- Risk Factors
- Is It Contagious?
What is Chagas disease?
Chagas disease (also termed American trypanosomiasis) is an infection caused by a protozoan parasite (Trypanosoma cruzi) that can result in acute inflammatory skin changes (chagomas) and eventually may cause infection and inflammation of many other body tissues, especially those of the heart and intestinal tract.
The disease was named after Dr. Carlos Chagas, who discovered the disease in 1909. The disease may have three phases in an individual:
- acute, with mild or no symptoms that may last weeks to about two months;
- intermediate or indeterminate phase that has few if any symptoms and may last 10-20 years or longer; and
- chronic phase that appears after about 20 years, with the more severe symptoms appearing from gradual chronic organ damage (especially to the heart and intestine, although other organs may be affected) with symptoms that usually remain for life.
People with Chagas disease seen in the U.S. usually have acquired it while living in a country where the disease is endemic (Mexico and Central and South America). It is a tropical disease.
The U.S. Centers for Disease Control and Prevention (CDC) estimates about 8-11 million people are infected in countries where the disease is endemic. The parasites are transferred to humans by the bite of blood-sucking triatomine bugs in the subfamily Triatominae, also termed "kissing bugs."
The disease has been diagnosed in the U.S., mainly in immigrants from South and Central America. Triatomine bugs have been detected in Texas, and recently the CDC communicated that the bugs have now been found in 28 states, including California and Pennsylvania.
American trypanosomiasis (Chagas disease) is distinguished from African trypanosomiasis (sleeping sickness or African sleeping sickness) by the part of the world where they occur, their vectors, and their different symptoms and different treatments (see Table 1).
|American trypanosomiasis||African trypanosomiasis|
|Cause||T. cruzi||T. brucei (subspecies)|
|Main vector||Triatomine bugs (also termed kissing bugs)||Tsetse fly|
|Main symptoms||Chagomas, heart, gastrointestinal||Chancres, nighttime insomnia, seizures|
|Treatment||Benznidazole, nifurtimox; symptomatic treatments in chronic phase||Suramin, melarsoprol, pentamidine, eflornithine|
What causes Chagas disease?
- Chagas disease is caused by a protozoan parasite named Trypanosoma cruzi. Infection of humans occurs when an insect vector (mainly Triatominae or kissing bugs, a subfamily of the family Reduviidae and sometimes referred to as reduviid bugs) deposits feces that contains the parasites on human skin.
- The parasites then enter the mammalian (human) host through the bug bite, or breaks in the skin or conjunctiva. Occasionally, the parasites enter through mucosal cells of the mouth or airway when ingested or inhaled. The bugs often bite and/or deposit feces near the eyes and lips; when the parasites enter the skin, swelling and redness (termed a chagoma) often develop.
- The term kissing bugs comes from the appearance of these symptoms that resemble skin changes that occur with prolonged kissing (hickies). In some individuals, the parasites eventually go into the bloodstream and lodge in various organs, especially the muscular structure of the organs. The parasites multiply and eventually cause chronic symptoms related to the particular involved organ or organs that can include life-threatening cardiac failure, arrhythmias, poor gastrointestinal motility, meningoencephalitis, or death.
- Humans who live in poor or primitive housing conditions that border or invade the habitats of Triatominae bugs cause a break in the normal life cycle of the insect vectors (bugs) and their usual hosts (over 100 types of animals), termed the sylvatic cycle.
- The bugs then enter the world of humans and their domesticated animals (cats, dogs) and transmit T. cruzi to them. When T. cruzi is transmitted from bugs to humans or human pets and back to the bugs, the life cycle is referred to as the domiciliary cycle.
- The life cycle of T. cruzi is complex; it has multiple developmental stages in both the insect vector (Triatominae bugs, also termed triatomine bugs) and mammalian (human and animal) hosts. The figure below from the CDC shows the developmental stages that occur in both the sylvatic and domiciliary cycles.
What are the risk factors for Chagas disease?
- Living in an area where the vectors (kissing bugs) that spread the disease are plentiful is a major risk factor for Chagas disease. Such areas are impoverished areas in Mexico and Central and South America. Any residence that is infested with these vectors is a high-risk area; eliminating the areas where the vectors reside reduces the risk.
- Another risk factor is obtaining a blood transfusion, especially in an endemic region, if the blood donors are not screened for Chagas disease. This risk also occurs for recipients of donated organs.
- Immunocompromised patients have a higher risk for development of the disease, and some infected women with chronic Chagas (as many as 10%) may transmit the parasites to their newborns (congenital Chagas disease).
- Also, eating unwashed foods that are contaminated with feces from the infected bugs may cause Chagas disease (food-borne disease).
Is Chagas disease contagious?
- Chagas disease is not considered contagious from person to person; the parasite almost always requires a vector like the triatomine bug to transfer the parasite (T. cruzi) to humans. However, T. cruzi has been reported to be transferred to humans from blood transfusions, organ transplantation, from mother to infant through the placenta (congenital transmission), by ingestion, inhalation, and by laboratory accidents.
- Fortunately, these forms of transmission occur very infrequently. Researchers have demonstrated that in experimental conditions, bedbugs may become infected with T. cruzi from infected mice and then are able to reinfect mice, but human infection by bedbugs has not been documented to date.
- Not all triatomine bugs are infected with T. cruzi, and not every bite of the vector bug will cause infection; the transfer of the parasite from the bug to humans is not very efficient so getting the disease "is not easy," according to the CDC.
What are the symptoms of Chagas disease?
The symptoms and signs of Chagas disease can be quite variable and range from no symptoms at all to severe and distressing symptoms. The first symptoms and signs, when present in the acute phase, may include some of the following:
- Swelling and/or redness at the skin infection site (termed chagoma)
- Skin rash
- Swollen lymph nodes
- Headaches and body aches
- Nausea, vomiting, and/or diarrhea
- Abdominal discomfort or pain
- Liver and/or spleen enlargement
- Romaña sign (unilateral painless edema [swelling] of tissues around the eye)
- EKG changes suggestive of myocarditis and/or arrhythmias may occur
- Muscle aches
Most individuals who get the above acute-phase symptoms have them resolve spontaneously in about three to eight weeks. Occasionally, acute infections show chronic symptoms (listed below) if the patient's immune function is weakened.
Most investigators suggest that the intermediate or indeterminate phase has no symptoms (symptom-free people). This stage may last throughout the person's life, and the individuals may never know they have Chagas disease, especially if they had mild or no symptoms in the acute phase. However, this symptom-free stage may only last about 10-20 years in some patients before the chronic symptoms develop in about 10%-30% of those infected.
Some researchers compare the chronic phase of Chagas disease to HIV/AIDS. Whereas HIV/AIDS slowly attacks the immune system, Chagas disease slowly attacks the heart and the tissues of the gastrointestinal tract. Other investigators consider such a comparison as unwarranted publicity or hype to spotlight Chagas disease.
Symptoms of chronic Chagas disease vary according to the organs most affected; in most cases, the heart or the gastrointestinal tract (or both) show the most serious symptoms. Chronic Chagas disease symptoms may include the following:
- Irregular heartbeats
- Palpitations (abnormal heartbeat sensations)
- Fainting (syncope)
- Cardiomyopathy (chronic disease of the heart muscle)
- Congestive heart failure (dilated heart)
- Shortness of breath (dyspnea)
- Sudden death
- Chronic abdominal pain
- Chronic constipation
- Dilated esophagus and/or colon
- Difficulty swallowing
These symptoms are due to organ damage caused by the persistent presence of the parasites within the tissues of these organs. Chronic inflammation develops as the body reacts to the parasites; it affects the nerve cells or neurons in these tissues, causing electrical conduction changes in the heart (arrhythmias) and poor muscle tone in the intestines.
Diagnosis of Chagas disease
Although most acute-phase infections usually do not require specialists, often patients with chronic-phase Chagas disease may benefit from consultation with a cardiologist, gastroenterologist, and/or an infectious-disease specialist. Some patients may need a transplant surgeon. The physician team members are usually made up of physicians that are experts required according to the severity of each individual's chronic problems.
- Unless the person lives in an area where the chagomas associated with Chagas disease are well recognized, the acute phase is not often diagnosed. The majority of acute-phase infections are not diagnosed because many people develop nonspecific symptoms, and the people who get the infection usually are very poor, have primitive living conditions, and no access to medical care.
- Unfortunately, if Chagas disease is not diagnosed and treated in the early phase, those infections that progress to chronic phase are then are diagnosed in this later stage when they are not easily treated because the damage to the body organs is usually irreversible.
- There are multiple types of blood tests available to test for Chagas disease. Most are based on the host (human) production of antibodies directed against the infecting parasites, although direct microscopic examination of blood smears may visualize the parasites.
- However, microscopic visualization of the parasites usually requires confirmation by immunological studies because visually, the parasites may be confused with those seen in people with malaria, leishmaniasis, babesiosis, giardiasis, or African sleeping sickness. Microscopic preparation and examination should be performed by experienced lab technicians or experts in parasitology.
- In the U.S., the FDA approved an immunologic test (enzyme-linked immunosorbent assay or ELISA test) for Chagas disease by Ortho-Clinical Diagnostics in 2006. It detects antibodies formed against T. cruzi with high sensitivity and specificity and currently is the only FDA-approved test. Since 2007, about 800 blood-donor samples have been detected as Chagas-positive across the U.S. (see map, reference five). Other tests used in other countries (indirect immunofluorescence, hemagglutination) are less sensitive and specific but are still used. A Chagas radioimmune precipitation assay (Chagas RIPA) is used in research and with FDA permission in some clinical testing but is not widely available.
- Most cases of Chagas disease are diagnosed when individuals donate blood; most people are not aware they have been infected with T. cruzi. However, since blood and organ donation can pass the disease to other people, most labs now test donated blood and organs for Chagas disease with the approved ELISA assay. If the donors are positive, they are notified (diagnosed). The prevalence of Chagas-positive blood donors is estimated by various studies to widely range between about one positive case per 2,000-29,000 donors.
- Chronic-phase Chagas disease is diagnosed also with the above-mentioned blood tests, but these patients also often have physical findings that indicate the patient has chronic disease. Physical findings may include swelling of the extremities (peripheral edema), ascites, pulmonary congestion, and arrhythmias in patients with heart involvement.
- Patients with mainly chronic gastrointestinal involvement may have weight loss, severe gastroesophageal reflux, esophageal erosions, inability to swallow normally, or an enlarged colon (megacolon) with an enlarged abdomen. Many different diseases can cause these physical findings so it is important to know that the patient has a positive blood test for T. cruzi before concluding the person has Chagas disease. Conversely, if such physical findings and history of possible contact with Chagas vectors is present, then the blood tests could be done to either prove or rule out the diagnosis of Chagas disease in chronic phase.
- Other tests such as electrocardiography and Holter or heart-event monitoring, endoscopy, esophageal manometry (pressure measurements within the esophagus), or gastrointestinal motility studies are used to help determine the functionality of heart or gastrointestinal tissues in patients with chronic-phase Chagas disease.
Subscribe to MedicineNet's General Health Newsletter
What is the treatment for Chagas disease?
- Treatment for Chagas disease often depends on the phase of the disease and the age of the patient. Acute-phase treatment centers on killing the T. cruzi parasites with antiparasitic drugs. The prescription medications benznidazole (Rochagan, Ragonil) and nifurtimox (Lampit) may eliminate or reduce the number of parasites in the body. Some investigators suggest that drug-resistant parasites occur and others suggest these drugs of choice never eliminate all of the parasites. However, the CDC recommends drug treatment for "all people diagnosed with an acute (Chagas) infection, congenital infection, and for those with suppressed immune systems, and for all children with chronic infection. Adults with chronic infection may also benefit from treatment."
- The CDC advises caution about treating adults over 50 years of age and recommends that treatment plans for older adults be individualized. Both of these antiparasitic drugs are available in Central and South America. In the United States, however, the drugs can be obtained only through the CDC.
- During the intermediate or indeterminate phase, the vast majority of adult patients obtain no antiparasitic treatments; however, children in this stage of disease should continue drug therapy. The situation with adults may change as new investigations with antiparasitic drug treatments are being done in South America.
- Antiparasitic drug therapy of the chronic phase in adults is controversial. As quoted above, the CDC says adults with chronic infection may benefit from drug treatment, but most experts suggest there is no benefit to adults with chronic-phase Chagas disease. However, treatment of the symptoms of chronic Chagas disease is often necessary and can be life-prolonging or lifesaving.
- For example, pacemaker placement or even cardiac transplantation can be lifesaving to some patients who develop arrhythmias or cardiomyopathy.
- Surgical resection of the gastrointestinal tract may help alleviate some gastrointestinal problems.
- In addition, there are many medications available to treat specific arrhythmias and other bowel problems that may be seen in chronic Chagas disease; cardiac and gastrointestinal consultants often can help manage chronic-phase Chagas disease. Medication for the treatment of Chagas disease is available only through the CDC.
Is there a vaccine for Chagas disease?
- Currently, there is no vaccine available for humans to prevent Chagas disease. However, there are other ways available to humans to reduce or even prevent the disease. Most experts in Chagas disease agree that a majority of infections can be prevented by improving poor or primitive housing conditions. Judicious use of insecticides and education of people about home cleanliness for populations at risk for Chagas disease can augment good housing design.
- The principal goal is to prevent the vector (bugs) from establishing a domiciliary cycle in the home by making a home difficult for the bugs to invade or live in. For example, plaster-sealed walls in a home with a metal or shingle roof are far less likely to be populated by bug vectors than a mud-walled structure covered with a thatch roof, and a well-cleaned home is far less likely to have areas for bugs to hide and replicate than an unclean home. Several studies suggest this is an effective way to prevent Chagas disease. In addition, insect repellents and insecticides like Pyrethrin may reduce the chance of getting the disease by repelling or killing the vectors.
- Since blood transfusions can account for a large number of person-to-person transfers of T. cruzi, many blood banks around the world are now testing donated blood for antibodies to the parasite. If a blood sample is positive, the blood is discarded and the donor usually is notified and requested not to donate blood in the future. Similar situations occur with organ donors. Such methods help prevent Chagas disease.
What is the prognosis for Chagas disease?
In general, the prognosis for people who do not develop the chronic phase of Chagas disease is usually good. People who are diagnosed and treated in the acute phase of the disease usually have an excellent prognosis. However, individuals who go on to develop chronic-phase Chagas disease have a worse prognosis due to the damage caused to the heart, GI tract, and possibly other organs.
What are the complications of Chagas disease?
Most of the complications that develop with Chagas disease are seen in the chronic phase of the disease. Most of the complications are related to muscle changes (muscle atrophy, fibrosis, and inflammation) caused by the parasites in two body organs, the heart, and the GI tract. Consequently, heart failure and esophageal and colon enlargement (megaesophagus and megacolon) are serious complications of Chagas disease. These changes can result in weakness, difficulty swallowing, abdominal pain, and death. Other organs may also malfunction (ureters, bile duct, for example).
Hotez, P.J., E. Dumonteil, L. Woc-Colburn, J.A. Serpa, S. Bezek, et al. "Chagas Disease: The New HIV/AIDS of the Americas." PLoS Negl Trop Dis 6.5 (2012): e1498.
Kirchhoff, Louis. "Chagas Disease (American Trypanosomiasis)." Medscape.com. Nov. 10, 2014. <http://emedicine.medscape.com/article/214581-overview>.
"Mexico Distribution Map for Chagas' Disease." Insects, Disease, and History. <http://entomology.montana.edu/historybug/gallery/chagas_map_mexico.htm>.
Odero, Randy O. "African Trypanosomiasis Treatment & Medication." Medscape.com. Dec. 2, 2015. <http://emedicine.medscape.com/article/228613-treatment>.
Salazar, R., R. Castillo-Neyra, A.W. Tustin, et al. "Bed Bugs (Cimex lectularius) as Vectors of Trypanosoma cruzi." Am J Trop Med Hyg 17 (2014).
"South America Distribution Map for Chagas' Disease." Insects, Disease, and History. <http://entomology.montana.edu/historybug/gallery/chagas_map_sa.htm>.
United States. Centers for Disease Control and Prevention. "Parasites - American Trypanosomiasis (also known as Chagas Disease)." Dec. 19, 2017. <https://www.cdc.gov/parasites/chagas/gen_info/detailed.html>.
Top Chagas Disease Related Articles
8 Skin Warning Signs to Worry About in a RashMost of the rashes are harmless and may not indicate anything serious. However, if there are these accompanying symptoms along with the skin rash, it may signify something serious.
A rash can become serious if immediate medical assistance is not provided when a patient has the below symptoms including rash covers most of the body, continuous itching, fever, and difficulty breathing
Abdominal PainAbdominal pain can have many causes that range from mild to severe. Some of these causes include bloating, gas, colitis, endometriosis, food poisoning, GERD, IBS (irritable bowel syndrome), ovarian cysts, abdominal adhesions, diverticulitis, Crohn's disease, ulcerative colitis, gallbladder disease, liver disease, and cancers. Signs and symptoms of the more serious causes include dehydration, bloody or black tarry stools, severe abdominal pain, pain with no urination or painful urination. Treatment for abdominal pain depends upon the cause.
Bad Bugs: Identify Insects and Bug BitesWhat do bug bites look like? How do you treat bug bites? Why do bug bites burn? See spider bite pictures and learn how to identify bug bites from mosquitoes, bees, bed bugs, wasps, and more. See what their bites & stings look like and how to treat bug bites. For more details, enter a search for the specific insects or bugs as this slideshow is a brief introduction to the topic.
Bedbug BitesBedbugs (from the insect family Cimicidae) are small, reddish-brown tick-like insects that feed by sucking the blood of mammals. They are often found in poorly sanitized areas or in crowded living quarters.
Bed Bugs SlideshowWhat does a bedbug look like? Learn to ID bedbugs and bedbug bites. Get tips on how to prevent, treat, and get rid of bedbugs.
Bed Bugs QuizThat unexplained itching could be caused by bedbugs. Take the Bedbugs Quiz to learn the causes and symptoms of a bedbug infestation.
Bedbug Bites PictureThe first sign of bedbugs may be red, itchy bites on the skin, usually on the arms or shoulders. See a picture of Bedbug Bites and learn more about the health topic.
Congestive Heart Failure (CHF): Symptoms, Causes, Stages, TreatmentCongestive heart failure (CHF) refers to a condition in which the heart loses the ability to function properly. Heart disease, high blood pressure, diabetes, myocarditis, and cardiomyopathies are just a few potential causes of congestive heart failure. Signs and symptoms of congestive heart failure may include fatigue, breathlessness, palpitations, angina, and edema. Physical examination, patient history, blood tests, and imaging tests are used to diagnose congestive heart failure. Treatment of heart failure consists of lifestyle modification and taking medications to decrease fluid in the body and ease the strain on the heart. The prognosis of a patient with congestive heart failure depends on the stage of the heart failure and the overall condition of the individual.
DiarrheaDiarrhea is a change in the frequency and looseness of bowel movements. Symptoms associated with diarrhea are cramping, abdominal pain, and the sensation of rectal urgency. Causes of diarrhea include viral, bacterial, or parasite infection, gastroenteritis, food poisoning, and drugs. Absorbents and anti-motility medications are used to treat diarrhea.
ELISA TestsELISA stands for "enzyme-linked immunosorbent assay." This is a rapid immunochemical test that involves an enzyme (a protein that catalyzes a biochemical reaction). It also involves an antibody or antigen (immunologic molecules).
Enlarged Spleen (Splenomegaly) Symptoms, Signs, Causes,TreatmentAn enlarged spleen or splenomegaly is generally caused by other diseases or conditions such as infections, cancers, blood disorders, or decreased blood flow. Symptoms of an enlarged spleen are often unnoticed. A feeling of fullness after eating a small amount of food and not being able to eat large meals may be a symptom of an enlarged spleen. Treatment for an enlarged spleen depends upon the cause.
8 First Aid Kit Essentials for Scrapes, Cuts, Bug Bites, and MoreAre you always prepared for a first aid crisis? See which basic first aid items to pack to treat minor scrapes, cuts, and stings when you're on the go.
Plants and RashesYou may know to look for poison ivy's three-leaf stem, but what else do you know about rash-causing plants? WebMD explores myths and facts of poison plants.
Skin RashThe word "rash" means an outbreak of red bumps on the body. The way people use this term, "a rash" can refer to many different skin conditions. The most common of these are scaly patches of skin and red, itchy bumps or patches all over the place.
StrokeA stroke is an interruption of the blood supply to part of the brain caused by either a blood clot (ischemic) or bleeding (hemorrhagic). Symptoms of a stroke may include weakness, numbness, double vision or vision loss, confusion, vertigo, difficulty speaking, or understanding speech. A physical exam, imaging tests, neurological exam, and blood tests may be used to diagnose a stroke. Treatment may include administration of clot-busting drugs, supportive care, and in some instances, neurosurgery. The risk of stroke can be reduced by controlling high blood pressure, high cholesterol, diabetes, and stopping smoking.
Summer Skin QuizWhen it comes to summer, there plenty of hazards under the sun! Take the Summer Skin Hazards Quiz and clue in on the dangers to your summer skin!
Swollen Lymph Nodes (Lymphadenopathy)Lymph nodes help the body's immune system fight infections. Causes of swollen lymph nodes (glands) may include infection (viral, bacterial, fungal, parasites). Symptoms of swollen lymph nodes vary greatly, but may include fever, night sweats, toothache, sore throat, or weight loss. Causes of swollen lymph nodes also vary, but may include cancer, the common cold, mono, chickenox, HIV, and herpes. The treatment of swollen lymph nodes depends upon the cause.
Diagnose & Spot Zika Virus QuizWhat do you need to know about Zika? Take this quiz to learn the causes, symptoms, treatments and prevention methods for this infectious disease, and why pregnant women and babies should take extra precautions.