How is Chagas disease (American trypanosomiasis) transmitted?

Updated: Apr 26, 2019
  • Author: Louis V Kirchhoff, MD, MPH; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Answer

Historically, most transmission of T cruzi to humans has resulted from the contamination of vulnerable surfaces (eg, breaks in the skin, mucosae, and the conjunctivas) with the feces of infected vectors. However, as noted, vector-borne transmission has been reduced markedly in many endemic countries. Transfusion transmission was a major public health problem in endemic countries for decades, but, as accurate serologic assays for T cruzi infection were developed and screening of blood donors became mandatory and were implemented throughout the endemic range, this problem essentially has been eliminated. [16, 29, 30]

Not surprisingly, T cruzi can also be transmitted via transplantation of organs obtained from persons with chronic infection, and occasional reports of this in Latin America [31, 32] and in the United States [33, 34, 35] have appeared.

The rate of congenital (transplacental) transmission from mothers with chronic T cruzi infection to their newborns is about 5%, with a range of 2%-10% in various studies. [36] To date, no measures have been defined to reduce or eliminate this form of transmission. As transmission by vectors and through transfusion of contaminated blood have been reduced, the proportion of new T cruzi infections that result from congenital transmission has increased. Nonetheless, the total number of instances of congenital transmission certainly has decreased as seroprevalence rates have fallen. [37, 38, 39, 40, 41, 42, 43, 44]

In contrast to Toxoplasma gondii, vertical transmission of T cruzi is possible with successive pregnancies. Transmission of T cruzi via breast milk appears to be extremely rare, and chronic T cruzi infection is not a contraindication to breastfeeding. [45] Several instances of transmission of T cruzi to groups of people via ingestion of food or drink presumably contaminated with the feces of infected vectors have been reported. [46, 47, 48, 49] Finally, the facility of producing infective forms of T cruzi in the laboratory has resulted in numerous accidental transmissions in this context. [4, 50]


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