Less than 5 percent of U.S. dairy herds currently vaccinate for Johne’s disease, due in part to the fact that currently available vaccination technology usually is not economically feasible compared to disease–management alternatives. A new study published in the April 2012 edition of the Journal of Dairy Science sheds light on the types of new vaccination programs that could be more effective and economical in the future.
Researcher J. Cho, PhD and his colleagues at Cornell University looked at eight vaccination scenarios, which utilized current and developing Johne’s disease vaccines. All but two of the vaccine protocols were based on technologies that are not yet commercially available.
One of the research team’s main objectives was to determine what characteristics of emerging Johne’s vaccines would be the most beneficial to producers. They evaluated the epidemiological effect (how well the vaccine program would control the disease in the herd) of each scenario.
They then estimated economically justifiable monetary values at which vaccines became economically beneficial to a herd. A vaccine was deemed to have economic merit if the net present value (NPV) of a farm’s net cash flow was higher than the NPV of farms using no control or alternative, non-vaccine control measures.
The researchers found that:
- All hypothetical vaccine protocols in the study – even those determined to have relatively low efficacy – yielded higher NPV compared to no Johne’s control.
- Vaccine protocols determined to be “high-efficacy” generated an even higher NPV compared with alternative controls.
- Only one situation showed high-efficacy vaccination to be less economically beneficial than alternative control measures. In this case, a high-efficacy vaccine that reduces shedding of Johne’s-causing bacteria and the number of clinical disease cases was less economically beneficial than alternative control measures in highly infected herds.
Cho suggests that, based on these results, the best two options for successfully vaccinating to manage Johne’s disease are (1) using a high-efficacy vaccine that reduces susceptibility to the disease; followed by (2) using a high-efficacy vaccine that interrupts Johne’s disease impact via a variety of effects on infection by Johne’s-causing bacteria, the number of clinical disease cases, and progress of the disease in already-infected animals.