Tick-Borne Disease Transmission by Blood Donation Prevalent in Endemic Areas

October 11, 2005

Oct. 11, 2005 (San Francisco) -- The need to develop strategies to prevent transmission of tick-borne disease via blood transfusion is increasing as new reports continue to surface. Although not as much in the popular press as Lyme disease, Babesia microti is creating its own quieter havoc.

In a study presented here at the Infectious Diseases Society of America 43rd annual meeting, Megan Nguyen, BS, from the American Red Cross in Rockville, Maryland, presented data from a six-year study that showed the prevalence of B microti transmission via blood transfusion in areas where the tick is commonly found.

Examination of 13,573 samples from blood donors from 1999 to 2004 in endemic regions of Connecticut showed that 175 samples (1.3%) tested positive for B microti infection based on indirect fluorescent antibody testing.

Of these 175, 129 donors consented to participate in a three-year follow-up study in which they were tested by IFA for the presence of antibodies to B microti as well as receiving nested polymerase chain reaction (PCR) testing for parasitemia on a regular basis. Overall, 27 donors (21%) were found to have parasitemia as indicated by a positive PCR test, suggesting that some patients have persistent, ongoing infection.

In addition, parasitemia rates decreased from 55% in the first two years of the follow-up study to 3% in the third and final year. Ms. Nguyen said the study did not show a clear reason for this, adding that many factors could account for it.

Ms. Nguyen emphasized that "anybody who has had B microti is permanently prohibited from donating blood" and is registered in the blood bank system of the Red Cross nationwide. However, it is important to identify those people infected with B microti prior to blood donation. According to Ms. Nguyen, most of the transfusion-related transmission occurs through people who are infected with the tick-borne disease but who are asymptomatic.

Identifying infected people before they donate blood is therefore an important goal in reducing the risk of transfusion-related B microti transmission, but the best way to do this is not yet clear, she said.

Richard Whitley, MD, a professor of pediatrics at the University of Alabama in Birmingham who moderated the session, told Medscape that prospective blood donors are not currently screened routinely for tick-borne diseases, an issue that needs to be addressed by local blood banks.

However, Ms. Nguyen told Medscape she is hopeful "that there will be screening" or a U.S. Food and Drug Administration (FDA) approval for testing before donation. Unfortunately, she added, she does not know of any test under investigation for FDA approval.

IDSA 43rd Annual Meeting: Abstract LB-3. Presented Oct. 7, 2005.

Reviewed by Gary D. Vogin, MD