Further studies on the identification of pasteurellaceae from cattle lungs.
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Biomedical subjects
Publications and source records attributed to N J Gilmour.
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An experimental model of pneumonic pasteurellosis in sheep was used to investigate the role of serum antibody in resistance to this disease. Lambs which had been vaccinated with a sodium salicylate extract of Pasteurella haemolytica type A1 were protected against challenge with PI3 virus followed by P. haemolytica type A1 7 days later. The majority of untreated lambs and lambs which had received either 200 ml of antiserum to P. haemolytica or 200 ml of control serum intraperitoneally 18 h before infection with P. haemolytica type A1 succumbed to the challenge. Lymphocytes from vaccinated lambs showed a specific proliferative response when exposed to P. haemolytica type A1 sodium salicylate extract, and this response increased after exposure of these animals to P. haemolytica type A1 in aerosol. The results indicate that the humoral immune response alone is incapable of affording protection against experimental pasteurellosis and that cell-mediated immunity may play an important part in resistance to this disease.
The cultural characteristics of Moraxella bovis and Neisseria ovis from eyes of cattle and sheep were examined to determine which tests precisely identified the isolates. The elongation test to distinguish the bacillary M vovis from the coccal N ovis, the nitrate reduction and the litmus milk tests were found to be the most reliable.
Five adjuvants were compared for their ability to enhance the serological response of sheep to capsule extract of Pasteurella haemolytica biotype A serotype 6. Vaccines of this antigen were inoculated with incomplete Freund's adjuvant, complete Freund's adjuvant, incomplete Freund's adjuvant containing a water soluble extract of Mycobacterium tuberculosis, aluminium hydroxide gel or a combination of aluminium hydroxide gel and incomplete Freund's adjuvant. This latter vaccine induced significantly higher titres of antibody as measured by an indirect haemagglutination test than did any of the other vaccines. The aluminium hydroxide gel alone was shown to be the poorest adjuvant. The local reactions at the sites of inoculations produced by the aluminium hydroxide gel in incomplete Freund's adjuvant vaccine were not severe and were not detectable beyond one month after vaccination in the majority of the sheep.
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Pasteurellosis is an important cause of economic loss to the sheep industry. There are two distinct syndromes. The pneumonic form of the disease caused by P haemolytica biotype A occurs as pneumonia in flocks and sporadically in individual sheep. The septicaemic form, caused by P haemolytica biotype T is associated with hyper-acute disease and occurs most commonly in the autumn coinciding with the folding of hoggs on rape, turnips and improved pastures. The factors which predispose sheep to the different forms of the disease are poorly understood but recently it has been possible to reproduce pasteurella pneumonia experimentally.
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The serotypes of 406 strains of Pasteurella haemolytica were determined. These came from cases of pasteurellosis in sheep of all ages. Serotype A2 was the most frequent and comprised 33 per cent of all strains recovered. Serotypes T3, T4 and T10 comprised 16, 14 and 12 per cent of the total respectively. Serotypes A1 and A6 contributed 5 per cent each, A7, 18, A9, A11 and A12 a total of 8 per cent collectively, serotype A5 was not isolated at all while 6 per cent of strains were serologically untypable. More strains were received during September, October and November than at any other three-month period and in these months the T biotype predominated.
Since 1962, when the control of Johne's disease was last reviewed by the BVA technical development committee there have been no dramatic advances in diagnostic methods for Johne's disease or in methods of control. However, there has been a slow, but steady increase in knowledge of the various aspects of the disease. This article attempts to set out what is known and, more important, not known about the subject.
Sera from 775 adult milking cattle on 13 farms in Friesland and from 359 of the same cattle taken during the following year, were examined for evidence of infection with M johnei by the complement fixation, fluorescent antibody, haemagglutination, haemagglutination-lysis and immunodiffusion tests. Eighteen animals, not clinically affected but which had serologically positive tests were slaughtered and M johnei was isolated in cultures from 16. The fluorescent antibody test was as sensitive as the complement fixation test. The other tests were relatively insensitive and would only be of value as confirmatory tests in the presence of reactions to the first two tests. It is concluded that the use of the fluorescent antibody and the complement fixation test together was of value in detecting sub-clinical Mycobacterium johnei infection.
Sera from experimentally infected rabbits were used to test the specificity of the fluorescent antibody test. It was possible using mono-specific sera to differentiate antigenically Mycobacterium phlei, M fortuitum, M smegmatis, M avium, M intracellulare, M bovis (BCG) and M johnei. The cross-reactivity within the M avium and M intracellulare group was such that one antigen from these groups would detect infection within that group and exclude M johnei infection. The M phlei growth factor independent strain M johnei 316F was shown to be antigenically distinct from a M phlei dependent strain 9N96. There was loss of specificity when M avium infection was superimposed on a previous M johnei infection and when M johnei infection was superimposed on M avium infection.
In a series of 100 cattle in which there was no bacteriological or histopathological evidence of Mycobacterium johnei infection there were four positive reactions to the fluorescent antibody (FA) test with M johnei antigen and 20 to the complement fixation (CF) test. In a second series of 118 culled adult cattle M johnei infection was found in 26. The FA test was positive in 16 and the CF in 12 of those infected cattle. In 92 cattle with no evidence of M johnei infection the FA test was positive in seven and the CF test in 22.
In five calves experimentally infected with Mycobacterium avium and in 10 with M johnei it was shown that the serological response by the fluorescent antibody (FA) test was specific. The serological response in the M avium infected calves was transitory and lasted up to five months. The first evidence of a serological response with the FA test in the M johnei dosed calves occurred at four months, and all calves had reacted by nine months after dosing. At the 23 tests carried out between four and 32 months after dosing, when the experiment was terminated, an average of 5-8 animals was positive at any one test. Johne's disease was confirmed bacteriologically and histologically in six of the 10 calves though none had shown clinical signs.
A single injection of vaccine containing disrupted formol-killed Vibrio (campylobacter) fetus var intestinalis serotype V was shown to give good protection against abortion from an oral challenge of the same serotype administered simultaneously. Protection was also afforded by vaccination at the time of the first abortion in sheep infected orally one month previously. These results suggest that vaccination subsequent to an abortion might be of value in preventing a proportion of further abortions.