Proceedings of the 10th International Colloquium on Paratuberculosis

#120 Paratuberculosis vaccine interference with bovine tuberculosis diagnosis in farmed red
deer (Cervus elaphus)
Colin Grant Mackintosh, Ge<strong>of</strong>f de Lisle, Frank Griffin, AgResearch Invermay, Mosgiel, New Zealand; AgResearch
Wallaceville, Upper Hutt, New Zealand; University <strong>of</strong> Otago, Dunedin, New Zealand
Objective: To measure <strong>the</strong> accuracy <strong>of</strong> skin tests and ancillary blood tests for diagnosing bovine tuberculosis
(Tb) in farmed red deer that have been vaccinated within <strong>the</strong> previous 12 months with Silirum, a commercial
oil-adjuvanted Johne’s vaccine intended for use in cattle and deer.
Materials and Methods: Four groups <strong>of</strong> 15 three-month-old red deer received <strong>the</strong> following treatments:
Group 1 vaccinated with SilirumTm and challenged with M. bovis 20 weeks later; Group 2 vaccinated with
SilirumTm and not challenged; Group 3 not vaccinated but challenged with M. bovis: Group 4 not vaccinated
and not challenged. A bovine skin test (MCT) was conducted 12 weeks after Tb challenge, and a comparative
avian/bovine skin test (CCT) was conducted 24 weeks after challenge. The deer were slaughtered and
sampled 27 weeks after Tb challenge.
Results: All <strong>the</strong> deer in Groups 1, 2 and 3 were MCT positive (≥ 2 mm increase), while all Group 4 deer
were negative. In <strong>the</strong> CCT, only 36% <strong>of</strong> Group 1 were positive (ie increase at bovine site≥ avian site≥2 mm),
while Group 3 animals were all CCT positive and Group 4 were all negative. One vaccinated animal in Group 2
had avian = bovine reaction and was classed as CCT positive.
Vaccination also interfered with an IgG1 antibody ELISA for Tb (ETB) conducted 2 weeks post skin testing,
causing >80% false-positives in Group 2. Vaccination masked Tb infection in one Group 1 deer. At Week
46, all <strong>the</strong> deer that had only been challenged
Conclusion: This study showed that vaccination with Silirum has <strong>the</strong> potential to interfere with diagnostic
tests for bovine Tb in deer. Vaccination resulted in false-negative Tb tests in Tb-infected deer and falsepositive
Tb tests in uninfected deer.
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