Benefit-cost analysis of vaccination of horses as a strategy to control equine monocytic ehrlichiosis.

The research analyzes the costs and benefits of vaccinating horses in New York against equine monocytic ehrlichiosis (EME). The study finds that because of the low incidence density of EME in most regions of the state, it’s actually less costly not to vaccinate the horses.

Research methodology

• Using decision-tree analysis, the researchers handled data from a cross-sectional study and a case-control study.
• The team calculated the annual expected monetary loss per horse attributable to EME for vaccinated and non-vaccinated horses in New York.
• Since the risk of becoming seropositive depends on the county in which the horse is located, farm elevation, and the purpose of each horse, the researchers stratified the decision-tree analyses by these factors.

Results and findings

• The annual anticipated monetary loss per horse due to EME for horses vaccinated by veterinarians was found to range from $21 to $21.83 per horse per year. For horses vaccinated by owners themselves, it ranged from $10 to $10.83 per horse per year, and for non-vaccinated horses, the range was from $0 to $4.03 per horse per year.
• Considering that 78% of vaccinated horses were protected, and average losses associated with EME included the costs for horses that died, the researchers arrived at an annual incidence density at which anticipated monetary loss for vaccinated horses equals that for non-vaccinated horses: 12 cases per 1,000 horses per year for horses vaccinated by owners, and 25 cases per 1,000 horses per year for horses vaccinated by veterinarians.

Conclusions

• The study concludes that annual vaccination lowers monetary losses due to EME only when the annual incidence density is more than 12 to 25 cases per 1,000 horses per year.
• Specifically, in New York, where the incidence density of EME is low in most regions, expected monetary losses are minimized when horses are not vaccinated.