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Pathogen Page

Trypanosoma cruzi

I. General Information

1. NCBI Taxonomy ID:

2. Disease:

Chagas disease

3. Introduction

Chagas disease is a chronic, systemic, parasitic infection caused by the protozoan Trypanosoma cruzi, and was discovered in 1909. The disease affects about 8 million people in Latin America, of whom 30-40% either have or will develop cardiomyopathy, digestive megasyndromes, or both. In the past three decades, the control and management of Chagas disease has undergone several improvements. Large-scale vector control programmes and screening of blood donors have reduced disease incidence and prevalence. Although more effective trypanocidal drugs are needed, treatment with benznidazole (or nifurtimox) is reasonably safe and effective, and is now recommended for a widened range of patients. Improved models for risk stratification are available, and certain guided treatments could halt or reverse disease progression (Rassi et al., 2010).

4. Microbial Pathogenesis

Organ and tissue damage during acute T cruzi infection is caused by the parasite itself and by the host's acute immunoinflammatory response, which is elicited by the presence of the parasite. Findings from several studies in experimental models of T cruzi infection have suggested that a strong T-helper-1 immune response with both CD4 and CD8 cells, and characterised by the production of some specific cytokines—such as interferon γ, tumour necrosis factor α, and interleukin 12—is important in the control of parasitism. By comparison, production of interleukin 10 and transforming growth factor β is related to parasite replication by inhibition of macrophage trypanocidal activity. The T-helper-1 immune response has a protective role mainly through the synthesis of nitric oxide, which exerts a potent trypanocidal action. During chronic infection, the balance between immune-mediated parasite containment and damaging inflammation of the host tissues probably determines the course of disease. If the immunological response is inefficient, or paradoxically leads to tissue damage, both parasite load and immune-mediated inflammation increase. By contrast, a well executed immune response, in which parasite burden is lowered and inflammatory consequences are kept to a minimum, results in reduced tissue damage (Rassi et al., 2010).

5. Host Ranges and Animal Models

Chagas disease is transmitted to human beings and to more than 150 species of domestic animals (eg, dogs, cats, and guineapigs) and wild mammals (eg, rodents, marsupials, and armadillos) mainly by large, blood-sucking reduviid bugs of the subfamily Triatominae, within three overlapping cycles: domestic, peridomestic, and sylvatic. Although more than 130 species of triatomine bugs have been identified, only a handful are competent vectors for T cruzi. Triatoma infestans, Rhodnius prolixus, and Triatoma dimidiata are the three most important vector species in the transmission of T cruzi to man (Rassi et al., 2010).

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