Presentation on theme: "Development of Vaccine Approaches for Bovine Tuberculosis in Free- Ranging White-tailed Deer Mitchell Palmer, Ray Waters, Tyler Thacker National Animal."— Presentation transcript:
Development of Vaccine Approaches for Bovine Tuberculosis in Free- Ranging White-tailed Deer Mitchell Palmer, Ray Waters, Tyler Thacker National Animal Disease Center, ARS, USDA Ames, IA
Wildlife Vaccines -Challenges- Multiple species in natural transmission cycle Effective oral vaccine Safety of non-target species Fastidious feeding behavior Instability of vaccine in prevailing environmental conditions High reproductive rates and population turnover Requirement for low unit cost – Government funding (development, purchase, delivery)
Agent Mycobacterium tuberculosis complex > 99.95% sequence homology M. tuberculosis M. bovis – broadest host range M. caprae M. africanum M. canetti M. microti M. pinnipedii M. mungi
Cattle are often the original source of M. bovis in wildlife. As the prevalence of bovine tuberculosis decreases in livestock, the relative importance of wildlife reservoirs increases.
Tuberculosis Eradication tuberculosis leading cause of death – 10-25% of human tuberculosis due to M. bovis USDA eradication program – 15,000 deaths to M. bovis – 3x- number of foodborne deaths today Current surveillance is slaughter surveillance
Obstacles to Bovine Tuberculosis Eradication Importation of infected cattle – Need rapid, reliable and inexpensive test to at border crossings. Inability to Test and Remove Cattle – Need reliable, accurate tests to remove infected cattle without whole herd depopulation. Wildlife Reservoirs – Need for vaccines for wildlife. Safe vaccines Vaccine delivery systems – Need for vaccines for cattle. Infected vs Vaccinated
Tuberculosis in Wildlife Traditional eradication methods used for livestock DO NOT work with wildlife reservoirs. No country with an established wildlife reservoir of tuberculosis has successfully eradicated tuberculosis from domestic livestock. Vaccines viewed as possible control measure.
Mycobacterium bovis bacille Calmette-Guerín (BCG) BCG was developed Originally isolated from a cow. Continuous passage led to decreased virulence Oldest of vaccines in use today. World’s most widely used vaccine (3 billion doses since 1920). Vaccinated individual may have positive skin test. Albert Calmette Camille Guerin
Vaccination in the US
Efficacy Does vaccination prevent infection? Does vaccination prevent disease (lesion development)? Does vaccination decrease transmission?
Medial retropharyngeal LN Total Score
Medial retropharyngeal LN BCG Danish: no lesions BCG Pasteur and non-vaccinates: Stages I-V Lung BCG Danish: Stages I-III BCG Pasteur: Stages I- III Non-vaccinates: Stages I-IV
Oral vaccination of white-tailed deer with M. bovis BCG VaccinatesNon-vaccinates Gross Lesions2/1711/16 Microscopic Lesions4/1711/16 M. bovis isolation5/179/16 Number of tissues822 Med retro LNIIIIIIIV Vaccinates9000 Non-vaccinates269511
Is it safe? Adverse reactions Non-target species Public health concerns – Possible exposure through venison consumption
Will vaccination of deer interfere with cattle testing? Possible cattle exposure to BCG False positive skin test results False positive IFN-gamma test results
Cattle (n=12): no conversion on skin test or Bovigam, all culture results negative Unvaccinated sentinel deer (n=10) BCG SC vaccinated deer (n=19)
13 vaccinated deer 9 in-contact deer 7 calves 27 weeks of indirect contact No residual BCG No evidence of transmission of BCG from Vaccinated deer to cattle Immunological evidence of deer to deer transmission of BCG
Testing a molasses-based bait for oral vaccination of white- tailed deer (Odocoileus virginianus) against Mycobacterium bovis- M. R. Stafne, BS, Iowa State University, College of Veterinary Medicine Physical stability BCG Survivability Observations
Future Bait – Alternative Baits – Vaccine Delivery Mechanism – More field testing (attraction, stability, non-targets) Vaccine – Duration of immunity – Protection through secondary vaccination – Effect of high doses on protection Red tape – USDA, Michigan DNR, Michigan Department of Agriculture Approval for BCG in deer – Environmental impact statement, etc.