Effects of Inactivated <i>Mycobacterium bovis</i> Vaccination on Molokai-Origin Wild Pigs Experimentally Infected with Virulent <i>M. bovis</i>
Pauline Nol,
Morgan E. Wehtje,
Richard A. Bowen,
Suelee Robbe-Austerman,
Tyler C. Thacker,
Kristina Lantz,
Jack C. Rhyan,
Laurie A. Baeten,
Ramón A. Juste,
Iker A. Sevilla,
Christian Gortázar,
Joaquín Vicente
Affiliations
Pauline Nol
Centers for Epidemiology and Animal Health, Veterinary Services, Animal and Plant Health Inspection Service, United States Department of Agriculture, Fort Collins, CO 80526, USA
Morgan E. Wehtje
Centers for Epidemiology and Animal Health, Veterinary Services, Animal and Plant Health Inspection Service, United States Department of Agriculture, Fort Collins, CO 80526, USA
Richard A. Bowen
Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
Suelee Robbe-Austerman
National Veterinary Services Laboratory, Veterinary Services, Animal and Plant Health Inspection Service, United States Department of Agriculture, Ames, IA 50010, USA
Tyler C. Thacker
National Veterinary Services Laboratory, Veterinary Services, Animal and Plant Health Inspection Service, United States Department of Agriculture, Ames, IA 50010, USA
Kristina Lantz
National Veterinary Services Laboratory, Veterinary Services, Animal and Plant Health Inspection Service, United States Department of Agriculture, Ames, IA 50010, USA
Jack C. Rhyan
National Veterinary Services Laboratory, Veterinary Services, Animal and Plant Health Inspection Service, United States Department of Agriculture, Fort Collins, CO 80521, USA
Laurie A. Baeten
Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
Ramón A. Juste
NEIKER-Instituto Vasco de Investigación y Desarrollo Agrario, Animal Health Department, Derio, 48160 Bizkaia, Spain
Iker A. Sevilla
NEIKER-Instituto Vasco de Investigación y Desarrollo Agrario, Animal Health Department, Derio, 48160 Bizkaia, Spain
Christian Gortázar
SaBio Instituto de Investigación en Recursos Cinegéticos IREC, University Castilla la Mancha & CSIC, 13003 Ciudad Real, Spain
Joaquín Vicente
SaBio Instituto de Investigación en Recursos Cinegéticos IREC, University Castilla la Mancha & CSIC, 13003 Ciudad Real, Spain
The wild pig population on Molokai, Hawaii, USA is a possible reservoir for bovine tuberculosis, caused by Mycobacterium bovis, and has been implicated in decades past as the source of disease for the island’s domestic cattle. Heat-inactivated vaccines have been effective for reducing disease prevalence in wild boar in Spain and could prove useful for managing M. bovis in Molokai wild pigs. We designed an experiment to test this vaccine in wild pigs of Molokai genetics. Fifteen 3−4-month-old pigs were orally administered 106−107 colony forming units (cfu) of heat-inactivated M. bovis (Vaccinates; n = 8; 0.2 mL) or phosphate buffered saline (Controls; n = 7; 0.2 mL). Each dose was administered in a 0.5 mL tube embedded in a fruit candy/cracked corn mix. Boosters were given seven weeks post-prime in the same manner and dose. Nineteen weeks post-prime, pigs were orally challenged with 1 × 106 cfu of virulent M. bovis. Twelve weeks post-challenge, pigs were euthanized and necropsied, at which time 23 different tissues from the head, thorax, and abdomen were collected and examined. Each tissue was assigned a lesion score. Ordinal lesion score data were analyzed using non-parametric Wilcoxon Signed Rank test. Effect size was calculated using Cohen’s d. Four of eight Vaccinates and four of seven Controls had gross and microscopic lesions, as well as culture-positive tissues. Vaccinates had statistically lower lesion scores than Controls in the following areas: gross thoracic lesion scores (p = 0.013 Cohen’s d = 0.33) and microscopic thoracic lesion scores (p = 0.002, Cohen’s d = 0.39). There were no differences in head lesion scores alone, both gross and microscopic, nor were there differences when comparing combined gross and microscopic head and thoracic lesion scores. These results are indicative that this vaccination protocol affords a modest degree of infection containment with this vaccine in Molokai wild pigs.
