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Category: Bacterial Pathogenesis; Clinical Microbiology
Experimental Infection Models of Tuberculosis in Domestic and Wild Animals, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555817657/9781555812959_Chap35-1.gif /docserver/preview/fulltext/10.1128/9781555817657/9781555812959_Chap35-2.gifAbstract:
This chapter focuses principally on experimental infection of cattle since this model has many features that make it appealing as a model for the human disease. The experimental infection models of deer, possums, ferrets and badgers add to one’s understanding of tuberculosis and are compared to those in cattle. Models of bovine tuberculosis in cattle have been established to provide essential information for the development of new strategies of disease control, including improved methods for diagnosis and vaccination. In common with the human disease, it has been found that cell-mediated immune responses predominate in early bovine tuberculosis and that the development of an antibody response is often associated with advanced stages of infection. Use of an effective tuberculosis vaccine for cattle would be highly desirable in the countries that cannot control bovine tuberculosis by using the conventional “test and slaughter” strategy, whereby animals giving a positive skin reaction to tuberculin are identified as infected and slaughtered. The kinetics of immune responses to vaccination and subsequent challenge can be readily measured in cattle and provides insights into possible correlates of protection and disease. BCG vaccination sensitizes animals to tuberculin PPD-based diagnostic tests. Therefore, the development of differential diagnostic assays has concentrated on antigens whose genes are deleted or underexpressed in BCG but strongly expressed in virulent Mycobacterium bovis. The study of experimentally induced tuberculosis models in animals other than laboratory animals (mice, guinea pigs, and rabbits) can greatly expand one’s knowledge of tuberculosis.
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Effect of route of infection on lesion distribution in bovine tuberculosis. Data represent percentages of animals with tuberculous lesions detected in the major lymph nodes of the lower respiratory tract (LRT) (bronchial/mediastinal), of the upper respiratory tract (URT) (retropharyngeal/submaxillary), and of both of these regions (LRT and URT) following field infection (n = 2,886) ( 24 ) and experimental infection by the intranasal or intratracheal route (n = 9 for both).
Effect of route of infection on lesion distribution in bovine tuberculosis. Data represent percentages of animals with tuberculous lesions detected in the major lymph nodes of the lower respiratory tract (LRT) (bronchial/mediastinal), of the upper respiratory tract (URT) (retropharyngeal/submaxillary), and of both of these regions (LRT and URT) following field infection (n = 2,886) ( 24 ) and experimental infection by the intranasal or intratracheal route (n = 9 for both).
Effect of BCG vaccination and subsequent challenge of calves with M. bovis on IFN-γ released from whole-blood cultures stimulated with bovine PPD. All calves were challenged with 103 CFU of M. bovis intratracheally at 8 weeks after vaccination. The tuberculous-lesion status of calves after M. bovis challenge is as follows: ?, nonvaccinated calves that developed lesions (n = 10);○, nonvaccinated calves with no lesions (n = 6); ?, BCG-vaccinated calves that developed lesions (n = 6); ?, BCG-vaccinated calves with no lesions (n = 24). IFN-γ levels are presented as mean concentration; error bars represents standard error of the mean.
Effect of BCG vaccination and subsequent challenge of calves with M. bovis on IFN-γ released from whole-blood cultures stimulated with bovine PPD. All calves were challenged with 103 CFU of M. bovis intratracheally at 8 weeks after vaccination. The tuberculous-lesion status of calves after M. bovis challenge is as follows: ?, nonvaccinated calves that developed lesions (n = 10);○, nonvaccinated calves with no lesions (n = 6); ?, BCG-vaccinated calves that developed lesions (n = 6); ?, BCG-vaccinated calves with no lesions (n = 24). IFN-γ levels are presented as mean concentration; error bars represents standard error of the mean.
Positive correlation between ESAT-6-specific IFN-γ and disease severity. IFN-γ was released from whole-blood cultures stimulated with ESAT-6 at 11 weeks after M. bovis infection. Responses of individual cattle are shown in relation to the severity of disease observed at the postmortem examination: ?, BCG vaccinated calves; ○, nonvaccinated calves. OD450, optical density at 450 nm. Reprinted from reference 41, with permission
Positive correlation between ESAT-6-specific IFN-γ and disease severity. IFN-γ was released from whole-blood cultures stimulated with ESAT-6 at 11 weeks after M. bovis infection. Responses of individual cattle are shown in relation to the severity of disease observed at the postmortem examination: ?, BCG vaccinated calves; ○, nonvaccinated calves. OD450, optical density at 450 nm. Reprinted from reference 41, with permission
Use of cattle as a model for tuberculosis of humans
Use of cattle as a model for tuberculosis of humans