Complement fixation titers in cattle following intranasal inoculation of Hemophilus somnus.

Five bulls were inoculated intranasally with a live culture of Hemophilus somnus originally isolated from a clinical case of Hemophilus septicemia. Preinoculation and postinoculation blood samples were taken at weekly intervals for nine weeks for measuring complement fixation titers and daily postinoculation temperatures were taken for one week. Three animals had transient fever and slight lethargy was observed in two animals had a transitory rise in complement fixation titers in the second to fifth weeks postexposure while one animal which had been seronegative on preinoculation testing produced little serological response to the organism. The experiment demonstrated that the nasal instillation of young cattle using an originally pathogenic H. somnus isolate is capable of stimulating only transitory complement fixation antibody titer.     

Experimental Haemophilus somnus infection in pregnant cattle

Of five pregnant cows inoculated intravenously with 5 X 10(8) viable 'Haemophilus somnus', one aborted within 5 days and excreted 'H. somnus' from the vagina for a further 7 weeks. A second cow proceeded to full term parturition but both it and its apparently healthy calf persistently excreted 'H. somnus'. The other animals underwent normal full term calvings and 'H. somnus' was not isolated from them or their calves. Lesions attributable to 'H. somnus' were detected only in the aborted fetus which showed an acute generalized inflammatory cell response consistent with a systemic Gram-negative bacterial infection. 'H. somnus' was isolated from all fetal tissues, including the placenta. The fetus and placenta also showed evidence of damage prior to inoculation. The placental damage may have predisposed the fetus and placenta to infection with 'H. somnus'. The placental epithelial cells contained intracytoplasmic organisms with the morphological and antigenic properties of 'H. somnus'.     

Epidemiology of Haemophilus somnus infection in dairy cattle in Quebec.

Serological studies on Haemophilus somnus infection were carried out on 1795 cattle from 231 dairy herds in the province of Quebec. An epidemiological investigation was done in each of the dairy operations. Seroreactivity rate and mean log2 titer for all the sera were 55.4% and 4.1620 respectively. Cattle from eastern regions of Quebec demonstrated the lowest prevalence of H. somnus agglutinins. The percentage of seroreactor animals was 60.3 in herds of 100 cattle or more in comparison to 53.2 in herds of smaller size. About 75% of the animals from 16 herds in which one or more cattle showed nervous manifestations of undetermined origin over a one year period had antibodies to H. somnus. Herds in which respiratory diseases occurred had 59.6% seroreactor animals and herds in which weak calf syndrome was diagnosed over a one year period had 61.4% seroreactor animals. In 87 herds located within 20 km of feedlots, 61.8% of the sera had titers and the mean log2 titer was 4.4813.     

Atypical nervous lesion in Haemophilus somnus infection of cattle

Two cows affected with Haemophilus somnus were examined pathologically. Although manifested lesions were composed of fibrinopurulent meningitis without the usual parenchymatous lesions in the central nervous system, Haemophilus somnus was isolated in pure culture from the cerebral cortex of both cases. Presence of this atypical lesion in the nervous system should be kept in mind for the differential diagnosis of the disease.     

Ovine Haemophilus somnus: experimental intracisternal infection and antigenic comparison with bovine Haemophilus somnus.

Experimental infection was produced by two of four isolates of ovine Haemophilus somnus given by intracisternal inoculation into two to three-month-old lambs. Isolate 2041 (originally obtained from a septicemic lamb in Alberta) caused lethal infection in eight of nine lambs, isolate 67p from the prepuce of a normal lamb produced less acute disease in four of nine lambs, and the other two isolates (93p and 1190) caused no detectable disease. Significant lesions were limited to the brain and spinal cord. Purulent meningitis was characteristic but vasculitis or septicemia were not detected, perhaps due to the route of inoculation. Since a difference in virulence was noted among strains, we analyzed surface proteins thought to be virulence factors of bovine H. somnus. Protein profiles of bovine and ovine H. somnus done by sodium dodecyl sulphate-polyacrylamide gel electrophoresis showed similar patterns for virulent bovine isolates and ovine septicemic isolates. Preputial isolates showed a lower molecular mass major outer membrane protein than septicemic isolates. Antigenic analysis revealed that outer membrane proteins p270, p78, p76, p40, and p39 were detected in both ovine and bovine isolates except for 1190, which was probably not a true H. somnus isolate. Thus the preputial and septicemic isolates of ovine H. somnus were similar to bovine H. somnus in pathogenicity and in surface antigens.     

Isotypic antibody responses in cattle infected with Haemophilus somnus

Bovine antibody responses to Haemophilus somnus were compared on the basis of clinical and bacteriological findings. Serum IgG1 and IgM antibody titres were significantly increased in clinically normal cattle that were bacteriologically positive for H somnus from the nasal or vaginal mucosae compared with clinically normal, negative cows. IgG2 titres did not differ significantly between these two groups. However, IgG2 antibody was significantly higher in animals with H somnus disease (pneumonia or abortion) than in clinically normal cattle (whether bacteriologically positive or negative), while IgG1 and IgM titres did not differ between diseased and bacteriologically positive, clinically normal cattle. These antibody trends were duplicated in experimental H somnus abortion or pneumonia, with the greatest response occurring within the IgG2 subclass. Cattle vaccinated systemically with killed whole H somnus produced a predominant IgG2 response with minimal IgG1 and IgM responses. These results demonstrate that IgG2 antibody is consistently elevated in H somnus disease, and suggest that this response may be useful in discriminating diseased from asymptomatic cattle.     

Adrenal and thyroid dysfunctions in experimental Trypanosoma congolense infection in cattle.

Severe pathological changes were observed in the adrenal and thyroid glands of Zebu (Bos indicus) heifers infected with Trypanosoma congolense. In the adrenal glands, severe inflammatory changes characterised by mononuclear cellular infiltration in the subcapsular areas, zona glomerulosa, zona fasciculata and zona reticularis were observed. In addition, there were hyperaemia, haemorrhage and hyperplasia resulting in increased adrenal weight in the two heifers slaughtered on Days 50 and 70 post-infection (p.i.). In the medullary areas of these two heifers, there was only mononuclear cellular infiltration. In the two heifers slaughtered on Day 113, localised mononuclear cellular infiltration was observed in addition to cortical cell depletion and fibrosis, resulting in reduced adrenal weight when compared with the controls. In the thyroid glands of the infected heifers, gross enlargement of the follicles filled with pale staining colloids were observed in association with squamous metaplasia of the follicular epithelium and fibroplasia. Serum cortisol concentrations showed an appreciable but non-significant increase (P less than 0.05) between Weeks 2 and 6 p.i. in the infected heifers (5.6 +/- 0.86 ng ml-1 vs. 4.4 +/- 0.34 ng ml-1) when compared with the uninfected controls or the pre-infection level. Thereafter, cortisol levels declined though non-significantly throughout the rest of the study. However, there was a steady increase towards normal levels from Week 12 p.i. until the end of the experiment. Changes in the basal serum concentrations of thyroxine (T4) were also measured weekly. There was a progressive decrease in the levels of T4 from the third until the 11th week p.i., when the decrease became significant (P less than 0.05) and remained so until the 16th week when the experiment ended.     

The protective effect of vaccination against experimental pneumonia in cattle with Haemophilus somnus outer membrane antigens and interference by lipopolysaccharide.

A semi-purified outer membrane anionic antigen (AA) fraction was isolated from Haemophilus somnus by a modified procedure of anion exchange chromatography to yield a protein fraction free of lipopolysaccharides (LPS). The AA fraction (1 mg) was administered with or without the homologous lipopolysaccharide (10 micrograms/kg body weight) as vaccines to groups of cattle twice, three weeks apart. A control group which did not receive any antigen was included in the trial. Six weeks after the first vaccination, the animals were challenged intratracheally with a virulent pneumonic strain of H. somnus (70986) and observed for clinical signs of respiratory disease. The cattle were euthanized six days later and the lungs were evaluated for the severity of lesions macroscopically as well as histopathologically. Vaccination with AA alone provided the best protection against pneumonia as indicated by significantly lower clinical scores, less extensive gross lung lesions and mild histopathological lesions with immune cell infiltration. However, when AA was combined with LPS in the vaccination, this protective effect was negated and the animals showed more detrimental histopathological lesions than the controls.     

Immunohistochemical study of Hemophilus somnus, Mycoplasma bovis, Mannheimia hemolytica, and bovine viral diarrhea virus in death losses due to myocarditis in feedlot cattle

The purpose of this study was to determine the presence of Hemophilus somnus, Mycoplasma bovis, Mannheimia hemolytica, and bovine viral diarrhea virus (BVDV) in lesional tissues of feeder calves dying with myocarditis. Tissues from the heart and lungs of 92 calves dying with myocarditis in Alberta feedlots were immunohistochemically stained for the antigens of these agents. Tissues from 44 calves dying from noninfectious causes and 35 calves dying with pneumonia were tested as controls. Hemophilus somnus was found in cardiac lesions in the majority of myocarditis cases (70/92). Mycoplasma bovis was concurrently demonstrated in the hearts of 4/92 affected calves. No bacterial pathogens were found in heart tissues from the control groups of calves. Bovine viral diarrhea virus was demonstrated in the tissues of 4/92 myocarditis cases compared with those of 13/35 calves dying from pneumonia and 0/44 calves dying from noninfectious causes. The results demonstrate that H. somnus is the principle pathogen associated with myocarditis in feedlot calves and that the presence of BVDV is more common in these calves compared with calves dying of noninfectious causes. The findings also suggest that BVDV is an important pathogen in calves dying with gross postmortem lesions of pneumonia.     

Reproductive difficulties in cattle with antibody titers to Haemophilus somnus

A herd of Holstein cows was examined because of suspected embryonic death. Four cows had embryonic loss, and 2 cows had aborted. Paired serum samples were tested for antibodies to infectious bovine rhinotracheitis virus, bovine viral diarrhea virus, and Haemophilus somnus. Of 16 cows, 8 had antibody titers to H somnus greater than 1:1,024, and 3 had greater than or equal to four-fold changes in antibody titers to H somnus. Haemophilus somnus infection was active in this herd and may have been responsible for the herd's reproductive problems.     

Leukocyte migration inhibition after experimental trypanosome infection in cattle

Blood serum from cattle experimentally infected with trypanosomes was tested for its activity influencing granulocyte migration. Pooled porcine granulocytes were used in the migration assay. The inhibitory migration activity observed in serum samples of trypanosome infected animals implies the presence of mediators of cellular immunity. Values of migration indices express reciprocal events of inhibitory and stimulating events in infected animals. This study allowed to follow at least some aspects of the very complex cellular immune system and its functioning. The observed differences in migration values in serum of each animal speak for an individual immunological capacity to defy trypanosome infections. The variability in occurrence of the first inhibitory activity after infection supports the view of individual responsiveness. Distinct differences in migration values were observed in Dahomey cattle after primary and secondary challenge with trypanosomes. Serum from reinfected animals exhibited a marked decrease in inhibitory activity as compared to samples obtained after first infection. These observations suggest a modulation of the individual immune response after multiple challenge with trypanosomes of the same strain. This study demonstrates the involvement of cell mediated immune responses to trypanosome infections.     

Effects of Hemophilus somnus on the pregnant bovine reproductive tract and conceptus following cervical infusion

Three strains of Hemophilus somnus were infused into the posterior cervix of six pregnant cows. The organism persisted in the cervicovaginal region for eight to 87 days, and at parturition H. somnus was isolated from chorioallantois in four of six cows; placentitis developed, and fetal membranes were retained. All calves were born alive and no H. somnus was recovered from them. One cow died 14 days after parturition. The death was attributed to severe necrotizing metritis; H. somnus was not isolated from the uterus at death, but was isolated from the placenta at parturition and cervicovaginal mucus two days days later.     

Hemophilus somnus in the reproductive tracts of slaughtered cows: location and frequency of isolations and lesions

One hundred bovine female reproductive tracts were examined for the presence of Hemophilus somnus, and fifty were examined for gross and microscopic lesions. H. somnus was isolated from eight of 100 tracts. The isolation was made from the vagina in seven cows. Of 24 tracts in which the major vestibular gland was sampled, three were positive at this site, and two of these three also had the organism isolated from the vagina. Further investigations into the role of the major vestibular gland as a source for continuing infections of the reproductive tract of cattle were indicated. In this investigation, H. somnus was as likely to be found in a region without lesions as one with lesions.     

Inverse age resistance to experimental Babesia divergens infection in cattle

Two groups of calves, 1.5-2 and 7-11 months old respectively, and dairy cows were inoculated i.v. with 3 x 10(7) erythrocytes infected with Babesia divergens. High parasitaemia, fever and other clinical signs of babesiosis occurred among adult animals. A very low parasitaemia and a slightly increased body temperature but no other symptoms occurred in calves. these findings substantiate the conclusion that there exists an inverse age resistance against Babesia divergens. The kinetics of B. divergens IgG antibody formation were similar in all age groups. Consequently this antibody response was not the factor determining the development of the primary parasitaemia and thus the inverse age resistance phenomenon. However, age is not necessarily the only factor involved in the clinical expression of babesiosis. The kinetics of antibody formation was not associated with the intensity of the parasitaemia. In fact only about half the animals had a demonstrable parasitaemia although the antibody responses were similar in all age groups.