Chagas Disease

Chagas Disease, also known as American trypanosomiasis, is a parasitic disease mainly confined to the Americas and notably to Latin America. Increasing population mobility in past decades has led to a spreading of the disease to other continents.  Although the disease may be prevented by vector control, a large reservoir of the parasite in wild animals makes eradication impossible.  The parasite’s inherent capacity to evade the human immune system makes the development of vaccines difficult. New hopes focus on DNA vaccines.

Cause

The disease is caused by a protozoan parasite, Trypanosoma cruzi (T.cruzi).

The parasites are usually transmitted via the faeces of infected triatomine bugs, so called “kissing bugs” because of their tendency to suck blood on people’s faces.T.cruzi can also be transmitted through blood transfusions.   

Consequences

The disease occurs in two stages.  The acute phase in the first weeks or months after infection often shows no symptoms, or unspecific symptoms such as fever, headache, enlarged lymph glands, pallor, muscle pain, difficulty in breathing, swelling and abdominal or chest pain or vomiting.  One characteristic marker for Chagas disease is a skin lesion or purplish swelling of the eyelid on the side of the face near the bite wound, but this appears only in about 50% of infected people.  These symptoms usually resolve spontaneously. The infection persists and proceeds to the chronic phase.

During the acute phase a large number of parasites circulate in the blood, whereas during the chronic phase the parasite is hidden in the heart and digestive muscle.  Cell deaths in these target tissues lead to inflammation and cellular lesions causing cardiac and digestive disorders in about 40% of the patients.  Progressive damage to the heart muscle may ultimately lead to heart failure and sudden death.

Global burden

About 10 million people living in Latin American countries are affected by Chagas disease, with an additional estimated 400,000 living in non-endemic countries such as Spain and the United States.

Each year there are an estimated 40 000 new infections and 20 000 deaths attributed to Chagas disease.  

Vaccines

Chagas disease can be effectively treated with benznidazole and nifurtimox when administered soon after infection, but efficacy of the treatment diminishes rapidly with time after the infection.  Both medicines are not suitable for pregnant women or people with kidney or liver failure.  Nifurtimox is also not indicated for people with neurological disorders.

The current and most effective methods for prevention of the disease are vector control by insecticide spraying, bednets or house improvements to exclude the vector and blood screening.  There is no vaccine against Chagas disease at present, but more recently the potential of DNA vaccines for immunotherapy of acute and chronic Chagas disease is being tested by several research groups.