Chagas disease (also known as American trypanosomiasis)
Chagas disease (also known as American trypanosomiasis)
- 1 Chagas disease (also known as American trypanosomiasis)
- 2 Key facts
- 3 Distribution
- 4 Signs and symptoms
- 5 Treatment
- 6 Control and prevention
- 7 WHO response
- 8 Detailed FAQs
- 9 Chagas Disease (American Trypanosomiasis or Kissing Bug Disease)
- 9.1 Chagas disease (kissing bug disease) facts
- 9.2 Chagas Disease in Dogs
- 9.3 What is Chagas disease?
- 9.4 What is the history of Chagas disease?
- 9.5 What causes Chagas disease?
- 9.6 Is Chagas disease contagious?
- 9.7 Latest Infectious Disease News
- 9.8 Daily Health News
- 9.9 Trending on MedicineNet
- 9.10 What are the risk factors for Chagas disease?
- 9.11 What are symptoms and signs of Chagas disease?
- 9.12 How do health care professionals diagnose Chagas disease?
- 9.13 Subscribe to MedicineNet’s General Health Newsletter
- About 6 million to 7 million people worldwide, mostly in Latin America, are estimated to be infected with Trypansosoma cruzi, the parasite that causes Chagas disease.
- The main route of transmission (vector-borne transmission) has occurred in Latin America through the insect called triatomine bug, which can carry the Trypanosoma cruzi.
- Other routes of transmission include: oral (food-borne) transmission, blood/blood products transfusion, mother-to-child (congenital) and organ transplantation transmissions or even laboratory accident transmission.
- Chagas disease was once entirely confined to the Region of the Americas – principally Latin America – but in the last decades, due to population movements, most infected people live in urban settings (urbanization) and the disease has spread to other continents.
- Trypanosoma cruzi infection is curable if treatment is initiated soon after infection.
- In chronic patients, antiparasitic treatment can potentially prevent or curb disease progression and prevent tranmission, for instance, mother-to-child infection.
- Up to 30% of chronically infected people develop cardiac alterations and up to 10% develop digestive, neurological or mixed alterations which may require specific treatment.
- Vector control is the most useful method to prevent Chagas disease in Latin America.
- Blood screening is vital to prevent infection through transfusion and organ transplantation.
- Detection and treatment of girls and women of child-bearing with infection is essential, together with the screening of newborns and siblings of infected mothers without previous antiparasitic treatment.
- Chagas disease is a complex socio-economic, environmental (multidimensional) health problem and its different dimensions linked in a gearing mechanism justify the necessity of multi-sectorial approaches.
Chagas disease, also known as American trypanosomiasis, is a potentially life-threatening illness caused by the protozoan parasite Trypanosoma cruzi (T. cruzi) .
About 6 million to 7 million people worldwide are estimated to be infected with Trypansoma cruzi, the parasite that causes Chagas disease. Chagas disease is found mainly in endemic areas of 21 continental Latin American countries 1 , where it has been mostly transmitted to humans by contact with faeces or urine of triatomine bugs (vector-borne), known as ‘kissing bugs’, among many other popular names, depending on the geographical area.
Chagas disease is named after Carlos Ribeiro Justiniano Chagas, a Brazilian physician and researcher who discovered the disease in 1909. In May 2019, following up on decision of the 72 World Health Assembly, the World Chagas Disease Day was established to be celebrated on 14 April (the date of the year 1909 when Carlos Chagas diagnosed the first human case of the disease, a two-year old girl called Berenice).
Chagas disease was once entirely confined to continental rural areas of the Region of the Americas – principally Latin America (not in the Caribbean islands). Mainly because of the increased population mobility in the last decades, most infected people live in urban settings (urbanization) and the disease has been increasingly detected in the United States of America, Canada, and many European and some African, Eastern Mediterranean and Western Pacific countries.
In Latin America, T. cruzi parasites are mainly transmitted by contact with faeces/urine of infected blood-sucking triatomine bugs. These bugs, vectors that carry the parasites, typically live in the wall or roof cracks of homes and peridomiciliary structures, such as chicken coops, pens and warehouses, in rural or suburban areas. Normally they hide during the day and become active at night when they feed on mammalian blood, including human blood. They usually bite an exposed area of skin such as the face (hence its common name ‘kissing bug’), and the bug defecates or urinates close to the bite. The parasites enter the body when the person instinctively smears the bug faeces or urine into the bite, the eyes, the mouth, or into any skin break.
T. cruzi can also be transmitted by:
- consumption of food contaminated with T. cruzi through, for example, contact with faeces or urine of infected triatomine bugs or marsupials (causing outbreaks of foodborne transmission with more severe morbidity and higher mortality — infecting groups of people simultaneously with more frequent cases of servere disease and higher number of deaths);
- blood or blood product transfusion from infected donors;
- passage from an infected mother to her newborn during pregnancy or childbirth;
- organ transplants using organs from infected donors; and
- laboratory accidents.
Signs and symptoms
Chagas disease presents itself in 2 phases. The initial acute phase lasts for about 2 months after infection. During the acute phase, a high number of parasites circulate in the blood but in most cases, symptoms are absent or mild and unspecific. In less than 50% of people bitten by a triatomine bug, characteristic first visible signs can be a skin lesion or a purplish swelling of the lids of one eye. Additionally, they can present fever, headache, enlarged lymph glands, pallor, muscle pain, difficulty in breathing, swelling, and abdominal or chest pain.
During the chronic phase, the parasites are hidden mainly in the heart and digestive muscles. Up to 30% of patients suffer from cardiac disorders and up to 10% suffer from digestive (typically enlargement of the oesophagus or colon), neurological or mixed alterations. In later years the infection can lead to sudden death due to cardiac arrhythmias or progressive heart failure caused by the destruction of the heart muscle and its nervous system.
To kill the parasite, Chagas disease can be treated with benznidazole and also nifurtimox. Both medicines are nearly 100% effective in curing the disease if given soon after infection at the onset of the acute phase including the cases of congenital transmission. The efficacy of both diminishes, however, the longer a person has been infected and the adverse reactions are more frequent at older age.
Treatment is also indicated for those in whom the infection has been reactivated (for example, due to immunosuppression), and for patients during the early chronic phase. Infected adults, especially those with no symptoms, should be offered treatment because antiparasitic treatment can also prevent or curb disease progression and prevent congenital transmission in pregnant women. In other cases the potential benefits of medication in preventing or delaying the development of Chagas disease should be weighed against the duration of treatment (up to 2 months) and possible adverse reactions (occurring in up to 40% of treated adult patients).
Benznidazole and nifurtimox should not be taken by pregnant women or by people with kidney or liver failure. Nifurtimox is also contraindicated for people with a background of neurological or psychiatric disorders. Additionally, specific treatment for cardiac, or digestive or neurological manifestations may be required.
Control and prevention
Originally (more than 9000 years ago), T. cruzi only affected wild animals. It later spread to domestic animals and people. The large reservoir of T. cruzi parasites in wild animals of the Americas means that the parasite cannot be eradicated. Instead, the control targets are elimination of the transmission and early health-care access of the infected and ill population.
There is no vaccine for Chagas disease. T. cruzi can infect several species of the triatomine bugs, the vast majority of which are found in the Americas. Vector control has been the most effective method of prevention in Latin America. Blood screening is necessary to prevent infection through transfusion and organ transplantation and to increase detection and care of the affected population.
Depending on the geographical area, WHO recommends the following approaches to prevention and control:
- spraying of houses and surrounding areas with residual insecticides;
- house improvements and house cleanliness to prevent vector infestation;
- personal preventive measures such as bednets;
- good hygiene practices in food preparation, transportation, storage and consumption;
- screening of blood donors;
- testing of organ, tissue or cell donors and receivers;
- access to diagnosis and treatment of people with medical indication or recommendation to do antiparasitic treatment, especially children and women of child-bearing age before pregnancy; and
- screening of newborns and other children of infected mothers without previous antiparasitic treatment to do early diagnosis and provide treatment.
The medical care cost of patients with chronic cardiac, digestive, neurologic or mixed forms of the disease has been calculated to be >80% higher than the cost of spraying residual insecticide to control vectors and prevent infection.
Since the 1990s there have been important successes in parasite and vector control in Latin America, in the territories of the Southern Cone, Central America, Andean Pact and Amazonian Intergovernmental Initiatives, with the Pan American Health Organization Secretariat. These multinational initiatives led to substantial reductions in transmission and increased access to diagnosis and antiparasitic treatment.
In addition, the risk of transmission by blood transfusion has been extremely reduced through the universal screening in all blood banks of the Latin American countries and most European and Western Pacific countries with disease cases. These advances have been possible because of the strong commitment of Member States affected by the disease and the strength of their research and control organizations, together with support from many international partners.
In 2005 the World Health Organization recognized Chagas disease one neglected tropical disease. This facilitated a greater recognition of the disease on the international scene and facilitated to combat misinformation, lack of social demand and weak political commitment to solve the problems related with Chagas, as well as insufficient scientific research and development related with prevention, detection and comprehensive care, including diagnosis, treatment, medicine presentations, social aspects, information, education and communication tools.
At the same time, a series of additional challenges have to be faced. These include:
- maintaining and consolidating advances made in disease control and prevention;
- emergence of Chagas disease in regions previously considered to be free of the disease – such as the Amazon basin;
- persistence in regions where control had been in progress, such as the Chaco region of Argentina and the Plurinational State of Bolivia;
- spread of the disease mainly due to increasing population mobility between Latin America and the rest of the world;
- prevention of the consequences of the ignorance, stigma and/or discrimination associated with the disease; and
- enhanced access to diagnosis and treatment for millions of infected people.
To attain the goal of elimination of Chagas disease transmission and provide health care for infected or people suffering from the disease, both in endemic and non-endemic territories, WHO aims to increase networking at the global level and reinforce regional and national capacities, focusing on:
- strengthening world epidemiological surveillance and information systems;
- raising awareness about Chagas disease and affected populations;
- preventing transmission by blood transfusion and organ transplantation;
- promoting the identification of most adequate diagnostic tests and algorithms/protocols to increase screening and diagnosis of infections;
- expanding primary prevention of congenital transmission and case management of congenital and non-congenital infections; and
- promoting consensus on adequate updated case management; and,
- promoting the development of multidimensional approaches.
1 Argentina, Belize, Bolivia (Plurinational State of), Brazil, Chile, Colombia, Costa Rica, Ecuador, El Salvador, French Guiana, Guatemala, Guyana, Honduras, Mexico, Nicaragua, Panama, Paraguay, Peru, Suriname, Uruguay, and Venezuela (Bolivarian Republic of).
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What is Chagas disease?
Chagas disease is caused by the parasite Trypanosoma cruzi, which is transmitted to animals and people by insect vectors that are found only in the Americas (mainly, in rural areas of Latin America where poverty is widespread). Chagas disease (T. cruzi infection) is also referred to as American trypanosomiasis.
It is estimated that as many as 8 million people in Mexico, Central America, and South America have Chagas disease, most of whom do not know they are infected. If untreated, infection is lifelong and can be life threatening.
The impact of Chagas disease is not limited to only rural areas of Latin America in which vectorborne transmission (diseases transmitted by insects) occurs. Large-scale population movements from rural to urban areas of Latin America and to other regions of the world have increased the geographic distribution and changed the epidemiology of Chagas disease. In the United States and in other regions where Chagas disease is now found but is not endemic, control strategies should focus on preventing transmission from blood transfusion, organ transplantation, and mother-to-baby (congenital transmission).
How do people get Chagas disease?
People can become infected in several ways. In areas where Chagas disease is common, the main way is through vectorborne transmission. The insect vectors are called triatomine bugs. These blood-sucking bugs get infected with T. cruzi by biting an infected animal or person. Once infected, the bugs pass the parasites in their feces. The bugs are found in houses made from materials such as mud, adobe, straw, and palm thatch. During the day, the bugs hide in crevices in the walls and roofs. During the night, when the inhabitants are sleeping, the bugs emerge. Because they tend to bite people’s faces, triatomine bugs are also known as “kissing bugs”. After they bite and ingest blood, they defecate (poop) on the person. The person can become infected if T. cruzi parasites in the bug feces enter the body through mucous membranes or breaks in the skin. The unsuspecting, sleeping person may accidentally scratch or rub the feces into the bite wound, eyes, or mouth.
People also can become infected through
- Congenital transmission (from a pregnant woman to her baby);
- Blood transfusions;
- Organ transplantation;
- Consumption of uncooked food that is contaminated with feces (poop) from infected triatomine bugs; and
- Accidental laboratory exposure.
It is generally considered safe to breastfeed even if the mother has Chagas disease. However, if the mother has cracked nipples or blood in the breast milk, she should pump and discard the milk until the nipples heal and the bleeding resolves.
Chagas disease is not transmitted from person-to-person like a cold or the flu or through casual contact with infected people or animals.
If I have Chagas disease, should my family members be tested for the infection?
Possibly. They should be tested if they:
- Could have become infected the same way that you did, for example, by vectorborne transmission;
- Are your children and were born after you were infected; or if
- There are other reasons to think that they might have Chagas disease.
In what parts of the world is Chagas disease found?
People who have Chagas disease can be found anywhere in the world. However, transmission of the disease by kissing bugs (vectorborne transmission), only occurs in the Americas. Most people with Chagas disease became infected in rural areas of Mexico, Central America, and South America. In some regions of Latin America, efforts to eliminate kissing bugs, called vector control programs, have succeeded in stopping this type of disease spread. Vectorborne transmission does not occur in the Caribbean (for example, in Puerto Rico or Cuba). Rare vectorborne cases of Chagas disease have been noted in the southern United States.
What are the signs and symptoms of Chagas disease?
Much of the clinical information about Chagas disease comes from experience with people who became infected as children through contact with triatomines. The severity and course of an individual infection can vary based on a number of factors, including the age at which a person became infected, the way in which a person acquired the infection, or the particular strain of the T. cruzi parasite.
There are two phases of Chagas disease: the acute phase and the chronic phase. Both phases can be symptom free or life threatening.
Romaña’s sign, the swelling of the child’s eyelid, is a marker of acute Chagas disease. Swelling is due to Trypanosoma cruzi infecting the eyelid when bug feces are accidentally rubbed into the eye, or because the bite wound was on the same side of the child’s face as the swelling. Credit: WHO/TDR
Acute phase: During this phase, which lasts for the first few weeks or months infection, a person may have no symptoms or mild ones, such as fever, fatigue, body aches, headache, rash, loss of appetite, diarrhea, and vomiting. Because these symptoms are similar to those of other illnesses, most people do not know their illness is from infection with the T. cruzi parasite.
However, a doctor may be able to pick up other signs of infection, including mild enlargement of the liver or spleen, swollen glands, or swelling at the site of the bite (called a chagoma), where the parasite entered the body. Some people with acute phase infection may have swelling of the eyelids on the side of the face near the bite wound or where the bug poop was accidentally rubbed into the eye, called Romaña’s sign. Even if a person develops symptoms during the acute phase, they usually feel well within a few weeks or months but if the person is not treated with antiparasitic medication, the infection remains in the body. Rarely, young children (less than 5%) die from severe inflammation and infection of the heart muscle (myocarditis) or brain (meningoencephalitis). The acute phase also can be severe in people with weakened immune systems, such as patients taking chemotherapy or those with advanced HIV infection.
Chronic phase: During this phase, which can last for decades or even for the entirety of someone’s lifetime, most people have no symptoms. Approximately 20–30 percent of infected people develop
- Cardiac complications, which can include an enlarged heart, heart failure, altered heart rate or rhythm, and cardiac arrest (sudden death); and/or
- Gastrointestinal complications, which can include an enlarged esophagus (megaesophagus) or colon (megacolon) and can lead to difficulties with eating or pooping.
What should I do if I think I have Chagas disease?
You should discuss your concerns with your health-care provider, who will examine you and ask you questions (for example, about your health and where you have lived). Chagas disease is diagnosed by blood tests. If you are found to have Chagas disease, you should have a heart tracing test (electrocardiogram), even if you feel fine. You might be referred to a specialist for more tests and for treatment.
How is Chagas disease treated?
Two approaches to therapy, that can be life-saving include:
- Antiparasitic treatment, to kill the parasite; and
- Symptomatic treatment, to manage the symptoms and signs of infection.
Antiparasitic treatment is most effective early in the course of infection but is not limited to cases in the acute phase. In the United States, there are two types of treatments available. Benznidazole is approved by FDA for use in children 2–12 years of age and is commercially available at http://www.benznidazoletablets.com/en/ External external icon . Nifurtimox is not currently FDA approved and is available under an investigational protocol from CDC. Your health-care provider can talk with CDC staff about whether and how you should be treated. Most people do not need to be hospitalized during treatment.
Symptomatic treatment may help people who have cardiac or gastrointestinal problems from Chagas disease. For example, pacemakers and medications for irregular heartbeats may be life saving for some patients with chronic cardiac disease.
I plan to travel to a rural area of Latin America that might have Chagas disease. How can I protect myself from this infection?
No drugs or vaccines for preventing infection are currently available. Travelers who sleep indoors, in well-constructed facilities (for example, air-conditioned or screened hotel rooms), are at low risk for exposure to infected triatomine bugs that usually live in poor-quality dwellings and are most active at night. Preventive measures include spraying infested dwellings with long-lasting insecticides, using bed nets treated with long-lasting insecticides, wearing protective clothing, and applying insect repellent to exposed skin. Travelers should observe food and beverage precautions and avoid consuming salads, uncooked vegetables, unpeeled fruits, and unpasteurized fruit juices.
This information is not meant to be used for self-diagnosis or as a substitute for consultation with a health care provider. If you have any questions about the parasites described above or think that you may have a parasitic infection, consult a health care provider.
Chagas Disease (American Trypanosomiasis or Kissing Bug Disease)
Chagas disease (kissing bug disease) facts
Chagas Disease in Dogs
Can It Spread to Humans?
There are reports that dogs, especially in the southern U.S. and in particular, Texas, may be infected with these parasites and some reports imply there is a danger for humans to become infected because the vectors now reside in the southern U.S. However, the percentage of dogs found to be infected with the parasites is relatively low (about 8.8%) and it is often associated with dogs that are feral, strays, or abandoned. In Mexico, the infection rate of dogs is higher (about 17%-21%). However, all dogs are at some risk to become infected if they are bitten by the vector.
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 is the history of Chagas disease?
Chagas disease was named after Dr. Carlos Chagas, who first described the parasite Trypanosoma cruzi in infected humans in 1909 while working for the Oswaldo Cruz Institute in Brazil. Chagas discovered that the parasites are transmitted to humans by entering breaks in the skin after they are deposited on the skin in insect feces. Chagas was the first scientist to discover all aspects of a new infectious disease: its pathogen (T. cruzi), main insect vector (Triatominae, Triatoma genus, or kissing bugs), hosts (humans, mammals), clinical manifestations, and epidemiology. The parasite species was named cruzi to honor his employer and scientific mentor, Oswaldo Cruz.
Chagas disease is also known as American trypanosomiasis because it mainly occurs in the Americas where the triatomine insects (kissing bugs) usually are found. These bugs and the mammals they infect range from states along the U.S. border with Mexico through Central America to the South American countries (for example, Argentina, Bolivia), where the disease is endemic. Almost all cases diagnosed in the U.S. are in immigrants from other countries in the Americas.
The vector-borne disease is fairly common in Central and South America, with an estimated 7.7-15 million infected people worldwide. Children have more acute-phase symptoms than adults. Fortunately, vector-control programs are working as prevalence rates are dropping in Brazil and other countries that have implemented these programs. However, because of warming climate trends, some researchers predict that Chagas disease will become more prevalent in the U.S. This is predicted because the vectors that carry the parasites are being found more often in non-endemic areas like the U.S., especially in the southern and middle states. The bugs that transmit the parasite have been detected in 28 states in the U.S. and are likely to spread to others.
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.
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.
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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).
What are symptoms and signs 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.
How do health care professionals diagnose Chagas disease?
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.
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