Chagas disease

Chagas disease, also known as American trypanosomiasis, is a tropical parasitic disease caused by the protist Trypanosoma cruzi. It is spread mostly by insects known as Triatominae, or 'kissing bugs'. The symptoms change over the course of the infection. In the early stage, symptoms are typically either not present or mild, and may include fever, swollen lymph nodes, headaches, or local swelling at the site of the bite. After 8–12 weeks, individuals enter the chronic phase of disease and in 60–70% it never produces further symptoms. The other 30–40% of people develop further symptoms 10–30 years after the initial infection, including enlargement of the ventricles of the heart in 20–30%, leading to heart failure. An enlarged esophagus or an enlarged colon may also occur in 10% of people. T. cruzi is commonly spread to humans and other mammals by the blood-sucking 'kissing bugs' of the subfamily Triatominae. These insects are known by a number of local names, including: vinchuca in Argentina, Bolivia, Chile and Paraguay, barbeiro (the barber) in Brazil, pito in Colombia, chinche in Central America, and chipo in Venezuela. The disease may also be spread through blood transfusion, organ transplantation, eating food contaminated with the parasites, and by vertical transmission (from a mother to her fetus). Diagnosis of early disease is by finding the parasite in the blood using a microscope. Chronic disease is diagnosed by finding antibodies for T. cruzi in the blood. Prevention mostly involves eliminating kissing bugs and avoiding their bites. This may involve the use of insecticides or bed-nets. Other preventive efforts include screening blood used for transfusions. A vaccine has not been developed as of 2017. Early infections are treatable with the medication benznidazole or nifurtimox. Medication nearly always results in a cure if given early, but becomes less effective the longer a person has had Chagas disease. When used in chronic disease, medication may delay or prevent the development of end–stage symptoms. Benznidazole and nifurtimox cause temporary side effects in up to 40% of people including skin disorders, brain toxicity, and digestive system irritation. It is estimated that 6.6 million people, mostly in Mexico, Central America and South America, have Chagas disease as of 2015. In 2015, Chagas was estimated to result in 8,000 deaths. Most people with the disease are poor, and most do not realize they are infected. Large-scale population movements have increased the areas where Chagas disease is found and these include many European countries and the United States. These areas have also seen an increase in the years up to 2014. The disease was first described in 1909 by the Brazilian physician Carlos Chagas, after whom it is named. Chagas disease is classified as a neglected tropical disease. It affects more than 150 other animals. The human disease occurs in two stages: an acute stage, which occurs shortly after an initial infection, and a chronic stage that develops over many years. The acute phase lasts for the first few weeks or months of infection. It usually occurs unnoticed because it is symptom-free or exhibits only mild symptoms that are not unique to Chagas disease. These can include fever, fatigue, body aches, muscle pain, headache, rash, loss of appetite, diarrhea, nausea, swollen eyelids, and vomiting. The signs on physical examination can include mild enlargement of the liver or spleen, swollen glands, and local swelling (a chagoma) where the parasite entered the body. The most recognized marker of acute Chagas disease is called Romaña's sign, which includes swelling of the eyelids on the side of the face near the bite wound or where the bug feces were deposited or accidentally rubbed into the eye. Rarely, people may die from the acute disease due to severe inflammation/infection of the heart muscle (myocarditis) or brain (meningoencephalitis). The acute phase also can be severe in people with weakened immune systems. If symptoms develop during the acute phase, they usually resolve spontaneously within three to eight weeks in approximately 90% of individuals. Although the symptoms resolve, even with treatment the infection persists and enters a chronic phase. Of individuals with chronic Chagas disease, 60–80% will never develop symptoms (called indeterminate chronic Chagas disease), while the remaining 20–40% will develop life-threatening heart and/or digestive disorders during their lifetime (called determinate chronic Chagas disease). In 10% of individuals, the disease progresses directly from the acute form to a symptomatic clinical form of chronic Chagas disease.