What is Chagas disease?
Chagas disease, also known as American trypanosomiasis or South American trypanosomiasis, is a parasitic disease that affects millions of persons in both North and South America. More than 15 million persons are infected—most from Mexico south throughout South America—and about 50,000 die from the disease each year. More than 100 million are at risk of contracting the disease.
The protozoan Trypanosoma cruzi that causes Chagas disease is transmitted by the conenose bug (order Hemiptera, family Reduviidae, subfamily Triatominae), also known as the reduviid, assassin, or kissing bug. The feces of the bugs contain the parasites, which enter a human host through broken skin or mucous membranes. Entry of the parasites into cells in the subcutaneous tissue triggers an acute local inflammatory reaction. Within one to two weeks of infection, the trypanosomes spread to the regional lymph nodes and begin to multiply in the cells that phagocytose (digest) them. Chagas disease also can be transmitted by blood transfusion; by organ transplantation, especially heart; and by triatomine bugs.
Chagas disease is manifested in acute and chronic phases. Symptoms of the acute phase (most common in children) include anemia, loss of strength, nervous disorders, chills, muscle and bone pain, and varying degrees of heart failure. Death may ensue three to four weeks after infection. Symptoms of the chronic phase (most common in adults) include those of the acute phase, plus central and peripheral nervous dysfunction, which may last for many years and eventually lead to heart failure.
Unlike many other trypanosomes of humans, T. cruzi does not respond well to chemotherapy. The most effective drugs kill only the extracellular protozoa, but the intracellular forms defy the best efforts at eradication. The reproductive stages, which occur inside living host cells, seem to be shielded from the drugs. Nifurtimox and benznidazole have been shown to be somewhat effective in curing acute infections, but they require long treatment durations and have significant side effects.
In 1910, Carlos Chagas dissected a number of assassin bugs and found their hindguts swarming with trypanosomes some twenty years before they were known to cause disease. A century later, progress in controlling this harmful disease has been slow.
The 2005 report of the Scientific Working Group on Chagas Disease calls for, among other things, pediatric formulations of the two main drugs used to treat the disease, better diagnostic tools, better ways to screen donated blood to prevent transmission by transfusion, and improvements in control of the insects involved in transmission of the disease.
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