Avian infectious bronchitis in specific-pathogen-free chickens: quantitation of serum immunoglobulins by electroimmunoassay.

Immunoglobulin (Ig) levels in serums of individual 6-week-old specific-pathogen-free (SPF) chickens differed markedly. Quantitation by electroimmunoassay showed that the IgG level was quite low at 6 weeks of age (1.3 +/- 0.67 mg/ml), increased gradually with maturity, and by 16-18 weeks of age was 2.6 +/- 1.5 mg/ml. IgM levels were less variable during the same observation period (6-18 weeks, 2.4 +/- 0.50 to 2.2 +/- 0.86 mg/ml). IgA was high initially and decreased with age (6-18 weeks, 0.74 +/- 0.78 to 0.26 +/- 0.06 mg/ml). Single intratracheal vaccination with a moderate dose of live avian infectious bronchitis virus (IBV) and subsequent challenge-exposure with live virus via the respiratory tract did not markedly affect Ig levels. Birds vaccinated parenterally 2 or 3 times with live or killed IBV vaccines had a marked increase in serum IgG after similar challenge-exposure. IgA and IgM levels in vaccinated SPF birds approximated those in control SPF birds throughout the experimental period.

Local antibody response in avian infectious bronchitis: virus-neutralizing antibody in tracheobronchial secretions.

Specific-pathogen-free chickens were tested for local antibody response after respiratory exposure to live avian infectious bronchitis virus (IBV). Tracheobronchial secretions were obtained after intraocular-intratracheal vaccinations with Holland and Massachusetts 41 strains IBV. Low levels of immunoglobulin (Ig)A and IgG virus-neutralizing antibodies were detected in secretions after each of two vaccinations with a moderate dose (10(4) EID50), neutralizing activity in secretions was found mainly in IgG antibody. Only challenge exposure to Holland IBV resulted in a marked secondary secretion antibody response.

Viscerotropic velogenic Newcastle disease in turkeys: immune response following vaccination with either viable B1 strain or inactivated vaccine.

When used as a vaccine, live letogenic B1 Newcastle disease virus (NDV) protects turkeys against challenge-exposure to viscerotropic velogenic NDV (VVNDV). Low-level passively-immune poults were vaccinated one, two, or three times at various intervals and their immunity challenged at various times from 1 to 10 months of age. Newcastle disease virus was isolated readily from either the blood, trachea, or vent of turkeys in all challenge groups (through 5 months of age) on the 3rd to 6th days postchallenge (PC) but after 14 days PC was isolated rarely. Virus was isolated from turkeys that had high titers of serum hemagglutination-inhibition antibodies at the time of challenge. The anamnestic antibody response appeared to be stronger in poults that had low antibody titers prior to challenge-exposure to VVNDV. In a small-scale study with an inactivated VVNDV vaccine, vaccinated poults were protected against challenge with the homologous viscerotropic virus. Parallel control studies on the infectivity of viscerotropic NDV for turkeys indicated that resistance to VVNDV increased with age.

Viscerotropic velogenic Newcastle disease in Turkeys: virus shedding and persistence of infection in susceptible and vaccinated poults.

Susceptible turkeys and turkeys vaccinated with live lentogenic B1 strain Newcastle disease virus (NDV) were inoculated intracularly with viscerotropic velogenic (VV) Fontana strain NDV and studied for virus shedding and persistence of infection. Susceptible poults that survived infection (15%) continued to shed NDV from the intestinal tract up to 46 days postinoculation. Turkeys that were vaccinated with B1 strain NDV did not develop clinical signs when their immunity was challenged with VV Fontana strain virus. Virus was covered up to 53 days postchallenge (PC) from the cloaca of poults that were vaccinated once at 4 days of age and challenged at 1 month of age. Older turkeys that had been vaccinated one to three times did not generally shed virus after 4 days PC. Newcastle disease virus was recovered later in convalescence by the organ-culture method when swabs of trachea and cloaca were negative for virus. Persistent infection was detected as long as 88 days PC in organ cultures of cecal tonsil. Five of seven NDV isolants from organ cultures or from swabs caused fatal disease in chickens.

Viscerotropic velogenic Newcastle disease in turkeys: isolation of Newcastle disease virus from tracheal and cecal tonsil organ cultures.

Tracheal and cecal-tonsil organ cultures were made from vaccinated turkeys that had survived challenge of immunity with viscerotropic velogenic strain of Newcastle disease virus (NDV). Culture fluids were tested to show that latent infections did exist in the vaccinated and challenged turkeys, thus indicating a possible carrier state. NDV was recovered from 6 of 159 turkeys examined. Preliminary tests indicate that 4 isolants are velogenic and 2 are lentogenic.

Viscerotropic velogenic Newcastle disease in turkeys: vaccination against loss of egg production.

Live B1 Newcastle disease virus was administered to young turkeys either intraocularly or by driniking water, or by both methods. Protection against egg production loss was evaluated by challenge-exposure to viscerotropic velogenic Newcastle disease virus in drinking water. During 22 days postchallenge (PC), none of the vaccinated hens had morbidity, whereas 44% of the unvaccinated controls died 6-13 days PC. Percent egg production (PEP) of all groups 1-5 and 6-22 days PC were compared with their levels 1-5 days before challenge. For days 1-5 PC, changes were not significant. For days 6-22 PC, changes for all groups were siginficant lower. The controls had 0 production. Hens vaccinated only at 4 days or at 4 days and again at 4 weeks averaged one-third or less of prechallenge levels but were recovering. Those revaccinated at 4 months maintained 84-91% of their prechallenge levels and were considered satisfactory. Broodiness was a detracting factor in one group of hens vaccinated at 4 days, 4 weeks, and 51/2 months. They averaged two-thirds of prechallenge levels but were in decline.

Enzyme-linked immunosorbent assay for serum antibody to bovine respiratory syncytial virus: comparison with complement-fixation and neutralization tests.

An indirect enzyme-linked immunosorbent assay (ELISA) for the detection of serum antibody to bovine respiratory syncytial virus (BRSV) was developed and compared with complement-fixation (CF) and viral neutralization (VN) tests. Tissue culture-grown viral antigens were used in the tests. Serum samples from various sources were compared, including serum samples from 10 calves which were infected experimentally with BRSV by aerosol exposure. The ELISA compared favorably with the VN test for detecting serologic responses and for detecting passively acquired antibody in young calves. Approximately 98% (109/111) of field serum samples which were positive by the VN test were also positive by ELISA. The ELISA and the CF test both failed to detect early appearing (1 to 4 weeks after exposure) antibody in 2 experimental calves with subclinical infection with BRSV. The CF test appeared to be less specific in that it gave positive reactions with some sera which were negative by both the ELISA and the VN test. The CF test did not detect antibody in 50% of serum samples obtained at the farm from young feeder calves which were positive by both ELISA and the VN test. The ELISA appears to be a sensitive and specific serologic procedure for detecting serum antibody to BRSV and has the advantage of giving test results within several hours, whereas the VN test requires 5 to 6 days for completion.

Isolation of bovine syncytial virus from mesenteric lymph nodes of cattle.

Bovine syncytial virus was isolated from mesenteric lymph nodes of young dairy calves, beef cattle, and mature dairy cattle. Isolations were made in cocultures of lymph node specimens and bovine embryonic lung cells or by subpassage of cocultures in which cytopathic effects were not initially detected. The bovine syncytial viral isolates after storage at -65 C for 3 months in either infected cell cultures of supernate fluids from suspensions or sonically treated infected cell monolayers were usually recovered. Bovine syncytial virus also was recovered from cell cultures after storage for 6 months at -25 C.

Respiratory syncytial virus infection in transported calves.

Nasal swab samples were collected from calves on individual farms in Tennessee and sequentially at an auction barn and at a feedlot to detect respiratory syncytial virus (RSV). In 1976, RSV was isolated from 5 of 225 calves at the auction barn and from 13 of 92 calves examined at the feedlot. Of the 13 isolations, 11 were from calves with acute respiratory tract disease. Most (14/18) calves infected with RSV were also shedding parainfluenza-3 virus in their nasal secretions. Attempts to isolate RSV in the 1977 study were unsuccessful, but there was serologic evidence of RSV infection. Most calves had serum antibody to RSV when examined initially at the farm or at the auction barn. Approximately 46% (46/99) of calves in the 1976 study and 71% (40/56) of calves in the 1977 study had a greater than or equal to 4-fold increase in serum antibody titer to RSV from auction barn to feedlot sample collection.

Development and evaluation of an enzyme-linked immunosorbent assay for bovine antibody to Pasteurella haemolytica: constructing an enzyme-linked immunosorbent assay titer.

A 2-stage strategy was developed and evaluated for estimating serum antibody titer by use of ELISA and a series of dilutions. In stage 1, the linear response region and least-square estimate of the assay line slope were established from 9-point dilution assays. Provided that the reading was within the linear response region, this information was used in the stage-2 estimation of titer from a single absorbance reading. Operationally, 2 fixed dilutions were selected, one suitably low and one suitably high, to provide at least one reading within the linear region. The procedure should save considerable time when a large number of assays are to be performed. Stage 1 required approximately twenty 9-point assays, but all subsequent assays required only 2 fixed dilutions.

Colonization of the nasal passages of calves with Pasteurella haemolytica serotype 1 and regeneration of colonization after experimentally induced viral infection of the respiratory tract.

Healthy nonstressed calves were inoculated intranasally with or subjected to aerosol exposure to Pasteurella haemolytica serotype 1. Only 4 of 28 calves harbored the bacterium in enough numbers to be isolated from the nasal passages for more than 7 days. After apparent clearing from the nasal passages, 8 calves were inoculated intranasally with infectious bovine rhinotracheitis virus; 2 of these calves shed the P haemolytica during clinical illness due to the virus. The remaining 20 calves were aerosol-exposed to parainfluenza-3 virus; 6 of these calves shed P haemolytica during clinical illness due to the parainfluenza-3 virus.

Pasteurella haemolytica serotype 1 colonization of the nasal passages of virus-infected calves.

Nasal passages of calves with a virus-induced respiratory tract disease became colonized by Pasteurella haemolytica serotype 1 after they were inoculated intranasally with P haemolytica. Inoculation with infectious bovine rhinotracheitis virus caused a more severe clinical illness and resulted in a greater degree of colonization with P haemolytica than developed after inoculation with parainfluenza-3 virus. Nasal passages of parainfluenza-3 virus-inoculated calves were colonized to a greater degree with P haemolytica than were those of healthy, nonstressed calves. Calves were susceptible to P haemolytica colonization during or shortly after virus-induced illness, even though they had been previously exposed to P haemolytica and had serum antibody and nasal secretion antibody to P haemolytica.

Development and evaluation of an enzyme-linked immunosorbent assay for bovine antibody (IgG) to Pasteurella haemolytica.

The sensitivity of an indirect enzyme-linked immunosorbent assay (ELISA) for bovine IgG serum antibody to Pasteurella haemolytica was compared with that of an indirect hemagglutination (IHA) test. Pasteurella haemolytica serotypes were grown in a chemically defined cell culture medium, and soluble antigens released into the growth medium were used in the ELISA and IHA test. An ELISA with serotype-1 antigen consistently detected antibody in sera that were positive by IHA test (correlation, 99%). Sera reacting with serotype-1 ELISA antigens also reacted with ELISA antigens prepared from other serotypes. Although ELISA titers averaged 5 log2 units higher than IHA titers, plots of titers determined by the 2 methods were approximately linear. Titer increases detected in paired serum samples by either test were similar. The ELISA was more sensitive than was the IHA in detecting colostral IgG antibody in serum of newborn calves. The ELISA uses a simple, stable antigen preparation and detects antibody to P haemolytica serotypes that commonly infect cattle.

Pathogenic relationships of rotavirus, Escherichia coli, and other agents in mixed infections in calves.

Infection with agents interpreted as causing or contributing to diarrhea (rotavirus, coronavirus, enterotoxigenic Escherichia coli, and cryptosporidia) were demonstrated in 24 of 32 newborn calves that had naturally occurring diarrheal disease. The calves were from 12 herds in Iowa. Infections as well as enteric lesions and hypoglobulinemia occurred more frequently among diarrheal calves than among nondiarrheal calves from these same herds. In most calves, infections were mixed; ie, both viruses, one or both viruses plus cryptosporidia, or rotavirus plus enterotoxigenic E coli.