Blood donation screening forBabesia microti: feasibility and results

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: 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.

Cost-effectiveness of Babesia microti antibody and nucleic acid blood donation screening using results from prospective investigational studies

BACKGROUND

Babesia microti causes transfusion-transmitted babesiosis (TTB); currently, blood donor screening assays are unlicensed but used investigationally.

STUDY DESIGN AND METHODS

We developed a decision tree model assessing the comparative- and cost-effectiveness of B. microti blood donation screening strategies in endemic areas compared to the status quo (question regarding a history of babesiosis), including testing by: (1) universal antibody (Ab), (2) universal polymerase chain reaction (PCR), (3) universal Ab/PCR, and (4) recipient risk-targeted Ab/PCR. The model predicted the number of TTB cases, complicated TTB cases, cases averted, and quality-adjusted life years (QALYs). Economic outcomes included each strategy's per-donation cost, waste (number of infection-free units incorrectly discarded), and waste index (number wasted units/number true positives). Sensitivity analyses examined uncertainty in transmission probabilities, prevalence rates, and other key model inputs.

RESULTS

Universal PCR in four endemic states would prevent 24 to 31 TTB cases/100,000 units transfused (pht) at an incremental cost-effectiveness ratio (ICER) of $26,000 to $44,000/QALY (transmission probability dependent) and waste index of zero. Universal Ab/PCR would prevent 33 to 42 TTB cases pht at an ICER of $54,000 to $83,000/QALY and waste index of 0.05. The questionnaire is most wasteful (99.62 units wasted pht; 208.62 waste index), followed by the risk-targeted strategy (76.27 units wasted pht; 0.68 waste index). The model predicted zero cases of TTB or complicated TTB with universal Ab/PCR (versus [33, 42] and [13, 18] pht, respectively [no screening]). Results are highly sensitive to transmission probabilities.

CONCLUSIONS

Universal PCR in endemic states is an effective blood donation screening strategy at a threshold of $50,000/QALY. Using a higher cost-effectiveness ratio, universal Ab/PCR is the most effective strategy.