Recovery and viability of Orientia tsutsugamushi from packed red cells and the danger of acquiring scrub typhus from blood transfusion

BACKGROUND: The purpose of this study was to determine whether infective Orientia tsutsugamushi, the etiologic agent of scrub typhus, could survive normal blood banking processing and storage procedures. STUDY DESIGN AND METHODS: Mononuclear cells isolated from whole blood by density gradient centrifugation were inoculated with O. tsutsugamushi, Karp strain. Infection of the mononuclear cells was confirmed by Giemsa stain, direct fluorescent antibody assay, and polymerase chain reaction using primers specific for the groESL operon of O. tsutsogamushi.The quantity of rickettsia[ particles in each preparation was determined by direct counts from the Giemsa-stained preparations. Infected mononuclear cells were returned to their respective aliquots of packed red blood cells, which were then either stored at 4 degrees C or glycerolized and frozen at -70 degrees C. RESULTS: Rickettsiae survived up to 10 days (but not 30 days) of refrigerated storage and 45 days of frozen storage, as determined by inoculation of mice with 0.5-mL aliquots of the blood components. Infection of the mice was determined by illness, death, direct fluorescent antibody assay of peritoneal smears, polymerase chain reaction of blood, and enzyme-linked immunosorbent assay detection of antibodies in plasma. CONCLUSION: Because the quantity of rickettsiae injected into the mice was comparable to the quantity reported in the literature for human blood during natural infections, scrub typhus could present a risk in blood collected from donors in endemic areas. This may especially be true, because people can be rickettsemic before illness, after successful antibiotic treatment, and chronically after resolution of disease.