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14. The U.S. Blood is Increasingly Threatened by Parasites

Source: LABORATORY MEDICINE Title: “The Threat Of Chagas’ Disease in Transfusion Medicine: The Presence of Antibodies to Trypanosoma cruzi in the U.S. Blood Supply”, Date: April 1997, Authors: Alfred A. Pan, Ph.D., and Martin Winkler, Ph.D.

SSU Censored Researchers: Kecia Kaiser and Catherine Hickinbotham
Community Evaluator: Linda C. McCabe, MT(ASCP)

With increasing global migration comes the spread of infectious diseases that were once confined to specific areas of the world. A growing concern is the threat of transmission of Chagas’ disease through blood transfusions. Chagas’ disease affects several million individuals worldwide, and, in Latin America, causes more deaths than infection with HIV or hepatitis. ‘The World Health Organization (WHO) considers the control of Chagas’ disease to be ranked in third place after malaria and schistosomiasis control. At present, the U.S. Food and Drug Administration (FDA) has not approved any serologic test screening blood donors for antibodies to Trypanosoma cruzi, the parasite that causes the disease, although three U.S. manufacturers have received FDA approval of an antibody test. The Laboratory Medicine article focuses on the biology, transmission, prevalence in the United States, diagnostic tests, the potential for transmission, and challenges this disease presents to the U.S. blood banking and public health communities.

The disease is usually spread by the Reduviid bug (kissing bug), whose habitat ranges from northern California to northern Maryland, and south through the southern regions of Argentina. When taking a blood-meal from a human, the insect defecates, leaving behind an infective form of the parasite known as the metacyclic trypomastigote. These trypomastigotes enter the bloodstream, either by being scratched into the bite wound or by direct contact with the host’s mucosa. The parasite commonly invades cells of the liver, spleen, and lymphatic system, as well as cardiac, smooth, and skeletal muscles. The nervous system, intestinal mucosa, skin, gonads, bone marrow, and placenta may also become infected. The initial symptoms may include anemia, chills, nervous disorders, muscle and bone pain, and loss of strength. Death may occur three to four weeks after infection, although many people may live a long life even with this debilitating disease.

It is highly probable that infected donors are giving blood in North America. A study in Sacramento, California, indicated a rate of 1 in 2000 in the blood supply, and reactive specimens have been identified from blood banks in New Orleans and Miami.

Between 30,000-45,000 people with chronic Chagas’ disease are estimated to be living in the United States. Until recently, diagnosis has been difficult because no simple blood test has been available. Instead, clinicians have had to rely on tissue biopsy, or the cumbersome method of xenodiagnosis, which takes several weeks to perform. Therefore, many people in the U.S. with heart disease caused by Chagas’ are misdiagnosed regarding the root of their problem.

The American Red Cross has performed several studies to determine the rates of seropositive donors. They found that the median prevalence rate for all 18 centers showed 1 out of 340 donors to be at risk for T. cruzi infection. At present however, the FDA has not yet approved any test screening of blood donors for antibodies to Chagas’ Disease. Currently, all units of blood are screened for eight separate disease markers, but Chagas’ is not among them. How much more data is needed before donor screening is mandated to prevent Chagas’ disease from being in our blood supply? So far, three people have been identified as getting Chagas’ disease through blood transfusions in the U.S., and one person died after getting infected bone marrow. Will it take a wrongful death lawsuit before our blood supply is screened for this potentially fatal pathogen?

UPDATE BY AUTHOR ALFRED PAN, PH.D.: “Is Chagas’ disease an emerging disease in the U.S.? Perhaps we should call it an unrecognized disease. It is estimated that 16-18 million people are infected. Although these numbers appear large, few physicians know of its existence. There have been reported cases in North America and Europe. In Italy, estimates of 20,000 to 40,000 potential infectants of Chagas’ disease exist (Crovato and Rebora, 1997).

“There have been four studies (i.e. more than 10,000 specimens) conducted in the U.S. using a Chagas Ab EIA (enzyme immunoassay). The first study identified 14 of 13,209 donor samples (0.105 percent) as being reactive for antibody to T. cruzi. When sub-classified into Hispanic donors, an incidence rate of 1.5 percent (9 in 603) was revealed (Brashear, et al., Transfusion, 1995). In a second study by the Red Cross (Los Angeles and Miami), 23,978 at-risk and 25,587 control donations were tested. The EIA identified 34 donors (33 and 1, respectively) (Leiby, et al., 1997a). Seroprevalence rates indicated 0.14 percent and 0.07 percent, respectively. A third study at the Stanford Blood Center tested 39,776 donations. There were three confirmed specimens (Galel, et al., 1997). The last report tested 100,089 blood donors in an Oklahoma and Texas low-risk population. There were three confirmed samples. One positive donor was born in Mexico, and the other two reported no risk for T. cruzi; both were born in the U.S. (Leiby, et al., 1997b). In all studies, confirmation involved a Radioimmuoprecipitation assay (RIPA) (Kirchhoff, et al., 1987; Winkler, et al., 1995). Note that in some of the above investigations questionnaires failed to identify high-risk. Chagasic antibody reactive candidates.

“Additional studies in 1997 indicated similar seroprevalence rates. In Los Angeles, 1311 of 3320 donors were at risk to T. cruzi infection. Seven donors were reactive by a Chagas IgG ELISA, and six were reactive with RIPA (Shulman, et al., 1997). However, a study conducted in the Southeastern U.S. (Louisiana, Alabama, Mississippi, and Georgia) indicated that zero out of 6,013 were confirmed reactive (Barrett, et al., 1997). This is in contrast to a study where two specimens were identified as being reactive by the Chagas Ab EIA and confirmed at a New Orleans, Louisiana, blood bank (Pan, unpublished results).

“Individuals seropositive for antibodies to T. cruzi are donating in several areas of the U.S. A summary of studies indicate seroprevalence from 0.07 percent to 4.9 percent. Compare these numbers to an HIV p 24 Ag test recently instituted. After one year of testing an identification rate of 1 out of 5.25 million units (0.000019 percent) was found (Stramer, et al., 1997). The numbers of T. cruzi-infected blood donors still have an uncertain effect on the safety of the blood supply and the public health system.”

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