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Efficacy, immune responses and side-effects of vaccines against Johne's disease in young red deer ( Cervus elaphus ) experimentally challenged with Mycobacterium avium subsp paratuberculosis
Authors: Clark RG, de Lisle GW, Griffin JFT, Johnstone PD, Labes RE, Thompson BR, Mackintosh CGPublication: New Zealand Veterinary Journal, Volume 56, Issue 1, pp 1-9, Feb 2008
Publisher: Taylor and Francis
Animal type: Deer, Livestock, Production animal, Ruminant
Subject Terms: Animal remedies/veterinary medicines, Bacterial, Diagnostic procedures, Treatment/therapy, Immune system/immunology, Mycobacterial, Wasting disease/disorder, Infectious disease, Disease/defect, Vaccination
Article class: Scientific Article
Abstract: AIMS: To test the efficacy of a commercially available and an experimental vaccine against Johnes disease in young red deer (Cervus elaphus), using experimental challenge with live virulent Mycobacterium avium subsp paratuberculosis (M. ptb), measure injection-site reactions, and assess the effects of vaccination and challenge on results of subsequent skin tests and ancillary blood tests for bovine tuberculosis (Tb).
METHODS: Ninety 68-week-old red deer fawns were randomly allocated to three equal groups of 30, and received either a 1-ml S/C injection of either a commercially available whole-cell killed vaccine with a mineral-oil adjuvant (COM), or a live attenuated M. ptb experimental vaccine with a lipid adjuvant (EXP), or were unvaccinated controls. Ten weeks later (Week 10), all 90 fawns received an oral challenge with ~108 cfu of a bovine strain of M. ptb daily for 4 days. The fawns were regularly weighed and monitored for clinical signs of Johnes disease, and regularly blood-sampled and tested for antibodies to M. ptb, using the Paralisa test, an IgG1 ELISA, and for antibodies to Mycobacterium bovis, using a similar test. A mid-cervical tuberculin skin test (MCT) was administered at Week 23, and comparative cervical skin tests (CCTs) were administered at Weeks 37 and 57. All animals were electively killed at Week 59, injection sites inspected, gastrointestinal tracts examined for gross lesions, and samples taken for culture and histopathology.
RESULTS: There were no clinical cases of Johnes disease but, at slaughter, more gross lesions in intestinal lymph nodes were observed in Control (20%) than COM animals (0%; p<0.05). This latter group also had less severe histopathological lesions in samples of intestines and lymph nodes compared with the Control group (p<0.05), but not deer in the EXP group.
Over 89% of deer in all three groups were shown by culture to be infected with M. ptb, while only 2133% of faecal samples were culture-positive. Time to positive culture was longer for COM vs EXP and Control groups (p<0.01), reflecting fewer M. ptb organisms in samples from the ileocaecal valve (ICV) in that group continued
CONCLUSIONS: The experimental challenge with M. ptb produced subclinical Johnes disease in the majority of deer, but did not cause any clinical disease. The number and severity of gross and microscopic lesions was significantly reduced in the COM compared with Control and EXP groups; vaccination of the EXP group did not appear to give significant protection.
Deer vaccinated with the commercial vaccine are likely to give a false-positive reaction to the MCT but should have an avian reaction to the CCT, if it is carried out >12 months after vaccination. Most of the deer vaccinated with the commercial vaccine produced significant levels of antibodies against both M. ptb and M. bovis, which interfered with ancillary Tb tests. If this vaccine or similar oil-based vaccines are used on deer farms in the future, it may be advisable to only vaccinate animals destined for slaughter, that would not need to be Tb-tested, but would be works-monitored for evidence of Tb instead.
KEY WORDS: Red deer, Johnes disease, Mycobacterium paratuberculosis, vaccine, Gudair, efficacy, bovine tuberculosis skin testing
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