All about Chagas disease

Trypanosoma cruzi is a member of the same genus as the infectious agent of African sleeping sickness, but its clinical manifestations, geographical distribution, life cycle and insect vectors are quite different.

The disease was named after the Brazilian physician and infectologist Carlos Chagas, who first described it in 1909, but the disease was not seen as a major public health problem in humans until the 1960s. He discovered that the intestines of Triatomidae harbored a flagellate protozoan, a new species of the Trypanosoma genus, and was able to prove experimentally that it could be transmitted to marmoset monkeys that were bitten by the infected bug.

Chagas named the pathogenic parasite that causes the disease Schizotrypanum cruzi (later renamed to Trypanosoma cruzi), after Oswaldo Cruz, the noted Brazilian physician and epidemiologist who fought successfully epidemics of yellow fever, smallpox, and bubonic plague in Rio de Janeiro and other cities in the beginning of the 20th century. Chagas’ work is unique in the history of medicine because he was the only researcher so far to describe completely a new infectious disease: its pathogen, vector, host, clinical manifestations, and epidemiology. Nevertheless, he at least believed falsely until 1925, that the main infection route is by the bite of the insect - and not by its feces, as was proposed by his colleague Emile Brumpt 1915 and assured by Silveira Dias 1932, Cardoso 1938 and Brumpt himself 1939.

On another historical point of view, it has been hypothesized that Charles Darwin might have suffered from this disease as a result of a bite of the so-called Great Black Bug of the Pampas (vinchuca) (see Charles Darwin's illness). The episode was reported by Darwin in his diaries of the Voyage of the Beagle as occurring in March 1835 to the east of the Andes near Mendoza. Darwin was young and in general good health though six months previously he had been ill for a month near Valparaiso, but in 1837, almost a year after he returned to England, he began to suffer intermittently from a strange group of symptoms, becoming incapacitated for much of the rest of his life. Attempts to test Darwin's remains at the Westminster Abbey by using modern PCR techniques were met with a refusal by the Abbey's curator.

Medication for Chagas disease is usually only effective when given during the acute stage of infection. The drugs of choice are azole or nitroderivatives such as benznidazole[15] or nifurtimox (under an Investigational New Drug protocol from the CDC Drug Service), but resistance to these drugs has already been reported. Furthermore, these agents are very toxic and have many adverse effects, and cannot be taken without medical supervision. The antifungal agent Amphotericin B has been proposed as a second-line drug, but cost and this drug's relatively high toxicity have limited its use. Moreover, 10-year study of chronic administration of drugs in Brazil has revealed that current chemotherapy does not totally remove parasitemia. Thus, the decision about whether to use antiparasitic therapy should be individualized in consultation with an expert.

In the chronic stage, treatment involves managing the clinical manifestations of the disease, e.g., drugs and heart pacemaker for chronic heart failure and heart arryhthmias; surgery for megaintestine, etc., but the disease per se is not curable in this phase. Chronic heart disease caused by Chagas is now a common reason for heart transplantation surgery. Until recently, however, Chagas disease was considered a contraindication for the procedure, since the heart damage could recur as the parasite was expected to seize the opportunity provided by the immunosuppression that follows surgery. The research that changed the indication of the transplant procedure for Chagas disease patients was conducted by Dr. Adib Jatene's group at the Heart Institute of the University of São Paulo, in São Paulo, Brazil. The research noted that survival rates in Chagas patients can be significantly improved by using lower dosages of the immunosuppressant drug cyclosporin. Recently, direct stem cell therapy of the heart muscle using bone marrow cell transplantation has been shown to dramatically reduce risks of heart failure in Chagas patients. Patients have also been shown to benefit from the strict prevention of reinfection, though the reason for this is not yet clearly understood.