Today we’ll be discussing transfusion-transmitted babesiosis.
Transfusion-transmitted babesiosis is increasingly recognized as a challenge to blood transfusion safety.
Although babesiosis is often asymptomatic, approximately 20% of transfusion-associated cases are fatal.[1]
In the United States, babesiosis is most commonly caused by Babesia microti, transmitted by tick bites and endemic in the Northeast and upper Midwest.
Cases of transfusion-transmitted babesiosis are increasing, both in endemic and nonendemic areas. More than 150 cases have been reported since 1979, with 77% of these cases occurring since 2000.
In addition, reporting of transfusion-associated babesiosis only became mandatory in January, 2011. So incidence is likely underestimated.
No FDA-licensed blood donor screening assay exists, although donors are asked about tick bites and a history of babesiosis. In addition, donors from hyperendemic areas may also be excluded during months of peak transmission.
In an editorial, Drs. Melissa Cushing and Beth Shaz discuss the challenges of developing donor screening methods for Babesia and highlight three articles published in the journal Transfusion.[2]
Dr. Cushing, who is the Director of Transfusion Medicine and Cellular Therapy for the Department of Pathology and Laboratory Medicine at Cornell Medical College, had this to say:
(Audio Quote)
“Unlike with other recent infectious risks to the blood supply such as West Nile Virus, or platelet bacterial contamination, we have no effective mitigation strategy in place.
An effective strategy must balance patient risk with additional cost to the healthcare system as well as risks associated with further restrictions to the blood supply. When a safe and effective system for pathogen inactivation is finally available for red blood cells, this will provide the best solution for transfusion-transmitted babesiosis as well as other emerging tranfusion-transmitted infections. “
Developing effective screening algorithms is difficult because of two major reasons:
First, serologic testing causes donor loss, as non-infectious donors who still have detectable antibodies are excluded.
And second, PCR testing requires large sample volumes for adequate sensitivity.
In addition to Babesia microti, it was recently shown that transfusion-associated babesiosis can be caused by other species of Babesia, making all causes of babesiosis difficult to detect.[3]
A recent evaluation of a Babesia microti donor screening method in a Rhode Island hospital showed that none of the screened blood caused babesiosis. However, the study was not powered to detect a significant effect.[4]
Finally, a study by the American Red Cross[5] suggests that market withdrawal of donated products which were positive by serology or PCR could be an effective strategy for reducing transfusion-transmitted babesia.
At this point in time, there is no obvious answer as to which strategy is superior.
Since universal Babesia testing would be financially unsustainable, testing only selected blood components, units transfused to higher-risk patients, or only donors from endemic regions may be more practical.
Additionally, pathogen inactivation may help to address the growing challenge of transfusion-transmitted babesiosis, as well as other emerging transfusion-transmitted infections.
Thanks for watching Transfusion News. Be sure to join us for new editions of Transfusion News on the 15th and 30th of each month. In the meantime, you can always keep up to date with all of the latest news by visiting transfusionnews.com.
References:
1. Vannier E, Krause PJ. Human babesiosis. N Engl J Med 2012;366: 2397-407.
2. Cushing M, Shaz B. Transfusion-transmitted babesiosis: achieving successful mitigation while balancing cost and donor loss. Transfusion 2012;52: 1404-7.
3. Bloch EM, Herwaldt BL, Leiby DA, Shaieb A, Herron RM, Chervenak M, Reed W, Hunter R, Ryals R, Hagar W, Xayavong MV, Slemenda SB, Pieniazek NJ, Wilkins PP, Kjemtrup AM. The third described case of transfusion-transmitted Babesia duncani. Transfusion 2012;52: 1517-22.
4. Young C, Chawla A, Berardi V, Padbury J, Skowron G, Krause PJ. Preventing transfusion-transmitted babesiosis: preliminary experience of the first laboratory-based blood donor screening program. Transfusion 2012;52: 1523-9.
5. Johnson ST, Cable RG, Leiby DA. Lookback investigations of Babesia microti-seropositive blood donors: seven-year experience in a Babesia-endemic area. Transfusion 2012;52: 1509-16.
