What is ... Chagas disease?
Chagas disease, also known as American trypanosomiasis, is a potentially life-threatening illness caused by the protozoan parasite Trypanosoma cruzi.
Please find more information on this disease in the text below or watch expert interview:
What is the disease?
How dangerous is Chagas disease?
If untreated infection with Chagas disease is lifelong, can cause severe organ damage and is then life-threatening.
Who is at risk?
In endemic countries (see below), people living in rural areas are at greatest risk for acquiring infection.
Infection acquired from blood products, organ transplantation, or congenital transmission from infected mother to her newborn continues to pose a major threat.
How many people are affected by Chagas disease?
About 6 to 8 million people worldwide are estimated to be infected with Trypanosoma cruzi, the parasite that causes Chagas disease. Due to the lack of disease-specific symptoms, most of them do not know about their infection until many years later when serious organ symptoms occur.
Where is Chagas disease found?
Chagas disease is found mainly in endemic areas of 21 Latin American countries. Because of large-scale population movements from rural to urban areas and migration to other regions of the world, Chagas disease has been increasingly detected in the cities of Latin America, and previously non-endemic countries like the United States of America, Canada, many European and some Western Pacific countries.
How do people get Chagas disease?
Chagas disease is not transmitted from person-to-person but mainly through vector-borne transmission. The insect vectors are called triatomine bugs. After they bite and ingest blood, they defecate on the person. The person can become infected if Trypanosoma cruzi parasites in the bug feces enter the body through mucous membranes or breaks in the skin. The unsuspecting, sleeping person may accidentally scratch or rub the feces into the bite wound, eyes, or mouth.
People also can become infected through:
- congenital transmission from an infected pregnant woman to her baby
- blood transfusion
- organ transplantation
- consumption of uncooked food contaminated with feces from infected bugs
- accidental laboratory exposure
SYMPTOMS AND COURSE
What are the signs and symptoms of Chagas disease?
The most recognizable symptom 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.
Other, rather non-specific symptoms during the acute phase (see below) noted by less than 50 percent of the patients can include:
- body aches
The signs on physical examination can include:
- mild enlargement of the liver or spleen
- swollen glands
- local swelling called chagoma where the parasite entered the body
During the chronic phase (see below) up to 30 percent of patients develop:
cardiac complications, which can include an enlarged heart called cardiomyopathy, heart failure, altered heart rate or rhythm, and cardiac arrest
- intestinal complications, which can include an enlarged esophagus or colon and can lead to difficulties with eating or with passing stool
How is the disease developing?
There are two phases of Chagas disease: the acute phase and the chronic phase. Both phases can be symptom free or reveal heart and gastro-intestinal symptoms which can become life threatening.
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 and signs that are not specific to Chagas disease.
Even if symptoms develop during the acute phase, they usually fade away on their own, within a few weeks or months. Although the symptoms resolve, if untreated the infection persists.
Up to five percent of young children die from severe inflammation/infection of the heart muscle called myocarditis or brain called meningoencephalitis.
The acute phase also can be severe in people with weakened immune systems.
During the chronic phase, the infection may remain silent for decades or even for life.
DIAGNOSIS AND TREATMENT
How is Chagas disease diagnosed?
Chagas disease is diagnosed by blood tests. If you are found to have Chagas disease, you should have an electrocardiogram, even if you feel fine. You might be referred to a specialist for more tests and for treatment.
How is Chagas disease treated?
Treatment is most effective early in the course of infection but is not limited to cases in the acute phase. Most people do not need to be hospitalized during treatment.
To kill the parasite, Chagas disease can be treated with one of the two available drugs, benznidazole and nifurtimox. Both drugs are on the WHO List of Essential Medicines.
Both medicines are almost 100 percent effective in curing the disease if given soon after infection at the onset of the acute phase. However, the efficacy of both diminishes, the longer a person has been infected.
Infected adults, especially those with no symptoms, should be offered anti-parasitic treatment which can prevent or curb disease progression and prevent congenital transmission in pregnant women.
In those cases the potential benefits of medication in preventing or delaying the development of Chagas disease should be weighed against the long duration of treatment of up to two months and possible adverse reactions that occur in up to 40 percent of treated patients.
Benznidazole and nifurtimox should not be taken by pregnant women or by people with kidney or liver failure.
Nifurtimox is also contraindicated for people with a background of neurological or psychiatric disorders.
Additionally, specific treatment for cardiac or digestive manifestations may be required.
PREVENTION, CONTROL AND EDUCATION
How can I prevent infection?
As a resident of an endemic area you can
- improve your house and its cleanliness to prevent vector infestation
- seal cracks and gaps around windows, walls, roofs, and doors
- remove wood, brush, and rock piles near your house
- use screens on doors and windows and repair holes or tears
- make sure yard lights are not close to your house, they can attract the bugs
- seal holes and cracks leading to the attic, crawl spaces below the house and to the outside
- do not have pets sleep indoors, especially at night
- use bednets treated with long-lasting insecticides
- follow good hygiene practices in food preparation, transportation, storage and consumption
- ask authorities to send a vector control team to spray the house and surrounding areas with residual insecticides
- periodically check for the presence of bugs
As a traveler you are at low risk as long as you
- sleep indoors in well-constructed facilities like air-conditioned or screened hotel rooms
- wear protective long-sleeved clothing and apply insect repellent to exposed skin
- follow good hygiene practices in food preparation, transportation, storage and consumption
The basic situation:
- There are no drugs or vaccines for preventing an infection with Chagas disease
- Eradication of the vector is impossible due to the large reservoir of T. cruzi parasites in wild animals of the Americas
- Nevertheless vector control is the most effective method of prevention in Latin America
- Blood screening is necessary to prevent infection through transfusion and organ transplantation
- Screening of newborns and other children of infected mothers is mandatory to provide early diagnosis and treatment
TRANSMISSION, VECTOR AND VECTOR CONTROL
How is Chagas disease transmitted?
Chagas disease is transmitted by a vector, a living organism that transfers the pathogen from one infected human or animal to another. This vector is a nocturnal blood-sucking bug named Triatoma infestans exclusive to Latin America.
What exactly does the vector do?
The vectors are found in houses made from materials such as mud, adobe, straw, and palm thatch. During the day, they hide in crevices in the walls and roofs. During the night, when the inhabitants are sleeping, the bugs emerge. Because they tend to feed on people’s faces, triatomine bugs are also known as “kissing bugs”.
The bugs bite humans, mammals, reptiles and birds. They do it usually unnoticed in areas of the body where the skin is thinner. The bugs then suck blood and defecate. The person can become infected if Trypanosoma cruzi parasites in the bug feces enter the body through mucous membranes or breaks in the skin. The unsuspecting, sleeping person may accidentally scratch or rub the feces into the bite wound, eyes, or mouth
The bugs themselves get infected by biting an infected animal or infected person. Once infected, the bugs pass Trypanosoma cruzi parasites in their feces.
How can the vector be controlled?
Vector control started in the 1940s when the first organochlorine insecticides were developed. Although DTT was quickly found to be ineffective against most triatomine bugs, two other compounds, lindane and dieldrin were highly effective in killing the vector when sprayed over house walls.
The introduction of synthetic pyrethroid insecticides e.g. deltamethrin and cyfluthrin (both used in many Bayer products) in the early 1980s was a major advance in the control of domestic triatomines as they are more cost-effective and leave no unpleasant smell and marks on the treated walls.
Are there other means to fight the parasite?
In 1953 it was discovered that the dye crystal violet (aka Gentian Violet) kills T. cruzi in blood preservations. Since then the dye has been widely employed in blood banks in endemic areas to eliminate the parasite from blood used for transfusion.
What Challenges do we face with Chagas?
What are the difficulties and challenges in fighting Chagas disease?
- maintaining and consolidating advances made in disease control
- enhancing access to diagnosis and treatment for millions of infected people with special focus on children and women of child-bearing age.
- developing better diagnostics, medication with less side effects es-pecially for children and a vaccine to prevent infection
- increasing awareness of the disease among both the vulnerable pop-ulation and all decision-makers who have an impact on the elimina-tion of the disease
- overcoming the myths that chronic Chagas disease cannot be treated with current drugs and that transmission has been largely eliminated
- underfunding of vector control and decentralization of facilities and manpower
- spread of the disease due to increasing population mobility between Latin America and the rest of the world
- emergence of Chagas disease in regions previously considered to be free of the disease – such as the Amazon basin
- persistence in regions where control had been in progress, such as the Chaco region of Argentina, Paraguay and the Plurinational State of Bolivia
- overcoming the stigmatization of Chagas as a disease of poverty and the shame of going into treatment
INITIATIVES AND PARTNERS
What programs exist against Chagas disease?
Since the 1990s there have been important successes in parasite and vector control in Latin America. Multinational initiatives conducted by the WHO led to substantial reductions in intra-domiciliary transmission.
Over the last years, additionally, the risk of transmission by blood transfusion has been extremely reduced through the universal screening in all blood banks of the Latin American countries and most European and Western Pacific countries with the disease.
These advances have been possible because of the strong commitment of Member States affected by the disease and the strength of their research and control organizations, together with support from many international partners like governmental and non-governmental organizations, foundations and pharmaceutical companies.
Furthermore many of the affected countries have National Chagas Programs to educate the population. These provide information about the disease, its treatment and prevention through printed materials, radio and TV programs, educational materials, and mobile education teams that educate people on the ground.
What does Bayer contribute to the fight against Chagas disease?
Bayer has developed one of the two available medicines that are effective to treat Chagas disease.
It contains the active ingredient Nifurtimox, which is on the WHO List of Essential Medicines and had first been granted a license for treating Chagas disease under the trade name Lampit in 1967. Production was halted in 1997 due to insufficient demand but resumed again in 2000 in consultation with the WHO.
Since then Bayer has been supporting the WHO meeting an increasing annual demand. In 2017 Bayer donated 1.5 million tablets Lampit containing 120 mg of Nifurtimox.
This tablet strength is suitable for dosage regimens used in adults, but is too high for weight-adjusted dosing for babies and young children. That’s why, Bayer is currently developing a new formulation of Nifurtimox suitable for these pediatric patients and performed a large clinical study in children to generate safety and efficacy data in children 0-<18 years of age
This pediatric formulation will contain only 30 milligrams of Nifurtimox, and the new tablet will have a score line on it, so that it can be split exactly in half, making it possible to reduce the dose to only 15 milligrams when necessary. Furthermore, the new tablet will dissolve well in a little liquid, which will enable mothers to administer the drug to babies with their milk, or to children under the age of six with their food, since they can't swallow tablets.
However it is expected, that the new pediatric formulation will come to the market not earlier than 2020.
What is the societal burden of Chagas disease?
In 2013 a group of scientists funded by the Bill & Melinda Gates Foundation developed a Markov simulation model to estimate the global and regional health and economic burden of Chagas disease from the societal perspective.
Their Markov model structure had a 1 year cycle length and consisted of five states: acute disease, indeterminate disease, cardiomyopathy with or without congestive heart failure, megaviscera, and death.
Major model parameter inputs, including the annual probabilities of transitioning from one state to another, and present case estimates for Chagas disease came from various sources, including WHO and other epidemiological and disease-surveillance-based reports.
The scientists calculated annual and lifetime health-care costs and disability-adjusted life-years (DALYs) for individuals, countries, and regions. They used a discount rate of 3% to adjust all costs and DALYs to present-day values.
What are their findings?
On average, an infected individual incurs US $474 in health-care costs and 0.51 DALYs annually. Over his or her lifetime, an infected individual accrues an average net present value of $3456 and 3.57 DALYs.
Globally, the annual burden is $627.46 million in health-care costs and 806 170 DALYs. The global net present value of currently infected individuals is $24.73 billion in health-care costs and 29 385 250 DALYs. Conversion of this burden into costs results in annual per-person costs of $4660 and lifetime per-person costs of $27 684. Global costs are $7.19 billion per year and $188.80 billion per lifetime.
More than 10% of these costs emanate from the USA and Canada, where Chagas disease has not been traditionally endemic. A substantial proportion of the burden emerges from lost productivity from cardiovascular disease-induced early mortality.
What is their interpretation of their findings?
The economic burden of Chagas disease is similar to or exceeds those of other prominent diseases globally (eg, rotavirus $2.0 billion, cervical cancer $4.7 billion) even in the USA (Lyme disease $2.5 billion), where Chagas disease has not been traditionally endemic, suggesting an economic argument for more attention and efforts towards control of Chagas disease.
How did the history of the disease proceed?
- Chagas disease has infected humans for an estimated 11,000 years as signs of the disease has been discovered in mummies across the Americas
- in 1909 Carlos Ribeiro Justiniano Chagas, a Brazilian physician and researcher after whom the disease was later named, was the first to describe the disease.
Chagas succeeded in describing the complete mechanism of the disease: causative pathogen, vector, host, clinical manifestation and epidemiology. But he was wrong when he identified the bite of the blood-sucking bug Triatoma infestans itself as the main source of infection.
It was instead the French parasitologist Emile Brumpt who rightly observed that the transmission occurs when the insect’s feces contaminated with the pathogen Trypanosoma cruzi are rubbed into the wound or undamaged mucous membranes.
- in 1969 the disease was correctly described in its entirety by the British parasitologist Ralph Lainson – and it was also only then that Chagas was finally recognized as a major epidemiological problem.
- 7-10 million years ago, the ancestor of Trypanosoma cruzi was probably introduced to South American via bats approximately. When the first humans arrived in the New World, a sylvatic cycle of Chagas disease was then already well established.
Paleoparasitological data suggests that human American trypanosomiasis originated in the Andean area when people founded the first settlements in the coastal region of the Atacama Desert. Human activity leading to environmental changes, in particular deforestation, seems to be the main cause for the spread of Chagas disease.
- in the first few decades of the last century the sections of the population most affected were concentrated in the rural communities of Latin America where the vector occurred. This area stretches from the southern United States to the south of Argentina and Chile, across all of the South American continent. Over decades, migration towards the cities has resulted in many people moving to live in areas without risk of vectorial transmission, yet still in need of treatment for their previously acquired infection.
Additionally political repression and/or economic stagnation stimulated the flow of migration of T. cruzi-infected patients from the 17 Latin American countries endemic for Chagas disease to non-endemic countries and has led to a distribution of Chagas disease in Europe, North America and western Pacific region causing the disease to become a global health problem.