Chagas disease is named after the Brazilian physician Carlos Chagas, who discovered the disease in 1909. It is caused by the parasite Trypanosoma cruzi, which is transmitted to animals and people by insect vectors and is 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).
What are the symptoms?
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.
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.
How do you contract Chargas
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.
How does the disease develop
Chagas disease has an acute and a chronic phase. If untreated, infection is lifelong.
Acute Chagas disease occurs immediately after infection, and can last up to a few weeks or months. During the acute phase, parasites may be found in the circulating blood. This phase of infection is usually mild or asymptomatic. There may be fever or swelling around the site of inoculation (where the parasite entered into the skin or mucous membrane). Rarely, acute infection may result in severe inflammation of the heart muscle or the brain and lining around the brain.
Following the acute phase, most infected people enter into a prolonged asymptomatic form of disease (called “chronic indeterminate”) during which few or no parasites are found in the blood. During this time, most people are unaware of their infection. Many people may remain asymptomatic for life and never develop Chagas-related symptoms. However, an estimated 20–30% of infected people will develop severe and sometimes life-threatening medical problems over the course of their lives.
Complications of chronic Chagas disease may include
- Heart rhythm abnormalities that can cause sudden death;
- A dilated heart that doesn’t pump blood well; and
- A dilated esophagus or colon, leading to difficulties with eating or passing stool.
In people who have suppressed immune systems (for example, due to AIDS or chemotherapy), Chagas disease can reactivate with parasites found in the circulating blood. Reactivation can potentially cause severe disease.
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/.
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.
Protecting yourself against Chagas
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.
Where are triatomine bugs typically found?
Triatomine bugs (also called “kissing bugs”, cone-nosed bugs, and blood suckers) can live indoors, in cracks and holes of substandard housing, or in a variety of outdoor settings including the following:
- Beneath porches
- Between rocky structures
- Under cement
- In rock, wood, brush piles, or beneath bark
- In rodent nests or animal burrows
- In outdoor dog houses or kennels
- In chicken coops or houses
They are typically found in the southern United States, Mexico, Central America, and South America (as far south as southern Argentina). The map below details triatomine occurrence by U.S. state.
Eleven different species of triatomine bugs have been found in the southern United States: The links below will take you to the CDC website
- Paratriatoma hirsuta
- Triatoma gerstaeckeri
- Triatoma incrassata
- Triatoma indictiva
- Triatoma lecticularia
- Triatoma neotomae
- Triatoma protracta
- Triatoma recurva
- Triatoma rubida
- Triatoma rubrofasciata
- Triatoma sanguisuga
Triatomines are mostly active at night and feed on the blood of mammals (including humans), birds, and reptiles. Triatomine bugs live in a wide range of environmental settings, generally within close proximity to an animal the bug can feed on, called a blood host. In areas of Latin America where human Chagas disease is an important public health problem, the bugs nest in cracks and holes of substandard housing.
Because most indoor structures in the United States are built with plastered walls and sealed entryways to prevent insect invasion, triatomine bugs rarely infest indoor areas of houses. Discovery of the earlier stages of the bug (wingless, smaller nymphs) inside can be a sign of a triatomine infestation. When the bugs are found inside, they are likely to be in one of the following settings:
- Near the places your pets sleep
- In areas of rodent infestation
- In and around beds and bedrooms, especially under or near mattresses or night stands
