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Trypanosoma cruzi

Chaga’s disease is caused by the parasite, Trypanosoma cruzi. As many as 11 million persons in Mexico and in Central and South America carry the parasite and serve as a potential source of transfusion transmitted disease. More cases of Chagas disease are being diagnosed in the United States because of immigration of infected individuals from endemic countries. Most of these individuals have asymptomatic chronic disease. 

Chagas disease is most commonly spread from human to human via contact with infected vector insects, triatomines, which are also known as kissing bugs. T. cruzi can also be transmitted from mother to baby during pregnancy. There are an estimated 63 to 315 acute congenital infections with T. cruziannually in the United States. 

The incubation period is one to two weeks. The acute stage of Chagas disease is often asymptomatic or consists of flu-like symptoms that can last up to 2 months. Infants are at higher risk for developing severe manifestations, such as myocarditis or meningo-encephalitis during the acute stage. If untreated, infection becomes chronic. Most patients with chronic infection remain asymptomatic; however, 20%–30% develop cardiac or gastrointestinal complications, which can be fatal.

The actively motile (trypomastigote) form may be demonstrated in peripheral blood by stained smears during the acute phase. The parasite is not seen in the blood during the chronic phase. Diagnosis at this stage relies on serology or tissue biopsy. Serum from patients with suspected Chaga disease can be tested for T. cruziIgM and IgG antibodies by an indirect enzyme linked immunosorbent assay. Infected individuals usually begin producing antibodies to T. cruzi during the first month following exposure to the parasite. Antibody levels may fluctuate during the chronic phase of the disease and may become undetectable after several months. Uninfected individuals are not expected to have detectable levels of antibodies to T. cruzi.

Awareness of Chagas disease as a public health problem in the United States increased after the introduction of blood donor screening for Chagas disease in 2007. As of December 2017, at least 2,300 infected blood donors had been reported by blood banks across the United States. Estimates of the incidence of seropositive donors in the United States have ranged from 1 in 5400 to 1 in 25,000 donors. 

A limited number of transfusion-transmitted T. cruzicases have been identified in the U.S., most commonly from platelet transfusion. No fatalities have been reported to the FDA. Transfusion of red blood cells and platelets from infected donors carries the highest risk of transmission, approximately 38%. The risk of transmission from plasma components is considerably lower because T. cruziis killed by freezing. The lifetime risk of severe heart or intestinal problems in infected individuals averages about 30% and usually occurs many years after the initial infection. 

An immunoassay for antibodies to T. cruziwas introduced for blood donor screening in 2007, since persons with acute infections remain asymptomatic for long periods of time and T. cruzican survive for several weeks in refrigerated blood. Unlike other infectious disease agents, FDA requires testing of donors only one time at their index donation.

FDA requires hospitals to participate in a Look-back program, which involves identification of all recipients of previously transfused blood components from confirmed positive donors. Individuals with a history of Chagas disease are permanently deferred from donating blood.

References

  1. Montgomery SP, Starr MC, Cantey PT, Edwards MS, Meymandi SK. Neglected parasitic infections in the United States: Chagas disease. Am J Trop Med Hyg 2014;90:814–8
  2. Food and Drug Administration Center for Biologics Evaluation and Research. Amendment to guidance for industry: use of serological tests to reduce the risk of transmission of Trypanosoma cruzi infection in while blood and blood components intended for transfusion. Silver Spring, MD: US Department of Health and Human Services, Food and Drug Administration, Center for Biologics Evaluation and Research; 2016. https://www.fda.gov/downloads/BiologicsBloodVaccines/GuidanceComplianceRegulatoryInformation/Guidances/Blood/UCM528600.pdf
  3. AABB. Chagas Biovigilance Network: RIPA positive map. Bethesda, MD: AABB; 2017. http://www.aabb.org/research/hemovigilance/Pages/chagas.aspx
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