Mycobacterium bovis infection in cattle in Morocco: preparation and evaluation of chemical extracts for use in detection of immune responses

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1993
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Berrada, Jaouad
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Charles O. Thoen
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Veterinary Microbiology and Preventive Medicine
Our faculty promote the understanding of causes of infectious disease in animals and the mechanisms by which diseases develop at the organismal, cellular and molecular levels. Veterinary microbiology also includes research on the interaction of pathogenic and symbiotic microbes with their hosts and the host response to infection.
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Sodium deoxycholate (DOC) was utilized to extract immunologically-active cell wall components of virulent M. bovis and M. avium, isolated from cattle in Morocco and M. fortuitum as well as related organisms e.g., N. asteroides and R. equi. The extracts from M. bovis, N. asteroides, M. fortuitum, and M. avium, were fractionated by size exclusion chromatography using Sephadex S-200. Two fractions (1 and 2) were obtained at absorbance of 280 nm. Fraction 1 of M. bovis, M. avium, M. fortuitum and of N. asteroides and nonfractionated DOC extract of R. equi elicited delayed-type hypersensitivity responses in homologously or heterologously sensitized guinea-pigs. Significant enzyme-linked immunosorbent assay values were obtained using sera from cattle 4 weeks after sensitization with homologous bacterial preparations (p < 0.01). Significant ELISA cross-reactions were observed in M. bovis or M. avium sensitized calves, using heterologous antigens;Mycobacteriologic examinations conducted on tissues collected from 246 cows in 5 major abattoirs of Morocco, revealed that M. bovis was isolated from 29.67% of the cattle examined. Mycobacteria other than M. bovis (MOTT) were isolated from tissues of 23 carcasses (9.34%). Three had lesions compatible with tuberculosis; M. bovis was not isolated;An indirect enzyme-linked immunosorbent assay using M. bovis PPD or M. bovis DOC fraction 1 as antigens was used for detecting antibodies in sera of cattle from which M. bovis was isolated. The sensitivity for M. bovis PPD was 76.71% and for DOC extract of M. bovis was 79.45%; the specificity was of 90% and 92%, respectively. These values are similar to those achieved by the tuberculin skin test (71);Investigations conducted on five selected herds in Morocco using the cervical intradermal tuberculin test and ELISA revealed that cattle in three herds were tuberculous. The comparative cervical tuberculin test using M. bovis and M. avium PPD's at equal concentration was conducted within 24 hours of a positive or suspect skin response; no reactors were identified in the remaining two herds;Combination of ELISA and tuberculin skin test conducted on animals from tuberculous herds was found to be more sensitive than either test conducted alone.

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Fri Jan 01 00:00:00 UTC 1993