Factors affecting red deer skin test responsiveness to bovine and avian tuberculin and to phytohaemagglutinin

We studied the effect of management on the responsiveness of red deer (Cervus elaphus) to skin testing with mycobacterial and non-mycobacterial antigens. We hypothesized that individuals from populations of the same species under different management conditions would have a different immune responsiveness. Deer sampled in this study included 1041 adult animals from 6 Spanish farms and 111 adult wild deer. We injected four sites of the neck with 0.1 ml bovine purified protein derivative (PPD), 0.1 ml avian PPD, 0.1 ml negative control PBS and 0.1 ml of Phytohaemagglutinin (PHA, containing 250 μg) as positive control, and measured the skin fold increase at time 72 h. Bovine PPD reactors were identified in 5 of 6 farms and among wild deer. Apparent prevalence among wild deer (18.9%) was not significantly higher than among farmed deer (14.5%). Avian PPD reactors were found among all 7 study populations, but apparent prevalence was lower among wild deer (<1%) than among farmed deer (12.6%; p < 0.001). Deer management (farmed versus wild) was identified as a key factor affecting deer skin fold thickness increase in response both to mycobacterial (bPPD and aPPD) and non-mycobacterial antigens (PHA). The differences occurred in the same sense, regardless of some interactions; farmed deer showing higher values. The PHA skin fold increase was not affected by the PPD skin test results. We propose that using PHA as a positive control may help in the interpretation of between-population differences in tuberculin responses.