Brief overview
- Symptoms: Acute phase with fever, swelling at the site of entry (chagoma), or eyelid edema at the eye, in chronic phase complaints of heart failure, respiratory distress and gastrointestinal symptoms.
- Causes and risk factors:parasite (Trypanosoma cruzi), transmission mostly by predatory bugs, also from mother to unborn child, through blood donation or organ transplantation, poverty-associated disease
- Diagnosis: Detection of the pathogen and antibodies directed against it in the blood
- Treatment: antiparasitic agents, possibly heart transplantation if heart is damaged
- Prognosis and course: Very good if treated early; if chronic, damage to heart, digestive tract and nervous system; life-threatening complications are possible
- Prevention: Avoid insect bites in risk areas, use mosquito nets.
What is Chagas disease?
Chagas disease (American trypanosomiasis) is an infectious disease. It is caused by a single-celled parasite (Trypanosoma cruzi). The pathogen is transmitted mainly through the bites of predatory bugs. Predatory bugs live mainly in dry wood cracks and thatched roofs of simple dwellings (for example, mud huts).
The predatory bugs excrete the trypanosomes with their feces, which they deposit while sucking blood. If this gets into skin wounds, on mucous membranes, for example in the conjunctiva of the eyes, infection occurs. The time between the predatory bug bite and the outbreak of the disease (incubation period) is between five and 20 days.
It is also possible for an infected pregnant woman to transmit the pathogen to her unborn child. Less frequently, infected blood transfusions or organ transplants from infected donors are also possible routes of infection. In these cases, the incubation period is sometimes 30 to 40 days.
Chagas disease progresses in different stages. The end result is often a chronic disease, the consequences of which can be fatal.
Worldwide, about eight million people are infected with the pathogen that causes Chagas disease. The majority of these are inhabitants of endemic areas. Most of those infected hardly experience any symptoms and are therefore unaware of their infection. Nevertheless, they pass on the pathogen. An estimated 10,000 people worldwide die each year as a result of Chagas disease.
What are the symptoms of Chagas disease?
Acute phase of Chagas disease:
One third of all infected persons show acute symptoms of Chagas disease. Initially, the site where the pathogen has entered the body (for example, the bite site of the predatory bug) swells and reddens. Often a so-called chagoma forms, a swelling at the site of entry. The surrounding lymph nodes are also thickened. If the pathogens have entered the eye, a swelling of the eyelid develops, which physicians call Romaña’s sign.
Within a few days, the following symptoms appear:
- Fever
- Shortness of breath
- Abdominal pain
- Diarrhea
- Swelling of lymph nodes
- Enlargement of the liver and spleen
Newborns and infants, who are particularly commonly affected by acute Chagas disease, also often experience complications that may be fatal:
- inflammation of the heart muscle (myocarditis)
- encephalitis (inflammation of the brain)
Symptoms of acute Chagas disease persist for about four weeks. This is followed by the so-called indeterminate (that is, indefinite) phase of the disease. The majority of infected individuals then have no symptoms of Chagas disease.
Latent phase:
Chronic phase of Chagas disease:
In about 30 percent of those infected, Chagas disease is chronic. In most cases, inflammation of the heart muscle (myocarditis) and chronic heart failure (cardiac insufficiency) occur, possibly leading to sudden cardiac death.
In addition, the following symptoms are possible:
- Chest tightness and pain in the heart region (angina pectoris)
- Cardiac arrhythmias
- Partial or complete occlusion of an artery by blood clots (arterial embolism)
- Palpitations, palpitations
- Dilatation of the heart (megacor)
- Shortness of breath
- Pulmonary edema
In rare cases, symptoms of chronic Chagas disease occur in the digestive tract. Often it is then a pathological enlargement of the intestine (megacolon) and the esophagus (megaesophagus).
In the early stages, there is an increase in these symptoms:
- Diarrhea
- Severe abdominal pain
- Later chronic constipation
- Nausea
- Vomiting
- Chills
- Palpitations
If left untreated, megacolon is at risk of causing a life-threatening rupture of the intestine (perforation). Involvement of the lungs and nervous system is also possible, but very rare.
What are the causes and risk factors of Chagas disease?
When sucking blood, predatory bugs secrete infectious feces. If the feces come into contact with the conjunctiva of the eyes, mucous membranes or skin lesions, the pathogen enters the body. Because predatory bug bites are very itchy, sufferers often scratch themselves. Resulting small skin wounds make it easier for the pathogen to enter the body.
In rare cases, transmission of the Chagas disease pathogen occurs through blood transfusions or organ transplants. It also happens that infected pregnant women transmit the infection to their unborn babies.
How can Chagas disease be diagnosed?
The diagnosis of Chagas disease is composed of three parts:
First, a medical history is taken, with a description of symptoms and reference to South or Central American areas as the country of travel or origin providing initial clues to Chagas disease. The physician then determines further symptoms through a physical examination.
A definitive diagnosis is only possible with the aid of a blood test. An attempt is made to detect the pathogen microscopically in the blood. This is not always successful. For this reason, the blood is also tested for antibodies that are specifically directed against trypanosomes.
If Chagas disease is already in the chronic phase, effects on other organs such as the brain and heart can be detected by various examinations (for example, computed tomography (CT), magnetic resonance imaging (MRI)). To examine the heart, procedures such as cardiac ultrasound (echocardiography) and electrocardiography (ECG) are used.
How can Chagas disease be treated?
Two drugs are used to treat Chagas disease: benznidazole and nifurtimox. These drugs are so-called antiprotozoal agents. These are active ingredients that specifically combat and kill single-celled parasites. Affected people receive nifurtimox for about 120 days, and benznidazole for about half that time.
Neither drug should be taken by pregnant women or people with kidney or liver failure.
The two agents are successful only in the acute phase. In the latent phase, the effect of the therapy is controversial. In the chronic phase, no benefit from antiprotozoal agents has been demonstrated to date. Here, measures are directed at treating the symptoms that appear in the heart or in the digestive tract.
Chagas disease: disease course and prognosis
The prognosis for Chagas disease depends primarily on whether complications occur and how severely the heart is affected (for example, in the form of heart failure).
If, on the other hand, inflammation of the heart muscle or brain occurs during the acute phase of Chagas disease, this often ends fatally, especially in young children. In a chronic course, the course of the disease depends on the extent of the heart failure and the success of its treatment.
If the heart is irrevocably damaged, a heart transplant is often the last resort. Without therapy, affected individuals usually die of sudden cardiac death (due to heart failure). Other causes of fatal outcome of Chagas disease include pulmonary infarction, peritonitis and intestinal perforation.
How can Chagas disease be prevented?
If you plan to travel to areas at risk for Chagas disease, there are some measures you can take to prevent the disease.
Protect yourself from insect bites. Insect repellents provide good protection against predatory bugs and therefore against Chagas disease. They are available as sprays or lotions over the counter at any pharmacy. If you are outdoors, dense clothing impregnated with insect repellent will protect you.
There is no vaccination against Chagas disease.