Conglutinin and immunoconglutinin titers in stressed calves in a feedlot.

OBJECTIVE: To determine whether increased conglutinin titers are evident in stressed calves that do not develop respiratory tract disease in feedlots, compared with respiratory tract disease, and to determine the increase in immunoconglutinin titers. ANIMALS: 101 mixed-breed beef calves. PROCEDURE: Calves were processed at 4 farms of origin and allowed to remain with their dams for another 100 days. Calves from each farm were brought to a centrally located order-buyer barn. In a feedlot, 101 calves were assigned to pens and observed daily for clinical signs of acute respiratory tract disease. When sick calves were detected, they were treated with antibiotics and isolated in a pen for 4 days. Conglutinin and immunoconglutinin titers were determined for all calves. RESULTS: During the 28-day study, 73 calves developed respiratory tract disease, whereas 28 calves remained healthy. Mean conglutinin titers differed significantly among calves from the 4 farms. Significant differences were not detected in conglutinin titers among calves on the basis of sex, morbidity, or vaccination status against Mannheimia haemolytica at each farm, the order-buyer barn, or the feedlot on days 8, 15, and 28 after arrival. Immunoconglutinin titers in calves differed significantly among farms and morbidity status. CONCLUSIONS AND CLINICAL RELEVANCE: Mean conglutinin titers in calves do not appear to be associated with the incidence of acute respiratory tract disease; however, increased immunoconglutinin titers appear to be associated with recovery of stressed calves from respiratory tract disease during the first 15 days after arrival in a feedlot.

Coronavirus and Pasteurella infections in bovine shipping fever pneumonia and Evans' criteria for causation.

Respiratory tract infections with viruses and Pasteurella spp. were determined sequentially among 26 cattle that died during two severe epizootics of shipping fever pneumonia. Nasal swab and serum samples were collected prior to onset of the epizootics, during disease progression, and after death, when necropsies were performed and lung samples were collected. Eighteen normal control cattle also were sampled at the beginning of the epizootics as well as at weekly intervals for 4 weeks. Respiratory bovine coronaviruses (RBCV) were isolated from nasal secretions of 21 and 25 cattle before and after transport. Two and 17 cattle nasally shed Pasteurella spp. before and after transport, respectively. RBCV were isolated at titers of 1 x 10(3) to 1.2 x 10(7) PFU per g of lung tissue from 18 cattle that died within 7 days of the epizootics, but not from the lungs of the remaining cattle that died on days 9 to 36. Twenty-five of the 26 lung samples were positive for Pasteurella spp., and their CFU ranged between 4.0 x 10(5) and 2.3 x 10(9) per g. Acute and subacute exudative, necrotizing lobar pneumonia characterized the lung lesions of these cattle with a majority of pneumonic lung lobes exhibiting fibronecrotic and exudative changes typical of pneumonic pasteurellosis, but other lung lobules had histological changes consisting of bronchiolitis and alveolitis typical of virus-induced changes. These cattle were immunologically naive to both infectious agents at the onset of the epizootics, but those that died after day 7 had rising antibody titers against RBCV and Pasteurella haemolytica. In contrast, the 18 clinically normal and RBCV isolation-negative cattle had high hemagglutinin inhibition antibody titers to RBCV from the beginning, while their antibody responses to P. haemolytica antigens were delayed. Evans' criteria for causation were applied to our findings because of the multifactorial nature of shipping fever pneumonia. This analysis identified RBCV as the primary inciting cause in these two epizootics. These viruses were previously not recognized as a causative agent in this complex respiratory tract disease of cattle.

Bovine viral diarrhea viral infections in feeder calves with respiratory disease: interactions with Pasteurella spp., parainfluenza-3 virus, and bovine respiratory syncytial virus.

The prevalence of bovine viral diarrhea virus (BVDV) infections was determined in a group of stocker calves suffering from acute respiratory disease. The calves were assembled after purchase from Tennessee auctions and transported to western Texas. Of the 120 calves, 105 (87.5%) were treated for respiratory disease. Sixteen calves died during the study (13.3%). The calves received a modified live virus BHV-1 vaccine on day 0 of the study. During the study, approximately 5 wk in duration, sera from the cattle, collected at weekly intervals, were tested for BVDV by cell culture. Sera were also tested for neutralizing antibodies to BVDV types 1 and 2, bovine herpesvirus-1 (BHV-1), parainfluenza-3 virus (PI-3V), and bovine respiratory syncytial virus (BRSV). The lungs from the 16 calves that died during the study were collected and examined by histopathology, and lung homogenates were inoculated onto cell cultures for virus isolation. There were no calves persistently infected with BVDV detected in the study, as no animals were viremic on day 0, nor were any animals viremic at the 2 subsequent serum collections. There were, however, 4 animals with BVDV type 1 noncytopathic (NCP) strains in the sera from subsequent collections. Viruses were isolated from 9 lungs: 7 with PI-3V, 1 with NCP BVDV type 1, and 1 with both BVHV-1 and BVDV. The predominant bacterial species isolated from these lungs was Pasteurella haemolytica serotype 1. There was serologic evidence of infection with BVDV types 1 and 2, PI-3V, and BRSV, as noted by seroconversion (> or = 4-fold rise in antibody titer) in day 0 to day 34 samples collected from the 104 survivors: 40/104 (38.5%) to BVDV type 1; 29/104 (27.9%) to BVDV type 2; 71/104 (68.3%) to PI-3V; and 81/104 (77.9%) to BRSV. In several cases, the BVDV type 2 antibody titers may have been due to crossreacting BVDV type 1 antibodies; however, in 7 calves the BVDV type 2 antibodies were higher, indicating BVDV type 2 infection. At the outset of the study, the 120 calves were at risk (susceptible to viral infections) on day 0 because they were seronegative to the viruses: 98/120 (81.7%), < 1:4 to BVDV type 1; 104/120 (86.7%) < 1:4 to BVDV type 2; 86/120 (71.7%) < 1:4 to PI-3V; 87/120 (72.5%) < 1:4 to BRSV; and 111/120 (92.5%) < 1:10 to BHV-1. The results of this study indicate that BVDV types 1 and 2 are involved in acute respiratory disease of calves with pneumonic pasteurellosis. The BVDV may be detected by virus isolation from sera and/or lung tissues and by serology. The BVDV infections occurred in conjunction with infections by other viruses associated with respiratory disease, namely, PI-3V and BRSV. These other viruses may occur singly or in combination with each other. Also, the study indicates that purchased calves may be highly susceptible, after weaning, to infections by BHV-1, BVDV types 1 and 2, PI-3V, and BRSV early in the marketing channel.

Effects of tilmicosin treatment on Pasteurella haemolytica organisms in nasal secretion specimens of calves with respiratory tract disease.

OBJECTIVE: To determine the effect of tilmicosin treatment on number of Pasteurella haemolytica (PH) organisms in nasal secretion specimens of calves with respiratory tract disease. ANIMALS: 206 British mixed-breed beef calves, 2 to 5 months old. PROCEDURE: In 2 separate studies of outbreaks, calves (study 1, n = 101; study 2, n = 105) that developed respiratory tract disease after transport to a feedlot were treated with tilmicosin. Nasal secretion specimens were examined for PH organisms to determine the status of colonization. RESULTS: In both studies, PH serotypes A1 and A6 were isolated. In study 1, tilmicosin treatment eliminated or markedly reduced the number of PH organisms in calves on days 1, 4, and 5 after treatment. In study 2, tilmicosin treatment eliminated PH organisms in calves on days 1, 2, 5, and 6 after treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Overall, tilmicosin treatment increased the number of culture-positive calves that became culture-negative and decreased the number of culture-negative calves that became culture-positive for up to 6 days after treatment. Tilmicosin treatment decreased the number of PH organisms in nasal secretion specimens, which indicated that fewer PH organisms were available to infect the lungs or to infect other calves. By reducing colonization, prophylactic use of tilmicosin before transport or at the time of arrival at a feedlot is likely to reduce the incidence of acute respiratory tract disease in calves for the initial several days after arrival, which is the period when they are most susceptible to infectious organisms.

Isolation of respiratory bovine coronavirus, other cytocidal viruses, and Pasteurella spp from cattle involved in two natural outbreaks of shipping fever.

OBJECTIVE: To identify cytocidal viruses and Pasteurella spp that could be isolated from cattle involved in 2 natural outbreaks of shipping fever. ANIMALS: 105 and 120 castrated male 4- to 8-month-old feedlot cattle involved in 1997 and 1998 outbreaks, respectively. PROCEDURES: Nasal swab specimens and blood samples were collected, and cattle were vaccinated on arrival at an order-buyer barn from 4 local auction houses. Four days later, they were transported to a feedlot, and additional nasal swab specimens and blood samples were collected. Nasal swab specimens were submitted for virus isolation and bacterial culture; blood samples were submitted for measurement of respiratory bovine coronavirus (RBCV) hemagglutinin inhibition titers. RESULTS: 93 of 105 cattle and 106 of 120 cattle developed signs of respiratory tract disease during 1997 and 1998, respectively, and RBCV was isolated from 81 and 89 sick cattle, respectively, while at the order-buyer's barn or the day after arrival at the feedlot. During the 1997 outbreak, bovine herpesvirus 1 was isolated from 2 cattle at the order-buyer's barn and from 5 cattle 7 and 14 days after arrival at the feedlot, and parainfluenza virus 3 was isolated from 4 cattle 14 days after arrival at the feedlot. During the 1998 outbreak, bovine herpesvirus 1 was isolated from 2 cattle at the order-buyer's barn and on arrival at the feedlot and from 5 cattle 7 and 14 days after arrival at the feedlot, and parainfluenza virus 3 was isolated from 1 animal the day of, and from 18 cattle 7 and 14 days after, arrival at the feedlot. Pasteurella spp was cultured from 4 and 6 cattle at the order-buyer's barn and from 92 and 72 cattle on arrival at the feedlot during the 1997 and 1998 outbreaks, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that RBCV may play a causative role in outbreaks of shipping fever in cattle. More than 80% of the sick cattle shed RBCV at the beginning of 2 outbreaks when the Pasteurella spp infection rate was low.

Antibody responses to respiratory coronavirus infections of cattle during shipping fever pathogenesis.

Antibody responses against respiratory bovine coronavirus (RBCV) infections were monitored in cattle from the onset of a naturally occurring severe shipping fever (SF) epizootic to complete recovery of affected cattle or fatal outcomes. The infection with RBCV was detected in nasal secretions of 86 cattle, and 81 of them developed acute respiratory tract disease, including fatal pneumonia. Cattle nasally shedding RBCV at the beginning of the epizootic experienced characteristic primary immune responses with specific antibodies for hemagglutinin-esterase (HE) and spike (S) glycoproteins. Virus shedding in nasal secretions of the majority of the cattle ceased between days 7 and 14 with the appearance of HE- and S-specific antibodies. Nasal samples and lung tissues from 9 of the 10 fatal cases had high titers of RBCV, but these cattle had only IgM responses to RBCV infections. Cattle remaining negative in RBCV isolation tests entered this epizootic with antibodies against HE and S. Protection against respiratory tract disease was apparently associated with high level of opsonic and virus-neutralizing IgG2. The HE and S glycoproteins were recognized earliest by the bovine immune system while the N protein induced antibody responses during the later stage of initial infection and the early stage of reinfection. The membrane (M) glycoprotein was the least immunogenic of the major viral structural proteins.

In vivo production of neuraminidase by Pasteurella haemolytica in market stressed cattle after natural infection.

Pasteurella haemolytica (Ph) is the most important cause of the bovine acute fibrinohemorrhagic pneumonia that occurs in market stressed calves after shipment to feedyards. Recent characterization of neuraminidase production by these organisms has shown that all 16 serotypes produce an immunologically similar form of the enzyme. Anti-neuraminidase antibody against PhA1 and PhA6 was determined in 101 2- to 5-month-old calves, on their farms of origin, at the order buyer barn (OBB), and through 28 days in the feedyard. Half of the calves were vaccinated with a killed Ph serotype-A1 (PhA1) product. Nasal secretion and tonsil wash specimens were cultured for Ph and Pasteurella multocida (Pm). Serum antibody against PhA1 and PhA6 was measured by indirect hemagglutination (IHA), and anti-neuraminidase antibody was determined by the neutralization assay. At the feedyard, 73 calves had respiratory tract disease. IHA values ranged between 1:2 and 1:1024 for PhA1 and between 1:2 and 1:512 for Ph serotype A6 (PhA6). Forty-two, 24, and 28% of the calves were infected with PhA1, PhA6, and Pm, respectively. Ninety-six percent of the calves experienced an increase in anti-PhA1 neuraminidase antibody when sera drawn on feedyard day 28 were compared with sera drawn on the farm. These data demonstrate that the enzyme neuraminidase is produced in vivo in market stressed cattle after a natural Ph infection.

Rapid spread of a unique strain of Pasteurella haemolytica serotype 1 among transported calves.

OBJECTIVE: To determine the rate and mode of infectious spread of Pasteurella haemolytica among calves maintained under typical conditions during collection, transport, and the first month of feeding. ANIMALS: 101 two- to five-month-old Angus-crossbred calves. PROCEDURE: Samples obtained from cattle prior to and after they were transported to a feedlot were used for isolation and characterization of P haemolytica. Samples were also obtained from additional calves, some of which were sick, and these calves were then commingled with the transported calves for 3 days. A strain of P haemolytica that contains a rare deletion of the 4.2-kilobase streptomycin- and sulfonamide-resistance plasmid was inoculated into both palatine tonsils of 12 calves. Nasal secretions were aspirated from the ventral nasal meatus. Tonsillar wash specimens were procured. Pasteurella haemolytica organisms were quantitatively cultured and identified on the basis of colony morphology and response to specific antisera. Plasmids were isolated by an alkaline lysis procedure and identified by agarose gel electrophoresis. RESULTS: A single plasmid profile was observed from P haemolytica isolated from samples obtained prior to shipment. Commingled calves were shedding P haemolytica containing each known plasmid profile. After shipment, samples contained P haemolytica isolates with each known plasmid profile. The plasmid profile of the unique P haemolytica isolate was recovered from all 12 inoculated calves and 10 other calves. Some calves simultaneously shed P haemolytica isolates with differing plasmid profiles. CONCLUSIONS AND CLINICAL RELEVANCE: Pasteurella haemolytica serotype 1 was horizontally transmitted among calves within days of commingling, which continued after calves were transported to a feedlot.

Respiratory tract disease and mucosal colonization by Pasteurella haemolytica in transported cattle.

OBJECTIVES: To follow incidence of Pasteurella haemolytica (PH) in the upper respiratory tract of healthy calves at the farm and through the marketing process, and to determine the effect of vaccination on PH colonization of the upper respiratory tract and on the incidence of respiratory tract disease (RTD). ANIMALS: 2- to 5-month-old calves (n = 104) from 4 farms. PROCEDURE: Calves were vaccinated with a killed PH serotype-1 product. Nasal secretion and tonsil wash specimens were cultured for PH, and serum antibody was measured by indirect hemagglutination. Calves with RTD were treated with tilmicosin phosphate. RESULTS: At the feedyard, 73 calves had RTD. The incidence of RTD was significantly related to the farm of origin, and was inversely related to the PH serum titer at the farm, but was not influenced by vaccination. Isolations of PH serotype 1, however, were reduced by vaccination. The major serotypes of PH encountered were 1 and 6. CONCLUSION: Vaccination can reduce the frequency of colonization of the upper respiratory tract by PH.

Serotype-specific inhibition of colonization of the tonsils and nasopharynx of calves after Pasteurella haemolytica serotype A1 after vaccination with the organism.

Vaccination of cattle with a tissue culture-derived Pasteurella haemolytica serotype 1 vaccine elicited a serotype-specific inhibition of nasal and tonsillar colonization by the homologous serotype under field conditions. Calves (n = 101) originated from a single farm, where half the calves were vaccinated. The calves were delivered to an order-buyer barn 105 days later, and given a second dose of vaccine. At the order-buyer barn, calves were mixed with 27 calves, some of which had clinical signs consistent with respiratory tract disease. Also 12 of the original calves were infected with P haemolytica serotype 1 by tonsillar instillation. After 6 days at the order-buyer barn, calves were shipped 1,600 km by truck to a feedyard, and arrived the next day. Tonsillar wash and nasal secretion aspiration specimens were collected for culture of P haemolytica on days 1, 8, and 29 at the feedyard. Inhibition of colonization was evidenced by lower frequency of isolations from the vaccinates than from the nonvaccinates after transport to the feedyard. Selectively lowering the frequency of colonization by P haemolytica serotype 1 could reduce losses attributable to pneumonic pasteurellosis.

Serum antibody response to purified Pasteurella haemolytica capsular polysaccharide in cattle.

Capsular polysaccharide (CP) of Pasteurella haemolytica, biotype A, serotype 1, was purified and combined with saline solution, aluminum hydroxide, and Freund's incomplete (oil) adjuvant. Three groups of calves were administered the various antigen preparations. The CP in saline preparation was also administered to 5 mature cows. Second injections were given 4 weeks after the first. Weekly obtained serum samples were analyzed for P haemolytica-specific antibody, using the indirect hemagglutination assay, and CP-specific antibodies were detected, using an isotype-specific ELISA. Purified CP stimulated production of CP-specific IgM, IgG1, and IgG2 in calves and predominantly IgM and IgG1 in mature cows. Significant increases in CP antibody titers were not observed after the second injection of CP antigen in either calves or mature cows. The CP in oil adjuvant stimulated the highest mean CP-specific IgG1 and IgG2 responses, whereas the CP in aluminum hydroxide adjuvant stimulated the highest mean CP-specific IgM response.

Identification of Pasteurella haemolytica A1 isolates from market-stressed feeder calves by use of enzyme and antimicrobial susceptibility profiles.

An epidemiologic study of Pasteurella haemolytica serovar 1 (Ph1) in market-stressed feeder calves from 7 farms in eastern Tennessee was conducted. The nasal mucus of each calf was cultured sequentially at the farm of origin (day 0), at an auction market (day 133), and at a feedyard in Texas (days 141, 148, 155, and 169). Of the 103 calves tested, 77 were culture-positive, including 1 on day 0, 1 on day 133, 20 on day 141, 57 on day 148, 50 on day 155, and 14 on day 169. From the 143 Ph1 isolates, 20 enzyme profiles were determined by use of a commercial enzyme system that detects 19 enzymatic reactions; 4 antimicrobial susceptibility profiles were obtained, using the disk-diffusion method, which evaluated susceptibility to 11 antibacterial drugs. All isolates were positive for acid phosphatase and alkaline phosphatase, but were negative for alpha-galactosidase, alpha-mannosidase, beta-glucosidase, beta-glucuronidase, cystine aminopeptidase, N-acetyl-beta-glucosaminidase, and trypsin. Other positive enzyme reactions included: leucine aminopeptidase, 140 Ph1 isolates; phosphohydrolase, 90 isolates; alpha-fucosidase, 63 isolates; esterase (C4), 59 isolates; valine aminopeptidase, 30 isolates; esterase lipase (C8), 24 isolates; beta-galactosidase, 2 isolates; and alpha-glucosidase, chymotrypsin and lipase (C14), 1 isolate each. Thirty-four Ph1 profiles were identified, using combined enzyme and antimicrobial susceptibility profiles. The data indicate that the strains isolated during the feedyard period may have been determined more by farm of origin (P < or = 0.001) than by habitation with calves from other farms while in the feedyard.(ABSTRACT TRUNCATED AT 250 WORDS)

Specificity of bovine serum antibody to capsular carbohydrate antigens from Pasteurella haemolytica.

A more complete understanding of the bovine immune response to antigens of Pasteurella haemolytica biotype A, serotype 1, will improve control of bovine respiratory disease (BRD). Sera were obtained from blood samples of calves as they transited the market system of eastern Tennessee and were transported to a feedlot in Texas. The clinical histories and performance data were recorded and compared with serologic findings. The calves underwent a natural challenge of BRD. Serologic and bacteriologic evaluation indicated that P. haemolytica A1 was a significant component of the challenge. Serum antibody titers against P. haemolytica A1 capsular antigens (in enzyme-linked immunosorbent assay and hemolysin-in-gel test) increased by day 15 and continued at high levels through day 56. The animals that remained free of BRD had higher initial serum antibody concentrations than those that succumbed to BRD. The specificity of the immunoglobulin G subclass 1 (IgG1) anticapsular antibody to P. haemolytica A1 increased from day 8 to day 29 as evidenced by a decrease in P. haemolytica A2 absorption inhibition from 60% (day 8) to 15% (day 29). However, IgA, IgG2, and IgM were more serotype specific on both days 8 and 29. There were no significant changes in anti-P. haemolytica A2 antibody titers. Both in vitro complement-dependent bacteriolysis and C3 deposition on the surface of the bacteria increased significantly (P less than 0.01) in a serotype-specific fashion from day 8 to day 29. These calves showed a humoral immune response to capsular polysaccharide antigens of P. haemolytica A1. Such a response may be an important component of immunity to BRD.

Total and antigen-specific serum immunoglobulin isotype concentrations in hyperimmunized cattle that have undergone plasmapheresis.

The effects of prolonged plasmapheresis of cattle on total and antigen-specific immunoglobulin production were evaluated. Five adult cows were hyperimmunized by repeated IV administration of live, logarithmic-phase Pasteurella haemolytica A1 organisms. Three of the cows underwent plasmapheresis daily for 3 weeks. From 2 cows, serum was only obtained periodically. Anti-P haemolytica antibody was assayed by indirect hemagglutination and a kinetic-augmented, antigen-capture ELISA for capsular polysaccharide and lipopolysaccharide/outer membrane protein antigens. Total serum immunoglobulin concentration was determined for IgM, IgG1, and IgG2 by primary radial immunodiffusion. Anti-P haemolytica A1 activity increased rapidly after immunization. After beginning plasmapheresis, the antigen-specific antibody activities remained nearly constant. In general, antilipopolysaccharide/outer membrane protein activity (in terms of concentration) was higher than anti-capsular polysaccharide activity and was not affected as much by the plasmapheresis. Total serum Ig concentration decreased transiently by a small amount after beginning plasmapheresis.

Antibody complement-dependent bacteriolysis in experimentally induced pasteurellosis in mice.

Affinity-purified bovine immunoglobulin isotypes were bacteriolytic for Pasteurella haemolytica biotype A, serotype 1 (PHA-1). This bacteriolysis was specific and complement-dependent. The IgM and IgG1 were the most active isotypes in the classic complement cascade. These isotypes also induced bacteriolysis through the alternative complement cascade. The comparative bacteriolytic activities of IgG1 and IgM were equal within each cascade; however, the bacteriolytic activities of IgG1 and IgM were lower in the alternative cascade than in the classical cascade. The IgG2 was more bacteriolytic than IgA in the classic and alternative complement pathways. Bovine immunoglobulins passively protected C57BL/6 mice from experimentally induced pasteurellosis. There were no major differences in the protection among hyperimmune sera, purified IgM, or purified IgG. Mice were protected from PHA-1 by approximately 1.9 micrograms of IgG and 1.2 or 0.1 micrograms of IgM. Elimination of murine complement with cobra venom factor 3 reduced PHA-1 clearance in passively immunized C57BL/6 mice. The protective effect of IgM mediated resistance was highly dependent on an intact complement system. The intact complement cascade was associated with enhanced clearance of PHA-1 from the liver. Although PHA-1 was susceptible to antibody complement-mediated bacteriolysis in vitro, the dependence on an intact complement cascade was not absolute in experimentally induced murine septicemic pasteurellosis.

Antibodies to Pasteurella haemolytica somatic antigens in two models of the bovine respiratory disease complex.

Serum samples obtained from feeder calves before and after entry into the market system (days 0 to 7) were assayed for antibodies to Pasteurella hamolytica biotype A, serotype 1 capsular polysaccharide (CPS) and lipopolysaccharide/outer membrane protein (LPSp) by isotype in a kinetic-augmented, antigen-capture ELISA. These test results, plus indirect hemagglutination (IHA) antibody titers, and hemolysin-in-gel test (HIGT) findings were compared with clinical performance data during the initial 4 weeks in the feedlot (receiving period). High concentrations of HIGT antibody, at the point of initial assembly of feeder calves at weaning and during the subsequent 7-day marketing period, were associated with freedom from bovine respiratory disease (BRD) during the receiving period. High or rapidly increasing concentrations of anti-CPS IgG1 during the marketing period were also associated with less BRD. However, high concentrations of anti-LPSp IgG1 during the marketing period were associated with increased BRD during the receiving period. There was no correlation between the concentrations of antibody determined by IHA tests early in the marketing period and freedom from BRD during the receiving period. High concentrations of antibody determined by this test at entry into the feedlot (day 7) were associated with a high incidence of BRD. Calves vaccinated with a P haemolytica bacterin had significantly (P less than 0.05) higher HIGT values and concentrations of anti-LPSp IgG1 and IHA antibody than did nonvaccinated calves on entry into the feedlot (day 7). Vaccination appeared to have little effect on the amount of anti-CPS IgG1. Of all the tests used to quantitate antibody, the HIGT correlated best with clinical performance.(ABSTRACT TRUNCATED AT 250 WORDS)

Immune response to avian leukosis virus determined by the cell-mediated focus-reduction (CEMFOR) assay.

A cell-mediated focus-reduction (CEMFOR) assay was used to determine the sequential development of cell-mediated immunity to avian oncornaviruses and the nature of the cells participating in this immune reaction. Peripheral blood leukocytes of Leghorn chickens that had regressed Rous sarcoma virus-induced tumors or were immune to avian leukosis virus had CEMFOR activity. The response was biphasic early in the infection. Peripheral blood leukocytes from nonimmune chickens or viremic, immunologically tolerant chickens did not have CEMFOR activity. Sera from leukosis virus-immune chickens blocked CEMFOR activity. The early CEMFOR response was mediated by T-cells. The late response was mediated by an adherent cell population possibly augmented by the presence of T-cells.

A live Pasteurella haemolytica vaccine efficacy trial.

A live Pasteurella haemolytica serotype 1 vaccine was used in an efficacy trial conducted on 100 lightweight feeder calves purchased from a Florida ranch. Forty-one calves were inoculated with the vaccine intradermally in the neck. Fifty-nine calves served as nonvaccinated controls. Fourteen days later, the calves were shipped to an order buyer in eastern Tennessee, where the calves were mixed with 60 local calves in a community sale barn for 72 hours. After 3 additional days, the calves were shipped to a research feedlot in Bushland, Tex. They remained in the feedlot for 56 days, and the test was concluded 76 days after vaccination. The P haemolytica vaccine had no significant effect on performance, morbidity, or mortality. There was no significant difference between the vaccinated and nonvaccinated calves in the number of times Pasteurella was isolated. The calves became seropositive to bovine viral diarrhea virus, respiratory syncytial virus, and infectious bovine rhinotracheitis (IBR) virus during the 76-day experiment. All calves initially were seropositive to parainfluenza-3 virus. A virulent outbreak of IBR occurred 30 days after the calves arrived at the feedlot. Before the onset of IBR, the isolation of P haemolytica serotype 1 from nasal turbinates was rare (2 of 500 nasal swabs). After the IBR outbreak, P haemolytica serotype 1 was isolated from 40 of 92 calves.

Role of cell-mediated immunity (CMI) in chickens inoculated with avian leukosis/sarcoma virus.

Immunosuppression of chickens infected in ovo with avian leukosis virus (RAV-1) by the injection of antilymphocyte serum (ALS) did not significantly (P > 0.05) alter the incidence or distribution of lesions in chickens between 3 and 6 months of age as compared to control groups. Antilymphocyte serum treatment of Rous sarcoma virus [RSV (RAV-2)]-infected chickens significantly (P < 0.05) inhibited tumour regression and enhanced tumour metastasis. It was concluded that cell-mediated immunity was not a significant factor in effecting the survival of viraemic chickens Viraemic leukosis virus infected-chickens responded as well as normal chickens to sensitization to Mycobacterium tuberculosis H37Ra. The results were based on in vivo wattle tests and in vitro cell-mediated cytotoxicity assays. It was concluded that subclinical avian leukosis virus infection had no effect on the thymus-dependent lymphocyte (T-cell) population associated with cutaneous delayed hypersensitivity and cell-mediated cytotoxicity.