Excerpted from the MSF 2005 publication: Lessons Learned: "Chagas disease, an invisible threat in Nicaragua"
What is Chagas disease?
In 1909, the Brazilian doctor Carlos Chagas was the first person to discover a condition that damages the victim's heart, nervous and digestive system. The disease was named after the scientist who devoted his life studying the illness. One fourth of the entire population of Latin America is at risk of contracting Chagas, but no effective medication exists to treat the chronic stages of the disease, which continues to incapacitate and kill people in the middle of their lives.
How is Chagas disease transmitted?
How is Chagas disease transmitted? Chagas is an infectious disease caused by a parasite named Trypanosoma cruzi. It is transmitted by blood-sucking insects, called triatomines (chinches) or kissing bugs. When an infected bug stings, it deposits its faeces on the person's skin. When the person rubs his/her eyes, mouth, or bite wound, the parasite, which is in the bug's faeces, enters the bloodstream. Chagas can also be transmitted by blood transfusion, from mother to child during pregnancy or, less common, through organ transplants or contaminated foods. Clinical examination at the Health Post in Cuje, Municipality of Totogalpa
How does the disease manifest itself?
Chagas disease has two consecutive stages: acute and chronic. The acute stage may become manifest at any age. It begins when the parasite Trypanosoma cruzi enters the body and the bloodstream. In this stage, patients may feel a malaise, fever, shivers, tiredness, and present hepatomegaly and esplenomegaly. When the parasite enters the body through an area near the eyes or the conjunctiva, patients have an edema or swelling of the eyes, which is a characteristic sign of the acute infection (the RomaÃ?±a sign). However, the acute stage may also elapse with no signs or symptoms at all.
After four to eight weeks, these clinical manifestations will disappear and the patient will enter in the chronic indeterminate or "silent" period which cans last 5 to 20 years. Between 20% to 30% of the infected persons will pass on to the chronic phase with clinical manifestations, principally causing cardiac and/or digestive dysfunction.
How do you diagnose Chagas?
The diagnostic procedure for Chagas disease depends on the stage of the illness.
In the acute stage, numerous parasites are appearing in peripheral blood, and it is possible to detect them through parasitological tests: direct observation of the parasite in fresh blood, thick blood film examinations, and parasite concentration tests or the Strout method when the number of parasites in the blood is low.
These lab tests may be done at Health Centers, however, the lab staff requires adequate training for diagnostic procedures during this stage of the Chagas disease.
In the chronic stage, patients infected by T. cruzi create antibodies, or defenses against the parasite, primarily IgG antibodies. Several conventional diagnostic tests exist to detect these antibodies, such as indirect haemoaglutination, the indirect immunofluorescence (IFI) and the ELISA test.
Positive results in more than one of these tests is equal to a definitive diagnostic of the infection. These tests require trained staff, reagents with standardized technical procedures which must be submitted to quality controls and need preservation in appropriate conditions. The ideal serological test would be quick, inexpensive and easy to apply in one single step; would not require special instruments nor reagent refrigeration, and would be one hundred percent sensitive and specific. Such a test does not exist yet.