Submitted to: North Central Avian Disease Conference
Publication Type: Proceedings
Publication Acceptance Date: November 9, 2000
Publication Date: N/A
Turkey coryza is an highly contagious upper respiratory disease of turkeys caused by infection with Bordetella avium. The disease impairs growth and increases the susceptibility of young turkeys to other infections. In addition, it is associated with vaccine immunization failure well into the convalescent phase of the disease, perhaps due to immunosuppression. Depletion of thymic lymphocytes and decreased T-lymphocyte blastogenesis response to mitogen are reported features of immune-cell changes in coryza- affected turkeys. The purpose of the present study was to determine whether intraperitoneal administration of a purified dermonecrotic heat- labile toxin (DHLT) isolated from B. avium could produce lymphocyte depletion, as determined by quantitation of apoptosis in primary and secondary lymphoid organs of turkey poults. Sections each of bursa, thymus, and spleen were examined. Image processing, performed by Image Pro oPlusR version 4.0 for Windows (trademark) software, included color discrimination and area calculation. Analysis of variance (ANOVA) was used to determine significant sources of variation contributing to treatment means. Exposure of poults to DHLT produced lesions indicative of mild lymphocyte necrosis or apoptosis in the thymus and bursa of Fabricius. However, computer-assisted image analysis of lymphocyte apoptosis in bursal tissue did not substantiate the subjective assessment of lymphocyte depletion. Considerable morphologic variation existed between individuals within treatment groups. The spectrum of appearances of healthy tissue from subject to subject commands caution in interpretation of subjective findings.