Chagas disease
Later complications including
heart failure

Chagas disease, also known as American trypanosomiasis, is a tropical parasitic disease caused by the bite of kissing bugs. Most people who carry the disease are poor and unaware of the infection.

It is estimated that 6.2 million people, mostly in Mexico, Central America and South America, have Chagas disease, causing 7 900 deaths per year. 22.5% of new infections occurred through congenital transmission. Large-scale population migrations have carried Chagas disease to new regions, which now include the United States and many European countries.

What causes Chagas disease

Chagas disease, also known as American Trypanosomiasis, is a tropical parasitic disease. Chagas disease is caused by an infection of Trypanosoma Cruzi from a triatomine insect, or “kissing bug,” bite. T. cruzi can be transmitted by various triatomine bugs in the genera Triatoma, Panstrongylus, and Rhodnius.

This disease was described by Carlos Chagas in 1909, who was able to identify the parasite in the blood of humans and other animals bitten by triatomines. T. cruzi is a parasitic protozoan that typically resides in the tissues and blood of the host.

T. cruzi likely circulated in South American mammals long before the arrival of humans on the continent. It has been detected in ancient human remains across South America, from a 9 000-year-old Chinchorro mummy in the Atacama Desert (current day Chile and Peru).

Photo: Panstrogylus geniculatus a species of kissing bug.

Where is Chagas disease found

T. cruzi is found throughout North America and Latin America.

In the United States, triatomines carrying T. cruzi are primarily found in southern areas of the country as well as California. In addition, triatomines are common across all of Latin America, including Argentina, Chile, and Mexico.

While triatomines carrying T. cruzi have been found in countries in Asia and Africa, Chagas is not endemic in those countries.

Image: Chagas disease endemic countries (dark blue) and spread (light blue).

What are the symptoms of Chagas disease

Chagas disease occurs in two stages: an acute stage, which develops one to two weeks after the insect bite, and a chronic stage, which develops over many years. The acute stage is often symptom-free.

In the acute phase, when present, the symptoms are typically minor and not specific to any particular disease. They can include include fevers, headaches, a decrease in appetite, joint pain, nausea, vomiting, and diarrheal issues. Rarely, there may also be lesions present at the area of parasite entry. Some people develop a swollen nodule at the site of infection, which is called “Romaña’s sign” if it is on the eyelid, or a “chagoma” if it is elsewhere on the skin. More significant complications of the acute phase include myocarditis and disruptions in cardiac rhythm. In rare cases (less than 1 to 5%), infected individuals develop severe acute disease, which can cause life-threatening fluid accumulation around the heart, or inflammation of the heart or brain and surrounding tissues.

Unless treated with antiparasitic drugs, individuals remain chronically infected with T. cruzi after recovering from the acute phase.

Photo: An acute Chagas disease infection with swelling of the right eye (Romaña's sign)

Symptoms of the chronic phase of  Chagas disease are due to a variety of organ defects that happen over decades, such as the inflammation and dilation of heart chambers. 14–45% of people develop Chagas heart and experience heart palpitations and sometimes fainting due to irregular heart function. In many cases the first sign of Chagas heart disease is heart failure, thromboembolism, or chest pain associated with abnormalities in the microvasculature. Also common (10–21% of people) is damage to the digestive system, such as well as swelling of the lining of the esophagus and the colon. Those with enlarged esophagus often experience pain (odynophagia) or trouble swallowing (dysphagia), acid reflux, cough, and weight loss. Individuals with enlarged colon often experience constipation, which can lead to severe blockage of the intestine or its blood supply. Individuals with Chagas disease also could develop gallbladder abnormalities as well as gastric ulcers. Up to 10% of chronically infected individuals develop nerve damage that can result in numbness and altered reflexes or movement.

How can Chagas disease be prevented

Efforts to prevent Chagas disease have largely focused on vector control to limit exposure to triatomine bugs.

Insecticide-spraying programs have been the mainstay of vector control, consisting of spraying homes and the surrounding areas with insecticides. Houses can be plastered to eliminate cracks where triatomines could hide. Furthermore, since these insects are more likely to bite at night, sleeping under a bed net impregnated with insecticide would reduce the chances of being bit. Frequent use of insect repellents and wearing thick clothing and long pants can also prevent Chagas disease.

Blood transfusion was formerly the second-most common mode of transmission for Chagas disease. Effective screening has significantly reduced the risk of transmissions through blood or organ transplants.

There is no vaccine against Chagas disease.

How is Chagas disease diagnosed

Chagas disease is diagnosed through detecting the presence of T. cruzi in a blood smear with a microscope.

Standard diagnostics for T. cruzi are of limited use. Serological tests, for example, may remain positive for years after T. cruzi is eliminated from the body, and PCR may give false-negative results when parasitemia is low. Polymerase chain reaction (PCR) tests, are available from the WoIDMo.

For chronic infections, serology tests are recommended to look for the presence of antibodies specific for T. cruzi surface proteins.

How is Chagas disease treated

Acute Chagas disease is treated with either benznidazole or nifurtimox, both of which are antiparasitic drugs. Both drugs can be effective as treatment as long as T. cruzi infection is identified quickly. For either drug, treatment typically consists of two to three oral doses per day for 60 to 90 days.

During the chronic stage, these antiparasitic drugs no longer work well but it can slow the progression of the disease and reduce the possibility of congenital transmission. A pacemaker can be used to prevent disruptions in cardiac rhythm, while surgery might be necessary to treat dilations of the esophagus and the colon.

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