First World Chagas Disease Day: 14 April 2020

World Chagas Disease Day will be celebrated for the first time on 14 April 2020.

Background Information:

Chagas disease, also known as American trypanosomiasis, is a potentially life-threatening illness caused by the protozoan parasite Trypanosoma cruzi (T. cruzi).

Chagas disease is named after Carlos Ribeiro Justiniano Chagas, a Brazilian physician and researcher who discovered the disease in 1909. In May 2019, following up on decision of the 72 World Health Assembly, the World Chagas Disease Day was established to be celebrated on 14 April (the date of the year 1909 when Carlos Chagas diagnosed the first human case of the disease, a two-year old girl called Berenice).

Key Messages:

About 6 million to 7 million people worldwide, mostly in Latin America, are estimated to be infected with Trypansosoma cruzi, the parasite that causes Chagas disease.

Geographical Distribution:

Chagas disease was once entirely confined to the Region of the Americas – but in the last decades, due to population movements, most infected people live in urban settings (urbanization) and the disease has spread to the United States of America, Canada, and many European and some African, Eastern Mediterranean and Western Pacific countries.

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Transmission:

The main route of transmission (vector-borne transmission) has occurred in Latin America through the insect called triatomine bug, which can carry the Trypanosoma cruzi parasite. Infections are mainly transmitted by contact with faeces/urine of infected blood-sucking triatomine bugs. These bugs, vectors that carry the parasites, typically live in the wall or roof cracks of homes and peridomiciliary structures, such as chicken coops, pens and warehouses, in rural or suburban areas.

Normally they hide during the day and become active at night when they feed on mammalian blood, including human blood. They usually bite an exposed area of skin such as the face (hence its common name ‘kissing bug’), and the bug defecates or urinates close to the bite. The parasites enter the body when the person instinctively smears the bug faeces or urine into the bite, the eyes, the mouth, or into any skin break.

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Other routes of transmission include:

  • oral (food-borne) transmission,
  • blood/blood products transfusion,
  • mother-to-child (congenital) and
  • organ transplantation transmissions or even
  • laboratory accident transmission.

Symptoms and Signs:

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Chagas disease presents itself in 2 phases.

The initial acute phase lasts for about 2 months after infection. During the acute phase, a high number of parasites circulate in the blood but in most cases, symptoms are absent or mild and unspecific. In less than 50% of people bitten by a triatomine bug, characteristic first visible signs can be a skin lesion or a purplish swelling of the lids of one eye. Additionally, they can present fever, headache, enlarged lymph glands, pallor, muscle pain, difficulty in breathing, swelling, and abdominal or chest pain.

During the chronic phase, the parasites are hidden mainly in the heart and digestive muscles. Up to 30% of patients suffer from cardiac disorders and up to 10% suffer from digestive (typically enlargement of the oesophagus or colon), neurological or mixed alterations. In later years the infection can lead to sudden death due to cardiac arrhythmias or progressive heart failure caused by the destruction of the heart muscle and its nervous system.

In chronic patients, antiparasitic treatment can potentially prevent or curb disease progression and prevent tranmission, for instance, mother-to-child infection.

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Treatment:

To kill the parasite, Chagas disease can be treated with benznidazole and also nifurtimox. Both medicines are nearly 100% effective in curing the disease if given soon after infection at the onset of the acute phase including the cases of congenital transmission. The efficacy of both diminishes, however, the longer a person has been infected and the adverse reactions are more frequent at older age.

Treatment is also indicated for

  • those in whom the infection has been reactivated (for example, due to immunosuppression),
  • patients during the early chronic phase.

Infected adults, especially those with no symptoms, should be offered treatment because antiparasitic treatment can also prevent or curb disease progression and prevent congenital transmission in pregnant women.

In other cases the potential benefits of medication in preventing or delaying the development of Chagas disease should be weighed against the duration of treatment (up to 2 months) and possible adverse reactions (occurring in up to 40% of treated adult 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 or neurological manifestations may be required.

Prevention and Control:

Vector control is the most useful method to prevent Chagas disease in Latin America.

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Depending on the geographical area, WHO recommends the following approaches to prevention and control:

  • spraying of houses and surrounding areas with residual insecticides;
  • house improvements and house cleanliness to prevent vector infestation;
  • personal preventive measures such as bednets;
  • good hygiene practices in food preparation, transportation, storage and consumption;
  • screening of blood donors;
  • testing of organ, tissue or cell donors and receivers;
  • access to diagnosis and treatment of people with medical indication or recommendation to do antiparasitic treatment, especially children and women of child-bearing age before pregnancy; and
  • screening of newborns and other children of infected mothers without previous antiparasitic treatment to do early diagnosis and provide treatment.

The medical care cost of patients with chronic cardiac, digestive, neurologic or mixed forms of the disease has been calculated to be >80% higher than the cost of spraying residual insecticide to control vectors and prevent infection.

Blood screening is vital to prevent infection through transfusion and organ transplantation.

Detection and treatment of girls and women of child-bearing with infection is essential, together with the screening of newborns and siblings of infected mothers without previous antiparasitic treatment.

Useful Links:

Link to the WHO news release:

https://www.who.int/news-room/events/detail/2020/04/14/default-calendar/celebrating-world-chagas-disease-day-for-the-first-time-in-2020

Link to WHO fact sheet on Chagas Disease (updated 11 March 2020):

https://www.who.int/news-room/fact-sheets/detail/chagas-disease-(american-trypanosomiasis)

Link to WHO Question and Answer page on Chagas Disease:

https://www.who.int/news-room/q-a-detail/q-a-on-chagas-disease

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