Reduced Risk of Transfusion-Transmitted Babesiosis With Blood Donor Testing

To theEditor—Babesiosis is a tick-borne disease, caused primarily in the United States (US) by the protozoa Babesia microti that infects red blood cells (RBCs). Transmission can also occur by transfusion of RBCs collected from asymptomatic, infected blood donors. Babesia microti is endemic in the northeastern and northern midwestern states and is spreading in the US. Recognized first in New England in 1980, transfusion-transmitted babesiosis (TTB) reached an estimated incidence of 1 per 18 000 transfusions in endemic states by 2015 [1, 2] and is still likely underrecognized despite causing potentially severe disease or death in about 20% of cases [3].

In 2018, the US Food and Drug Administration (FDA) licensed the first nucleic acid test (NAT) for screening blood donors that detects asymptomatic Babesia infection. In May 2019, FDA released final guidance for blood centers to implement within 12 months to reduce the risk of TTB [4]. FDA currently recommends testing each donation using a licensed NAT in 14 B. microti–risk states and Washington, District of Columbia, and screening donors in the remaining states for a previous history of babesiosis [4]. According to the FDA guidance, blood centers may implement pathogen reduction using an FDA-approved pathogen reduction device that inactivates Babesia spp in platelet and plasma components instead of testing each donation or screening donors for a history of babesiosis. However, an FDA-approved pathogen reduction device is not yet available for whole blood or red blood cells.

According to the National Blood Utilization and Collection Survey, blood centers collected 11.5 million RBCs for 10.8 million RBC transfusions in the US in 2019 [5]. FDA requires blood centers to report Biological Product Deviations for TTB when a blood donor is implicated, or not ruled out, as the source of infection [6]. Only 3 TTB cases were reported in the 2 years after complete implementation of FDA's recommendations, compared with 44 in the 3 years prior to the release of the guidance (P < .01) (Table 1). Almost all (41/44 [93%]) TTB cases before implementation occurred in 10 of the 14 states in which FDA now recommends NAT on each donation, and 3 occurred in nonendemic states (Florida, Oklahoma, North Carolina). In the year after full implementation, the 3 reported TTB cases occurred in states that use babesiosis history screening only (Ohio, Oklahoma, West Virginia), and the implicated donations were not tested (Table 1). No cases of TTB were associated with NAT-negative index donations by infected donors (ie, a false-negative result) or NAT-negative donations by donors who subsequently had a NAT-positive donation (ie, a window period donation or an early low-grade infection below the limit of detection by NAT), based on an additional 780 reports submitted by 67 blood centers.

In conclusion, the national data from this report and regional data from blood centers [7] support the effectiveness of FDA's recommendations for NAT testing in Babesia high-risk states to reduce the risk of TTB in the US. In addition, our data highlight the importance of surveillance of blood safety through mandatory reporting by all licensed and registered blood collectors. Such reported data comprise blood donations in all states which perform Babesia NAT, as well as states which perform only babesiosis health history screening. FDA will continue to monitor reported cases of TTB and epidemiological data, to assess whether additional recommendations are needed to maintain blood safety.

Babesiosis and other tick-borne diseases are increasing in the US [8]. In a recent publication, the Centers for Disease Control and Prevention reported an overall 25% increase in tick-borne diseases between 2011 and 2019, and now consider an additional 3 states (Maine, New Hampshire, and Vermont) to have endemic transmission of babesiosis comparable to the other high-incidence northeastern states [8]. Apart from its value in maintaining safety of the blood supply, donor screening with NAT is a useful tool to assess the incidence of infection in endemic areas among healthy volunteer blood donors and monitor the spread of disease in new areas where risk of Babesia transmission is present.

Notes

Financial support. This work was supported by the U.S. Food and Drug Administration.

References

Author notes