

Abstract: The number of lymphocytes in chicken blood samples decreased and the number of heterophils increased in response to stressors and to increasing levels of corticosterone in the chicken feed. The ratio of heterophils to lymphocytes was less variable than the number of heterophil or lymphocyte cells, and the range of values for this ratio was greater than the range of values for heterophils and lymphocytes among control and experimental groups. The heterophil/lymphocyte ratio appears to be a more reliable indicator of levels of corticosterone in the feed and to social stress than were the plasma corticosteroid levels.

Characteristics of Marek's disease viruses isolated from vaccinated commercial chicken flocks: association of viral pathotype with lymphoma frequency.

Abstract: Fifty-three Marek's disease (MD) virus (MDV) isolates were obtained from turkey-herpesvirus-vaccinated broiler or layer flocks with excessive MD losses, from control field flocks without excessive MD losses, and from laboratory collections. Twelve isolates were typed as very virulent (vvMDVs) on the basis of excessive pathogenicity for vaccinated chickens, 31 were typed as virulent (vMDVs), and 10 were typed as nonpathogenic (npMDVs). The npMDVs could be distinguished from turkey herpesviruses by cultural and serologic criteria. Compared with standard vMDVs, the vvMDVs appeared clearly more pathogenic; they caused greater depression in body and bursal weights and induced more deaths through the early mortality syndrome, more lymphomas, and more visceral and fewer neural lymphomas in susceptible and resistant chickens. However, no antigenic differences between vvMDVs and vMDVs were detected. The vvMDVs were obtained from both broiler and layer flocks in five widely separated states but may only recently have become prevalent, since none were represented among 10 MDV isolates obtained before 1975. The frequency of isolation of vvMDVs from flocks with excessive MD losses (9/27) was threefold higher than that from control flocks (1/10), suggesting an association of this viral pathotype with vaccine breaks. The npMDVs were also widely distributed but were isolated only from control flocks, thus suggesting that npMDVs may augment turkey-herpesvirus-induced vaccinal immunity.

Epizootiology of avian influenza--simultaneous monitoring of sentinel ducks and turkeys in Minnesota.

Abstract: Isolation-reared mallards (Anas platyrhynchos) were placed on ponds in turkey-rearing areas in Minnesota, and their cloacae were periodically swabbed to attempt isolating virus from embryonated chicken eggs. Nearby turkeys were sampled by taking cloacal and tracheal swabs as well as blood samples. Hemagglutinating viruses were identified at the National Veterinary Services Laboratory, U.S. Department of Agriculture, Ames, Iowa. During this two-year study, the weekly influenza virus-isolation rate from ducks varied from 0 to 24.4%. A total of 213 influenza viruses were isolated from the ducks. Twenty-six influenza virus subtypes were detected. Ninety-seven flocks of turkeys were diagnosed as having influenza by virus isolation and/or serology. Eight influenza virus subtypes were involved in the turkey outbreaks, and seven of these were also detected in the ducks and/or other avian species. The weekly infection rate of the sentinel ducks correlated directly with observations of wild ducks at the monitoring sites. Influenza virus was isolated from water samples collected near the sentinel duck sites during the study.

Identification and serological differentiation of several reovirus strains isolated from chickens with suspected malabsorption syndrome.

Abstract: Five virus strains designated CO8, 43A, 45, 81-5, and 82-9 were isolated from the intestines of 3-to-6-week-old broilers showing signs and lesions consistent with malabsorption syndrome. The strains were identified as reoviruses based on their effect on chicken embryo kidney cells, morphology, chloroform, iododeoxyuridine and heat sensitivity, hemagglutination ability, pathogenicity in embryos, and replication cycle. Relatedness values, determined by cross-neutralization studies, revealed that the strains could be classified into three distinct serotypes. Two of the serotypes did not share antigenic relationship with strain S1133, which has been used in the field to vaccinate chickens against viral arthritis.

Field trials with a bivalent vaccine (HVT and SB-1) against Marek's disease.

Abstract: White leghorn chickens on five farms were given a bivalent Marek's disease (MD) vaccine consisting of turkey herpesvirus (HVT) and SB-1 (a nononcogenic MD virus); other chickens received only HVT. The farms had histories of "vaccination failures," presumably owing to an exceptionally virulent challenge MD virus. The bivalent vaccine uniformly protected chickens better than HVT alone between 12 and 16-20 weeks of age, when serious MD losses occurred. During that period, total mortality in groups given both viruses ranged from 0.39 to 1.26% (mean 0.86%), whereas that in HVT-vaccinated groups not exposed to SB-1 varied from 1.92 to 7.44% (mean 3.43%). Chickens in pens or rows with close contact to those given bivalent vaccine also had low MD mortality rates (0.46-1.06%, mean 0.77%), probably from the spread of SB-1.

Rapid serological profiling by enzyme-linked immunosorbent assay. I. Measurement of antibody activity titer against Newcastle disease virus in a single serum dilution.

Abstract: An enzyme-linked immunosorbent assay (ELISA) was developed to measure specific antibody activity in sera of chickens exposed to Newcastle disease virus (NDV). A near-linear relationship existed between the log of the corrected absorbance of antisera at a single working dilution and the corresponding observed serum titers as determined by a standard serial-dilution method. Regression analysis was used to construct a standard curve and extract an equation from this relationship. The equation was used to convert corrected absorbance readings of the single working dilution directly into predicted ELISA antibody activity titers. In a comparative study, a correlation (P less than 0.01) was found between ELISA and hemagglutination-inhibition (HI) antibody titers to NDV. ELISA titers were as much as 160 times greater than the HI titers. ELISA was also able to detect much lower levels of antibody activity than the HI test.

Maternal antibody and its effect on infectious bursal disease immunization.

Abstract: Chickens vaccinated with infectious bursal disease virus (IBDV) early in life and revaccinated with an inactivated, oil-adjuvant IBDV vaccine at 18 weeks of age produced and maintained high levels of virus-neutralizing (VN) antibody through 10 months of lay. VN-antibody titers of chicks hatched from eggs laid during the same period closely matched the average VN-antibody titers of the dams. A sequential study of the decline rates of IBDV maternal antibody (MAB) in unvaccinated and IBDV-vaccinated chicks showed that the vaccine virus did not accelerate the antibody depletion rate in vaccinated chicks. Chicks carrying high IBDV MAB showed no active immune response to vaccination with commercial IBDV vaccines. They were also refractory to a pathogenic field isolate of IBDV (FV). However, chicks with low levels of MAB responded to both vaccine virus and the FV, although their response to vaccine virus was milder and delayed.

Pathology of the Skeleton and Tendons of Broiler Chickens Reared to Roaster Weights. I. Crippled Chickens

Abstract: The incidence of cripples among broiler chickens kept until 74 days of age was greatest in chickens fed ad libitum and kept in batteries. The incidence was lower in chickens kept in floor pens and was reduced by feed restriction. Crippling was due to long-bone distortion, rupture of the gastrocnemius tendon, and spondylolisthesis. Long-bone distortion was the most common defect and could be divided into valgus and varus deformation. The former was more important in chickens less than 7 weeks of age, and the latter was more important in older chickens. Tibial dyschondroplasia was found in some chickens with long-bone distortion, and the possible significance of this abnormal cartilage as a cause of long-bone distortion is discussed.

Micro neuraminidase-inhibition assay for classification of influenza A virus neuraminidases.

Abstract: SUMMARY A neuraminidase-inhibition (NI) assay performed in microtiter plates is described. This micro-NI assay is a modification of the NI assay recommended by the World Health Organization. It reduces the quantity of reagents required and permits antigenic classification of many isolates simultaneously. To determine the accuracy and sensitivity of this micro-NI assay, 110 influenza A viruses, representing all subtypes, based upon the nine known neuraminidases (NAs), were classified by both the micro-NI and macro-NI assays in two separate laboratories. The NAs were identified accurately by the micro-NI assay. Virus mixtures were detected by both assays, although the macro-NI was clearly more sensitive. The micro-NI assay was also suitable for testing sera for the presence of antibodies to the NAs. Although the micro-NI assay did not provide the quantitation of the macro-NI assay, it did prove to be a rapid method for virus classification and antibody studies on influenza A viruses.

Evaluation and use of a micro-broth dilution procedure for testing sensitivity of fermentative avian mycoplasmas to antibiotics.

Abstract: A micro-broth dilution procedure is described for testing the sensitivity of glucose-fermenting avian mycoplasmas to antibiotics. A systematic evaluation was made of potential sources of variation that could affect the reliability of this procedure. Strain WVU 1853 of Mycoplasma synoviae (MS) was used as a standard culture and was tested against the antibiotics erythromycin, spiramycin, streptomycin, tetracycline, tiamulin, and tylosin. Inoculum density, duration of incubation before the test was read, and initial pH of the medium significantly affected test results. Type of serum and concentration of pig serum in the medium had little effect, provided the test was read when the phenol red indicator in the medium of a culture control (without antibiotic) had changed from deep red (pH 7.8) to orange-yellow (pH 7). The presence of bacterial inhibitors in the medium, the solvents used to dissolve some antibiotics, the use of thawed or actively growing cultures, and the number of passages of the culture before testing did not appear to be significant causes of test variation. By controlling important sources of variation, a standardized test was developed that gave reproducible results. The standardized test was used to determine the sensitivity to antibiotics of 49 strains of M. gallisepticum (MG), eight strains of MS, five strains of M. pullorum, seven strains of M. gallinaceum, and one strain of M. columborale. Minimum inhibitory concentrations of the macrolide antibiotics were lower for the majority of MG strains than for the other Mycoplasma species tested. However, some strains of MG showed acquired resistance to the macrolide antibiotics. These strains also showed increased resistance to lincomycin and tiamulin.

Virus isolations from pet birds submitted for importation into the United States.

Abstract: From October 1973 to September 1981, 2,882,111 birds were offered for importation into the United States. All were quarantined for 30 days, and specimens were submitted to the laboratory for virus-isolation studies. Viruses were isolated from specimens from 26.3% (598/2,274) of the quarantined lots of birds. Viscerotropic velogenic Newcastle disease virus (VVNDV) was isolated from 141 lots. Nonviscerotropic velogenic Newcastle disease virus (VNDV) was isolated from six lots. All VVNDV- and VNDV-positive lots were refused entry. The percentage of lots refused entry declined from 31.6% in 1974 to 2.9% in 1981. Mesogenic Newcastle disease virus (NDV) was isolated from three lots, and lentogenic NDV was isolated from 23 lots. Lots positive for mesogenic and lentogenic NDV were allowed to enter the United States. Hemagglutinating (HA) viruses other than NDV were isolated from 24.5% (373/1,521) of the lots imported through privately owned quarantine facilities. Of the 8,563 HA viruses isolated, 1,558 were selected for identification. Forty-six percent were identified as paramyxovirus (PMV)-2, 34% were PMV-3, and 20% were influenza A viruses possessing the hemagglutinin subtypes H3, H4, H7, and H10 and the neuraminidase subtypes N1, N6, N7, and N8. The frequency of PMV-2 and PMV-3 isolations fluctuated from year to year, whereas the frequency of isolations of influenza A viruses decreased from 64% in 1974 to 0.2% in 1981. Viruses that did not agglutinate chicken red blood cells were isolated from 52 lots. Psittacine herpesvirus (Pacheco's disease) was isolated from 25 lots of psittacines. Viruses identified by electron microscopy as reoviruses were isolated from 24 lots.(ABSTRACT TRUNCATED AT 250 WORDS)

The pathogenesis of infectious bursal disease: serologic, histopathologic, and clinical chemical observations.

Abstract: Infectious bursal disease in 35-day-old specific-pathogen-free (SPF) chickens was characterized clinically by its acute onset and brief duration. Clinical signs included depression, anorexia, diarrhea, and polyuria. A detectable precipitin antibody response occurred between 3 and 5 days postinoculation. Evaluation of pooled serum samples obtained from infectious bursal disease virus (IBDV)-infected chickens revealed transient changes in potassium, cholesterol, uric acid, lactate dehydrogenase, serum glutamic-oxalic transaminase, and serum proteins. Individual serum samples analyzed for uric acid concentration indicated that several IBDV-infected chickens had serum uric acid concentrations above the normal comparison range. Histopathologic examination of lymphoid and nonlymphoid tissues from IBDV-infected SPF chickens affirmed that the predominant lesion was lymphoid necrosis in the bursa of Fabricius. Other lymphoid organs were much less severely affected and possessed greater regenerative potential. Nonspecific and relatively mild changes were found in the liver and kidney: hepatic lipidosis and necrosis, renal intratubular crystalline deposits (probably urates), and increased ectopic lymphoid foci. There was no evidence of immune-complex-mediated arteritis/vasculitis in the sartorius muscle or any other tissue examined. Histopathologic and ultrastructural evidence of glomerulonephritis was rare but compatible with acute immune complexemia.

Studies on the pathogenesis of staphylococcal osteomyelitis in chickens. I. Effect of stress on experimentally induced osteomyelitis.

Abstract: SUMMARY A single strain of Staphylococcus aureus was used to study the pathogenesis of osteomyelitis in chickens. The disease was consistently reproduced in 6-week-old broiler chickens when 1 X 105 or more organisms were given intravenously. Severe feed restriction, debeaking, and single or multiple injections of corticosteroids delayed the appearance and decreased the severity of lesions due to staphylococcal infection. This increased resistance was associated with increased numbers of circulating heterophils and monocytes. No correlation between the presence of tibial dyschondroplasia

Survival of Coccidia in Poultry Litter and Reservoirs of Infection

Abstract: SUMMARY The survival of coccidia was studied in poultry litter, dust, soil, and invertebrate animals. The populations of coccidia in litter were recorded during broiler growout in 16 broiler houses and in floor-pen trials involving anticoccidial drugs. The viability of oocysts declined rapidly in poultry litter regardless of the species; it was retained best in 40% moisture at 4 C. Sporocysts from broken oocysts did not survive even short exposure to poultry litter. Survival of oocysts was poorest at temperatures higher than 4 C, regardless of the carrier. In four floor-pen experiments designed to study the efficacy of anticoccidial drugs, the oocyst counts correlated in a general way with lesion scores and performance, indicating the oocyst counts might be useful along with other parameters to judge the effectiveness of drugs. Coccidia were transmitted to susceptible chicks by feeding them darkling beetles, flies, or house dust from poultry houses. More carrier samples were positive during the warmer months. Oocyst counts in litter of commercial poultry houses were very low during the first or last weeks of broiler growout but were high during the normal 3-to-6-week stress period. These results confirm the poor survival of oocysts in poultry litter and suggest that carryover from one flock to the next depends on the survival of a few oocysts in dust or arthropod vectors.

Mycoplasma gallisepticum (MG)--laboratory and field studies evaluating the safety and efficacy of an inactivated MG bacterin.

Abstract: A highly antigenic isolate of Mycoplasma gallisepticum (MG) was utilized in the production of an inactivated, oil-emulsified MG bacterin (MGB). Laboratory tests indicated that the bacterin was capable of protecting chickens from clinical signs of MG caused by intrasinus challenge with the R, S-6, PG-31, or 1150 strain of MG. Vaccinated turkeys also were protected from clinical signs of disease when challenged with MG. Use of the MGB in chickens under laboratory conditions resulted in a reduction in airsacculitis from 44% in nonvaccinates to 10% in vaccinates and further reduced the number of organisms present in the trachea post-challenge. Commercial chickens vaccinated subcutaneously midway or lower in the nape of the neck showed no untoward effects due to the bacterin. Those improperly vaccinated at the base of the skull developed a transient edema around the eye(s). This swelling did not appear to affect the performance of the chickens and had been reabsorbed by the next observation period. Subcutaneous inoculation should be at the mid or lower neck region. Field trials at a commercial egg operation comparing production efficiency showed that chickens vaccinated with the MGB had higher egg production, a greater percentage of eggs graded large and over, a smaller percentage of undergrades, and better feed conversion than chickens vaccinated with a live-culture, low-virulence Conn-F strain vaccine. The results of these studies indicate that the oil-emulsified MG bacterin is safe and highly efficacious.

Optimizing the Enzyme-linked Immunosorbent Assay for Evaluating Immunity of Chickens to Newcastle Disease

Abstract: Experiments employing the various steps and reagents used in the enzyme-linked immunosorbent assay (ELISA) were conducted to produce an ELISA with the highest sensitivity and specificity possible for detecting Newcastle disease antibodies in chicken sera. Of the four types of antigen tested, crude antigen gave inconsistent results. However, an alcohol-precipitated antigen prepared from infectious allantoic-amniotic fluids was as satisfactory as more highly purified virus preparations. Other factors found to be extremely important were a 0.5M concentration of NaCl in the diluent and wash solutions used in the procedure, and a pH of 13 for sensitizing solution for maximum specific binding of the antigen to the microplate plastic wells. A comparison was made between the hemagglutination-inhibition (HI) titers of 550 known chicken sera and the corresponding ELISA values. Although the ELISA is much more sensitive than the HI test, there was a general but not a direct correlation between the two tests. The ELISA did not give more information than the HI test concerning protection against an NDV-induced drop in egg production. Preliminary observations indicated that this ELISA procedure is also applicable for turkey sera.

Embryo Vaccination Against Marek's Disease with Serotypes 1, 2 and 3 Vaccines Administered Singly or in Combination

Abstract: Marek's disease virus (MDV) vaccines of serotypes 1 and 2 administered in 18-day-old embryonated eggs induced better protection against post-hatch challenge at 3 days with virulent MDV than vaccines given at hatch. Embryonal vaccination with a polyvalent vaccine containing equal quantities of serotypes 1 and 2 of MDV and serotype 3 virus (turkey herpesvirus, HVT) was also significantly more effective than post-hatch vaccination. These and earlier results indicate that protective efficacy of single or combined Marek's disease vaccine serotypes against post-hatch challenge at 3 days can be substantially improved if the vaccines are injected into 18-day embryos rather than at hatch. Injection of vaccines of serotypes 1 or 2 into embryonated eggs or hatched chicks did not cause detectable gross or microscopic lesions in chickens. Vaccine viruses of serotypes 1 and 2 could be isolated from spleen cells of chickens 1 week post-vaccination, and the titer of recoverable viruses was higher in chickens that received the vaccines at the 18th day of embryonation than in chickens vaccinated at hatch. Although embryo vaccination with HVT usually provided better protection than post-hatch vaccination against early post-hatch challenge with variant pathotypes of MDV, the protection was poor regardless of vaccination protocol. If challenge with variant pathotypes of MDV was delayed until embryonally or post-hatch HVT-vaccinated chickens were 21 days of age, protection of chickens by HVT was not enhanced. Thus, resistance induced by embryonal vaccination with HVT was qualitatively similar to that induced by post-hatch vaccination with this virus.

Evaluation of the hemagglutination-inhibition test for measuring the response of chickens to avian infectious bronchitis virus vaccination

Abstract: An infectious bronchitis virus (IBV) hemagglutination-inhibition (HI) test was used to assay serum-antibody titers after IBV vaccination of IBV-susceptible specific-pathogen-free broilers and commercial layers. Three-week-old broilers were vaccinated via eye-drop with IBV strains that represent the antigenic spectrum of commercial vaccines--Holland, Massachusetts 41 (41 Ms), Connecticut 46, Florida 18288, or JMK strain--and revaccinated 3 weeks later with either the same or a heterologous strain. Weekly serum samples were tested by IBV HI with homologous and heterologous antigens. Vaccinates, except for those vaccinated with the Holland strain, were HI-positive with homologous but not heterologous antigens by 1 to 2 weeks postvaccination. Sixteen-week-old IBV-vaccinated commercial layers were revaccinated with IBV Holland 52 (H 52) strain and subsequently infected with Arkansas 99 (Ark 99) and SE 17 strains. In contrast to the limited HI cross-reactivity of serum from IBV-vaccinated broilers, there were extensive cross-reactions in HI tests with 41 Ms, H 52, Ark 99, and SE 17 antigens of revaccinated layers. These results demonstrate that the IBV HI test is more strain-specific than previous reports indicate, especially when the test samples are from early postvaccination.

Rapid hematogenous dissemination of Aspergillus fumigatus and A. flavus spores in turkey poults following aerosol exposure.

Abstract: Cultures of blood samples taken from 3-week-old turkey poults exposed to aerosolized spores of either Aspergillus fumigatus or A. flavus for 15 min yielded organisms. Aspergillus fumigatus was also isolated from brain and liver tissue samples taken immediately after exposure. Exfoliated cells from the lungs of 10 poults exposed to aerosolized spores of A. fumigatus were allowed to attach to glass slides in tissue culture. Several types of the fixed and stained cells had attached or ingested spores of A. fumigatus. Macrophages were the predominant cell type with ingested spores, although other cell types may be involved in the transport of spores of A. fumigatus into the blood stream after aerosol exposure.

Infection and immune responses in chickens exposed to Salmonella typhimurium.

Abstract: SUMMARY The transmission of Salmonella typhimurium among adult chickens maintained in wire-floored cages was examined. Within 6 days, organisms had spread from infected seed chickens to the majority of uninoculated chickens. Initially, organisms were found in the intestinal tract alone, but by day 20, all chickens were infected, and most of these had organisms in the liver, spleen, and intestinal tract. Antibodies to whole bacterial cells and lipopolysaccharide were detected in the serum and bile of all chickens from day 24. Clearance of organisms from the tissues was not apparent until after day 33. Cell-mediated immunity to salmonella antigens was also induced in chickens that naturally acquired the infection. The role of these parameters of immunity in the clearance of organisms is discussed.

Development of an attenuated apathogenic reovirus vaccine against viral arthritis/tenosynovitis

Abstract: A fully attenuated apathogenic reovirus vaccine was developed by 235 serial passages of S1133 strain avian reovirus in embryonating chicken eggs and 100 additional passages in chicken embryo fibroblast (CEF) cultures, 65 of which were cultured at 32 C. Chickens with and without maternal antibodies to avian reovirus were vaccinated subcutaneously at 1 day of age and challenged via footpad at 14 days of age. It appeared that the 40th, 66th, and 100th CEF passage levels were apathogenic at doses ranging from 10(2.5) to 10(6.8) TCID50/chick. No gross or microscopic lesions of tenosynovitis developed in vaccinated chicks. Vaccinated chicks were protected against challenge; unvaccinated control chickens were not.

A classification of laboratory strains of avian mycoplasma serotypes by direct immunofluorescence.

Abstract: Direct immunofluorescence (IF) was used to assess cross-reactivity among 41 laboratory strains representing 11 serotypes of avian mycoplasmas. All the strains could be separated into distinct serotypes except the C-O-D-P group, which showed cross-relatedness unlike that demonstrated by other serological methods. With two exceptions, serotype C strains consistently cross-reacted with only the serotype P conjugate; the serotype O strain cross-reacted with the P and C conjugates. The two serotype C exceptions were found to be misclassified, as was the serotype P strain. Direct IF was found to be a quick, reliable method for measuring serological relatedness.

Parvovirus-Like Enteropathy in Missouri Turkeys

Abstract: A viral enteric disease of young turkeys characterized by stunting of affected birds, diarrhea, and increased mortality is described. Eosinophilic intranuclear inclusion bodies were found in the absorptive epithelial cells of the ileum. Electron microscopy of formalin-fixed tissue revealed that the intestinal inclusions contained numerous loosely packed 15-to 20-nm hexagonal particles. The size, shape, and intranuclear location have been used to tentatively identify these particles as parvoviruses.

Differentiation Among Bacteria Isolated from Turkeys with Coryza (Rhinotracheitis)

Abstract: Gram-negative bacteria isolated from turkeys with coryza in the United States, the Federal Republic of Germany, and the Republic of South Africa were compared with known Alcaligenes species and Bordetella bronchiseptica. The turkey isolates were separated into three distinct groups based on biochemical and physiologic tests. Forty of the 68 isolates studied (group I) were different from Alcaligenes sp. and B. bronchiseptica. Isolates in group I produced a heat-labile hemagglutinin and did not grow on Simmons' citrate agar. Isolates in group II (25 isolates) were similar to A. faecalis and A. odorans, grew on Simmons' citrate agar, and did not produce a hemagglutinin. Isolates in group III were B. bronchiseptica. Isolates from groups I and II caused coryza in poults. Group III isolates were not pathogenic.

Development and evaluation of an ELISA for the detection of antibody to infectious laryngotracheitis virus in chickens.

Abstract: SUMMARY An enzyme-linked immunosorbent assay (ELISA) for the detection of antibody to infectious laryngotracheitis (ILT) virus in chickens was developed and compared with the serum-neutralization assay. The ELISA routinely yielded 16-to-32-fold higher titers than the serum-neutralization test. To overcome the requirement for large amounts of purified viral antigen, the microtiter trays were initially coated with an antibody prepared against purified ILT virus. A relatively crude viral preparation could then be used to coat the trays. Sera from specific-pathogen-free chickens less than 12 weeks of age did not show nonspecific binding, although 2.7% of all sera from chickens between 13 and 64 weeks of age had nonspecific activity. The majority of nonspecific reactors came from one highly inbred flock of specific-pathogen-free chickens. A number of modifications of ELISA procedures reported to reduce the nonspecific binding of chicken sera were investigated. Treatment of the serum or the plate and changes in the composition of the diluent did not increase the relative sensitivity of the anti-ILT assay.

Characteristics and Pathogenicity of Two Avian Reoviruses Isolated from Chickens with Leg Problems

Abstract: Two reoviruses identified as 172 and 176 were isolated from the hock of 2-to-3-week-old broiler breeders exhibiting leg problems. Oral-ocular or intraplantar inoculation of day-old specific-pathogen-free or broiler chickens produced severe mortality (60-100%) within 2 to 6 days. The main lesions observed were tenosynovitis as well as necrosis and congestion of the liver, spleen, kidneys, and bursa of Fabricius.

Influenza A outbreaks in Minnesota turkeys due to subtype H10N7 and possible transmission by waterfowl.

Abstract: Avian influenza outbreaks in Minnesota involving the H10N7 subtype occurred on two turkey farms in 1979 and on a third in 1980. The H10N7 (Hav2 Neq1) subtype had not previously been detected in turkeys in Minnesota or reported in the United States. The clinical signs ranged from severe, with a mortality rate as high as 31%, to subclinical. Antigenically indistinguishable viruses were isolated from healthy mallards on a pond adjacent to the turkey farms, suggesting that the virus responsible for the outbreak may have been introduced by feral ducks.

Influence of formulation on the efficacy of experimental oil-emulsion Newcastle disease vaccines.

Abstract: SUMMARY Twenty-one experimental oil-emulsion vaccines with different emulsifier contents, aqueous-to-oil ratios, and antigen concentrations were compared by immunization of 4-week-old chickens. Vaccines that contained oil-phase (Arlacel 80) and aqueous-phase (Tween 80) emulsifiers induced 2-to-4-fold higher hemagglutination-inhibition titers than vaccines with only the oil-phase emulsifier. The emulsion vaccines containing both emulsifiers were also more stable at 37 C and less viscous than those containing only the oil-phase emulsifier. Vaccines that had different aqueous-to-oil ratios and contained different quantities of allantoic-fluid antigen (1.2% to 50% of the vaccine volume) induced similar protection against challenge, but hemagglutination-inhibition titers were proportional to the amount of antigen

Optimization of Parameters for Detecting Antibodies against Infectious Bronchitis Virus Using an Enzyme-Linked Immunosorbent Assay: Temporal Response to Vaccination and Challenge with Live Virus

Abstract: Critical parameters affecting sensitivity and specificity of an enzyme-linked immunosorbent assay (ELISA) for avian infectious bronchitis virus (IBV) were evaluated and optimized. The use of purified IBV as antigen at 50 ng protein/well and high-ionic-strength serum dilution buffer has resulted in a test with minimal nonspecific binding of chicken immunoglobulins and very high sensitivity. Optimum conditions for serum dilution, conjugate dilution, and substrate incubation were determined for minimizing background and nonspecific reactions. The use of this test in a controlled challenge study with chickens vaccinated with live IBV demonstrated its effectiveness in monitoring circulating antibody levels to infectious bronchitis. The IBV ELISA, which is rapid, inexpensive, highly sensitive, and capable of handling very large numbers of samples, should provide the poultry industry with a reliable means for IBV flock monitoring.

Pathogenesis of infectious bursal disease in chickens infected with virus at various ages.

Abstract: Chickens free from infectious bursal disease (IBD) maternal antibody were inoculated with a virulent strain of IBD virus at 1, 5, or 11 weeks of age. Chickens inoculated at 5 weeks developed severe clinical signs and had reduced levels of serum complement within 2-4 days postinoculation, but those inoculated at 1 or 11 weeks did not. However, at 1, 2, 4, and 8 days postinoculation, the rate of virus recovery from different tissues, severity of microscopic lesions, and frequency of detection of viral antigens in lymphoid organs of chickens inoculated at 5 weeks were comparable to those of chickens inoculated at 1 or 11 weeks of age. These findings suggest that age resistance to clinical manifestations of IBD is probably independent of the ability of virus to replicate and induce lesions in the host.