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Risk of Babesia Infection by Blood Transfusion and Potential

Strategies for Donor Testing: Introduction

Sanjai Kumar, PhDDivision of Emerging and Transfusion-Transmitted

DiseasesOffice of Blood Research and Review

CBER, FDA

Blood Products Advisory Committee MeetingJuly 26, 2010

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Issue for BPAC

• Based on a risk analysis, do the available data support development of a regionally selective donor testing strategy to reduce the risk of transfusion-transmitted babesiosis.

• Please comment on the suitability of donor screening either by a nucleic acid-based test, an antibody test, or both, given the current technology limitations.

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Background – I

• Babesiosis, a tick-borne zoonosis, is caused by infection with intraerythrocytic protozoans of genus Babesia that belong to phylum Apicomplexea.

• The most prevalent species in U.S. is Babesia microti. The other reported species are B. duncani (formerly called WA1-type Babesia) and related organisms (CA1-type Babesia) and “B. divergens-like” agents such as MO1.

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Life Cycle of Babesia microti

White-tailed deer(Host to ticks)

White-footed mouse(Reservoir host)

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Background – II

• Endemic transmission is reported mostly in Northeastern, Mid-Atlantic and Upper Midwestern states including Connecticut, Rhode Island, New York, Massachusetts, New York, New Jersey, New York, Wisconsin and Minnesota

• Several other states without recognized prevalence areas also reported babesiosis cases due to infections acquired during travel to endemic areas

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• Clinical illness ranges from asymptomatic to mild to life-threatening severe disease. Neonates, immuno-compromised and asplenic persons and elderly are at the highest risk of severe disease.

• Highest number of clinical cases and transfusion-transmitted cases of babesiosis are reported in the U.S.

• Currently, babesiosis is not a reportable disease in all states, and is not a nationally notifiable disease.

Background – III

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Geographical distribution of babesiosis beneficiary claims in different states in 2008

(n =1543; CMS dataset)

428

211

207128

90

8080

50

40

37

21

16

15

13

12

12

> 100 100 – 50 49 – 25 24 – 12

4 States4 States 2 States6 States

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Transfusion-Transmitted Babesiosis (TTB) in the U.S. - I

• TTB first reported in 1979

• Since then, more than 100 cases and 11 deaths reported

– The majority TTB cases caused by B. microti

– A few non-B. microti cases of TTB

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Transfusion-Transmitted Babesiosis (TTB) in the U.S. - II

• TTB a particular concern in neonates

- In 2007, three infections in neonates at a Rhode Island hospital from a single donor

- In 2009, three infections at a Virginia hospital from a single donor

• While under-reported, B. microti is one of the most frequently reported transfusion-transmitted infectious agents.

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FDA Fatality Reports Suggest Increased Risk of TTB Since 2005

Fiscal Year No. of Reports

FY98 1

FY99- FY05 0

FY06- FY08 9

FY10 1

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Babesia Transmission is Regional while TTB Risk is Systemic

• Most TTB is acquired in the same region where blood is collected and used, however– TTB has occurred in non-prevalence areas from

donors who had traveled to a recognized endemic area

• Among 9 fatalities, 4 implicated donors and 5 recipients did not live in an endemic area

• 17 ab-positive implicated donors, 11 were from endemic areas while 4 were from non-endemic areas

– Donors who normally reside in endemic areas may donate elsewhere

– Blood products are often shipped between widely separated regions across the U.S.

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Transfusion-transmitted babesiosis cases in the U.S. between 2004-2008

(n =63; CDC data based on state of donation)

1

11

1

1

1

1

112

44

615

13 4

4

2 States1 State14 States

> 10 10 – 5< 5

For two cases state of donation is unknown

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Clinical Presentation of TTB

• TTB can be asymptomatic or present as a flu-like or fulminant febrile illness, usually within 1 to 9 weeks post-transfusion (though delays of 3 months can occur)

• Fatality rates vary from 3%-20%

• Signs and symptoms resemble natural infection– Flu-like illness accompanied by hemolysis is

characteristic

– Altered mental status, renal failure, pulmonary compromise, Adult Respiratory Distress Syndrome, and Disseminated Intravascular Coagulopathy are seen in severe cases

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Variable Geographic Risk of TTB

• Earlier reports suggested that approximately 16% of the US population live in areas where tick-borne Babesia transmissions occur (mainly NJ, NY, CT, RI, MA, WI, MN)

• In endemic areas, risk of Babesia infection varies greatly and is highly localized

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Areas of Babesia Transmission are Expanding

• Emergence of tick-borne Babesia infections

- Increased recognition and diagnosis of babesiosis

- Increasingly closer human habitat to ticks

- Significantly increased deer/tick populations

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Tick-borne Transmission is Seasonal, while TTB Risk is

All Year• The tick-borne Babesia transmission season

is generally from May through September, however– 8/9 fatal TTB cases were transfused

between August and December. – A TTB case in April was presumed due to a

donation from an asymptomatic chronically infected person

– Seropositive and/or parasitemic donors have been found all year round

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Blood Components that are Implicated to Cause TTB

• TTB has been caused by RBCs and platelets

– B. microti in banked RBC survive at 4o C for at least 35 days

– Cryopreserved RBCs can cause TTB

– Leukocyte reduction and irradiation do not clear parasites

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Current Strategies to Prevent TTB are Insufficient

• Using a standardized, FDA-recognized donor history questionnaire, donors are asked if they have ever had babesiosis

– Donors with a clinical history of babesiosis are deferred indefinitely, however

– Most babesiosis is asymptomatic and can persist for months to years, rendering questioning largely ineffective

• Tick bite history is both poorly sensitive and non-specific

• Donor deferral for residence in or travel to an endemic region of the US is impractical due to impact on supply

• No FDA-approved laboratory tests are available to screen blood donors for Babesia infections

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Mitigating the Risk of TTB: FDA Babesia Workshop 2008

Scientific Agenda

• Biology, Pathogenesis, Transmission and Epidemiology of Babesiosis

• Risk of Babesia Infection through Transfusion of Blood and Blood Components

• Laboratory Tests to Detect Babesia Infections

• Possible Approaches to Minimize the Risk of Transfusion-Transmitted Babesiosis

• Panel Discussion

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FDA Workshop on TTB - I

• Babesia-endemic regions were recognized in several parts of the US

– Current and more detailed epidemiological maps of Babesia endemicity are needed to identify where donors and therefore recipients are most at risk

• Donors who are asymptomatic carriers with low-grade parasite burdens present the greatest risk to recipients

– PCR has been positive in approximately 50% of seropositive donors

• Additional studies are needed to determine the rate and duration of infection and parasite burden in asymptomatic carriers

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FDA Workshop on TTB - II

• Further studies are needed to determine the utility of available laboratory tests for identifying asymptomatic infections in blood donors

• Novel detection technologies are needed to better identify donors who are currently infected versus those with past infection

• Novel testing strategies are needed to better identify, defer and potentially reenter Babesia at-risk donors

• Selective testing strategies may be needed in order to provide screen-negative blood components for use in neonates and other immune-compromised recipients

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FDA Workshop on TTB - III

• Based on recommendations of a panel of experts, a task force was established to identify research opportunities and to develop candidate donor screening strategies for TTB

– The task force is led by the AABB

– Members from ABC, ARC, CDC and FDA

• A key focus is on promoting advancements in donor test technology.

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Donor Testing for Babesiosis: Nature of the Challenge

• Donors who are asymptomatic carriers are thought to be the primary source of TTB.

• Babesiosis in donors can persist with low-grade, asymptomatic parasitemia for months to >2 years.

• The minimal infectious dose in TTB is not known, nor is the level of parasite burden in asymptomatic carriers.

• There is no recommendation to treat persons with asymptomatic Babesia infections.

• Both clinical cases and TTB cases are underreported.

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Current Test Technologies and their Limitations for Screening

Donors for Babesia Infections - I

• Microscopy (Wright or Giemsa stains of thick and thin blood films) lacks the sensitivity to detect low-grade parasitemias

• Inoculation of blood samples in sensitive animal models (hamster or mouse for B. microti; gerbils for B. divergens) is impractical

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Current Test Technologies and their Limitations for Screening

Donors for Babesia Infections - II

• A laboratory-developed nucleic acid test (NAT) and antibody tests have been used to diagnose Babesia infections.

• Both NAT and antibody-based tests have limitations for use in donor screening.

• Lack of sufficient genomic/proteomic cross-reactivity between B. microti and non-B. microti species

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NAT as Donor Screening Test for Babesia - I

• Several versions of laboratory-developed PCR tests are available.

• Sensitivity of PCR has been demonstrated as equal to or superior to blood-film microscopy

• Parasitemia may be very low during the early phase of acute infection (window period) and in asymptomatic infections (chronic phase)

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NAT as Donor Screening Test for Babesia - II

• As a result, a few infected red cells may be potentially present in a unit of donated blood.

• Thus, to be effective, a NAT-based test must be highly sensitive.

• The limit of detection of NAT for Plasmodium falciparum (another intraerythrocytic parasite) is 20 parasites per ml of blood.

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NAT as Donor Screening Test for Babesia - III

•Technologies such as use of large volume of blood sample for DNA/RNA preparation, or concentration of infected red cells before testing would improve the assay sensitivity

• In addition, use of multiple copy gene(s) as target for NAT may also improve the assay sensitivity

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Detection of Anti-babesial Antibodies as Evidence of Exposure - I

• IFA, ELISA and Western blot have been used for diagnosis and epidemiological studies.

• IFA is highly sensitive for acute babesiosis cases. However, IFA is not adapted for high through-put donor screening.

• Similarly, the available Western blot is not suitable for high through-put donor screening.

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Detection of Anti-babesial Antibodies as Evidence Exposure - II

• Parasite-antigen lysate, recombinant protein and peptide-based ELISA tests have been used.

• ELISA tests developed and used so far have had poor specificity.

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Detection of Anti-babesial Antibodies as Evidence of Exposure - III

• Anti-Babesia antibody positivity in the U.S. ranged between 0.3% to 17.8% suggesting either low assay specificities or very high rates of asymptomatic infections.

• IgG titers may persist for months or years and cannot distinguish current from past infections. Antibody testing would then cause deferral of recovered donors who would not transmit babesiosis.

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Detection of Anti-babesial Antibodies as Evidence of

Exposure - IV• Novel antibody-based tests for Babesia are needed

• To be effective for donor screening, these tests should be

- Highly sensitive (able to detect early window period cases and asymptomatic chronic infections) and specific (low false-positive reactions)

- Adapted for high through-put donor screening platform

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FDA’s Strategy to Mitigate TTB Risk

• Identification of Babesia risk in individual states based on clinical cases of babesiosis, TTB cases, and based on FDA risk assessment model

• Evaluation of the current laboratory methods for their value as donor screening tests

• A two-phase strategy to donor testing for Babesia

• Need for highly sensitive and specific nucleic acid and antibody based tests to screen donors for Babesia

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BPAC Agenda

• Epidemiology of Babesiosis, Including Transfusion-Associated Infection, Barbara Herwaldt, M.D., CDC

• Experience With Testing Blood Donors for Babesia, David Leiby, Ph.D., American Red Cross

• Analysis of Risk of Babesia Infection in U.S. Blood Donors, Mark Walderhaug, Ph.D., OBE, FDA

• FDA Perspective, Sanjai Kumar, Ph.D., DETTD, FDA

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1. Do the FDA risk analysis and the available CMS and CDC datasets together support the concept of regional testing of blood donors for Babesia infections?

2. Given the current sensitivity limitation of NAT for Babesia, please comment on whether the public health benefits of NAT testing warrant consideration of broad-based regional testing of donors by NAT.

3. Considering the current technologies, please comment on the suitability of antibody testing for Babesia infections in blood donors.

Questions to the Committee

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Acknowledgements

OBRR/FDAHira Nakhasi, Paul Mied, Robin Biswas, David Asher, Jay

Epstein

OBE/FDAMark Walderhaug, Richard Forshee, Steven Anderson

CDC

Barbara Herwaldt