Transfusion-transmitted Babesia spp.: a changing landscape of epidemiology, regulation, and risk mitigation.

Babesia spp. are tick-borne parasites with a global distribution and diversity of vertebrate hosts. Over the next several decades, climate change is expected to impact humans, vectors, and vertebrate hosts and change the epidemiology of Babesia. Although humans are dead-end hosts for tick-transmitted Babesia, human-to-human transmission of Babesia spp. from transfusion of red blood cells and whole blood-derived platelet concentrates has been reported. In most patients, transfusion-transmitted Babesia (TTB) results in a moderate-to-severe illness. Currently, in North America, most cases of TTB have been described in the United States. TTB cases outside North America are rare, but case numbers may change over time with increased recognition of babesiosis and as the epidemiology of Babesia is impacted by climate change. Therefore, TTB is a concern of microbiologists working in blood operator settings, as well as in clinical settings where transfusion occurs. Microbiologists play an important role in deploying blood donor screening assays in Babesia endemic regions, identifying changing risks for Babesia in non-endemic areas, investigating recipients of blood products for TTB, and drafting TTB policies and guidelines. In this review, we provide an overview of the clinical presentation and epidemiology of TTB. We identify approaches and technologies to reduce the risk of collecting blood products from Babesia-infected donors and describe how investigations of TTB are undertaken. We also describe how microbiologists in Babesia non-endemic regions can assess for changing risks of TTB and decide when to focus on laboratory-test-based approaches or pathogen reduction to reduce TTB risk.

International survey of strategies to mitigate transfusion-transmitted Trypanosoma cruzi in non-endemic countries, 2016-2018.

BACKGROUND AND OBJECTIVES: Chagas disease, caused by Trypanosoma cruzi, is endemic to Mexico, Central and South America. While initially limited to the Americas, emigration of infected persons triggered geographically broader blood safety challenges. To mitigate transfusion-transmitted Chagas (TTC), transfusion services implemented approaches including risk factor questions and serologic testing. We sought to understand and compare strategies in non-endemic countries. MATERIALS AND METHODS: Transfusion services in International Society of Blood Transfusion (ISBT)-affiliated organizations and members of the ISBT Working Party on Transfusion-Transmitted Infectious Diseases were invited to complete an online survey on T. cruzi mitigation strategies. The survey queried about cases of TTC, risk factors, testing methodology, educational materials, pathogen reduction, donor/product management, donor deferral and perceived public health concerns surrounding TTC. RESULTS: Responses were received from 27 institutions in 22 countries. Most countries (77.3%) reported no historical TTC cases, while 18.2% reported 1-5 cases and 4.5% reported 6-10 cases. Concern about Chagas among the general public and public health authorities was low, but 12 of 25 blood centres reported moderate/high concern. Overall, 17 countries mitigated for TTC: 15 used risk factor questions and 10tested for T. cruzi antibodies. Ten countries used pathogen reduction but not specifically to prevent TTC. CONCLUSION: While Chagas is rarely cited as a public health concern, blood centres in many non-endemic countries, including those outside the Americas, implemented measures to mitigate risk. Mitigation focussed on risk factors associated with Latin American immigrants and serologic testing. Thus, despite the rarity of TTC, many non-endemic countries continue to address it as an ongoing blood safety risk.

Emerging tick-borne diseases and blood safety: summary of a public workshop.

Tick-borne agents of disease continue to emerge and subsequently expand their geographic distribution. The threat to blood safety by tick-borne agents is ever increasing and requires constant surveillance concomitant with implementation of appropriate intervention methods. In April 2017, the Food and Drug Administration organized a public workshop on emerging tick-borne pathogens (excluding Babesia microti and Lyme disease) designed to provide updates on the current understanding of emerging tick-borne diseases, thereby allowing for extended discussions to determine if decisions regarding mitigation strategies need to be made proactively. Subject matter experts and other stakeholders participated in this workshop to discuss issues of biology, epidemiology, and clinical burden of tick-borne agents, risk of transfusion-transmission, surveillance, and considerations for decision making in implementing safety interventions. Herein, we summarize the scientific presentations, panel discussions, and considerations going forward.

International survey on the impact of parasitic infections: frequency of transmission and current mitigation strategies.

BACKGROUND AND OBJECTIVES: Globally, blood safety interventions have been successful in mitigating risk of the major transfusion-transmitted (TT) viruses. However, strategies that address risk from parasites are comparatively limited. TT parasites are often regional in nature, posing unique challenges; we sought to understand their impact on blood safety. MATERIALS AND METHODS: An electronic questionnaire was distributed to transfusion medicine leaders in 100 countries. The survey focused on specific questions pertaining to four parasitic diseases: babesiosis, Chagas, leishmaniasis and malaria. Respondents provided data on historical TT cases, local epidemiology, policies to mitigate risk and an assessment of public health perceptions for each aetiologic agent. RESULTS: Twenty-eight (28%) surveys were returned from countries in Europe (n = 13), the Americas (n = 6), Africa (n = 4), Asia (n = 3) and Oceana (n = 2). Historically, no cases of TT leishmaniasis were reported, TT babesiosis was exclusive to Canada and the USA, TT Chagas was limited to the Americas and Spain, while TT malaria was cosmopolitan. Mitigation efforts varied widely; malaria was the most frequently tested parasitic disease. The public's perception of risk for parasitic agents was low, while that of health authorities in endemic countries was higher. CONCLUSION: The global impact of parasitic infections on blood safety and related mitigation efforts varied widely by parasite epidemiology, test availability, public health priorities and socioeconomic constraints. While parasites continue to pose a risk to blood safety, the successful mitigation of viral risk has elevated the prominence of TT parasites in many locations, thereby requiring consideration of mitigation efforts.

Frequency of Trypanosoma cruzi parasitemia among infected blood donors with a potential association between parasite lineage and transfusion transmission.

BACKGROUND: Trypanosoma cruzi is endemic to the Americas where it demonstrates multiple lineages over a vast geographic range (i.e., United States to Argentina). These lineages possess divergent geographic and biologic characteristics, including variations in disease manifestations. Herein, we report the frequency of parasitemia among seropositive US blood donors and the potential association between parasite lineage and transfusion transmission. STUDY DESIGN AND METHODS: Blood donors identified as T. cruzi seropositive during screening were enrolled in follow-up studies, including hemoculture testing and a risk factor questionnaire. Positive hemocultures were expanded to obtain sufficient parasites for molecular lineage determination and analysis. Country of birth, obtained from the questionnaire, was used to predict parasite lineage in the absence of demonstrable parasitemia for infected donors. RESULTS: Eighteen (6.8%) of 263 seropositive donors were hemoculture positive. Among the 17 hemocultures expanded for lineage determination, TcV was identified more frequently (n = 12), compared to TcI (n = 2), TcII (n = 1), and TcVI (n = 2). When presumptive parasite lineages were compared to hemoculture results, only two of 157 (1.3%) TcI versus 13 of 38 (34.2%) TcII/TcV/TcVI non-US donors were parasitemic; three of 44 (6.8%) US donors were TcV or TcVI. CONCLUSIONS: Based on lineage determination for donors with parasitemia; hemoculture positivity associated with presumptive parasite lineage; and implicated donors from US, Canadian, and Spanish transfusion cases, donors from Southern South America are significantly more likely to have parasitemia and transmit infection to blood recipients (TcII, TcV, or TcVI vs. TcI). Thus, parasite lineage may be associated with risk of transfusion-transmitted T. cruzi.

Screening of Blood Donations for Zika Virus Infection - Puerto Rico, April 3-June 11, 2016.

Transfusion-transmitted infections have been documented for several arboviruses, including West Nile and dengue viruses (1). Zika virus, a flavivirus transmitted primarily by Aedes aegypti mosquitoes that has been identified as a cause of congenital microcephaly and other serious brain defects (2), became recognized as a potential threat to blood safety after reports from a 2013-2014 outbreak in French Polynesia. Blood safety concerns were based on very high infection incidence in the population at large during epidemics, the high percentage of persons with asymptomatic infection, the high proportion of blood donations with evidence of Zika virus nucleic acid upon retrospective testing, and an estimated 7-10-day period of viremia (3). At least one instance of transfusion transmission of Zika virus has been documented in Brazil after the virus emerged there, likely in 2014 (4). Rapid epidemic spread has followed to other areas of the Americas, including Puerto Rico.

Do leukoreduction filters passively reduce the transmission risk of human granulocytic anaplasmosis?

BACKGROUND: Human granulocytic anaplasmosis, caused by Anaplasma phagocytophilum, poses an increasing public health risk in the United States. Since 2000, case reports have increased annually; 2782 cases were reported in 2013. Despite the increasing frequency of clinical cases, only eight cases of transfusion-transmitted anaplasmosis (TTA) have been reported. We investigated if current leukoreduction practices impact transfusion risk. STUDY DESIGN AND METHODS: Whole blood units (WBUs) with integral red blood cell (RBC) leukoreduction filters were collected and spiked with A. phagocytophilum-infected HL-60 cells equivalent to 0.01, 1, or 5% of total neutrophils. After 24 hours at 4°C WBUs were processed into plasma and RBCs, the latter subsequently leukoreduced (LR RBCs). To evaluate the removal of A. phagocytophilum by filtration, pre- and postfiltration samples were compared by culture and polymerase chain reaction (PCR). RESULTS: Compared to Day 0 or Day 1 positive controls, LR RBCs demonstrated reduced levels of A. phagocytophilum by culture and PCR. At 0.01% infection levels LR RBCs yielded no positive cultures and a log reduction of 2.5 by PCR. Similarly, at 1 and 5% infections levels, LR RBCs produced only 44% (4/9) and 56% (5/9) positive cultures, respectively. PCR results were comparable, 3.0 log reduction for 1% and 3.3 log reduction for 5% infection levels. CONCLUSIONS: The recent increase in TTA suggests that A. phagocytophilum may represent an emerging blood safety issue. However, the current study indicates that the widespread practice of leukoreduction might passively reduce, but not eliminate, TTA risk. In the absence of viable testing or pathogen inactivation and/or reduction options, leukoreduction may offer some protection from transmission risk.

Reduction of Leishmania donovani infectivity in whole blood using riboflavin and ultraviolet light.

BACKGROUND: Leishmaniasis is a vector-borne disease caused by the protozoan parasite Leishmania sp. that is transmitted by sandflies. Travelers to endemic areas, and US military personnel stationed in the Middle East, are at risk for contracting the disease. STUDY DESIGN AND METHODS: Whole blood (WB) units were spiked with human monocytes infected with L. donovani amastigotes to a final concentration of approximately 10(5) infected cells/mL. After riboflavin (RB) addition, units were exposed to 80 J/mLRBCs ultraviolet (UV) light. One pretreatment (collected after RB addition) and one posttreatment sample were collected, serially diluted in culture medium, and incubated at 22°C for up to 5 weeks. Parasite viability was determined by microscopic observation for replicating promastigote forms. RESULTS: Mirasol treatment of 3 units of L. donovani-infected WB with RB and UV light resulted in a parasite reduction of 2.3 ± 0.12 log. CONCLUSIONS: Partial reduction of L. donovani can be achieved in WB using RB and UV light. This technology may be useful when potential donors are exposed to Leishmania sp. during residence, travel, or military deployment to an endemic area.

Comparative evaluation of 11 commercialized rapid diagnostic tests for detecting Trypanosoma cruzi antibodies in serum banks in areas of endemicity and nonendemicity.

Chagas disease is one of the main public health issues in Latin America. Increasingly during the past few decades, Trypanosoma cruzi infection has been detected in North America, Europe, and the Western Pacific, mainly as a result of population movement. The limited availability of rapid serological diagnostic tests hinders rapid diagnosis and early treatment in areas of endemicity and nonendemicity. In collaboration with 11 national reference laboratories (NRLs) from different geographical areas, we evaluated the performances of commercialized serological rapid diagnostic tests (RDT) for T. cruzi infection. Eleven commercialized T. cruzi infection RDTs were evaluated on a total of 474 samples extensively tested with at least three different techniques for Chagas disease, maintained at controlled low temperatures, and stored in the serum banks of the 11 NRLs. We measured the sensitivity, specificity, and concordance of each RDT and provided an additional questionnaire to evaluate its ease of use. The selected RDTs in this study were performed under controlled laboratory conditions. Out of the 11 RDTs, we found 8 of them to be useful, with the cassette format favored over the strip. We did not observe significant differences in RDT performances in the different regions. Overall, the performance results were lower than those disclosed by the manufacturers. The results of this evaluation validate the possibility of using RDTs to diagnose Chagas disease, thereby decreasing the time to treatment at a primary health care facility for patients who are willing to be treated. Further studies should be conducted in the laboratory and in the field to confirm these data, expressly to evaluate reproducibility in resource-limited settings, or using whole blood in clinical settings in areas of endemicity and nonendemicity.

A longitudinal study of Babesia microti infection in seropositive blood donors.

BACKGROUND: Babesia infection is caused by intraerythrocytic tick-borne parasites. Cases of transfusion-transmitted babesiosis have been increasingly recognized. To date, no Babesia test has been licensed for screening US blood donors. We conducted a longitudinal study to assess the course and markers of Babesia infection among seropositive donors identified in a seroprevalence study. STUDY DESIGN AND METHODS: Eligible donors had B. microti indirect fluorescent antibody (IFA) titers of 64 or greater. Enrollees were monitored up to 3 years, by IFA and three methods for evidence of parasitemia: B. microti nested polymerase chain reaction (PCR) analysis (at two laboratories), hamster inoculation, and blood-smear examination. RESULTS: Among 115 eligible donors, 84 (73%) enrolled. Eighteen enrollees (21%) had evidence of parasitemia for 30 total specimens (17% of 181), which were collected in 9 different months and tested positive by various approaches: PCR (25 specimens/16 persons), hamster inoculation (13 specimens/8 persons), and blood smear (one specimen positive by all three approaches). Overall, 14 persons had one or more specimen with positive PCR results at both laboratories (12 persons) and/or had parasitologically confirmed infection (eight persons). Three of nine persons who had more than one specimen with evidence of parasitemia had nonconsecutive positives. Several enrollees likely had been infected at least 1 year when their last positive specimen was collected. The final three specimens for seven persons tested negative by all study methods, including IFA. CONCLUSION: Seropositive blood donors can have protracted low-level parasitemia that is variably and intermittently detected by parasitologic and molecular methods. Donor-screening algorithms should include serologic testing and not solely rely on molecular testing.

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 U.S. 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.

Babesia microti real-time polymerase chain reaction testing of Connecticut blood donors: potential implications for screening algorithms.

BACKGROUND: Babesia microti, an intraerythrocytic parasite, has been implicated in transfusion transmission. B. microti seroprevalence in Connecticut (CT) blood donors is approximately 1%; however, it is not known what percentage of donors is parasitemic and poses a risk for transmitting infection. Therefore, we determined the prevalence of demonstrable B. microti DNA in donors from a highly endemic area of CT and compared observed rates with concurrent immunofluorescence assay (IFA) testing results. STUDY DESIGN AND METHODS: Blood samples from consenting donors in southeastern CT were collected from mid-August through early October 2009 and tested by IFA for immunoglobulin G antibodies and real-time polymerase chain reaction (PCR) for B. microti DNA. IFA specificity was determined using blood donor samples collected in northwestern Vermont (VT), an area nonendemic for Babesia. RESULTS: Of 1002 CT donors, 25 (2.5%) were IFA positive and three (0.3%) were real-time PCR positive. Among the three real-time PCR-positive donors, two were also IFA positive, while one was IFA negative and may represent a window period infection. The two IFA- and real-time PCR-positive donors appeared to subsequently clear infection. The other real-time PCR-positive donor did not provide follow-up samples. Of 1015 VT donors tested by IFA, only one (0.1%) was positive, but may have acquired infection during travel to an endemic area. CONCLUSION: We prospectively identified several real-time PCR-positive blood donors, including an IFA-negative real-time PCR-positive donor, in an area highly endemic for B. microti. These results suggest the need to include nucleic acid testing in planned mitigation strategies for B. microti.

Babesia microti seroprevalence in Minnesota blood donors.

BACKGROUND: The increasing frequency of transfusion-transmitted babesiosis represents a concern for the safety of the US blood supply. The agent responsible for the disease, the intraerythrocytic parasite Babesia microti, is naturally transmitted to humans by a tick bite and is endemic in areas of the Northeast and Upper Midwest United States. In this study, we explored B. microti seroprevalence in blood donors from different areas of Minnesota (MN). STUDY DESIGN AND METHODS: We tested 2150 blood donors in MN for the presence of antibodies against B. microti using an immunofluorescent assay (IFA). Donors identified as positive (≥64) were also tested by real-time polymerase chain reaction (PCR) for the presence of parasite DNA. Seropositive donors were contacted by phone and asked questions regarding tick exposure. Donors positive by IFA were indefinitely deferred from donating blood. RESULTS: A total of 2150 donations were tested between October 2010 and November 2011. Forty-two donors (2.0%) were positive by IFA and one was also PCR positive. All positive donors reported extended outdoor activities, 12 recalled finding ticks on their body, and six had flu-like symptoms since their last blood draw. CONCLUSIONS: This study provides new data about B. microti seroprevalence in MN blood donors. Possibly because the targeted collection areas were mostly expected to be endemic for the parasite, the observed seroprevalence levels were higher than expected, although the geographic distribution of positive donors did not completely overlap with the distribution of reported clinical cases in MN.

Riboflavin and ultraviolet light reduce the infectivity of Babesia microti in whole blood.

BACKGROUND: Babesia microti is the parasite most frequently transmitted by blood transfusion in the United States. Previous work demonstrated the efficacy of riboflavin (RB) and ultraviolet (UV) light to inactivate B.microti in apheresis plasma and platelet units. In this study we investigated the effectiveness of RB and UV light to reduce the levels of B.microti in whole blood (WB). STUDY DESIGN AND METHODS: WB units were spiked with B. microti-infected hamster blood. Spearman-Karber methods were used to calculate infectivity of each sample in terms of hamster infectious dose 50% (HID50 ) value. After RB addition, the units were illuminated with 80 J/mLRBC UV light. Two samples were collected: one before illumination and one after illumination. The samples were serially diluted and dilutions injected into a group of five naive hamsters. Four weeks postinoculation (PI), blood was collected from the animals and evaluated by microscopic observation. RESULTS: One pilot study showed a good dose response in the animals and demonstrated that sample infectivity could be calculated in terms of an HID50 . Three additional replicates were performed in the same manner as the pilot study, but with fewer dilutions. Infectivity values were consistent between the experiments and were used to calculate log reduction. The posttreatment reduction of B. microti for all the experiments was more than 5 log. CONCLUSIONS: The data collected indicate that use of RB and UV is able to decrease the parasite load in WB units thus reducing the risk of transfusion-transmitted B. microti from blood components containing B. microti-infected RBCs.

Antibody levels correlate with detection of Trypanosoma cruzi DNA by sensitive polymerase chain reaction assays in seropositive blood donors and possible resolution of infection over time.

BACKGROUND: The clinical significance of anti-Trypanosoma cruzi low-level reactive samples is incompletely understood. Polymerase chain reaction (PCR)-positive rates and antibody levels among seropositive blood donors in three countries are described. STUDY DESIGN AND METHODS: Follow-up samples were collected from T. cruzi-seropositive donors from 2008 through 2010 in the United States (n = 195) and Honduras (n = 58). Also 143 samples from Brazil in 1996 to 2002, originally positive by three serologic assays, were available and paired with contemporary follow-up samples from these donors. All samples were retested with Ortho enzyme-linked immunosorbent assay (ELISA). PCR assays were performed on coded sample panels by two laboratories (Blood Systems Research Institute [BSRI] and American Red Cross Holland Laboratory [ARC]) that amplified kinetoplast minicircle DNA sequences of T. cruzi. RESULTS: PCR testing at BSRI yielded slightly higher overall sensitivity and specificity (33 and 98%) compared with those at the ARC (28 and 94%). Among seropositive donors, PCR-positive rates varied by country (p < 0.0001) for the BSRI laboratory: Brazil (57%), Honduras (32%), and the United States (14%). ELISA signal-to-cutoff ratios (S/CO) were significantly higher for PCR-positive compared to PCR-negative donors (p < 0.05 for all comparisons). Additionally, PCR-negative Brazilian donors exhibited greater frequencies of antibody decline over time versus PCR-positive donors (p = 0.003). CONCLUSION: For all three countries, persistent DNA positivity correlated with higher ELISA S/CO values, suggesting that high-level seroreactivity reflects chronic parasitemia. Significant S/CO declines in 10% of the PCR-negative Brazilian donors may indicate seroreversion after parasite clearance in the absence of treatment.

Transfusion-transmitted Babesia spp.: bull's-eye on Babesia microti.

Babesia spp. are intraerythrocytic protozoan parasites of animals and humans that cause babesiosis, a zoonotic disease transmitted primarily by tick vectors. Although a variety of species or types of Babesia have been described in the literature as causing infection in humans, the rodent parasite Babesia microti has emerged as the focal point of human disease, especially in the United States. Not only has B. microti become established as a public health concern, this agent is increasingly being transmitted by blood transfusion: estimates suggest that between 70 and 100 cases of transfusion-transmitted Babesia (TTB) have occurred over the last 30 years. A recent upsurge in TTB cases attributable to B. microti, coupled with at least 12 fatalities in transfusion recipients diagnosed with babesiosis, has elevated TTB to a key policy issue in transfusion medicine. Despite clarity on a need to mitigate transmission risk, few options are currently available to prevent the transmission of B. microti by blood transfusion. Future mitigation efforts may stress serological screening of blood donors in regionalized areas of endemicity, with adjunct nucleic acid testing during the summer months, when acute infections are prevalent. However, several hurdles remain, including the absence of a licensed blood screening assay and a thorough cost-benefit analysis of proposed interventions. Despite current obstacles, continued discussion of TTB without proactive intervention is no longer a viable alternative.

Lookback investigations of Babesia microti-seropositive blood donors: seven-year experience in a Babesia-endemic area.

BACKGROUND: Human babesiosis in the United States is primarily attributable to infection with the intraerythrocytic protozoan parasite, Babesia microti. Transfusion-transmitted Babesia (TTB) is a mounting blood safety concern; approximately 100 US cases of TTB have been reported since 1980. In response, market withdrawal (MW) and/or lookback (LB) has been advocated for cellular components derived from Babesia-positive blood donors. STUDY DESIGN AND METHODS: Immunofluorescence assay (IFA) and selective polymerase chain reaction (PCR) testing of Connecticut donors was conducted from 1999 through 2005. MW/LB was initiated following established procedures on cellular components derived from IFA and/or PCR-positive donors. Recipients of these associated components were offered IFA and PCR testing for B. microti. RESULTS: A total of 208 seropositive donors were identified, with 474 donations and 656 cellular components subject to MW/LB. Sixty-three recipients were tested for B. microti; eight (12.7%) were IFA and/or PCR positive. A significantly higher proportion of B. microti-positive recipients were identified by LB in 1999 to 2000 (5 of 15, 33.3%) than after implementation of seropositive donor deferral in 2001 (3 of 48, 6.3%). Significant differences in positive LBs were also found when comparing index (50% positive) to previous donations (7.3% positive), and when comparing demonstrably parasitemic to nonparasitemic donors, 33.3 and 2.9%, respectively. CONCLUSIONS: Recipients of components from B. microti-positive donors were infected via transfusion, with index donations from parasitemic donors posing the greatest transmission risk. This report of B. microti transmission detected through LB, coupled with ongoing TTB cases, indicates that interventions are needed to reduce transmission of B. microti to US blood recipients.

Trypanosoma cruzi infection in North America and Spain: evidence in support of transfusion transmission.

BACKGROUND: The United States, Canada, and Spain perform selective testing of blood donors for Trypanosoma cruzi infection (Chagas disease) to prevent transfusion transmission. The donor, product, and patient characteristics associated with transfusion-transmitted infections are reviewed and the infectivity of components from donors with serologic evidence of infection is estimated. STUDY DESIGN AND METHODS: A systematic review of transfusion-transmitted T. cruzi cases and recipient tracing undertaken in North America and Spain is described. Cases were assessed for the imputability of the evidence for transfusion transmission. RESULTS: T. cruzi infection in 20 transfusion recipients was linked to 18 serologically confirmed donors between 1987 and 2011, including 11 identified only by recipient tracing. Cases were geographically widely distributed and were not associated with incident or autochthonous infections. Index clinical cases were described only in immunocompromised patients. All definite transmissions (n = 11) implicated apheresis or whole blood-derived platelets (PLTs), including leukoreduced and irradiated products. There is no evidence of transmission by red blood cells (RBCs) or frozen products, while transmission by whole blood transfusion remains a possibility. Recipient tracing reveals low component infectivity from serologically confirmed, infected donors of 1.7% (95% confidence interval [CI], 0.7%-3.5%) overall: 13.3% (95% CI, 5.6%-25.7%) for PLTs, 0.0% (95% CI, 0.0%-1.5%) for RBCs, and 0.0% (95% CI, 0%-3.7%) for plasma and cryoprecipitate. CONCLUSIONS: T. cruzi is transmitted by PLT components from some donors with serologic evidence of infection. Evidence of transmission before the implementation of widespread testing in the countries studied is sparse, and selective testing of only PLT and fresh whole blood donations should be considered.

Evaluating pathogen reduction of Trypanosoma cruzi with riboflavin and ultraviolet light for whole blood.

BACKGROUND: Trypanosoma cruzi, the protozoan parasitic agent of Chagas disease, can be transmitted by blood transfusion. In 2007, most US blood banks started screening blood donations for T. cruzi, but the cost and perceived need of the test have been the subject of ongoing discussion. In this study, we evaluated the ability of the Mirasol System (CaridianBCT), which uses riboflavin (RB) and ultraviolet light to inactivate pathogens, to reduce the levels of infectious T. cruzi in whole blood (WB). STUDY DESIGN AND METHODS: WB units were inoculated with 4, 40, 400, and 4000 trypomastigotes/mL. After addition of RB and illumination at various energy levels, the samples were tested for the presence of live parasites by hemoculture. RESULTS: All preillumination samples exhibited T. cruzi growth in hemoculture, while postillumination samples from units containing 4 and 40 trypomastigotes/mL showed no signs of viable parasites after 16 weeks of culture. In contrast, at both 400 and 4000 parasites/mL, two of the three units were positive for viable parasites. CONCLUSIONS: The total log reduction observed for T. cruzi was 3.5 log or greater, but less than 4.5 log. This level of reduction is likely to be orders of magnitude higher than what would be expected in a tainted blood donation, indicating that the Mirasol System could be effective at preventing transfusion of the causative agent of Chagas disease.