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Chagas disease (also known as American Trypanosomiasis) is a disease caused by a protozoan known as Trypanosoma cruzi. The disease commonly affects the heart and digestive system tissues. Chagas disease first started in Latin America and it is very common in this region; it is a very common cause of heart failure in South America.
What is Chagas Disease?
Chagas disease discovery occurred in 1908/1909 by Carlos Chagas (a Brazilian doctor) and the disease was named after him. Chagas disease is one of the most common causes of heart disease in Central and South America; this disease is thought to have caused sickness in Charles Darwin during his voyage on the H.M.S. Beagle ship.
Chagas Disease Epidemiology
Human Chagas’ disease occurs primarily in rural Central and South America and also occurs in the United States (Texas). Acute Chagas’ disease occurs rarely in the United States, but the chronic form is seen with increasing frequency in immigrants from Latin America. The disease is seen primarily in rural areas because the reduviid bug lives in the walls of rural huts and feeds at night. It bites preferentially around the mouth or eyes, hence the name “kissing bug”. According to the World Health Organization (WHO), the number of infected persons in the year 2000 was estimated at 16 million to 18 million. Statistics from the Center for Disease Control (CDC), estimates that more than 300,000 persons with Trypanosoma cruzi infection live in the United States of America and most of them got infected from endemic countries.
Chagas Disease Transmission
- Transmission of Chagas disease occurs mainly by bite from a vector bug that goes by different names as Triatoma, kissing bug, Cone-nose bug or the Reduviid bug. This bug is called the kissing bug because it bites on the face. The trypanosomes are taken into the blood when the bug defecates near the site of the bite wound and the individual rubs the feces into the bite or other orifices such as the mouth or eyes. The trypanosomes are actually excreted in the feces; it is not the bite that causes the direct transmission.
- Chagas’ disease can also be transmitted through blood transfusions or organ transplants from infected donors.
- A fetus in the womb can get infected with Trypanosoma cruzi from an infected mother. This occurs because the Trypanosoma cruzi can cross the placenta.
- Reactivation of chagas disease may occur in immunosuppressed persons
Chagas Disease Symptoms
The symptoms and signs of Chagas disease occur in two phases: the acute phase and chronic phase. The acute phase lasts for 2 months with resolution of the disease in many and a few progressing to chronic phase which leads to death.
Acute Phase Symptoms of Chagas Disease
- One-sided eye swelling with redness of the eye (conjunctivitis) a sign called Romanas sign
- Facial edema (facial swelling)
- Nodular swelling at the site of the bite called Chagoma
- Lymphadenopathy (lymph node enlargements)
- Hepatosplenomegaly (enlargement of the liver and spleen) A bite around the eye can result in unilateral palpebral swelling called Romaa’s sign.
- Meningo-encephalitis may occur less frequently
The acute phase of Chagas disease resolves within 2 months; in most affected patients, the disease remains asymptomatic (no symptoms) but in few people, the disease progresses to the Chronic phase.
Chronic Phase Signs of Chagas Disease
- Megacolon (dilated colon causing constipation)
- Dilated Essophagus (megaesophagus) causing dysphagia and aspiration pneumonia
- Cardiac arrhythmias (irregular heart rate)
- Heart failure
Chagas Disease Diagnosis
- The acute phase of American Trypanosomiasis (Chagas disease) is diagnosed by identifying trypomastigotes in blood smear under the microscope.
- Stained specimen of bone marrow aspirate or muscle biopsy specimen may show amastigotes
- Culture of the organism can be done
- Xenodiagnosis this is done by using an uninfected reduviid bug to feed on the patients blood and after few weeks the intestinal contents of the bug are examined, if the organism is found in the bug, it means the patient has the infection. This test is particularly helpful in diagnosis of the chronic disease as there are few trypomastigotes in the blood.
- Serologic tests such as indirect fluorescent antibody test (IFAT) are faster to help in diagnosis. Other serologic tests include indirect hemagglutination test and complement fixation tests.
Chagas Disease Treatment/Cure
- Nifurtimox is used for treatment of Chagas disease but side effects of this drug include convulsions and nausea. Nifurtimox is only effective in treatment of the acute phase of chagas disease. It works by killing the trypomastigotes in the blood only. It lacks the ability to kill the amastigotes in tissue which are the cause of the fatal chronic disease.
- Benznidazole can be used if Nifurtimox is not available.
- There is no drug treatment for the chronic form of chagas disease
- Antiarrhythmic drugs and pacemakers may be used in cardiac disease
- Surgery can be done for gastrointestinal complications
Chagas Disease Prevention
- Prevention of Chagas disease basically involves insect control to prevent bite from the reduviid bug
- Improved housing conditions to ensure cleanliness (avoid mud walls and thatched roofs)
- Clearing the bushes around the house
- Testing blood for the presence of antibodies against Trypanosoma cruzi before transfusion
Complications of Chagas disease
- Hepatosplenomegaly (enlargement of the liver and spleen)
- Megacolon and megaesophagus
- Heart failure due to dilated cardiomyopathy