Summary
American trypanosomiasis, also called Chagas disease, is a strictly American parasitosis caused by flagellated protozoa of the Trypanosoma cruzi genus. The disease affects around 16 to 18 million people in the endemic zones of Latin America, from Texas to the North of Argentina with 40% of cases occurring in Brazil. T. cruzi is transmitted by the bite (during the nocturnal period) of several species of haematophageous bugs that infest daubed or thatched roofs and walls of shelters built in the poorer rural zones. The parasites are excreted in the faeces of the bugs and penetrate human hosts through the mucosa or through scratches in the skin. The parasite is also transmitted through transfusions and transplantation, and from mother to child through the placenta or breast milk. After localised multiplication, the parasite is then dispersed to target organs (principally the intestinal or cardiac nerve plexus) through invasion of the bloodstream. The acute phase following infection is generally asymptomatic but may lead to fever, malaise, myalgia, headaches and a furuncle-like lesion (Chagoma) usually in the head region. Conjunctival contamination leads to the formation of a pathognomonic complex known as Romana's sign: a usually painless oedema of one or both eyelids accompanied by swelling of the lymph nodes and, in some cases, conjunctivitis. This acute stage may be fatal in young children (in cases with cerebral oedema), but in most cases the symptoms disappear spontaneously within 4-8 weeks. In more than one third of infected individuals, the chronic phase of the disease appears after a period of latency lasting between 10 and 30 years. This chronic phase manifests as irreversible lesions mainly affecting the cardiac (20 to 40% of cases), digestive (megaoesophagus and megacolon in 6 to 15% of cases) and neurological (3% of cases) systems. The chronic form is also associated with a risk of chronic encephalopathy and sudden death. Diagnosis is made following detection of trypanosomes in the blood in the acute phase or through serological testing. Treatment of the acute phase involves administration of nifurtimox or benznidazole. The chronic cardiopathy and organ enlargement require adapted management. Prophylaxis revolves around an anti-vector approach and improvement of living conditions. *Author: Dr L. Paris (May 2006)*.
