Analyzing actual risk in malaria-deferred donors through selective serologic testing

Background Approximately 150,000 US blood donors are deferred annually for travel to malaria-endemic areas. However, the majority do not travel to the high-risk areas of Africa associated with transfusion-transmitted malaria (TTM) but visit low-risk areas such as Mexico. This study tests for Plasmodium infection among malaria-deferred donors, particularly those visiting Mexico. Study Design and Methods Blood donors deferred for malaria risk (travel, residence, or previous infection) provided blood samples and completed a questionnaire. Plasma was tested for Plasmodium antibodies by enzyme immunoassay (EIA); repeat-reactive (RR) samples were considered positive and tested by real-time polymerase chain reaction (PCR). Accepted donors provided background testing data. Results During 2005 to 2011, a total of 5610 malaria-deferred donors were tested by EIA, including 5412 travel deferrals. Overall, 88 (1.6%) were EIA RR; none were PCR positive. Forty-nine (55.7%) RR donors previously had malaria irrespective of deferral category, including 34 deferred for travel. Among 1121 travelers to Mexico, 90% visited Quintana Roo (no or very low risk), but just 2.2% visited Oaxaca/Chiapas (moderate or high risk). Only two Mexican travelers tested RR; both previously had malaria not acquired in Mexico. Conclusions Travel to Mexico represents a large percentage of US donors deferred for malaria risk; however, these donors primarily visit no- or very-low-risk areas. No malaria cases acquired in Mexico were identified thereby supporting previous risk estimates. Consideration should be given to allowing blood donations from US donors who travel to Quintana Roo and other low-risk areas in Mexico. A more effective approach to preventing TTM would be to defer all donors with a history of malaria, even if remote.