1. Risk of Babesia Infection by Blood Transfusion and Potential Strategies for Donor Testing: Introduction
Sanjai Kumar, PhD
Division of Emerging and Transfusion-Transmitted Diseases
Office of Blood Research and Review
CBER, FDA
Blood Products Advisory Committee Meeting
July 26, 2010

2. 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.

3. 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.

4. Life Cycle of Babesia microti
White-tailed deer
(Host to ticks)
White-footed mouse
(Reservoir host)

5. 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

6. Background – III
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.

7. Geographical distribution of babesiosis beneficiary claims in different states in 2008 (n =1543; CMS dataset)
428
211
207
128 90 80 50 40 37 21 16 15 13 12
> 100
100 – 50
49 – 25
24 – 12
4 States
2 States
6 States

8. 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 8

9. 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. 9

10. FDA Fatality Reports Suggest Increased Risk of TTB Since 2005
Fiscal Year
No. of Reports
FY98 1
FY99- FY05
FY06- FY08 9
FY10 10

11. 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. 11

12. Transfusion-transmitted babesiosis cases in the U. S
Transfusion-transmitted babesiosis cases in the U.S. between (n =63; CDC data based on state of donation) 1 2 4 6 15 13
2 States
1 State
14 States
> 10
10 – 5
< 5
For two cases state of donation is unknown

13. 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 13

14. 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 14

15. 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 15

16. 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 16

17. 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 17

18. 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 18

19. 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 19

20. 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 20

21. 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 21

22. 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. 22

23. 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. 23

24. 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 24

25. 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 25

26. 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) 26

27. 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. 27

28. 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 28

29. 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. 29

30. 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. 30

31. 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. 31

32. 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 32

33. 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

34. 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

35. Questions to the Committee
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?
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.
Considering the current technologies, please comment on the suitability of antibody testing for Babesia infections in blood donors.

36. Acknowledgements OBRR/FDA
Hira Nakhasi, Paul Mied, Robin Biswas, David Asher, Jay Epstein
OBE/FDA
Mark Walderhaug, Richard Forshee, Steven Anderson
CDC
Barbara Herwaldt