Chagas Disease

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