by Dr. Jaclynn Moskow
In 1909, Brazilian physician Carlos Chagas learned of a local phenomenon in which blood-sucking insects were biting people on the face during sleep. On April 14, he dissected one such insect and found parasitic euglenoids living inside of it (1). Dr. Chagas named the parasite Trypanosoma cruzi (T. cruzi) and, in this moment, discovered both the causative agent and vector of “Chagas Disease.”
On April 14, 2021, we recognize the second annual World Chagas Disease Day (2). Chagas disease, also known as American Trypanosomiasis, is endemic to Latin America. It can lead to severe cardiac, neurologic, and gastrointestinal disease – and in some cases is fatal, causing about 12,000 deaths each year (3).
The Chagas disease represents the third-largest tropical disease burden worldwide, after malaria and schistosomiasis (4). It has likely been with us for thousands of years, as T. cruzi DNA has been recovered from ancient mummies and bone fragments (1).
Triatomine bugs, also known as “kissing bugs”, “cone-nosed bugs”, or “bloodsuckers”, are the vectors for Chagas disease. They acquire T. cruzi after biting infected animals or humans and transmit the parasite to others through their feces. There are over 150 species of domestic and wild animals that serve as reservoirs for Chagas disease (5), including dogs, cats, pigs, rabbits, raccoons, rats, bats, armadillos, and monkeys.
Triatomine bugs are commonly found in rural areas, in houses made from materials such as mud, adobe, straw, and palm thatch (6). They feed at night. If they defecate on an individual and T. cruzi gains access to the body via a mucus membrane or break in the skin, the transmission of Chagas disease may occur.
Vertical transmission of Chagas disease is possible during pregnancy. Chagas disease can also be transmitted via blood transfusion and organ transplantation, and there is some evidence that it may be transmitted through sex and in rare instances through consumption of game meat. It can also be acquired by consuming food or water contaminated with insect remains (4).
The incubation period for Chagas disease depends upon the mode of transmission. Vectorially transmitted cases usually manifest in one-to-two weeks, while orally transmitted cases may take up to 3 weeks – and transfusion-based cases up to 120 days (5).
Chagas disease has an acute and chronic phase. The acute phase is often asymptomatic or mild in nature and usually resolves spontaneously (5). The acute phase may begin with the development of a “chagoma” – an indurated area of erythema and swelling with local lymph node involvement (7). “Romana’s sign” consists of painless edema of the eyelids and periocular tissues (resulting from conjunctival inoculation) and is usually unilateral. Patients in the acute phase may develop fever, malaise, and anorexia. Generalized lymphadenopathy and mild hepatosplenomegaly may be present. Rarely, meningoencephalitis or severe myocarditis with arrhythmias and heart failure may occur.
10% to 30% of acute infections will progress to chronic disease. Chronic disease may present years or decades after the initial infection. Cardiac manifestations include arrhythmias, thromboembolism, and cardiomyopathy. Arrhythmias may present as episodes of vertigo, syncope, or seizures. Congestive heart failure may develop, leading to death. Cerebral disease can also occur and is characterized by headache, seizures, focal neurological deficits, and evidence of ischemia and infarct. Gastrointestinal manifestations include megaesophagus and megacolon. Dysfunction of the urinary bladder is also reported. Chagas disease has an overall case-fatality rate of 10% (7).
Patients with chronic Chagas disease who become immunosuppressed may experience a reactivation of the infection. In individuals with concurrent HIV/AIDS and Chagas disease, the central nervous system is the most commonly affected site, and space-occupying lesions often occur. (8).
Diagnosis and Treatment
Chagas disease may be diagnosed through visualization of protozoa in blood or tissue, serology, xenodiagnosis, or PCR. The anti-parasitic medications Nifurtimox or Benznidazole can be used for treatment. Treatment is curative in approximately 50-80% of acute-phase cases, and 20-60% of chronic phase cases (9). Treatment is curative in greater than 90% of congenital cases when given within the first year of life (10). Treatment of pregnant women is not recommended (11).
Vector-borne transmission of Chagas disease only occurs in the Americas. Approximately 121 million individuals are at risk in Central and South America and Mexico. If you have a GIDEON account, click here to explore our Chagas disease outbreak map. An estimated 8 million people are currently infected (12).
Vector-borne transmission of Chagas disease is exceedingly rare in the United States, with 28 cases documented between 1955 and 2015 (13). About 300,000 people are currently living in the United States with Chagas disease that was acquired in Latin America (14). In Europe, the prevalence of T. cruzi infection among Latin American migrants is approximately 6% (4).
In 2007, two notable outbreaks occurred as the result of ingestion of sources contaminated with T. cruzi. 166 cases occurred in Brazil from contaminated food and 128 cases in Venezuela from contaminated juice (4).
Vector-control programs centered around the widespread use of insecticides have led to some success in decreasing the prevalence of Chagas disease. This progress, however, has been recently complicated by the emergence of insecticide-resistant vectors.
Falling death rates of Chagas disease (Trypanosomiasis – American), 1990 – 2016
Individuals living in endemic areas can decrease their risk of contracting the disease by completing home improvement projects aimed at disrupting triatomine bug nests. These nests are commonly found beneath porches, between rocky surfaces, in wood/brush piles, rodent burrows, and chicken coops (15). Individuals traveling to endemic areas can decrease their risk of contracting the disease by applying insect repellent, wearing protective clothing, and using bed nets.
The screening of blood products for Chagas disease is another important prevention strategy. In most endemic countries, all blood donations are tested for T. cruzi antibodies. In countries in which cases are imported, screening strategies vary (16, 17). In the United States, all first-time blood donors are tested. In Canada, the UK, and Spain, only donors considered “at-risk” are tested (such as those who previously lived in, or recently traveled to, Latin America). In Sweden, individuals who lived in endemic countries for more than five years are precluded from donating blood, while in Japan, only individuals with a known history of Chagas disease are excluded. In China, blood donors are not currently screened for Chagas disease.
Recently, a new surveillance system for Chagas disease has been implemented in some countries where malaria is also endemic; microscopy technicians have been trained to identify T. cruzi in malaria films (18).
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(1) D. Steverding, “The history of Chagas disease”, Parasites & Vectors, vol. 7, no. 1, p. 317, 2014. Available: 10.1186/1756-3305-7-317
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(3) B. Lee, K. Bacon, M. Bottazzi and P. Hotez, “Global economic burden of Chagas disease: a computational simulation model”, The Lancet Infectious Diseases, vol. 13, no. 4, pp. 342-348, 2013. Available: 10.1016/s1473-3099(13)70002-1
(4) “Trypanosomiasis – American Worldwide Distribution”, GIDEON Informatics, Inc, 2021. [Online]. Available: https://app.gideononline.com/explore/diseases/trypanosomiasis-american-12460/worldwide
(5) A. Rassi, A. Rassi and J. Marin-Neto, “Chagas disease”, The Lancet, vol. 375, no. 9723, pp. 1388-1402, 2010. Available: 10.1016/s0140-6736(10)60061-x
(6) “Parasites – American Trypanosomiasis (also known as Chagas Disease): Detailed FAQs”, Centers for Disease Control and Prevention, Global Health, Division of Parasitic Diseases and Malaria, 2021. [Online]. Available: https://www.cdc.gov/parasites/chagas/gen_info/detailed.html#intro
(7) “Trypanosomiasis – American”, GIDEON Informatics, Inc, 2021. [Online]. Available: https://app.gideononline.com/explore/diseases/trypanosomiasis-american-12460
(8) A. Vaidian, L. Weiss, and H. Tanowitz, “Chagas’ disease and AIDS”, Kinetoplastid Biol Dis, vol. 3, no. 1, p.2, 2004. Available: 10.1186/1475-9292-3-2
(9) J. Guarner, “Chagas disease as example of a reemerging parasite”, Seminars in Diagnostic Pathology, vol. 36, no. 3, pp. 164-169, 2019. Available: 10.1053/j.semdp.2019.04.008
(10) F. Machado et al., “Chagas Heart Disease”, Cardiology in Review, vol. 20, no. 2, pp. 53-65, 2012. Available: 10.1097/crd.0b013e31823efde2
(11) E. Howard, P. Buekens and Y. Carlier, “Current treatment guidelines for Trypanosoma cruzi infection in pregnant women and infants”, International Journal of Antimicrobial Agents, vol. 39, no. 5, pp. 451-452, 2012. Available: 10.1016/j.ijantimicag.2012.01.014
(12) “Chagas disease (American trypanosomiasis): Epidemiology”, World Health Organization, 2021. [Online]. Available: https://www.who.int/chagas/epidemiology/en/
(13) S. Montgomery, M. Parise, E. Dotson and S. Bialek, “What Do We Know About Chagas Disease in the United States?”, The American Journal of Tropical Medicine and Hygiene, vol. 95, no. 6, pp. 1225-1227, 2016. Available: 10.4269/ajtmh.16-0213
(14) “Parasites – American Trypanosomiasis (also known as Chagas Disease): Epidemiology & Risk Factors”, Centers for Disease Control and Prevention, Global Health, Division of Parasitic Diseases and Malaria, 2019. [Online]. Available: https://www.cdc.gov/parasites/chagas/epi.html
(15) “Parasites – American Trypanosomiasis (also known as Chagas Disease): Triatomine Bug FAQs”, Centers for Disease Control and Prevention, Global Health, Division of Parasitic Diseases and Malaria, 2020. [Online]. Available: https://www.cdc.gov/parasites/chagas/gen_info/vectors/index.html
(16) A. Angheben et al.,”Chagas disease and transfusion medicine: a perspective from non-endemic countries”, Blood Transfus, vol. 13, no. 4, pp. 40-50, 2015. Available: 10.2450/2015.0040-15
(17) V. Mangano, M. Prato, A. Marvelli, G. Moscato and F. Bruschi, “Screening of at‐risk blood donors for Chagas disease in non‐endemic countries: Lessons from a 2‐year experience in Tuscany, Italy”, Transfusion Medicine, vol. 31, no. 1, pp. 63-68, 2020. Available: 10.1111/tme.12741
(18) “Chagas disease (American trypanosomiasis): Prevention of Chagas Disease”, World Health Organization, 2021. [Online]. Available: https://www.who.int/chagas/disease/prevention/en/