Chagas' Disease

Definition

Chagas' disease is named after Dr. Carlos Chagas who first found the organism in the early 1900s. It involves damage to the nerves that control the heart, digestive and other organs, and eventually leads to damage to these organs. Worldwide, Chagas' disease affects over 15 million persons, and kills 50,000 each year. Researchers believe that the parasite that causes the disease is only found in the Americas.

Description

When a person is infected with Chagas' disease, the parasite known as Trypanosoma cruzi first causes a mild, short-lived period of "acute" illness; then after a long period without symptoms, the effects of the infection begin to appear. The heart, esophagus, and colon are most frequently involved. These organs become unable to contract properly, and begin to stretch or dilate.

Causes and symptoms

T. cruzi is carried by insects or bugs known as reduviid or "kissing bugs." These insects are very common in Central and South America where they inhabit poorly constructed houses and huts. The insects deposit their waste material, exposing inhabitants to the parasites. The parasites then enter the body by way of a cut or via the eyes or mouth. T. cruzi can also be transmitted by blood transfusion. Eating uncooked, contaminated food or breastfeeding can also transmit the disease. The reduviids, in turn, become infected with the parasite by biting infected animals and humans.

There are three phases related to infection:

• Acute phase lasts about two months, with non-specific symptoms of low grade fever, headache, fatigue, and enlarged liver or spleen.
• Indeterminate phase lasts 10-20 years, during which time no symptoms occur, but the parasites are reproducing in various organs.
• Chronic phase is the stage when symptoms related to damage of major organs (heart, esophagus, colon) begin.

In the chronic phase, irregularities of heart rhythm, heart failure, and blood clots cause weakness, fainting, and even sudden death.

Esophageal symptoms are related to difficulty with swallowing and chest pain. Because the esophagus does not empty properly, food regurgitates into the lungs causing cough, bronchitis, and repeated bouts of pneumonia. Inability to eat, weight loss, and malnutrition become a significant factor in affecting survival.

Involvement of the large intestine (colon) causes constipation, distention, and abdominal pain.

Diagnosis

The best way to diagnose acute infection is to identify the parasites in tissue or blood. Occasionally it is possible to culture the organism from infected tissue, but this process usually requires too much time to be of value. In the chronic phase, antibody levels can be measured. Efforts to develop new, more accurate tests are ongoing.

Treatment

In most cases treatment of symptoms is all that is possible. Present medications can reduce the duration and severity of an acute infection, but are only 50% effective, at best, in eliminating the organisms.

Cardiac effects are managed with pacemakers and medications. Esophageal complications require either endoscopic or surgical methods to improve esophageal emptying, similar to those used to treat the disorder known as achalasia. Constipation is treated by increasing fiber and bulk laxatives, or removal of diseased portions of the colon.

Prognosis

Those patients with gastrointestinal complications often respond to some form of treatment. Cardiac problems are more difficult to treat, particularly since transplant would rekindle infection.

Prevention

Visitors traveling to areas of known infection should avoid staying in mud, adobe, or similar huts. Mosquito nets and insect repellents are useful in helping to avoid contact with the bugs. Blood screening is not always effective in many regions where infection is common. It is necessary to carefully screen people who have emigrated from Central and South America before they make blood donations.

KEY TERMS

Achalasia— An esophageal disease of unknown cause, in which the lower sphincter or muscle is unable to relax normally, and leads to the accumulation of material within the esophagus.

Endoscopy— Exam using an endoscope (a thin flexible tube which uses a lens or miniature camera to view various areas of the gastrointestinal tract). When the procedure is performed to examine certain organs such as the bile ducts or pancreas, the organs are not viewed directly, but rather indirectly through the injection of x ray.

Parasite— An organism that lives on or in another and takes nourishment (food and fluids) from that organism.

Regurgitation— Flow of material back up the esophagus and into the throat or lungs.

Resources

OTHER

Centers for Disease Control. 〈http://www.cdc.gov/nccdphp/ddt/ddthome.htm〉.

Chagas disease

Chagas disease is a human infection that is caused by a microorganism that establishes a parasitic relationship with a human host as part of its life cycle. The disease is named for the Brazilian physician Carlos Chagas, who described in 1909 the involvement of the flagellated protozoan known as Trypanosoma cruzi in a prevalent disease in South America.

The disease is confined to North, South, and Central America. Reflecting this, and the similarity of the disease to trypanosomiasis, a disease that occurs on the African continent, Chagas disease has also been dubbed American trypanosomiasis. The disease affects some 16 to 18 million each year, mainly in Central and South American. Indeed, in these regions the prevalence of Chagas disease in the population is higher than that of the Human Immunodeficiency Virus and the Hepatitis B and C viruses . Of those who acquire Chagas disease, approximately 50,000 people die each year.

The agent of Chagas disease, Trypanosoma cruzi, is a member of a division, or phylum, called Sarcomastigophora. The protozoan is spread to human via a bug known as Reduviid bugs (or "kissing bugs"). These bugs are also known as triatomines. Examples of species include Triatoma infestans, Triatoma brasiliensis, Triatoma dimidiata, and Triatoma sordida.

The disease is spread because of the close proximity of the triatomine bugs and humans. The bugs inhabit houses, particularly more substandard houses where cracks and deteriorating framework allows access to interior timbers. Biting an already infected person or animal infects the bugs themselves. The protozoan lives in the digestive tract of the bug. The infected bug subsequently infects another person by defecating on them, often while the person is asleep and unaware of the bug's presence. The trypanosomes in the feces gain entry to the bloodstream when feces are accidentally rubbed into the bite, or other orifices such as the mouth or eyes.

Chagas disease can also be transmitted in the blood. Acquisition of the disease via a blood transfusion occurs in thousands of people each year.

The association between the Reduviid bug and poor quality housing tends to make Chagas disease prevalent in underdeveloped regions of Central and South America. To add to the burden of these people, some 30% of those who are infected in childhood develop a chronic form of the disease 10 to 20 years later. This long-lasting form of Chagas disease reduces the life span by almost a decade.

Chagas disease may be asymptomatic (without symptoms)—or can produce a variety of symptoms. The form of the disease that strikes soon after infection with Trypanosoma cruzi tends to persist only for a few months before disappearing. Usually, no treatment is necessary for relief from the infection. Symptoms of this type of so-called acute infection include swelling at the site of the bug bite, tiredness, fever, enlarged spleen or liver, diarrhea, and vomiting. Infants can experience a swelling of the brain that can be fatal.

The chronic form of Chagas disease can produce more severe symptoms, including an enlarged heart, irregularities in heart function, and the enlargement and malfunction of the digestive tract. These symptoms are of particular concern in those people whose immune system is not functioning properly.

Currently, there is no vaccine or other preventative treatment for Chagas disease. Avoidance of habitats where the Reduviid bug lives is the most prudent precaution. Unfortunately, given the economic circumstances of those most at risk, this option is not easily attainable. Trypanosoma cruzi can also be transmitted in the blood. Therefore, screening of blood and blood products for the presence of the protozoan is wise. Once again, however, the poverty that often plays a role in the spread of Chagas disease may also be reflected in less than adequate medical practices, including blood screening.

See also Parasites; Zoonoses

Chagas's disease A disease that can affect humans and other animals. It occurs chiefly in Central and S. America. The causal agent is a protozoon, Trypanosoma cruzi. The pathogen is transmitted by blood-sucking bugs. Symptoms may include anaemia and various signs of heart, gland, and nervous-system involvement. The disease is named after the Brazilian physician Carlos Chagas. Charles Darwin may have been infected with this disease in S. America, and some have suggested that his continual ill-health in later years was due to it.

Chagas's disease A disease that can affect humans and other animals. It occurs chiefly in Central and South America. The causal agent is a protozoon, Trypanosoma cruzi. The pathogen is transmitted by blood-sucking bugs. Symptoms may include anaemia and various signs of heart, gland, and nervous-system involvement. The disease is named after the Brazilian physician Carlos Chagas (1879–1934).