A comparison of three rapid diagnostic methods for the detection of rotavirus infection in calves

Three techniques for the detection of rotavirus in faecal samples from calves with neonatal gastroenteritis were compared. A preliminary study indicated that reverse passive haemagglutination (RPHA) was at least as sensitive as the enzyme-linked immunosorbent assay (ELISA). These two immunoassays were compared with the detection of viral RNA by polyacrylamide gel electrophoresis (PAGE) on 209 field samples. Of the 77 samples in which at least one test gave a positive result, 69 were positive by both RPHA and PAGE, but only 49 were also positive by ELISA, indicating a lower sensitivity for the latter test. The overall agreement between RPHA and PAGE was 96%. The reasons for the discrepancies between the tests are discussed.     

Growth of Mycoplasma bovis in organ cultures of bovine foetal trachea and comparison with Mycoplasma dispar

Inoculation of tracheal organ cultures from bovine foetuses with Mycoplasma bovis resulted in a loss of cellular structure of the lamina propria, followed 20-22 days later by lifting and detachment of overlying epithelium. The effect was associated with large numbers of M. bovis, identified by immunoperoxidase labelling and electromicroscopy, infiltrating between the epithelial cells and amassing in the lamina propria, especially in the region of the basement membrane of the epithelium. Ciliary activity was undiminished for up to 18 days following inoculation and little or no cytopathic effect on the ciliated epithelium was seen in spite of the close proximity of large numbers of organisms. In contrast, M. dispar was restricted to the margin of the ciliated epithelium where, as previously reported, it caused pyknosis, sloughing and flattening of the epithelium with consequent loss of ciliary activity. The cytopathology observed for each mycoplasma bore a close similarity to the behaviour of the two mycoplasmas in vivo and it is suggested that the organ culture system may be a useful and relevant system to elucidate the pathogenic mechanisms for each mycoplasma.     

Partial characterization of a Legionella pneumophila serogroup 1 immunodominant antigenic determinant recognized by a monoclonal antibody. Legionella specific antigenic determinant

A monoclonal antibody was used to characterize a serogroup 1 specific Legionella pneumophila Philadelphia strain 1 antigenic determinant. A quantitative fluorometric assay was developed to quantitate the antibody sites (2.7 +/- 0.4 X 10(5)) on Legionella bacteria and to determine the physico-chemical parameters of the antibody-antigen interaction (at 4 degrees C: delta G = -10.9 Kcal X mol-1, delta H = 1.7 Kcal X mol-1, delta S = 45 cal X K-1 X mol-1). The same method was used to study the modification or the removal of the antigen by chemical and enzymatic means (trypsin, papain, lysozyme, acetone, chloroform-methanol and Tris-EDTA); only Tris-EDTA extraction resulted in a significant decrease in antibody binding sites. Inhibition studies of the fluorescein-labelled antibody binding were performed with different sugars of which only L-fucosylamine was inhibitory, and with other monoclonal antibodies to Legionella pneumophila serogroup 1 in order to compare their fine specificity and affinity. The results indicate that the epitope recognized was an immunodominant carbohydrate including an aminodideoxyhexose and carried by the lipopolysaccharide.     

Interaction of bovine immunoglobulins with complement

Whereas complement (C) in rabbit serum (CR) was bound by bovine antibodies in seven different IgG1 preparations, only two IgG1 preparations could bind the C in guinea pig serum (CGP). Addition of the Clq component of CR to CGP was alone sufficient to render the C-cascade in CGP activable in the presence of bovine erythrocytes sensitized with specific antisera, i.e. reagents. Normal bovine serum was also capable of restoring the haemolytic activity of CGP. However, the bovine serum was much more temperature sensitive than was CR and, as was observed in the sera from MZ twins, it showed considerable variation both in titre values and in prozones when added to CGP.     

Characterisation of the outer membrane protein antigens of British field isolates of Moraxella bovis

Outer membranes of a single isolate of Moraxella bovis were prepared and their purity evaluated by a comparison of the iodinated proteins from whole cells and on outer membranes. The protein patterns of the outer membranes of 10 isolates were examined by SDS-polyacrylamide gel electrophoresis, and the antigenic relationship between proteins of different isolates determined by immunoblotting, using antiserum produced against the outer membrane of the single isolate of M. bovis. The overall protein pattern of the different isolates was similar although not identical, but, significantly, only three separate immunogenic proteins were common to all the isolates under examination.     

The development of eimerian infections during the first eight months of life in unweaned beef calves in a dry tropical region of Australia

The development of coccidial infections in 21 free-ranging, unweaned beef calves from birth to 8 months was investigated by examining faecal samples for oocysts. Most calves commenced shedding oocysts within a month of birth, and had shed all nine species identified by 3-4 months. Oocysts were shed by three calves as young as 12 and 13 days. The oocysts species shed earliest, and the commonest thereafter, were Eimeria bovis, E. ellipsoidalis and E. zuernii. Although several oocyst counts between 5.0 X 10(3) and 114.0 X 10(3)g-1 of faeces of these potentially pathogenic species were recorded there was no clinical disease. Some calves shed oocysts approximately four times more frequently than others, and individual species counts greater than or equal to 5.0 X 10(3)g-1 were confined to 10 of the calves. Intermittent oocyst shedding continued throughout the study with a similar distribution of oocyst species from all calves.     

Effect of cutting and vacuum cleaning on the digestibility of oats by horses

Three mature Quarter Horse geldings were used in 2 Latin square experiments to measure the effect of cutting and vacuum cleaning of oats on digestibility. The horses were fed at the maintenance level of digestible energy (DE) as recommended by the NRC.¹²The data were analyzed by Latin square analysis of variance, and Tukey's t test was used to determine any differences between specific means.No significant differences among treatments were observed during either experiment, indicating that the digestibility of nutrients from oats was not affected by cutting and vacuum cleaning. Differences in the digestibility of the ether extract (EE) fraction between periods of experiment 1 were noted.