Risk analysis of quarantine station performance: a case study of the importation of equine infectious anemia virus-infected horses into California.

This research analyzed the risk of unintentionally releasing horses infected with Equine Infectious Anemia Virus (EIAV) into California through quarantine stations. The study used a computer model to simulate different scenarios and assess the impact of increasing quarantine periods. The results suggested that an increased quarantine period does not necessarily reduce the risk of releasing EIAV-infected horses, especially considering current low prevalence in exporting countries.

Simulation Model

• The researchers developed a computer simulation model to evaluate the risk of importing and mistakenly releasing EIAV-infected horses into California. This model was used to analyze the effectiveness of both the existing and alternative quarantine procedures.
• To achieve robust statistics, the model ran through 150,000 iterations, simulating fifteen different scenarios where 10,000 horses were assumed to be imported into California over a 14-year period.

Model Predictions

• The simulation results indicated that given the current low prevalence of EIAV in exporting countries, an extended quarantine period would not reduce the number of EIAV-infected horses that are mistakenly set free from quarantine. This is a counter-intuitive result and possibly a testament to the efficacy of existing procedures.
• In a worst-case scenario, where the prevalence of EIAV is high in exporting countries, the model predicted that California might import 10 horses infected with EIAV. From these, 1 horse or none could elude detection and consequently be released if the quarantine period is 3 or 14 days, respectively. This suggests that while extending the quarantine period isn’t beneficial in low prevalence scenarios, it can be effective when the prevalence is high.

Application of the Model

• While this particular study focused on the risk of importing EIAV-infected horses into California, the model developed here can also be applied to other quarantine situations. The robust nature of the model allows it to be used to evaluate the importation risk for not only EIAV but also other diseases. Thus, it can potentially help in refining quarantine procedures and reducing the risk of disease transmission through imports.