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Chagas Disease in the US: An Underestimated Emerging Infectious Disease Threat

Amesh A. Adalja, MD, FACP, FACEP, November 14, 2014

While many emerging infectious diseases are characterized by rapid, explosive outbreaks, some may be marked by an insidious, unrecognized spread. Recent data have shown the surreptitious spread of the vectorborne Chagas disease in parts of the US, a situation that can lead to serious consequences if not addressed.

Kissing Bug Vector

Chagas disease, or American trypanosomiasis, results from the introduction of the parasite Trypanosoma cruzi into the body through the actions of a “kissing bug” (triatomine bug) vector. The bug feeds on mammalian blood, most often biting people on the face while they sleep (hence the name “kissing”). During its blood meal, the vector defecates the organism, which then enters the host through breaks in the skin. The resulting infection can range from asymptomatic to flulike symptoms to devastating cardiac and intestinal symptoms, including dilated cardiomyopathy and megacolon. If the disease is recognized and treated early with antimicrobial therapy such as nifurtimox and benznidazole, complications can be averted. Those with Chagas disease can spread the infection to others via transfused blood that may harbor T. cruzii.1

Texas Blood Donors and Autochthonous Transmission

Chagas disease has traditionally been thought to be largely restricted to South and Central America, and little attention has been paid to it in the US. However, a recent study illustrates that the pathogen has expanded its range and is a real threat north of the border. Studying blood donors from 5 centers in Texas that are part of the AABB Chagas Biovigilance Network, Garcia et al found that 1 in 6,500 carry the disease, potentially transforming the blood supply into a vector for spread of this disease—a situation that prompted testing of donors nationwide beginning in 2007. Garcia also found that prevalence increased with age, Hispanic race, and residence in higher poverty level zip codes.2

In a separate study that Garcia presented at the meeting of the American Society of Tropical Medicine and Hygiene, 17 individuals with Chagas disease were followed and 41% had evidence of cardiac complications.3 Of the 17, 6 had not traveled a significant amount outside the US  and did not have foreign-born mothers, indicating that local transmission had occurred. Indeed, another study revealed that over 70% of local kissing bugs in Texas carry the pathogen.1

American Trypanosomiasis—Fully American

The growing evidence that the kissing bug, like all vectors, does not recognize borders should prompt wider investigation to determine the true prevalence of T. cruzi in the US. Studies are focused largely on blood donors, potentially failing to capture the true burden of disease. Treatment of Chagas disease can stave off serious complications, including cardiac complications. But unless awareness of the disease is increased, many will not receive therapy. Additionally, there are no FDA-approved medications for Chagas disease, and the unapproved treatments must be obtained from CDC—another complication to treating patients efficiently.

References

  1. Undiagnosed, undertreated Chagas disease emerging as US public health threat. MedicalXpress website. November 4, 2014.  http://medicalxpress.com/news/2014-11-undiagnosed-undertreated-chagas-disease-emerging.html. Accessed November 12, 2014.
  2. Garcia MN, Woc-Colburn L, Rossman SN, et al. Trypanosoma cruzi screening in Texas blood donors, 2008-2012. Epidemiol Infect 2014. [Epub ahead of print]. http://dx.doi.org/10.1017/S0950268814002234.
  3. Garcia MN, Murray KO, Woc-Colburn L, et al. Chagas disease transmission and cardiac manifestations among Texas blood donors. Paper presented at: 63rd Annual Meeting of the American Society of Tropical Medicine and Hygiene; November 2-6, 2014; New Orleans, LA.