DISPATCHES Table. Results of serologic testing and PCR analyses of specimens collected from a California resident with babesiosis and donors of packed red blood cells, 2007* Specimen source Patient Residence California Date of transfusion† – Donor 1 Maine Jan 1 Donor 2 Maine Jan 1 Donor 3 California Jan 22 Donor 4 California Jan 23 Donor 5 California Jan 24 Donor 6 California Jan 24 *IFA, immunofluorescent antibody. †Involving blood products from specified donor. ‡<8 is considered a negative titer for total B. microti antibody. IFA tests conducted at the Centers for Disease Control and Prevention Reference Diagnostic Laboratory. Date of specimen collection Feb 12 Feb 20 Feb 26 Feb 26 Feb 21 Feb 22 Feb 21 Feb 21 B. microti test results PCR IFA Positive <8‡ – 64 Negative 256 – <8 – <8 – <8 – <8 – <8 are concentrated (5). He frequented tick-infested areas and This case demonstrates that, even among transfused is likely to have become infected in late August 2006, when patients who show atypical symptoms of babesiosis, the he sought treatment for fever, chills, weight loss, and fa- possibility of infection should be considered if they have tigue and was tested for various infections, including Lyme received blood products from disease-endemic areas and disease and ehrlichiosis. At that time, he was not tested for display abnormal blood cell counts, such as low iron and babesiosis. His health improved without a speciﬁc diag- low leukocyte counts. Generalized debilitation associated nosis or treatment, and he remained asymptomatic, but he with cancer and chemotherapy may have masked Babesia- evidently was parasitemic when he donated blood on De- related symptoms in this patient and undermined his im- cember 20, 2006. Blood products from this donation were mune response. This case also underscores the widening included in the transfusion the patient received on January seasonal and geographic boundaries of babesiosis. Tick- 1, 2007. Between October 2005 and the blood donation on borne babesiosis usually peaks from July through Sep- December 20, 2006, the donor made 3 donations. tember (4), but because asymptomatic Babesia infection All other recipients of blood products from this donor can persist for months to years, especially in untreated were residents of Maine. They were notiﬁed of the need persons (7,8), transfusion-associated infection can occur for serologic testing; none were reported to be infected (V. throughout the year. Geographic limitations in babesiosis Rea, pers. comm.). are virtually erased by the mobility of donors and blood products. The blood bank involved in this case has blood Conclusions collection centers in California and Maine but provides Babesiosis was documented in a man with metastatic blood products to hospitals throughout southern Califor- cancer who resided in an area nonendemic for B. microti. nia and the East Coast. Medical evaluation for babesiosis On the basis of laboratory and epidemiologic informa- in both febrile and afebrile transfusion patients should tion, we concluded that the patient acquired the infection include a Giemsa-stained thin blood smear, an acute se- via transfusion of infected PRBCs donated in a disease- rologic evaluation by IFA testing and a convalescent se- endemic area thousands of miles away. The 12-day period rologic evaluation by IFA testing taken 4–6 weeks apart from donation to transfusion was within the maximum 35 (9), and PCR evaluation of whole blood. days that B. microti has been known to remain viable in The varied clinical spectrum of babesiosis makes its refrigerated blood (7). The period from time of transfusion detection in blood donors challenging. This case exem- exposure until positive smear was ≈6 weeks; incubation pe- pliﬁes the limitations in screening healthy asymptomatic riods for transfusion-related cases have ranged from weeks donors for babesiosis. Available screening tests to detect to many months (B. Herwaldt, pers. comm.). We had ten- Babesia spp. postdonation are not cost-effective and have tatively hypothesized that the patient might have acquired inadequate sensitivity (7,10). Nucleic acid testing and in- the infection in Oregon, where he spent substantial time activation procedures may provide useful options for de- outdoors, but remained asymptomatic until he became ill tecting Babesia spp. in the future (7,11). Until effective with cancer; however, we rejected this hypothesis because screening procedures are available, however, diagnosis of human cases of babesiosis have never been documented in babesiosis in blood donors will continue to be based pri- Oregon (or in Utah where the man also visited) and because marily on clinical observation. infections acquired in western states are more likely to be caused by local Babesia agents. 786 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 15, No. 5, May 2009