Streamlined Analysis for Evaluating the Use of Preharvest Interventions Intended to Prevent Escherichia coli O157:H7 Illness in Humans

Abstract

The U.S. Department of Agriculture Food Safety Inspection Service is responsible for ensuring the safety of meat, poultry, and egg products consumed in the United States. Here we describe a risk assessment method that provides quantitative criteria for decision makers tasked with developing food safety policies. To demonstrate the utility of this method, we apply it to a hypothetical case study on the use of an Escherichia coli O157:H7 cattle vaccine to prevent human illness caused by consuming beef. A combination of quantitative risk assessment methods and marginal economic analysis are used to describe the maximum cost per unit that would still allow the vaccine to be a cost-effective intervention as well as the minimum effectiveness it could have at a fixed cost. We create two economic production functions where the input is number of vaccinated cattle and the output is human illnesses prevented. The production functions are then used for marginal economic analysis to assess the cost/benefit ratio of using the vaccine to prevent foodborne illness. In our case study, it was determined that vaccinating the entire U.S. herd at a cost of between $2.29 and $9.14 per unit (depending on overall effectiveness of the vaccine) would be a cost-effective intervention for preventing E. coli O157:H7 illness in humans. In addition, we determined that vaccinating only a given fraction of the herd would be cost effective for vaccines that are less effective or more costly. For example, a vaccine costing $9.00 per unit that had a 100% efficacy but required 100% herd coverage for immunity would be cost effective for use in about 500,000 cattle each year-equating to an estimated 750 human illnesses prevented per annum. We believe this approach could be useful for public health policy development in a wide range of applications.

An Outcomes Model to Evaluate Risks and Benefits of Escherichia coli Vaccination in Beef Cattle

“…In our study, the relationship between the number of human illnesses and vaccinated cattle was quite linear (R 2 = 0.99), similar to the model of Withee et al (2009). By comparison, we also modeled a reduction in concentration on/in carcasses/ feces as well as prevalence of shedders due to vaccination (Fig.…”

“…Figure 2 and Table 3 show the relationship between the predicted number of human cases of O157 and the number of feedlot cattle vaccinated (termed ''production function'' in Withee et al, 2009). The model demonstrated that the number of human illnesses attributed to consumption of O157-contaminated ground beef can be greatly reduced by vaccination.…”

Simplified framework for predicting changes in public health from performance standards applied in slaughter establishments

“…If a positive correlation exists between the prevalence of contaminated carcasses and the levels of Salmonella on contaminated carcasses, then the assumed independence leads to conservative estimates of the reduction in illnesses associated with a reduction in prevalence. A similar assumption was explained with respect to Escherichia coli O157 and beef previously (Withee et al, 2009). …”

A review of the metrics for One Health benefits

“…(1), (3), (5), (13)(14)(15)(16), (25)(26)(27), (36), (38), (40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50) Improvement in human or animal health or well-being, e.g.…”