Chagas disease
Chagas disease, also known as American trypanosomiasis, is a parasitic infection caused by the protozoan Trypanosoma cruzi, primarily transmitted through bites or feces of infected conenose bugs, commonly referred to as kissing, assassin, or vampire bugs. The disease predominantly affects populations in Latin America, where it is estimated that six to seven million people are infected, with approximately 30,000 new cases diagnosed each year. Chagas disease manifests in two phases: an acute phase, especially prevalent in children, characterized by symptoms such as anemia, chills, and heart failure; and a chronic phase in adults, which can lead to severe complications like nervous system dysfunction and heart failure.
The treatment options for Chagas disease include medications such as nifurtimox and benznidazole, which are most effective when administered early in the acute phase, though they come with potential side effects. Efforts to control the disease have been historically slow, prompting initiatives like World Chagas Disease Day to raise awareness and advocate for improved healthcare. Preventive measures involve insecticide applications, housing improvements, and routine screenings, particularly for blood donors and newborns of infected mothers. Overall, Chagas disease remains a significant public health challenge, particularly in endemic regions.
Chagas disease
ANATOMY OR SYSTEM AFFECTED: Immune system, nervous system, skin
DEFINITION: An acute disease that is most common in children and caused by the protozoan Trypanosoma cruzi.
CAUSES: Protozoan transmitted by conenose bug (also called assassin, kissing, or vampire bug) through bite or feces
SYMPTOMS: Acute phase includes anemia, loss of strength, nervous disorders, chills, muscle and bone pain, heart failure, sometimes death; chronic phase also includes central and peripheral nervous system dysfunction eventually leading to heart failure
DURATION: Acute and chronic
TREATMENTS: Nifurtimox and benznidazole for acute infections
Causes and Symptoms
Chagas disease, also known as American trypanosomiasis or South American trypanosomiasis, is a parasitic disease that affects millions of people in both North and South America. The World Health Organization (WHO) estimated in 2023 that between six and seven million people worldwide are infected with the parasite that causes the disease, most of them in twenty-one Latin American countries. According to the Pan American Health Organization (PAHO), about thirty thousand people are diagnosed annually. Of those, about twelve thousand die. PAHO estimated that about seventy million people in the Americas are at risk of contracting the disease.
The US Centers for Disease Control and Prevention estimated in 2022 that some 300,000 people living in the United States had Chagas disease. However, due to lack of awareness and reporting requirements, the true number of infections is likely higher. Most infections were acquired abroad, but local transmission within the US is possible. By the end of 2017, six states had surveillance systems for tracking transmission.
The protozoan Trypanosoma cruzi that causes Chagas disease is transmitted by conenose bugs (order Hemiptera, family Reduviidae, subfamily Triatominae), also known as assassin bugs, vampire bugs, or kissing bugs. The feces of the bugs contain the parasites, which enter a human host through broken skin or mucus membranes.
Entry of the parasites into cells in the subcutaneous tissue triggers an acute local inflammatory reaction. Within one to two weeks of infection, the trypanosomes spread to the regional lymph nodes and begin to multiply in the cells that phagocytose (ingest) them.
Chagas disease also can be transmitted by blood transfusion; by organ transplantation, especially heart transplantation; rarely, by consumption of food contaminated with the parasite; or by passage from an infected mother to an infant during pregnancy or childbirth.
Chagas disease is manifested in acute and chronic phases. Symptoms of the acute phase (most common in children) include anemia, loss of strength, nervous disorders, chills, muscle and bone pain, and varying degrees of heart failure. Death may ensue three to four weeks after infection. It is also possible for no symptoms to present during this phase but for damage to occur within the body nonetheless.
Symptoms of the chronic phase (most common in adults) include those of the acute phase, plus central and peripheral nervous dysfunction, which may last for many years and eventually lead to heart failure. About three in ten infected people die of heart failure. Damage to the gastrointestinal tract, such as enlargement of the colon, are also possible.
Treatment and Therapy
Unlike many other trypanosomes of humans, T. cruzi does not respond well to chemotherapy. The most effective drugs kill only the extracellular protozoa, while the intracellular forms defy the best efforts at eradication. The reproductive stages, which occur inside living host cells, seem to be shielded from the drugs.
If given soon after infection, at the beginning of the acute phase, nifurtimox and benznidazole are “almost 100% effective in curing the disease,” according to WHO. However, they require long treatment durations and have significant side effects, and their efficacy is inversely proportional to the length of time between infection and treatment.
Perspective and Prospects
In 1910, Carlos Chagas dissected a number of assassin bugs and found their hindguts swarming with trypanosomes some twenty years before they were known to cause disease. A century later, progress in controlling this harmful disease has been slow.
The 2005 report of the Scientific Working Group on Chagas Disease called for, among other things, formulations of the two main drugs used to treat the disease and better diagnostic tools, better ways to screen donated blood to prevent by transfusion, and improvements in control of the insects involved in transmission of the disease.
In May 2019, World Chagas Disease Day was established to raise awareness and lobby for better health care for those infected. It is celebrated annually on April 14, the day in 1909 when Carlos Chagas diagnosed the first human case of the disease.
Preventive measures include indoor applications of insecticide, use of treated bed nets and insect repellents, housing upgrades, and personal hygiene practices to guard against triatomine infestation and exposure. Routine screenings for Chagas disease are also being implemented in some countries, and particularly for blood donors and newborns of infected mothers.
Bibliography
Andalo, Paula. “Doctors Push for More Aggressive Efforts to Fight Chagas Disease, a Silent Killer.” NBC News, 15 Aug. 2023, www.nbcnews.com/health/health-news/doctors-push-aggressive-efforts-fight-chagas-disease-silent-killer-rcna99859. Accessed 1 Mar. 2024.
“Chagas Disease.” MedlinePlus, US National Library of Medicine, 4 Dec. 2022, medlineplus.gov/ency/article/001372.htm. Accessed 1 Mar. 2024.
“Chagas Disease.” Pan American Health Organization, 2022, www.paho.org/en/topics/chagas-disease. Accessed 1 Mar. 2024.
“Chagas Disease (Also Known as American Trypanosomiasis).” World Health Organization, 6 Apr. 2023, www.who.int/news-room/fact-sheets/detail/chagas-disease-(american-trypanosomiasis). Accessed 1 Mar. 2024.
Dorn, Patricia L., et al. “Autochthonous Transmission of Trypanosoma cruzi, Louisiana.” Emerging Infectious Diseases, vol. 13, no. 2, 2007, pp. 605–7. Academic Search Complete, search.ebscohost.com/login.aspx?direct=true&db=a9h&AN=24532765&site=ehost-live. Accessed 2 Mar. 2017.
Mascola, L., et al. “Chagas Disease after Organ Transplantation—Los Angeles, California, 2006.” Morbidity and Mortality Weekly Report, 28 July 2006, pp. 798–800. Academic Search Complete, search.ebscohost.com/login.aspx?direct=true&db=a9h&AN=21760833&site=ehost-live. Accessed 2 Mar. 2017.
Perleth, Matthias. Historical Aspects of American Trypanosomiasis (Chagas’ Disease). Peter Lang, 1997.
Schramski, Sam. “Scientists Have Their Eyes on Chagas Disease and the ‘Kissing Bugs’ That Help Spread It.” WHYY, 16 Dec. 2022, whyy.org/segments/scientists-have-their-eyes-on-chagas-disease-and-the-kissing-bugs-that-help-spread-it/. Accessed 1 Mar. 2024.
WHO Expert Committee on the Control of Chagas Disease. Control of Chagas Disease: Second Report of the WHO Expert Committee. World Health Organization, 2002. WHO IRIS, apps.who.int/iris/handle/10665/42443. Accessed 2 Mar. 2017.