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Chagas Disease
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Chagas disease is an infectious disease caused by the parasite Trypanosoma cruzi. It is spread from person to person by the bite of a type of insect called a reduviid bug (also called a kissing bug, assassin bug, or triatomine). These insects are found only in the Americas, and typically people who get the disease live in poverty-stricken areas of rural Latin America.
The disease has both an acute and a chronic phase. The acute phase can last several months while patients have fever, fatigue, body aches and other symptoms. The chronic phase is lifelong, but symptoms may or may not occur, and many chronically infected people don't realize they are infected. In some cases, chronic disease leads to gastrointestinal and heart conditions. Treatment to kill the parasite is available.
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Other Names
- American trypanosomiasis
- T. cruzi infection
Signs and Symptoms
Much of what is known about the symptoms of Chagas disease comes from experience with adults who became infected as children after being bitten by the reduviid bug. The disease might act differently in people infected at other times of life, in other ways, or with different strains of the T. cruzi parasite.
There are two phases of Chagas disease: the acute phase and the chronic phase. Both phases can range from symptom-free to life-threatening.
Acute phase
The acute phase usually lasts from 4 to 8 weeks.[1] It usually occurs unnoticed because it causes few symptoms, or symptoms that could be due to any number of diseases. These may include:
The signs on physical examination can include enlarged liver or spleen, swollen glands, and local swelling (a chagoma) at the spot where the insect bit and the parasite entered the body. The most recognized marker of acute Chagas disease is called Romaña's sign, which is swelling of the eyelids on the side of the face that first became infected. This swelling is caused by the bite itself, bug feces, or accidental transfer of feces into the eye by rubbing. Even if symptoms develop during the acute phase, they usually fade away on their own, within a few weeks or months. The infection persists if untreated, even when the symptoms go away. Rarely, young children in the acute phase of Chagas disease die from severe inflammation/infection of the heart muscle (myocarditis) or brain (meningoencephalitis). The acute phase also can be severe in people with weakened immune systems, such as the elderly or those with HIV.
Chronic phase
Usually, the chronic phase has no symptoms. The infection may remain "silent" for decades or even for life; this is called the "indeterminate form" of the disease, and about three-quarters of infected people stay in this stage and never get worse.[1] However, in about one-quarter of patients with chronic Chagas disease, complications can arise.
- Cardiac complications, including an enlarged heart (cardiomyopathy), heart failure, altered heart rate or rhythm, and cardiac arrest (sudden death)[2]
- Intestinal complications, including an enlarged esophagus (megaesophagus) or colon (megacolon) and can lead to difficulties with eating or with passing stool.
The average life-time risk of developing one or more of these complications is about 30%.
Causes
Chagas disease is caused by the parasite Trypanosoma cruzi, and its most frequent way of spreading is through the bite of the reduviid bug. See How Chagas Disease is Spread.
The parasite is closely related to the ones that cause African sleeping sickness and leishmaniasis.
Diagnosis
In the acute phase, the diagnosis is easily made by a blood test. The trypanosomes (parasites) can be seen in the blood under a microscope, and can be grown in cultures. In the chronic stage, diagnosis is far more difficult. Testing now involves long-term blood culture, and tests that check to see if the body has produced antibodies to T. cruzi. The detection of the more life-threatening complications of Chagas disease, such as complete heart block, are made by electrocardiogram, which may show a right bundle block pattern. This is a blockage in one of the electrical circuits that keep the heart beating. It indicates damage to the heart muscle.
Treatment
Treatment takes two approaches, and both are potentially life-saving. Antiparasitic treatment kills the parasite, and symptomatic treatment treats the symptoms of infection.
Antiparasitic treatment
Antiparasitic treatment is most effective early in the course of infection but is not only given in the acute phase. In the United States, this type of treatment is available through the . Treatment is with one of two drugs, either benznidazole (Radanil) for 60 days or nifurtimox (Lampit) for 90 days. In the US, neither drug is approved, and must be obtained from the Centers for Disease Control (CDC).[1]
These drugs, introduced decades ago, can have significant side effects and are not 100% effective. Side effects include nerve damage causing a tingling sensation, skin sensitivity to the sun, dizziness, nausea, and vomiting, among others. Patients must be monitored while they are being treated to watch for signs of severe side effects.[1]
Symptomatic treatment
Symptomatic treatment helps to relieve the cardiac or intestinal symptoms. For example, pacemakers and medications for irregular heartbeats may be life-saving for some patients with chronic cardiac disease. Amiodarone (Cordarone) is often used to treat abnormal heart rhythms. Surgery may be necessary to treat gastrointestinal complications.
Chances of Developing Chagas Disease
The incidence of Chagas disease varies widely. Most Chagas disease occurs in Central and South America. Outside those endemic areas, the disease is rare. In some regions of Latin America, vector-control programs that kill reduviid bugs have succeeded in stopping the spread of disease. Chagas disease is not endemic in the Caribbean (for example, it is not found in Puerto Rico or Cuba). Rare vector-borne cases of Chagas disease have been reported in the southern United States.
It is estimated that as many as 8 to 10 million people in Mexico, Central America, and South America have Chagas disease, most of whom don't know they are infected.[1] If untreated, infection is lifelong and can be life-threatening. This means that people who migrated from endemic areas have a lifelong risk of developing complications from the disease.
The effects of Chagas disease are not limited to the rural areas in Latin America where the reduviid bug spreads the disease. Large-scale migration 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 focus on preventing transmission from blood transfusion, organ transplantation, and mother-to-baby (congenital transmission).
Prevention
Chagas disease cannot be prevented by drugs or vaccines. Travelers who sleep indoors, in well-constructed facilities (for example, air-conditioned or screened hotel rooms), are at low risk for exposure to infected reduviid bugs. These bugs usually infest poor-quality dwellings and are most active at night. Ways to prevent the disease for both travelers and residents include spraying infested dwellings with residual-action insecticides, using bed nets treated with long-lasting insecticides, wearing protective clothing, and applying insect repellent to exposed skin. In addition, people at risk should be aware that the disease can spread in other ways, such as through uncooked meat or blood transfusions.
How Chagas Disease is Spread
People can become infected with Chagas in several ways. In Chagas-endemic areas, the main way is by getting bitten by a reduviid bug, a method called vector-borne transmission. These blood-sucking bugs become infected themselves by biting an infected animal or person. Once infected, the bugs pass T. cruzi 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. Reduviid bugs are also known as “kissing bugs” because they tend to feed on people’s faces. The bug defecates on the skin after biting and ingesting blood. The person becomes 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 can become infected in several other ways:
- Eating uncooked food contaminated with feces from infected bugs
- Transmission from a pregnant woman to her baby (about 1% to 5% of pregnancies)[1][3]
- Blood transfusion (about 20% of recipients of infected blood will get the disease)[4]
- Organ transplantation[5]
- Accidental laboratory exposure
It is generally considered safe for a baby to breastfeed 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 through casual contact like a cold or the flu.
Research
Continued research into the biology of T. cruzi has yielded potential drug targets.[6] These drugs target enzymes and other proteins that are only produced by the parasite and not by the human host. Drugs that only affect parasites' proteins can minimize the risk of side effects to humans. Many of the most promising drugs contain lead.
For a list of government-sponsored clinical trials that may need patients, visit ClinicalTrials.gov.
History
Chagas disease is named after the Brazilian physician Carlos Chagas, who described it in 1909.[7]
Epidemiology
About 8 to 10 million people in Mexico, Central America, and South America are infected with the T. cruzi parasite. In the United States, about 100,000 people are infected, most of whom acquired the infection outside the US.[1] Donor blood in the US has been screened for Chagas disease since January 2007, after a six-month study of donated blood by the American Red Cross found that about one in every 4,655 units of donated blood contained antibodies to the parasite.[8]
In areas where the disease is common, infections are usually acquired in childhood.[1]
Interesting Facts
- Charles Darwin (1809-1882), one of the developers of the theory of evolution, suffered from a disease that repeatedly left him severely debilitated. Darwin was one of the first to propose the theory of evolution, but the disease made further intellectual thought very difficult. For over 40 years he suffered from symptoms such as vertigo, dizziness, malaise, cramps, vomiting, fatigue, skin blisters, insomnia, depression, and many other conditions. Dr. Saul Adler, an Israeli doctor of tropical medicine, was first to propose that Darwin was suffering from Chagas disease.[9] Indeed, Darwin was bitten by the bug vector on one of his voyages. However, the hypothesis that Darwin had the disease remains controversial.
- Chagas disease is considered a "neglected tropical disease," one for which there has been little research or funding compared with the "big three" infectious diseases AIDS, tuberculosis, and malaria.[10]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Bern C, Montgomery SP, Herwaldt BL. Evaluation and treatment of Chagas disease in the United States: a systematic review. JAMA. 2007 Nov 14;298(18):2171-81. Abstract | Full Text
- ↑ Rassi A Jr, Rassi SG, Rassi A. Sudden death in Chagas' disease. Arq Bras Cardiol. 2001 Jan;76(1):75-96. Abstract | Full Text
- ↑ Torrico F, Alonso-Vega C, Suarez E, et al. Maternal Trypanosoma cruzi infection, pregnancy outcome, morbidity, and mortality of congenitally infected and non-infected newborns in Bolivia. Am J Trop Med Hyg. 2004;70(2):201-209. Abstract | Full Text
- ↑ Schmunis GA, Cruz JR. Safety of the blood supply in Latin America. Clin Microbiol Rev. 2005 Jan;18(1):12-29. Erratum in: Clin Microbiol Rev. 2005 Jul;18(3):582. Abstract | Full Text
- ↑ Barsoum RS. Parasitic infections in organ transplantation. Exp Clin Transplant. 2004 Dec;2(2):258-67. Abstract | Full Text
- ↑ Duschak VG, Couto AS. An insight on targets and patented drugs for chemotherapy of Chagas disease. Recent Patents Anti-Infect Drug Disc. 2007;2:19-51. Abstract
- ↑ Wendel S and Brener Z. Historical aspects. In: Chagas Disease—American Trypanosomiasis: its impact on transfusion and clinical medicine. S. Wendel, Z. Brener, M.E. Camargo, A. Rassi, eds. ISBT 1992, Sao Paolo, Brazil.
- ↑ Centers for Disease Control and Prevention (CDC). Blood donor screening for chagas disease--United States, 2006-2007. MMWR Morb Mortal Wkly Rep. 2007 Feb 23;56(7):141-3. Abstract | Full Text
- ↑ Adler S. Darwin's illness. Br Med J. 1965 May 8;1(5444):1249-50. Abstract | Full Text
- ↑ Balasegaram M, Balasegaram S, Malvy D, Millet P. Neglected diseases in the news: a content analysis of recent international media coverage focussing on leishmaniasis and trypanosomiasis. PLoS Negl Trop Dis. 2008 May 14;2(5):e234. Abstract | Full Text
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