Chagas Update

This January, in the interest of the safety of the community blood supply, Bonfils Blood Center will begin testing all donors with the licensed T. cruzi assay. Ninety-eight percent of the nation's blood supply will be tested for the antibodies to this parasite beginning in 2008, making testing for Chagas the standard of care. However, since Chagas is not a sexually transmitted disease there is hope that, once the test is mandated, only some donors will need to be tested, not all. Bonfils will be working closely with several researchers in order to collect enough information to determine if subset testing is a valid Chagas testing strategy to meet patient safety expectations while being fiscally responsible. Following is information regarding the origin, transmission and treatment of the disease.

Background: In January 2007, The Food and Drug Administration (FDA) licensed a serologic-based Trypanosoma cruzi  (T. cruzi) assay for blood donor screening. T. cruzi is the causative agent for Chagas disease. Although the assay is not currently mandated, it is estimated that 98 percent of the blood collected in the United States will be tested by the beginning of 2008. Chagas is a rare disease; transfusion-transmitted Chagas is rarer still. The population currently perceived at highest risk for Chagas is that of Latin American decent. The number of people in the U.S. reporting Latin American descent continues to increase.

Epidemiology: An estimated 11 million people are infected in Mexico, Central and South America. Chagas is especially common in rural communities. Modes of transmission include bites from the insect vector (autochthonous), congenital, oral and blood transfusion or organ transplantation. Five cases of autochtonous Chagas have been reported in the U.S. since the mid 1950’s: three cases in children in the Corpus Christi, Texas, one adult in California and one recent case in Louisiana. Limited seroprevalence studies in the U.S. donor population suggests that 0.01-0.02 percent of the population may have antibodies to Chagas.

Infectious Agent: The parasite is Trypansoma cruzi, which is transmitted predominantly by the insect vectors Triatoma dimidiata and Rhodnius prolixis, commonly known as kissing bugs due to their propensity to bite humans near the mouth. T. cruzi has been isolated from insects, domestic and wild animals in the southern two-thirds of the U.S.

Tranfusion/Transplantation Related Risk: Seven cases of transfusion-associated transmission have been documented in the U.S. and Canada during the past 20 years, all occurring in immunosuppressed recipients. Many more cases have been described in Latin America, where the disease is considered endemic.

Clinical Presentation: Infection can exist in an acute or chronic form. The patient, unfortunately, may be without any signs or symptoms. Acute: Symptoms include fever, body aches and rash. Signs may include swollen glands, chagoma (localized swelling at bite entry) or Romana’s sign (swelling of eyelids/face on side of face where patient was bitten). Chronic:  Patients have an approximately 30 percent risk of developing cardiomyopathy, megaesophagus or megacolon.

Treatment: Treatment of Chagas is difficult and best obtained early in the infection. Symptomatic relief is possible. The Centers of Disease Control (CDC) is currently evaluating treatment options, information about which will become available on their Web site. 

Clinical testing: The donor screening test is currently not licensed for diagnostic purposes, although it may be in the future. The CDC, the local public health agency and most local infectious disease experts have been gearing up to provide additional information for clinical testing options once donor testing begins in a given area.

Patient counseling: Currently all donors testing repeat reactive by the screening test are indefinitely deferred from further blood donation, even if follow-up testing is negative. Based on limited data, only 20-25 percent of repeat reactive screening tests are positive by additional testing. Patients who have ever received blood from donors testing positive by the screening alone, however, may still be notified of the possible risk of transfusion transmission (lookback). The AABB, the national organization of the transfusion industry, at this time suggests only testing at-risk family members of donors who are confirmed positive or family members with a similar history of exposure to vectors in an endemic area (e.g., the children of seropositive women). 

For additional information please visit the following Web sites:  www.cdc.gov/ or www.aabb.org/.

Distribution of Endemic Chagas Disease in the Americas

Source:  Wikipedia

Stages of T. cruzi infection

Source: CDC

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