Effects of Population Movement on the Risk of Chagas Disease in the California Blood Supply: A Preliminary Model
- Presenter:
Mon June 5, 2006 9:30-10:45 Room Alumni Lounge
Rationale: Chagas disease is a parasitic disease found predominantly in Latin America, including Mexico. Mexico routinely screens for Chagas disease in their blood supply, however there is currently no screening of the United States blood supply for Chagas disease. Although there are only a few documented cases of chagas attributed to blood transfusions, symptoms of this disease often don’t manifest until 10-30 years after contracting the disease. In addition with the increase in migration from Mexico to parts of the United States, the risk may be increasing.
Objectives: The objectives of this paper is to present a preliminary model of chagas disease transmission risk in the California and Mexican blood supply based on both the migration within Mexico from endemic to non-endemic areas in the migration from Mexico to California.
Methodology: We developed a model of migration and transmission risk for Chagas disease in Mexico and California. We used existing prevalence of chagas in the migrating population and probability estimates of blood donation, likelihood of having Chagas disease, infectivity depending on blood fractionation type, and other factors, to estimate the rate of seropositivity and risk of contracting Chagas from donated blood. We conduct a sensitivity analysis for the uncertain parameters.
Results: The base case California analysis we demonstrated a seropositivity rate of 0.015, and an immigrant donation rate of 0.01232. We estimated that the current verbal screen would eliminate only 0.000542 donations and that each unit given would be fractionated to go to 2.5 recipients. Sensitivity analysis showed that if the immigrant population continues to increase and the current efforts continue to increase blood donation from 1 to 10% in Hispanic communities, then the risk of contracting Chagas disease from blood transfusion in California increases from about 112 to 913 individuals. If the seropositivity rate of Mexican Immigrants is varied from the low rate of 0.000222 to the highest rate of 0.023, then the number of Californians contracting Chagas goes from about 1 person to 172 persons. When the infectivity is varied from a low of 0.01 to a high of 0.34, then the annual number contracting Chagas disease in California goes from only 11 to 384.
Conclusion: We suggest that more data collection is needed so that a more refined model can be made to estimate risk of Chagas disease to Californians receiving blood. However, from the current estimates, we feel that the risk of contracting Chagas disease from the blood supply is high enough to warrant testing, at least in the high risk areas with high population movement from endemic areas.
