Chagas disease

Chagas disease, also known as American trypanosomiasis, is a tropical parasitic illness caused by the protozoan Trypanosoma cruzi. It is primarily transmitted to humans through contact with the faeces of infected triatomine bugs, commonly known as “kissing bugs.” The disease is endemic in many parts of Latin America and poses a major public health challenge due to its chronic and often silent progression, which can lead to serious cardiac and digestive complications.

Background and Discovery

Chagas disease was first described in 1909 by Brazilian physician Carlos Ribeiro Justiniano Chagas, after whom the disease is named. He identified both the parasite and its insect vector while studying rural communities in Brazil. Since then, Chagas disease has been recognised as one of the most significant parasitic diseases in the Americas.
The World Health Organization (WHO) classifies it as a neglected tropical disease (NTD) because it primarily affects poor, rural populations with limited access to healthcare. However, due to increased migration and blood transfusion risks, cases have also been reported in North America, Europe, and parts of Asia.

Causative Agent and Transmission

The causative organism, Trypanosoma cruzi, is a flagellated protozoan parasite that exists in two major forms in its life cycle: the trypomastigote (found in human blood) and the amastigote (found inside host cells).
The main vector, the triatomine bug, becomes infected when feeding on the blood of an infected animal or human. The parasite is transmitted to humans when the bug defecates near a bite wound or mucous membrane; scratching the bite site allows the parasite-laden faeces to enter the bloodstream.
Other routes of transmission include:

• Congenital transmission (from mother to child during pregnancy).
• Blood transfusion and organ transplantation from infected donors.
• Consumption of contaminated food or drink containing the parasite.
• Laboratory accidents involving exposure to infected material.

Epidemiology and Distribution

Chagas disease affects approximately 6–7 million people worldwide, with the majority of cases occurring in Latin America. The disease is most prevalent in countries such as Brazil, Argentina, Bolivia, Mexico, and Colombia.
However, due to increasing migration, globalisation, and improved diagnostic techniques, Chagas disease has spread beyond traditional endemic regions. Imported cases have been reported in the United States, Spain, and Italy, leading to concerns about transmission through non-endemic routes like blood transfusions.

Stages and Clinical Manifestations

Chagas disease progresses through two distinct phases — the acute phase and the chronic phase — each with different clinical characteristics.

• Acute Phase (Lasts 6–8 weeks):
  • Occurs shortly after infection.
  • Symptoms are often mild or absent, leading to underdiagnosis.
  • Common signs include fever, fatigue, swollen lymph nodes, headache, and local swelling at the site of the insect bite (known as a chagoma).
  • When infection occurs via the eye, it may cause Romaña’s sign — swelling of one eyelid.
  • Severe acute infection can occasionally result in myocarditis or meningoencephalitis, especially in children.
• Chronic Phase (May last decades):
  • Follows an asymptomatic or indeterminate period that can last for years.
  • Around 20–30% of infected individuals eventually develop chronic complications, mainly involving the heart or digestive system.
  • Cardiac manifestations: Chronic myocarditis, heart failure, arrhythmias, and sudden cardiac death.
  • Digestive manifestations: Enlargement of the oesophagus (megaoesophagus) or colon (megacolon), leading to swallowing difficulties and severe constipation.

Without treatment, chronic Chagas disease can be life-threatening due to progressive organ damage.

Diagnosis

Diagnosis depends on the phase of infection:

• Acute Phase: Detection of T. cruzi parasites in blood samples through microscopic examination or molecular methods such as polymerase chain reaction (PCR).
• Chronic Phase: As parasites are few in number, serological tests (such as ELISA, indirect haemagglutination, or immunofluorescence assays) are used to detect antibodies against T. cruzi.

Screening of blood donors and pregnant women is vital in endemic regions to prevent transmission.

Treatment and Management

Treatment is most effective during the acute phase but can also benefit chronic cases, especially younger patients. Two antiparasitic drugs are currently available:

• Benznidazole
• Nifurtimox

Both drugs kill the parasite and can prevent progression to chronic complications if administered early. Treatment in chronic stages focuses on managing cardiac and digestive symptoms through supportive care, including:

• Pacemaker implantation or antiarrhythmic therapy for cardiac complications.
• Surgical management of severe digestive tract enlargement.

Preventive measures such as blood screening, improved housing conditions, and insect control remain essential to disease management.

Prevention and Control Strategies

Since there is no vaccine for Chagas disease, prevention focuses on vector control and transmission interruption. Major strategies include:

• Insecticide spraying in infested houses to reduce triatomine populations.
• Improving housing conditions, especially replacing thatched roofs and cracked walls where bugs hide.
• Health education campaigns to raise awareness in rural areas.
• Blood screening in endemic and non-endemic countries to prevent transfusion-related transmission.
• Prenatal screening for pregnant women from endemic regions.

Public health programmes in Latin America, such as the Southern Cone Initiative, have successfully reduced vector-borne transmission in several countries.

Global and Public Health Significance

Chagas disease remains a serious public health concern, particularly in rural and marginalised communities. It imposes a heavy socio-economic burden due to its chronic disability and high mortality associated with cardiac complications. The World Health Organization and the Pan American Health Organization continue to promote initiatives aimed at eliminating domestic transmission and expanding access to treatment.
Globalisation has turned Chagas disease from a regional problem into an emerging global health issue. International collaborations now focus on improving diagnostic methods, developing new drugs, and addressing non-vector transmission routes in developed countries.

Research and Future Directions

Recent research in molecular biology, vector ecology, and immunology has improved understanding of T. cruzi biology and pathogenesis. Efforts are underway to:

• Develop new antiparasitic drugs with shorter treatment courses and fewer side effects.
• Explore vaccine candidates that could offer long-term protection.
• Strengthen surveillance systems in non-endemic regions.