Transfusion-transmitted babesiosis in Rhode Island

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.

Global meta-analysis on Babesia infections in human population: prevalence, distribution and species diversity

Human babesiosis is an emerging tick-borne protozoan zoonosis caused by parasites of the genus Babesia and transmitted by ixodid ticks. It was thought to be a public health problem mainly for the immunocompromised, however the increasing numbers of documented cases among immunocompetent individuals is a call for concern. In this systematic review and meta-analysis, we reported from 22 countries and 69 studies, an overall pooled estimate (PE) of 2.23% (95% CI: 1.46-3.39) for Babesia infections in humans. PEs for all sub-groups varied significantly (p < 0.05) with a continental range of 1.54% (95% CI: 0.89-2.65) in North America to 4.17% (95% CI: 2.11-8.06) in Europe. PEs for country income levels, methods of diagnosis, study period, sample sizes, Babesia species and targeted population ranged between 0.43% (95% CI: 0.41-0.44) and 7.41% (95% CI: 0.53-54.48). Babesia microti recorded the widest geographic distribution and was the predominant specie reported in North America while B. divergens was predominantly reported in Europe. Eight Babesia species; B. bigemina, B. bovis, B. crassa-like, B. divergens, B. duncani, B. microti, B. odocoilei and B. venatorum were reported in humans from different parts of the world with the highest prevalence in Europe, lower middle income countries and among individuals with history of tick bite and other tick-borne diseases. To control the increasing trend of this emerging public health threat, tick control in human settlements, the use of protective clothing by occupationally exposed people and the screening of transfusion blood in endemic countries are recommended.Abbreviations AJOL: African Journals OnLine, CI: Confidence interval, CIL: Country income level, df: Degree of freedom, HIC: Higher-income countries, HQ: High quality, I²: Inverse variance index, IFAT: Indirect fluorescent antibody test, ITBTBD: Individuals with tick-bite and tick-borne diseases, JBI: Joanna Briggs Institute, LIC: Lower-income countries, LMIC: Lower middle-income countries, MQ: Medium quality, NA: Not applicable, N/America: North America, OEI: Occupational exposed individuals, OR: Odds ratio, PE: Pooled estimates, PCR: Polymerase chain reaction, Prev: Prevalence, PRISMA: Preferred Reporting System for Systematic Reviews and Meta-Analyses, Q: Cochran's heterogeneity statistic, QA: Quality assessment, Q-p: Cochran's p-value, qPCR: Quantitative polymerase chain reaction, S/America: South America, Seq: Sequencing, UMIC: Upper middle-income countries, USA: United States of America.

Transfusion transmitted babesiosis: A systematic review of reported cases

BACKGROUND

Transfusion transmitted babesiosis (TTB) has a high mortality rate but may go unrecognized, particularly in non-endemic areas. We therefore conducted a systematic review to better characterize clinical aspects of TTB.

METHODS

A literature search was conducted in PubMed and CINAHL databases, from which 25 eligible articles describing 60 TTB patients met criteria for data extraction.

RESULTS

Symptom evaluation was provided for 25 implicated donors: 18/25 (72%) were asymptomatic while 7/25 (28%) had mild flu-like symptoms but were asymptomatic at time of donation. It was common for a single donor or donation to infect multiple patients. Where reported, species included B. microti - 54/60 (90%), B. duncani - 3/60 (5%), and B. divergens-like/MO-1 - 1/60 (2%). Most TTB patients (44/60, 73%) resided in endemic states, while most TTB deaths 6/9 (67%) occurred in non-endemic states. Severity of hemolysis was proportional to degree of parasitemia. Mortality in our series was 9/60 (15%); most deaths occurred at extremes of the age spectrum: 6/9 non-survivors were aged >55 years, 2/9 were <1 year, only 1/9 was 2-54 years. Number of comorbidities was higher among non-survivors (median = 4) compared to survivors (median = 1).

CONCLUSIONS

All implicated donors (for which symptoms data were reported) resulting in TTB infections were asymptomatic at the time of donation, and it was common for a single donor or donation to infect multiple patients. Mortality of TTB appeared highest among those with more comorbidities and in non-endemic states. Heightened awareness of this diagnosis is key in its recognition.

Preclinical safety assessment of pathogen reduced red blood cells treated with amustaline and glutathione

BACKGROUND

The nucleic acid targeted pathogen reduction (PR) system utilizing amustaline (S-303) and glutathione (GSH) is designed to inactivate blood-borne pathogens and leukocytes in red blood cell concentrates (PR-RBCC). Inactivation is attained after amustaline intercalates and forms covalent nucleic acid adducts preventing replication, transcription, and translation. After pathogen inactivation, amustaline spontaneously hydrolyzes to S-300, the primary negatively charged reaction product; amustaline is below quantifiable levels in PR-RBCC. GSH quenches free unreacted amustaline.

STUDY DESIGN AND METHODS

The genotoxic and carcinogenic potential of PR-RBCC, the reaction by-products, and S-300 were assessed in accordance with the International Conference on Harmonization (ICH) guidelines and performed in compliance with the Food and Drug Administration (FDA) good laboratory practice standards, 21 CFR Part 58. in vitro bacterial reverse mutagenicity and chromosomal aberration assays were performed with and without exogenous S9 metabolic activation, and in in vivo clastogenicity and carcinogenic assays using validated murine models.

RESULTS

PR-RBCCs were not genotoxic in vitro and in vivo and were non-carcinogenic in p53^+/- transgenic mice transfused over 26 weeks. Estimated safety margins for human exposure ranged from >90 to >36 fold for 2 to 5 PR-RBCCs per day, respectively. PR-RBCCs and S-300 did not induce chromosome aberration in the in vivo murine bone marrow micronucleus assay at systemically toxic doses.

CONCLUSIONS

PR-RBCCs did not demonstrate genotoxicity in vitro or in vivo and were not carcinogenic in vivo. These studies support the safety of PR-RBCCs and suggest that there is no measurable genotoxic hazard associated with transfusion of PR-RBCCs.

Heavy parasitemia in babesiosis treated without adjunctive red cell exchange

Babesiosis is a tick-borne infectious disease caused by the protozoa Babesia but transplacental, and transfusion transmission may occur. While most infections are asymptomatic, rarely, it can present with a severe, life-threatening illness. Treatment is primarily with antibiotics, but red cell exchange (RCE) has been used in more severe cases which are characterized by high-grade parasitemia, evidence of severe hemolysis and or multi-organ failure. A threshold parasite level of 10% has arbitrarily been applied as an indication for RCE; however, this threshold is not evidence-based. We report on three cases of severe babesiosis in which we considered the use of RCE on the basis of a parasite level greater than 10%, but the procedure was not performed. We deferred RCE on account of the good clinical state of the patient and the absence of end-organ failure. All patients were followed daily until discharge. Two of these patients had been splenectomized, and each received a single unit of red blood cells during the hospitalization. The third patient had a long history of refractory lymphoma and was pancytopenic requiring multiple transfusions during the years before the diagnosis of babesiosis. She had transfusion-transmitted babesiosis from a red blood cell transfused 46 days prior to diagnosis. All three patients responded well to antibiotics, and none expired. This small case series suggests that requests for RCE solely on the basis of an arbitrary level of parasitemia should be questioned and the clinical state and evidence of end-organ failure considered in the decision to perform RCE.

Superior real-time polymerase chain reaction detection of Babesia microti parasites in whole blood utilizing high-copy BMN antigens as amplification targets

BACKGROUND

Babesiosis is a zoonotic disease transmitted to humans by the bite of infected ticks and caused by apicomplexan parasites, most commonly Babesia microti. Additionally, blood and blood products collected from asymptomatically infected blood donors may cause transfusion-transmitted infections in recipients. Highly sensitive molecular assays that detect parasite nucleic acid are needed for laboratory diagnosis and to identify and defer clinically silent but parasitemic blood donors.

STUDY DESIGN AND METHODS

Here we report the development and analytical and clinical characterization of a real-time polymerase chain reaction (RT-PCR)-based assay for the detection of B. microti genomic DNA in whole blood. We evaluate the detection of Babesia parasites using two separate targets, the traditional18S ribosomal subunit gene (Bm18S) and members of the abundant BMN family of seroreactive antigens (BmBMN).

RESULTS

Analytical sensitivity determination using a probit analysis demonstrated an analytical sensitivity of 30.9 parasites/mL for 18S amplification and 10.0 parasites/mL for BMN amplification The BMN primer set also demonstrates superior sensitivity for serial dilution panels prepared from clinically diagnosed Babesia-infected blood samples, generally detecting 10-fold more dilute nucleic acid.

CONCLUSIONS

Cumulatively, our data demonstrate that RT-PCR detection of the BMN family of seroreactive antigens reflects a sensitive and superior assay for the detection of B. microti in whole blood samples.

Transmission of Babesia microti Parasites by Solid Organ Transplantation

Infection with this parasite should be included in differential diagnosis of fever and anemia after blood transfusion or organ transplantation.

Babesia microti, an intraerythrocytic parasite, is tickborne in nature. In contrast to transmission by blood transfusion, which has been well documented, transmission associated with solid organ transplantation has not been reported. We describe parasitologically confirmed cases of babesiosis diagnosed ≈8 weeks posttransplantation in 2 recipients of renal allografts from an organ donor who was multiply transfused on the day he died from traumatic injuries. The organ donor and recipients had no identified risk factors for tickborne infection. Antibodies against B. microti parasites were not detected by serologic testing of archived pretransplant specimens. However, 1 of the organ donor’s blood donors was seropositive when tested postdonation and had risk factors for tick exposure. The organ donor probably served as a conduit of Babesia parasites from the seropositive blood donor to both kidney recipients. Babesiosis should be included in the differential diagnosis of unexplained fever and hemolytic anemia after blood transfusion or organ transplantation.

Transfusion-transmitted babesiosis: is it time to screen the blood supply?

PURPOSE OF REVIEW

This review summarizes the current status of blood screening to prevent transfusion-transmitted babesiosis (TTB).

RECENT FINDINGS

Babesia microti has recently been determined to be the most common transfusion-transmitted pathogen in the United States. Patients who acquire TTB often experience severe illness with an associated mortality rate of about 20%. Recent studies have demonstrated that laboratory screening using B. microti antibody and/or PCR assays can effectively identify infectious blood donors and that this approach may offer a cost- effective means of intervention. Pathogen inactivation methods may offer an alternative solution. None of these methods has yet been licensed by US Food and Drug Administration, however, and current efforts to prevent TTB rely on excluding blood donors who report having had babesiosis.

SUMMARY

TTB imposes a significant health burden on the United States population. Further research is needed to better inform decisions on optimal screening strategies and reentry criteria, but given the acute need and the currently available screening tools, initiation of blood donor screening to prevent TTB should be given high priority.

First detection and molecular identification of Babesia microti in Rattus losea captured from the offshore Kinmen Island of Taiwan

Babesia microti was firstly detected and identified in brown country rats (Rattus losea, Swinhoe) captured from the offshore Kinmen Island of Taiwan. The prevalence of Babesia infection in 283 rodents was screened by polymerase chain reaction (PCR) assay using a piroplasma-conserved primer set (Piro A/B) and the thirty-seven PCR-positive rodents were further examined by PCR using a species-specific primer set (Bab 1/4) targeting the gene encoding the nuclear small-subunit ribosomal RNA (18S rRNA) of Babesia species. B. microti was detected only in Rattus losea with a total infection rate of 9.9% (28/283). Positivity examined by species-specific PCR (9.9%) is higher than examined by blood smear (4.6%). Sequence and phylogenetic analyses revealed that Babesia species detected in Taiwan were genetically affiliated to the genotypes of B. microti, and can be easily distinguished from other genotypes of Babesia parasites by neighbour-joining and maximum-parsimony methods. Intra- and inter-species analysis also indicate that all these Taiwan species have a lower level of genetic divergence (genetic distance values <0.084) within the genotypes of B. microti, and were genetically more distant to other genotypes (>0.218) of Babesia parasites. This study provides the first evidence of B. microti identified in R. losea in Taiwan, and the high prevalence of Babesia infection in R. losea may imply its possible role served as reservoir host for maintaining an enzoonotic cycle of Babesia transmission in Kinmen Island. The possible vector tick responsible for the transmission of Babesia infection need to be further identified.

Transfusion-transmitted anaplasmosis from a leukoreduced platelet pool

BACKGROUND

Human granulocytic anaplasmosis is an emerging tick-borne illness. Anaplasma phagocytophilum resides intracellularly, can cause asymptomatic infection, and can survive blood component refrigeration conditions for at least 18 days. To date, eight cases of transfusion-transmitted anaplasmosis (TTA) have been reported: seven attributed to red blood cell (RBC) units, five of which were prestorage leukoreduced using RBC leukoreduction filters, and one involving a process leukoreduced apheresis platelet (PLT) unit. Here, we report a case of TTA from a whole blood-derived PLT pool.

STUDY DESIGN AND METHODS

Donation segments from the 7 units of RBCs and two PLT pools transfused were examined. Fast protocol multiplex real-time A. phagocytophilum polymerase chain reaction (PCR) and serologic testing for immunoglobulin (Ig)M and IgG antibodies to A. phagocytophilum by enzyme immunoassay were performed.

RESULTS

Transmission was confirmed by positive A. phagocytophilum PCR and serology in one of 16 donors and by positive PCR and seroconversion in the recipient.

CONCLUSION

This is the first confirmed case of TTA from a whole blood-derived PLT pool prepared from PLT concentrates leukoreduced by in-line filtration of PLT-rich plasma.

Babesiosis Occurrence among the Elderly in the United States, as Recorded in Large Medicare Databases during 2006-2013

Background

Human babesiosis, caused by intraerythrocytic protozoan parasites, can be an asymptomatic or mild-to-severe disease that may be fatal. The study objective was to assess babesiosis occurrence among the U.S. elderly Medicare beneficiaries, ages 65 and older, during 2006–2013.

Methods

Our retrospective claims-based study utilized large Medicare administrative databases. Babesiosis occurrence was ascertained by recorded ICD-9-CM diagnosis code. The study assessed babesiosis occurrence rates (per 100,000 elderly Medicare beneficiaries) overall and by year, age, gender, race, state of residence, and diagnosis months.

Results

A total of 10,305 elderly Medicare beneficiaries had a recorded babesiosis diagnosis during the eight-year study period, for an overall rate of about 5 per 100,000 persons. Study results showed a significant increase in babesiosis occurrence over time (p<0.05), with the largest number of cases recorded in 2013 (N = 1,848) and the highest rates (per 100,000) in five Northeastern states: Connecticut (46), Massachusetts (45), Rhode Island (42), New York (27), and New Jersey (14). About 75% of all cases were diagnosed from May through October. Babesiosis occurrence was significantly higher among males vs. females and whites vs. non-whites.

Conclusion

Our study reveals increasing babesiosis occurrence among the U.S. elderly during 2006–2013, with highest rates in the babesiosis-endemic states. The study also shows variation in babesiosis occurrence by age, gender, race, state of residence, and diagnosis months. Overall, our study highlights the importance of large administrative databases in assessing the occurrence of emerging infections in the United States.

Broad-range survey of tick-borne pathogens in Southern Germany reveals a high prevalence of Babesia microti and a diversity of other tick-borne pathogens

Abstract Ticks harbor numerous pathogens of significance to human and animal health. A better understanding of the pathogens carried by ticks in a given geographic area can alert health care providers of specific health risks leading to better diagnosis and treatments. In this study, we tested 226 Ixodes ricinis ticks from Southern Germany using a broad-range PCR and electrospray ionization mass spectrometry assay (PCR/ESI-MS) designed to identify tick-borne bacterial and protozoan pathogens in a single test. We found 21.2% of the ticks tested carried Borrelia burgdorferi sensu lato consisting of diverse genospecies; a surprisingly high percentage of ticks were infected with Babesia microti (3.5%). Other organisms found included Borrelia miyamotoi, Rickettsia helvetica, Rickettsia monacensis, and Anaplasma phagocytophilum. Of further significance was our finding that more than 7% of ticks were infected with more than one pathogen or putative pathogen.

Transfusion-Transmitted Babesiosis During Total Hip Arthroplasty

Babesiosis is a potentially life-threatening zoonotic disease that is endemic to the northeastern United States and increasing in prevalence worldwide. Transmitted by the same Ixodes tick responsible for Lyme disease, the intraerythrocytic parasite Babesia causes a wide range of clinical presentations--from asymptomatic carriage to a fulminant course with rapid deterioration. Symptoms typically present 1 to 6 weeks after inoculation, with the gradual onset of fatigue, malaise, weakness, and intermittent or sustained fever as high as 40.9°C. Severe cases are associated with parasitemia greater than 4%, alkaline phosphatase greater than 125 U/L, and white blood cell counts greater than 5×10(9)/L. Definitive diagnosis is made by microscopic examination of thin blood smears, polymerase chain reaction, and indirect immunofluorescent antibody testing. The increasing frequency of babesiosis paired with a lack of blood-donor screening assays poses a serious threat to the safety of the US blood supply. Although babesiosis is responsible for 3.6% of transfusion-related deaths, the Food and Drug Administration has yet to approve mandatory screening for the parasite in donated blood. Historically, transfusion-transmitted babesiosis has been thought to be isolated to the immunocompromised patient population. However, a recent case of transfusion-transmitted babesiosis in an immunocompetent patient following total hip arthroplasty is the first reported in the literature and may represent a growing risk to a far greater segment of the population than previously thought. This article summarizes the current state of transfusion-transmitted babesiosis and the detrimental impact of this infection on blood transfusion safety.

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.

Risk assessment of transfusion-associated babesiosis in Tyrol: appraisal by seroepidemiology and polymerase chain reaction

BACKGROUND

After malaria, babesiosis is the second most common transfusion-transmitted parasitic disease in the United States. In Europe, one reported transfusion case, concerning Babesia microti, occurred in Germany.

STUDY DESIGN AND METHODS

Due to the fact that Babesia spp. are present in Tyrolean ticks, the aim of this study is to assess the occurrence of immunoglobulin (Ig)G antibodies against the Babesia divergens complex, including B. divergens and Babesia venatorum (EU1), as well as B. microti by screening a representative collective of 988 blood donors from North and East Tyrol (Austria) with indirect immunofluorescence antibody test. Additionally, we investigated 206 local ixodid ticks for the presence of babesial DNA by polymerase chain reaction.

RESULTS

Seroprevalence data resulted in rates of 2.1% for IgG antibodies against the B. divergens complex and 0.6% against B. microti in Tyrolean blood donors. All sera could be confirmed by independent retesting. Our data indicate that cross-reactivity is high between B. divergens and B. venatorum and lower than 19.8% between B. divergens and B. microti.

CONCLUSIONS

This study shows that Babesia spp. are present in the Tyrols, which blood donors come into serologic contact with, and that we have to consider how to sustain blood product safety concerning this new challenge. Additionally, it is the first description of B. venatorum in the Tyrols, found in one Ixodes ricinus at the Italian border.

Babesia: impact of cold storage on the survival and the viability of parasites in blood bags

BACKGROUND

Babesia represents one of the major infectious threats to the blood supply since clinically silent infections in humans are common and these can be life-threatening in certain recipients. It is important to understand the effect of blood storage conditions on the viability of Babesia as this will impact the occurrence and severity of transfusion-transmitted babesiosis.

STUDY DESIGN AND METHODS

Babesia divergens was introduced into blood bags containing leukoreduced red blood cells (RBCs) and stored at 4°C for 0 to 31 days. Samples were withdrawn for assessment of the presence, morphology, and viability of parasites. Blood smears were made immediately on removal from blood bags at different time intervals and evaluated by blood film microscopy. RBCs withdrawn from the bags were also cultured for 8 days using conditions optimal for parasite reproduction and growth to allow assessment of parasite viability.

RESULTS

After 24 hours of storage at 4°C, there was a substantial reduction of parasitemia in the blood bags, which was maintained throughout storage. This decrease was accompanied by a change in morphology of parasites, with the number of altered parasites increasing through the period of storage. However, viability was maintained through 31 days of cold storage with a lag in achieving exponential growth seen in the parasites subjected to longer periods of refrigeration.

CONCLUSION

Refrigeration of B. divergens leads to an alteration of parasite morphology and a decrease in parasite numbers. However, there are sufficient parasites that are robust enough to survive 31 days of storage at 4°C and yield high end-point parasitemia.

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.

Development of a real-time polymerase chain reaction assay for sensitive detection and quantitation of Babesia microti infection

BACKGROUND

Babesia microti, the most frequently implicated pathogen in transfusion-transmitted babesiosis, is widely endemic in the Northeast and upper Midwestern United States. High seroprevalence in endemic areas limits antibody-based donor screening. A high-performance molecular test is needed to identify donors in the preseroconversion window phase as well as to discriminate past serologic exposure with parasite clearance from continued parasitemia.

STUDY DESIGN AND METHODS

Frozen Babesia-spiked whole blood was microcentrifuged, and the supernatant transferred and microcentrifuged again to concentrate the parasite. The DNA was extracted and amplified using real-time polymerase chain reaction (PCR) using Babesia-specific primers. The assay was employed in three series of experiments: 1) a validation and optimization spiking experiment, 2) a blinded serial dilution probit analysis to determine the limit of detection, and 3) evaluation of two blinded panels of clinical samples from possible babesiosis cases.

RESULTS

At a decreasing inoculum of 445, 44.5, and 4.45 copies/mL, the assay had positive rates of 100, 97.5, and 81%, respectively. The blinded probit analysis demonstrated a detection rate of 95 and 50% at 12.92 and 1.52 parasites/2 mL of whole blood, respectively. Evaluation of clinical samples showed 13 of 21 samples to be positive, with a range of 85 to 4.8 million parasites/mL. There were no positives detected among 48 healthy donors

CONCLUSION

We have developed a highly sensitive and specific, quantitative real-time PCR-based assay for detection of B. microti that could have a useful role in blood screening. It can also be employed broadly to understand Babesia epidemiology, disease pathogenesis, and host immunology.

A cluster of transfusion-associated babesiosis in extremely low birthweight premature infants

Babesiosis is a parasitic infection of the red blood cells most often acquired by a tick bite. As it has also been known to be transmitted vertically and via transfusion, neonates have occasionally been reported with the infection. Here, we report a series of three premature neonates who acquired babesiosis via blood transfusion from a single donor, one of whom had difficulty clearing the infection and required multiple antimicrobials.

Multiplex assay detection of immunoglobulin G antibodies that recognize Babesia microti antigens

Human babesiosis, a blood-borne infection caused by several species of Babesia, including B. microti, is an emerging disease that is endemic in the Northeast, upper Midwest, and Pacific Northwest regions of the United States. Risk factors for babesiosis include exposure to the infected tick vector and blood transfusions from infected donors. In this work, we cloned and expressed two of the immunodominant antigens from B. microti and used them in a multiplex bead format assay (MBA) to detect parasite-specific IgG responses in human sera. The MBA using recombinant B. microti secreted antigen 1 (BmSA1) protein was more specific (100%) and slightly more sensitive (98.7%) than the assay using a truncated recombinant BMN1-17 construct (97.6% and 97.4%, respectively). Although some antibody reactivity was observed among sera from confirmed-malaria patients, only one Plasmodium falciparum sample was simultaneously positive for IgG antibodies to both antigens. Neither antigen reacted with sera from babesiosis patients who were infected with Babesia species other than B. microti. Both positive and negative MBA results were reproducible between assays and between instruments. Additional studies of these recombinant antigens and of the multiplex bead assay using blood samples from clinically defined babesiosis patients and from blood donors are needed to more clearly define their usefulness as a blood screening assay.

Preventing transfusion-transmitted babesiosis: preliminary experience of the first laboratory-based blood donor screening program

BACKGROUND

Babesiosis is the most common transfusion-transmitted infection reported to the Food and Drug Administration (FDA). We developed and implemented the first laboratory-based blood donor screening program for Babesia microti to help reduce and prevent transfusion-transmitted babesiosis (TTB) and report results for the initial year.

STUDY DESIGN AND METHODS

Selective B. microti donor screening was performed using real-time polymerase chain reaction (PCR) and indirect immunofluorescence assay (IFA) to reduce the incidence of TTB in neonates and pediatric sickle cell and thalassemia patients under an FDA-approved investigational new drug application. We compared the reports of TTB in these patients in the first 12 months of the study with those of patients who received unscreened blood from 2005 to 2010.

RESULTS

There were 2113 units tested with 2086 negative results, 26 positive IFA results (1.23%), and one indeterminate PCR result (0.05%). No reported case of TTB occurred with any B. microti-screened unit transfused to the targeted patients (0/787 units) or to any patient who received the screened units (0/2086 units). Before screening, there were seven cases of TTB in neonates, sickle cell, and thalassemia patients from 6500 unscreened units (one case/929 units) and 24 cases in the total transfused population from 496,545 units distributed (one case/20,686 units).

CONCLUSION

Implementation of B. microti IFA and PCR screening is compatible with blood center operations to provide tested units. While the results after 1 year are not powered to demonstrate a change in the rate of TTB after testing, they are encouraging.

Clinical presentation and treatment of transfusion-associated babesiosis in premature infants

We review here 7 cases of neonatal transfusion-associated babesiosis at a NICU in the northeast United States. Transfusion from 2 infected units of blood resulted in the 7 cases described. The clinical presentation was highly variable in this cohort; the extremely low birth weight neonates were the most severely affected. Antibiotic therapy was effective in neonates with mild and asymptomatic infection; however, double-volume exchange blood transfusion with prolonged multidrug treatment was required for the 2 most severe cases. The risk of Babesia microti infection is not eliminated through current blood-bank practices. Neonatologists in endemic areas should have a high index of suspicion for babesiosis in premature infants exposed to blood transfusions.

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.

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.