Submitted to: International Conference on Mycobacterium bovis
Publication Type: Proceedings
Publication Acceptance Date: September 1, 1995
Publication Date: N/A
Technical Abstract: Administration of dexamethasone (Dex), a synthetic glucocorticoid, has been used in cattle to model immunosuppression caused by stress. The purpose of this study was to determine the effect of stress, as modeled by injection of Dex, on skin test responses in cattle. Twenty-eight cattle, sensitized by injection of heat-killed Mycobacterium bovis, were used. Cattle were divided into Dex-treated and nontreated groups. The experimental design was as follows: Day 0, measurement of background skin thickness and ID injection of M. avium and M. bovis purified protein derivatives (PPD) for comparative cervical skin tests (CCT); Day 3, measurement of skin thickness at injection sites; Days 3-6, injection of treated group with 20 mg Dex (IM); Day 7, measurement of background skin thickness and injection of PPD using opposite side of the neck; Day 10, measurement of skin thickness at sites injected on Day 7. Eighty-seven days after second injection of PPD, experiment was repeated using 20 of 28 cattle for a total of 48 observations. Reaction sizes to both PPD's were smaller in Dex-treated cattle (n=25) than in nontreated cattle (n=23). Results of the CCT conducted on day 0 were positive for 24 Dex-treated cattle and 23 nontreated cattle. However, results of the CCT conducted on day 7 were positive for 7 Dex-treated cattle and 19 nontreated cattle. Results of this study indicate that stress adversely affects the CCT performance.