Chagas disease
Template:Short description Template:Use dmy dates Template:Featured article Template:Infobox medical condition (new) Chagas disease, also known as American trypanosomiasis, is a tropical parasitic disease caused by Trypanosoma cruzi. It is spread mostly by insects in the subfamily Triatominae, known as "kissing bugs". The symptoms change throughout the infection. In the early stage, symptoms are typically either not present or mild and may include fever, swollen lymph nodes, headaches, or swelling at the site of the bite.<ref name=WHO2019>Template:Cite web</ref> After four to eight weeks, untreated individuals enter the chronic phase of disease, which in most cases does not result in further symptoms.<ref name=Molina2018/><ref name=Bern2015/> Up to 45% of people with chronic infections develop heart disease 10–30 years after the initial illness, which can lead to heart failure. Digestive complications, including an enlarged esophagus or an enlarged colon, may also occur in up to 21% of people, and up to 10% of people may experience nerve damage.<ref name=Molina2018/>
Template:Nowrap is commonly spread to humans and other mammals by the kissing bug's bite wound and the bug's infected feces.<ref name=CDC>Template:Cite web</ref> The disease may also be spread through blood transfusion, organ transplantation, consuming food or drink contaminated with the parasites, and vertical transmission (from a mother to her baby).<ref name=WHO2019/> Diagnosis of early disease is by finding the parasite in the blood using a microscope or detecting its DNA by polymerase chain reaction.<ref name=Bern2015/> Chronic disease is diagnosed by finding antibodies for Template:Nowrap in the blood.<ref name=Gua2019>Template:Cite journal</ref>
Prevention focuses on eliminating kissing bugs and avoiding their bites.<ref name=WHO2019/> This may involve the use of insecticides or bed-nets.<ref>Template:Cite web</ref> Other preventive efforts include screening blood used for transfusions. Early infections are treatable with the medications benznidazole or nifurtimox, which usually cure the disease if given shortly after the person is infected, but become 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 often cause side effects, including skin disorders, digestive system irritation, and neurological symptoms, which can result in treatment being discontinued.<ref name=Molina2018/><ref name=Santi2022>Template:Cite journal</ref> New drugs for Chagas disease are under development,<ref name=Porta2023>Template:Cite journal</ref> and while experimental vaccines have been studied in animal models,<ref name=Rios2019/><ref name=Vermelho2019/> a human vaccine has not been developed.
It is estimated that 6.5 million people, mostly in Mexico, Central America and South America, have Chagas disease as of 2019,<ref name="WHO2019"/><ref name="GBD2019"/> resulting in approximately 9,490 annual deaths.<ref name="GBD2019"/> Most people with the disease are poor,<ref name=Rassi2012>Template:Cite journal</ref> and most do not realize they are infected.<ref>Template:Cite book</ref> Large-scale population migrations have carried Chagas disease to new regions, which include the United States and many European countries.<ref name=WHO2019/> The disease affects more than 150 types of animals.<ref name=Rassi2010>Template:Cite journal</ref>
The disease was first described in 1909 by Brazilian physician Carlos Chagas, after whom it is named.<ref name=WHO2019/> Chagas disease is classified as a neglected tropical disease.<ref name=NTD2017>Template:Cite web</ref>
Signs and symptoms
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Chagas disease occurs in two stages: an acute stage, which develops one to two weeks after the insect bite, and a chronic stage, which develops over many years.<ref name="Molina2018"/><ref name="Bern2015"/><ref name=PD7/> The acute stage is often symptom-free.<ref name="Molina2018"/> When present, the symptoms are typically minor and not specific to any particular disease.<ref name=Bern2015>Template:Cite journal</ref> Signs and symptoms include fever, malaise, headache, and enlargement of the liver, spleen, and lymph nodes.<ref name="WHO2019"/><ref name="Molina2018"/><ref name="Bern2015"/> Sometimes, people develop a swollen nodule at the site of infection, which is called "Romaña's sign" if it is on the eyelid, or a "chagoma" if it is elsewhere on the skin.<ref name="Bern2015"/><ref>Template:Cite web</ref> In rare cases (less than 1–5%), infected individuals develop severe acute disease, which can involve inflammation of the heart muscle, fluid accumulation around the heart, and inflammation of the brain and surrounding tissues, and may be life-threatening. The acute phase typically lasts four to eight weeks and resolves without treatment.<ref name="Molina2018"/>
Unless treated with antiparasitic drugs, individuals remain infected with Template:Nowrap after recovering from the acute phase. Most chronic infections are asymptomatic, which is referred to as indeterminate chronic Chagas disease. However, over decades with the disease, approximately 30–40% of people develop organ dysfunction (determinate chronic Chagas disease), which most often affects the heart or digestive system.<ref name="Molina2018"/><ref name="Bern2015"/>
The most common long-term manifestation is heart disease, which occurs in 14–45% of people with chronic Chagas disease.<ref name="Molina2018"/> People with Chagas heart disease often experience heart palpitations, and sometimes fainting, due to irregular heart function. By electrocardiogram, people with Chagas heart disease most frequently have arrhythmias. As the disease progresses, the heart's ventricles become enlarged (dilated cardiomyopathy), which reduces its ability to pump blood. In many cases the first sign of Chagas heart disease is heart failure, thromboembolism, or chest pain associated with abnormalities in the microvasculature.<ref name="Nunes2018"/>
Also common in chronic Chagas disease is damage to the digestive system, which affects 10–21% of people.<ref name="Molina2018"/> Enlargement of the esophagus or colon are the most common digestive issues.<ref name="PD7"/> Those with enlarged esophagus often experience pain (odynophagia) or trouble swallowing (dysphagia), acid reflux, cough, and weight loss. Individuals with enlarged colon often experience constipation, and may develop severe blockage of the intestine or its blood supply. Up to 10% of chronically infected individuals develop nerve damage that can result in numbness and altered reflexes or movement.<ref name="Molina2018"/> While chronic disease typically develops over decades, some individuals with Chagas disease (less than 10%) progress to heart damage directly after acute disease.<ref name="Nunes2018">Template:Cite journal</ref>
Signs and symptoms differ for people infected with Template:Nowrap through less common routes. People infected through ingestion of parasites tend to develop severe disease within three weeks of consumption, with symptoms including fever, vomiting, shortness of breath, cough, and pain in the chest, abdomen, and muscles.<ref name="Molina2018"/> Those infected congenitally typically have few to no symptoms, but can have mild non-specific symptoms, or severe symptoms such as jaundice, respiratory distress, and heart problems.<ref name="Molina2018"/> People infected through organ transplant or blood transfusion tend to have symptoms similar to those of vector-borne disease, but the symptoms may not manifest for anywhere from a week to five months.<ref name="Molina2018"/> Chronically infected individuals who become immunosuppressed due to HIV infection can have particularly severe and distinct disease, most commonly characterized by inflammation in the brain and surrounding tissue or brain abscesses.<ref name="Bern2015"/> Symptoms vary widely based on the size and location of brain abscesses, but typically include fever, headaches, seizures, loss of sensation, or other neurological issues that indicate particular sites of nervous system damage.<ref>Template:Cite journal</ref> Occasionally, these individuals also experience acute heart inflammation, skin lesions, and disease of the stomach, intestine, or peritoneum.<ref name="Bern2015"/>
Cause
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Chagas disease is caused by infection with the protozoan parasite Template:Nowrap, which is typically introduced into humans through the bite of triatomine bugs, also called "kissing bugs".<ref name="Bern2015"/> When the insect defecates at the bite site, motile Template:Nowrap forms called trypomastigotes enter the bloodstream and invade various host cells.<ref name=CDC/> Inside a host cell, the parasite transforms into a replicative form called an amastigote, which undergoes several rounds of replication.<ref name=CDC/> The replicated amastigotes transform back into trypomastigotes, which burst the host cell and are released into the bloodstream.<ref name="Molina2018"/> Trypomastigotes then disseminate throughout the body to various tissues, where they invade cells and replicate.<ref name="Molina2018"/> Over many years, cycles of parasite replication and immune response can severely damage these tissues, particularly the heart and digestive tract.<ref name="Molina2018"/>
Transmission
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T. cruzi can be transmitted by various triatomine bugs in the genera Triatoma, Panstrongylus, and Rhodnius.<ref name="Molina2018"/> The primary vectors for human infection are the species of triatomine bugs that inhabit human dwellings, namely Triatoma infestans, Rhodnius prolixus, Triatoma dimidiata and Panstrongylus megistus.<ref name="AlbaSoto2019"/> 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.<ref>Template:Cite book</ref> The bugs tend to feed at night, preferring moist surfaces near the eyes or mouth.<ref name=PD7/><ref name="AlbaSoto2019">Template:Cite book</ref> A triatomine bug can become infected with Template:Nowrap when it feeds on an infected host.<ref name=PD7/> Template:Nowrap replicates in the insect's intestinal tract and is shed in the bug's feces.<ref name=PD7/> When an infected triatomine feeds, it pierces the skin and takes in a blood meal, defecating at the same time to make room for the new meal.<ref name=PD7>Template:Cite book</ref> The bite is typically painless, but causes itching.<ref name=PD7/> Scratching at the bite introduces the Template:Nowrap-laden feces into the bite wound, initiating infection.<ref name=PD7/>
In addition to classical vector spread, Chagas disease can be transmitted through the consumption of food or drink contaminated with triatomine insects or their feces.<ref name=Robertson2016>Template:Cite journal</ref> Since heating or drying kills the parasites, drinks and especially fruit juices are the most frequent source of infection.<ref name=Robertson2016/> This oral route of transmission has been implicated in several outbreaks, where it led to unusually severe symptoms, likely due to infection with a higher parasite load than from the bite of a triatomine bug—<ref name=Gua2019/><ref name=Robertson2016/>a single crushed triatomine in a food or beverage harboring T cruzi can contain about 600,000 metacyclic trypomastigotes, while triatomine fecal matter contains 3,000-4,000 per μL.<ref>Template:Cite web</ref>
T. cruzi can be transmitted independent of the triatomine bug during blood transfusion, following organ transplantation, or across the placenta during pregnancy.<ref name="Molina2018"/> Transfusion with the blood of an infected donor infects the recipient 10–25% of the time.<ref name="Molina2018"/> To prevent this, blood donations are screened for Template:Nowrap in many countries with endemic Chagas disease, as well as the United States.<ref name=Gua2019/> Similarly, transplantation of solid organs from an infected donor can transmit Template:Nowrap to the recipient.<ref name="Molina2018"/> This is especially true for heart transplant, which transmits T. cruzi 75–100% of the time, and less so for transplantation of the liver (0–29%) or a kidney (0–19%).<ref name="Molina2018"/> An infected mother can pass Template:Nowrap to her child through the placenta; this occurs in up to 15% of births by infected mothers.<ref name=Messenger2018>Template:Cite journal</ref> As of 2019, 22.5% of new infections occurred through congenital transmission.<ref name="Bern2019">Template:Cite journal</ref>
Pathophysiology
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In the acute phase of the disease, signs and symptoms are caused directly by the replication of Template:Nowrap and the immune system's response to it.<ref name="Molina2018"/> During this phase, Template:Nowrap can be found in various tissues throughout the body and circulating in the blood.<ref name="Molina2018"/> During the initial weeks of infection, parasite replication is brought under control by the production of antibodies and activation of the host's inflammatory response, particularly cells that target intracellular pathogens such as NK cells and macrophages, driven by inflammation-signaling molecules like TNF-α and IFN-γ.<ref name="Molina2018"/>
During chronic Chagas disease, long-term organ damage develops over years due to continued replication of the parasite and damage from the immune system. Early in the course of the disease, Template:Nowrap is found frequently in the striated muscle fibers of the heart.<ref name="Bonney2019">Template:Cite journal</ref> As disease progresses, the heart becomes generally enlarged, with substantial regions of cardiac muscle fiber replaced by scar tissue and fat.<ref name="Bonney2019"/> Areas of active inflammation are scattered throughout the heart, with each housing inflammatory immune cells, typically macrophages and T cells.<ref name="Bonney2019"/> Late in the disease, parasites are rarely detected in the heart, and may be present at only very low levels.<ref name="Bonney2019"/>
In the heart, colon, and esophagus, chronic disease leads to a massive loss of nerve endings.<ref name="Nunes2018"/> In the heart, this may contribute to arrhythmias and other cardiac dysfunction.<ref name="Nunes2018"/> In the colon and esophagus, loss of nervous system control is the major driver of organ dysfunction.<ref name="Nunes2018"/> Loss of nerves impairs the movement of food through the digestive tract, which can lead to blockage of the esophagus or colon and restriction of their blood supply.<ref name="Nunes2018"/>
The parasite can insert kinetoplast DNA into host cells, an example of horizontal gene transfer. Vertical inheritance of the inserted kDNA has been demonstrated in rabbits and birds. In chickens, offspring carrying inserted kDNA show symptoms of disease despite carrying no live trypanosomes.<ref name=Texeira>Template:Cite journal</ref> In 2010, integrated kDNA was found to be vertically transmitted in five human families.<ref name=Hecht>Template:Cite journal</ref>
Diagnosis
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The presence of T. cruzi in the blood is diagnostic of Chagas disease. During the acute phase of infection, it can be detected by microscopic examination of fresh anticoagulated blood, or its buffy coat, for motile parasites; or by preparation of thin and thick blood smears stained with Giemsa, for direct visualization of parasites.<ref name="Bern2015"/><ref name=Gua2019/> Blood smear examination detects parasites in 34–85% of cases. The sensitivity increases if techniques such as microhematocrit centrifugation are used to concentrate the blood.<ref name="Molina2018"/> On microscopic examination of stained blood smears, Template:Nowrap trypomastigotes appear as S or U-shaped organisms with a flagellum connected to the body by an undulating membrane. A nucleus and a smaller structure called a kinetoplast are visible inside the parasite's body; the kinetoplast of Template:Nowrap is relatively large, which helps to distinguish it from other species of trypanosomes that infect humans.<ref name="Bain2015">Template:Cite book</ref>
Alternatively, T. cruzi DNA can be detected by polymerase chain reaction (PCR). In acute and congenital Chagas disease, PCR is more sensitive than microscopy,<ref name="Bern2019"/> and it is more reliable than antibody-based tests for the diagnosis of congenital disease because it is not affected by the transfer of antibodies against Template:Nowrap from a mother to her baby (passive immunity).<ref>Template:Cite journal</ref> PCR is also used to monitor Template:Nowrap levels in organ transplant recipients and immunosuppressed people, which allows infection or reactivation to be detected at an early stage.<ref name="Molina2018"/><ref name="Bern2015"/><ref name="Bern2019"/>
In chronic Chagas disease, the concentration of parasites in the blood is too low to be reliably detected by microscopy or PCR,<ref name="Molina2018"/> so the diagnosis is usually made using serological tests, which detect immunoglobulin G antibodies against Template:Nowrap in the blood.<ref name=Gua2019/> Two positive serology results, using different test methods, are required to confirm the diagnosis.<ref name="Bern2015"/> If the test results are inconclusive, additional testing methods such as Western blot can be used.<ref name="Molina2018"/>
Various rapid diagnostic tests for Chagas disease are available. These tests are easily transported and can be performed by people without special training.<ref name="Luquetti2019">Template:Cite book</ref> They are useful for screening large numbers of people and testing people who cannot access healthcare facilities, but their sensitivity is relatively low,<ref name="Molina2018"/> and it is recommended that a second method is used to confirm a positive result.<ref name="Luquetti2019"/><ref name="Gurtler2019">Template:Cite journal</ref>
T. cruzi parasites can be grown from blood samples by blood culture, xenodiagnosis, or by inoculating animals with the person's blood. In the blood culture method, the person's red blood cells are separated from the plasma and added to a specialized growth medium to encourage multiplication of the parasite. It can take up to six months to obtain the result. Xenodiagnosis involves feeding the blood to triatomine insects, and then examining their feces for the parasite 30 to 60 days later.<ref name="Luquetti2019"/> These methods are not routinely used, as they are slow and have low sensitivity.<ref name=emed>Template:Cite web</ref><ref name="Luquetti2019"/>
Prevention
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Efforts to prevent Chagas disease have largely focused on vector control to limit exposure to triatomine bugs. Insecticide-spraying programs have been the mainstay of vector control, consisting of spraying homes and the surrounding areas with residual insecticides.<ref name=Cueto2015>Template:Cite journal</ref> This was originally done with organochlorine, organophosphate, and carbamate insecticides, which were supplanted in the 1980s with pyrethroids.<ref name=Cueto2015/> These programs have drastically reduced transmission in Brazil and Chile,<ref name=PD7/> and eliminated major vectors from certain regions: Triatoma infestans from Brazil, Chile, Uruguay, and parts of Peru and Paraguay, as well as Rhodnius prolixus from Central America.<ref name="Nunes2018"/> Vector control in some regions has been hindered by the development of insecticide resistance among triatomine bugs.<ref name=Cueto2015/> In response, vector control programs have implemented alternative insecticides (e.g. fenitrothion and bendiocarb in Argentina and Bolivia), treatment of domesticated animals (which are also fed on by triatomine bugs) with pesticides, pesticide-impregnated paints, and other experimental approaches.<ref name=Cueto2015/> In areas with triatomine bugs, transmission of Template:Nowrap can be prevented by sleeping under bed nets and by housing improvements that prevent triatomine bugs from colonizing houses.<ref name=PD7/>
Blood transfusion was formerly the second-most common mode of transmission for Chagas disease.<ref name=Angheben2015/> Template:Nowrap can survive in refrigerated stored blood, and can survive freezing and thawing, allowing it to persist in whole blood, packed red blood cells, granulocytes, cryoprecipitate, and platelets.<ref name=Angheben2015/> The development and implementation of blood bank screening tests have dramatically reduced the risk of infection during a blood transfusion.<ref name=Angheben2015>Template:Cite journal</ref> Nearly all blood donations in Latin American countries undergo Chagas screening.<ref name=Angheben2015/> Widespread screening is also common in non-endemic nations with significant populations of immigrants from endemic areas, including the United Kingdom (implemented in 1999), Spain (2005), the United States (2007), France and Sweden (2009), Switzerland (2012), and Belgium (2013).<ref name=Lidani2019>Template:Cite journal</ref> Serological tests, typically ELISAs, are used to detect antibodies against Template:Nowrap proteins in donor blood.<ref name=Angheben2015/>
Other modes of transmission have been targeted by Chagas disease prevention programs. Treating Template:Nowrap-infected mothers during pregnancy reduces the risk of congenital transmission of the infection.<ref name=Messenger2018/> To this end, many countries in Latin America have implemented routine screening of pregnant women and infants for Template:Nowrap infection, and the World Health Organization recommends screening all children born to infected mothers to prevent congenital infection from developing into chronic disease.<ref name=WHO2019/><ref name=Bonney2014>Template:Cite journal</ref> Similarly to blood transfusions, many countries with endemic Chagas disease screen organs for transplantation with serological tests.<ref name="Molina2018"/>
There is no vaccine against Chagas disease.<ref name=Santi2022/> Several experimental vaccines have been tested in animals infected with Template:Nowrap and were able to reduce parasite numbers in the blood and heart,<ref>Template:Cite journal</ref> but no vaccine candidates had undergone clinical trials in humans as of 2016.<ref>Template:Cite journal</ref>
Management
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Chagas disease is managed using antiparasitic drugs to eliminate T. cruzi from the body, and symptomatic treatment to address the effects of the infection.<ref name=Gua2019/> As of 2018, benznidazole and nifurtimox were the antiparasitic drugs of choice for treating Chagas disease,<ref name="Molina2018"/> though benznidazole is the only drug available in most of Latin America.<ref name="Ribeiro2019"/> For either drug, treatment typically consists of two to three oral doses per day for 60 to 90 days.<ref name="Molina2018"/> Antiparasitic treatment is most effective early in the course of infection: it eliminates Template:Nowrap from 50 to 80% of people in the acute phase (WHO: "nearly 100 %"<ref>WHO. (13 April 2022). "Chagas disease (also known as American trypanosomiasis". Fact sheets.</ref>), but only 20–60% of those in the chronic phase.<ref name=Gua2019/> Treatment of chronic disease is more effective in children than in adults, and the cure rate for congenital disease approaches 100% if treated in the first year of life.<ref name="Molina2018"/> Antiparasitic treatment can also slow the progression of the disease and reduce the possibility of congenital transmission.<ref name="WHO2019"/> Elimination of Template:Nowrap does not cure the cardiac and gastrointestinal damage caused by chronic Chagas disease, so these conditions must be treated separately.<ref name=Gua2019/> Antiparasitic treatment is not recommended for people who have already developed dilated cardiomyopathy.<ref name="Nunes2018"/>
Benznidazole is usually considered the first-line treatment because it has milder adverse effects than nifurtimox, and its efficacy is better understood.<ref name="Molina2018"/><ref name="Bern2019"/> Both benznidazole and nifurtimox have common side effects that can result in treatment being discontinued. The most common side effects of benznidazole are skin rash, digestive problems, decreased appetite, weakness, headache, and sleeping problems. These side effects can sometimes be treated with antihistamines or corticosteroids, and are generally reversed when treatment is stopped.<ref name="Molina2018"/> However, benznidazole is discontinued in up to 29% of cases.<ref name="Molina2018"/> Nifurtimox has more frequent side effects, affecting up to 97.5% of individuals taking the drug.<ref name="Molina2018"/> The most common side effects are loss of appetite, weight loss, nausea and vomiting, and various neurological disorders including mood changes, insomnia, paresthesia and peripheral neuropathy.<ref name="Molina2018"/> Treatment is discontinued in up to 75% of cases.<ref name="Molina2018"/><ref name="Bern2019"/> Both drugs are contraindicated for use in pregnant women and people with liver or kidney failure.<ref name="WHO2019"/> As of 2019, resistance to these drugs has been reported.<ref name="Ribeiro2019">Template:Cite journal</ref>
Complications
[edit]In the chronic stage, treatment involves managing the clinical manifestations of the disease. The treatment of Chagas cardiomyopathy is similar to that of other forms of heart disease.<ref name="Molina2018"/> Beta blockers and ACE inhibitors may be prescribed, but some people with Chagas disease may not be able to take the standard dose of these drugs because they have low blood pressure or a low heart rate.<ref name="Molina2018"/><ref name="Nunes2018"/> To manage irregular heartbeats, people may be prescribed anti-arrhythmic drugs such as amiodarone, or have a pacemaker implanted.<ref name="Bern2015"/> Blood thinners may be used to prevent thromboembolism and stroke.<ref name="Nunes2018"/> Chronic heart disease caused by untreated T. cruzi infection is a common reason for heart transplantation surgery.<ref name="PD7"/> Because transplant recipients take immunosuppressive drugs to prevent organ rejection, they are monitored using PCR to detect reactivation of the disease. People with Chagas disease who undergo heart transplantation have higher survival rates than the average heart transplant recipient.<ref name="Nunes2018"/>
Mild gastrointestinal disease may be treated symptomatically, such as by using laxatives for constipation or taking a prokinetic drug like metoclopramide before meals to relieve esophageal symptoms.<ref name="Bern2015"/><ref name="Oliveira2019"/> Surgery to sever the muscles of the lower esophageal sphincter (cardiomyotomy) may be performed in more severe cases of esophageal disease,<ref name="Oliveira2019">Template:Cite book</ref> and surgical removal of the affected part of the organ may be required for advanced megacolon and megaesophagus.<ref name="Bern2015"/><ref name="emed"/>
Epidemiology
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In 2019, an estimated 6.5 million people worldwide had Chagas disease, with approximately 173,000 new infections and 9,490 deaths each year.<ref name="GBD2019">Template:Cite web</ref> The disease resulted in a global annual economic burden estimated at US$7.2 billion in 2013, 86% of which is borne by endemic countries.<ref name=Lidani2019/><ref name=econ/> Chagas disease results in the loss of over 800,000 disability-adjusted life years each year.<ref name="Molina2018"/>
The endemic area of Chagas disease stretches from the southern United States to northern Chile and Argentina, with Bolivia (6.1%), Argentina (3.6%), and Paraguay (2.1%) exhibiting the highest prevalence of the disease.<ref name="Molina2018">Template:Cite journal</ref> Within continental Latin America, Chagas disease is endemic to 21 countries: Argentina, Belize, Bolivia, Brazil, Chile, Colombia, Costa Rica, Ecuador, El Salvador, French Guiana, Guatemala, Guyana, Honduras, Mexico, Nicaragua, Panama, Paraguay, Peru, Suriname, Uruguay, and Venezuela.<ref name="WHO2019"/><ref name="Molina2018"/> In endemic areas, due largely to vector control efforts and screening of blood donations, annual infections and deaths have fallen by 67% and more than 73% respectively from their peaks in the 1980s to 2010.<ref name="Molina2018"/><ref name=Moncayo2017>Template:Cite book</ref> Transmission by insect vector and blood transfusion has been completely interrupted in Uruguay (1997), Chile (1999), and Brazil (2006),<ref name=Moncayo2017/> and in Argentina, vectorial transmission had been interrupted in 13 of the 19 endemic provinces as of 2001.<ref name=TDR1>Template:Cite press release</ref> During Venezuela's humanitarian crisis, vectorial transmission has begun occurring in areas where it had previously been interrupted, and Chagas disease seroprevalence rates have increased.<ref name=Grillet2019>Template:Cite journal</ref> Transmission rates have also risen in the Gran Chaco region due to insecticide resistance and in the Amazon basin due to oral transmission.<ref name="Molina2018"/>
While the rate of vector-transmitted Chagas disease has declined throughout most of Latin America, the rate of orally transmitted disease has risen, possibly due to increasing urbanization and deforestation bringing people into closer contact with triatomines and altering the distribution of triatomine species.<ref name="Robertson2016"/><ref name="Alarcon2019">Template:Cite book</ref><ref name="Hotez2017">Template:Cite journal</ref> Orally transmitted Chagas disease is of particular concern in Venezuela, where 16 outbreaks have been recorded between 2007 and 2018.<ref name="Grillet2019">Template:Cite journal</ref>
Chagas exists in two different ecological zones. In the Southern Cone region, the main vector lives in and around human homes. In Central America and Mexico, the main vector species lives both inside dwellings and in uninhabited areas. In both zones, Chagas occurs almost exclusively in rural areas, where Template:Nowrap also circulates in wild and domestic animals.<ref name=NatRev>Template:Cite journal</ref> Template:Nowrap commonly infects more than 100 species of mammals across Latin America including opossums (Didelphis spp.),<ref name="Wilkowsky-2022">Template:Cite web</ref> armadillos, marmosets, bats, various rodents<ref name="Telleria-Tibayrenc-2010">Template:Cite book</ref> and dogs<ref name="Wilkowsky-2022" /> all of which can be infected by the vectors or orally by eating triatomine bugs and other infected animals.<ref name="Telleria-Tibayrenc-2010" /><ref name="Wilkowsky-2022" /> For entomophagous animals this is a common mode.<ref name="Wilkowsky-2022" /> Didelphis spp. are unique in that they do not require the triatomine for transmission, completing the life cycle through their own urine and feces.<ref name="Wilkowsky-2022" /> Veterinary transmission also occurs through vertical transmission through the placenta, blood transfusion and organ transplants.<ref name="Wilkowsky-2022" />
Non-endemic countries
[edit]Though Chagas is traditionally considered a disease of rural Latin America, international migration has dispersed those with the disease to numerous non-endemic countries, primarily in North America and Europe.<ref name="WHO2019"/><ref name=Lidani2019/> As of 2020, approximately 300,000 infected people are living in the United States,<ref name="mmwr">Template:Cite journal</ref> and in 2018 it was estimated that 30,000 to 40,000 people in the United States had Chagas cardiomyopathy.<ref name="Nunes2018"/> The vast majority of cases in the United States occur in immigrants from Latin America,<ref name="Nunes2018"/><ref name="Bern2019"/> but local transmission is possible. Eleven triatomine species are native to the United States, and some southern states have persistent cycles of disease transmission between insect vectors and animal reservoirs,<ref name="Molina2018"/><ref name="Bern2019"/> which include woodrats, possums, raccoons, armadillos and skunks.<ref name="Montgomery2014">Template:Cite journal</ref> However, locally acquired infection is very rare: only 28 cases were documented from 1955 to 2015.<ref name="Molina2018"/><ref name="mmwr"/> As of 2013, the cost of treatment in the United States was estimated to be US$900 million annually (global cost $7 billion), which included hospitalization and medical devices such as pacemakers.<ref name=econ>Template:Cite journal</ref>
Chagas disease affected approximately 68,000 to 123,000 people in Europe as of 2019.<ref name="Alonso2019">Template:Cite book</ref> Spain, which has a high rate of immigration from Latin America, has the highest prevalence of the disease. It is estimated that 50,000 to 70,000 people in Spain are living with Chagas disease, accounting for the majority of European cases.<ref name="Velasco2020"/> The prevalence varies widely within European countries due to differing immigration patterns.<ref name="Alonso2019"/> Italy has the second highest prevalence, followed by the Netherlands, the United Kingdom, and Germany.<ref name="Velasco2020">Template:Cite journal</ref>
History
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T. cruzi likely circulated in South American mammals long before the arrival of humans on the continent.<ref name="Steverding2014"/> Template:Nowrap has been detected in ancient human remains across South America, from a 9000-year-old Chinchorro mummy in the Atacama Desert, to remains of various ages in Minas Gerais, to an 1100-year-old mummy as far north as the Chihuahuan Desert near the Rio Grande.<ref name="Steverding2014">Template:Cite journal</ref> Many early written accounts describe symptoms consistent with Chagas disease, with early descriptions of the disease sometimes attributed to Miguel Diaz Pimenta (1707), Template:Ill (1735), and Theodoro J. H. Langgaard (1842).<ref name = "Steverding2014" />
The formal description of Chagas disease was made by Carlos Chagas in 1909 after examining a two-year-old girl with fever, swollen lymph nodes, and an enlarged spleen and liver.<ref name="Steverding2014"/> Upon examination of her blood, Chagas saw trypanosomes identical to those he had recently identified from the hindgut of triatomine bugs and named Trypanosoma cruzi in honor of his mentor, Brazilian physician Oswaldo Cruz.<ref name="Steverding2014"/> He sent infected triatomine bugs to Cruz in Rio de Janeiro, who showed the bite of the infected triatomine could transmit Template:Nowrap to marmoset monkeys as well.<ref name="Steverding2014"/> In just two years, 1908 and 1909, Chagas published descriptions of the disease, the organism that caused it, and the insect vector required for infection.<ref name=Kropf2009>Template:Cite journal</ref><ref name="Chagas_1909">Template:Cite journal</ref><ref name="Chagas_1909b">Template:Cite journal (in Portuguese with German full translation as "Ueber eine neue Trypanosomiasis des Menschen.")</ref> Almost immediately thereafter, at the suggestion of Miguel Couto, then professor of the Template:Ill, the disease was widely referred to as "Chagas disease".<ref name=Kropf2009/> Chagas' discovery brought him national and international renown, but in highlighting the inadequacies of the Brazilian government's response to the disease, Chagas attracted criticism to himself and to the disease that bore his name, stifling research on his discovery and likely frustrating his nomination for the Nobel Prize in 1921.<ref name=Kropf2009/><ref>Template:Cite journal</ref>
In the 1930s, Salvador Mazza rekindled Chagas disease research, describing over a thousand cases in Argentina's Chaco Province.<ref name="Steverding2014"/> In Argentina, the disease is known as mal de Chagas-Mazza in his honor.<ref>Template:Cite web</ref> Serological tests for Chagas disease were introduced in the 1940s, demonstrating that infection with Template:Nowrap was widespread across Latin America.<ref name="Steverding2014"/> This, combined with successes eliminating the malaria vector through insecticide use, spurred the creation of public health campaigns focused on treating houses with insecticides to eradicate triatomine bugs.<ref name=Cueto2015/><ref name="Steverding2014"/> The 1950s saw the discovery that treating blood with crystal violet could eradicate the parasite, leading to its widespread use in transfusion screening programs in Latin America.<ref name="Steverding2014"/> Large-scale control programs began to take form in the 1960s, first in São Paulo, then various locations in Argentina, then national-level programs across Latin America.<ref name=Dias2015>Template:Cite journal</ref> These programs received a major boost in the 1980s with the introduction of pyrethroid insecticides, which did not leave stains or odors after application and were longer-lasting and more cost-effective.<ref name=Steverding2014/><ref name=Dias2015/> Regional bodies dedicated to controlling Chagas disease arose through support of the Pan American Health Organization, with the Initiative of the Southern Cone for the Elimination of Chagas Diseases launching in 1991, followed by the Initiative of the Andean countries (1997), Initiative of the Central American countries (1997), and the Initiative of the Amazon countries (2004).<ref name=Cueto2015/>
Research
[edit]Treatments
[edit]Fexinidazole, an antiparasitic drug approved for treating African trypanosomiasis, has shown activity against Chagas disease in animal models. As of 2019, it is undergoing phase II clinical trials for chronic Chagas disease in Spain.<ref name="Ribeiro2019">Template:Cite journal</ref><ref name="Deeks2019">Template:Cite journal</ref> Other drug candidates include GNF6702, a proteasome inhibitor that is effective against Chagas disease in mice and is undergoing preliminary toxicity studies, and AN4169, which has had promising results in animal models.<ref name="Vermelho2019">Template:Cite journal</ref><ref name="Kratz2019">Template:Cite journal</ref>
Several experimental vaccines have been tested in animals. In addition to subunit vaccines, some approaches have involved vaccination with attenuated Template:Nowrap parasites or organisms that express some of the same antigens as Template:Nowrap but do not cause human disease, such as Trypanosoma rangeli or Phytomonas serpens. DNA vaccination has also been explored. As of 2019, vaccine research has mainly been limited to small animal models.<ref name="Rios2019">Template:Cite journal</ref>
Diagnostic tests
[edit]As of 2018, standard diagnostic tests for Chagas disease were limited in their ability to measure the effectiveness of antiparasitic treatment, as serological tests may remain positive for years after Template:Nowrap is eliminated from the body, and PCR may give false-negative results when the parasite concentration in the blood is low. Several potential biomarkers of treatment response are under investigation, such as immunoassays against specific Template:Nowrap antigens, flow cytometry testing to detect antibodies against different life stages of Template:Nowrap, and markers of physiological changes caused by the parasite, such as alterations in coagulation and lipid metabolism.<ref name="Nunes2018"/>
Another research area is the use of biomarkers to predict the progression of chronic disease. Serum levels of tumor necrosis factor alpha, brain and atrial natriuretic peptide, and angiotensin-converting enzyme 2 have been studied as indicators of the prognosis of Chagas cardiomyopathy.<ref name="Balouz2017"/>
T. cruzi shed acute-phase antigen (SAPA), which can be detected in blood using ELISA or Western blot,<ref name="Messenger2018"/> has been used as an indicator of early acute and congenital infection.<ref name="Balouz2017">Template:Cite journal</ref> An assay for Template:Nowrap antigens in urine has been developed to diagnose congenital disease.<ref name="Messenger2018"/>
See also
[edit]- Drugs for Neglected Diseases Initiative
- Chagas: Time to Treat campaign
- Association for the Promotion of Independent Disease Control in Developing Countries
References
[edit]External links
[edit]Template:Commons category Template:Offline
- Chagas information at the U.S. Centers for Disease Control
- Chagas information from the Drugs for Neglected Diseases initiative
- Chagas disease information for travellers from the International Association for Medical Assistance to Travellers
Template:Medical condition classification and resources Template:Diseases of Poverty Template:Protozoal diseases Template:Authority control