Chagas
Causative agents
Chagas disease is caused by the trypanosome Trypanosoma cruzi. It is spread by the kissing bug vector. The acute phase is often asymptomatic. In some cases symptoms do not appear for many years after infection. Death from the disease is most often caused by damage to the heart. In some areas, the true statistics of this disease may be hidden behind heart disease statistics.[1]
Statistics
Chagas disease is endemic to 18 countries in the Americas, ranging from Mexico to Argentina, with around 25 million people at risk. It is estimated that each year there are 750,000 new cases and 14,000 deaths from the disease.[2] In Brazil, approximately 1 in 756 mothers are seropositive for Chagas disease.[3] In Paraguay, that number rises to 1 in 10.[4] Other parts of Latin America experience infection rates greater than 1 in every 2 people.[5] Nearly 10% of pregnant women with positive serology for T. cruzi transmit the parasite to their fetus.[6]
Modes of Transmission
In addition to transmission through the insect vector, T. cruzi has been documented to be transmitted through blood transfusion,[6] crossing the mother’s placenta to infect the fetus (this form of transmission was correlated with high parasitemia),[7] ingestion (ie of vector contaminated fruit juices),[8]organ transplants,[9] and on rare occasions through breast feeding[10].
Methods of diagnosis
Trypanosomatid parasites can be as numerous as 10,000/mL or can be less than 100/mL (well below the detection limit for blood smear).[11] Common methods of diagnosis for Chagas disease include serology, hemocultures, xenodiagnosis and blood smears. While serology is the current standard for diagnosis of T. cruzi infection, numerous reports have shown that PCR detects T. cruzi DNA in seronegative individuals.[12-16]
Annotated Bibliography
1. Leiby, D.A., M.H. Fucci, and R.J. Stumpf, Trypanosoma cruzi in a low- to moderate-risk blood donor population: seroprevalence and possible congenital transmission. Transfusion, 1999. 39(3): p. 310-5.
2. Anonymous, BVGH Global Health Primer. 2007, Bio Ventures for Global Health: Washington DC.
3. Neto, E.C., et al., Newborn screening for congenital infectious diseases. Emerg Infect Dis, 2004. 10(6): p. 1068-73.
4. Russomando, G., et al., Treatment of congenital Chagas' disease diagnosed and followed up by the polymerase chain reaction. Am J Trop Med Hyg, 1998. 59(3): p. 487-91.
5. Basombrio, M.A., et al., [The transmission de Chagas disease in Salta and the detection of congenital cases]. Medicina (B Aires), 1999. 59 Suppl 2: p. 143-6.
6. Wendel, S. and A.L. Gonzaga, Chagas' disease and blood transfusion: a New World problem? Vox Sang, 1993. 64(1): p. 1-12.
7. Hermann, E., et al., Congenital transmission of Trypanosoma cruzi is associated with maternal enhanced parasitemia and decreased production of interferon- gamma in response to parasite antigens. J Infect Dis, 2004. 189(7): p. 1274-81.
8. da Silva Valente, S.A., V. de Costa Valente, and H.F. Neto, Considerations on the epidemiology and transmission of Chagas disease in the Brazilian Amazon. Mem Inst Oswaldo Cruz, 1999. 94 Suppl 1: p. 395-8.
9. Barcan, L., et al., Transmission of T. cruzi infection via liver transplantation to a nonreactive recipient for Chagas' disease. Liver Transpl, 2005. 11(9): p. 1112-6.
10. Ferreira, C.S., et al., Pasteurization of human milk to prevent transmission of Chagas disease. Rev Inst Med Trop Sao Paulo, 2001. 43(3): p. 161-2.
11. Mugasa, C.M., et al., Detection of Trypanosoma brucei parasites in blood samples using real-time nucleic acid sequence-based amplification. Diagn Microbiol Infect Dis, 2008. 61(4): p. 440-5.
12. Salomone, O.A., et al., Trypanosoma cruzi in persons without serologic evidence of disease, Argentina. Emerg Infect Dis, 2003. 9(12): p. 1558-62.
13. Wincker, P., et al., High correlation between Chagas' disease serology and PCR-based detection of Trypanosoma cruzi kinetoplast DNA in Bolivian children living in an endemic area. FEMS Microbiol Lett, 1994. 124(3): p. 419-23.
14. Wincker, P., et al., PCR-based diagnosis for Chagas' disease in Bolivian children living in an active transmission area: comparison with conventional serological and parasitological diagnosis. Parasitology, 1997. 114 ( Pt 4): p. 367-73.
15. Avila, H.A., et al., Detection of Trypanosoma cruzi in blood specimens of chronic chagasic patients by polymerase chain reaction amplification of kinetoplast minicircle DNA: comparison with serology and xenodiagnosis. J Clin Microbiol, 1993. 31(9): p. 2421-6.
16. Gomes, M.L., et al., Chagas' disease diagnosis: comparative analysis of parasitologic, molecular, and serologic methods. Am J Trop Med Hyg, 1999. 60(2): p. 205-10.
Items of Interest
International Products
Cooperative Diagnostics provides a variety of real-time PCR tests for infectious diseases around the world. Follow the links below to access resources for international products:
