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Trypanosoma cruzi

Chagas disease is caused by the protozoan parasite, Trypanosoma cruzi. As many as 300,000 persons in the United States and 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.


T. cruzi can be transmitted by infected insect vectors, from mother to baby (congenital) and, much less commonly, through organ transplantation or blood transfusion from an infected donor.  Mammals, especially rodents and marsupials, are reservoirs of T. cruzi in a sylvatic cycle, but humans, dogs, and cats can also serve as reservoirs in areas where the parasite is endemic. Infected insect vectors are called triatomines, which are also known as kissing bugs. The parasite is passed in the triatomine’s feces and infection occurs when feces contaminate a break in the skin or conjunctiva.


The incubation period is one to two weeks.  Acute T. cruzi infection is rarely identified because it usually causes a mild nonspecific illness or is asymptomatic. Some patients experience flu-like symptoms that may last up to 2 months. Infants are at higher risk for developing severe manifestations, such as myocarditis or meningoencephalitis during the acute stage.


Without treatment, infection persists for the lifetime of the infected person and can result in gastrointestinal disease or serious cardiac manifestations, including heart failure, stroke, or life-threatening ventricular arrhythmias in approximately 30% of those who are chronically infected.


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 Chagas disease can be tested for T. cruzi IgM 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.


Blood donor screening for T. cruzi antibodies in the U.S. blood supply was first implemented in 2007 because persons with acute infections remain asymptomatic for long periods of time and T. cruzi can survive for several weeks in refrigerated blood. Positive results from blood donor screening for T. cruzi antibodies should be followed by diagnostic testing. Diagnosis of chronic Chagas disease is based on positive results from at least two serologic tests that use different techniques and different antigen preparations because no single test is sufficiently sensitive and specific for diagnosis. Unlike other infectious diseases, FDA requires testing of donors only one time at their index donation.


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. cruzi cases have been identified in the U.S., most commonly from platelet transfusion. No fatalities have been reported to 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. cruzi is 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.


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.




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.


3.     AABB. Chagas Biovigilance Network: RIPA positive map. Bethesda, MD: AABB; 2017.

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