Chagas disease.In this study, investigators reconstructed the behavior of Chagas disease Cha·gas disease or Cha·gas-Cruz disease n. See South American trypanosomiasis. (American trypanosomiasis American trypanosomiasis a disease of humans caused by Trypanosoma cruzi in which many animal species can act as carriers. The disease in dogs includes anemia, debility and splenomegaly; in cats there are posterior paralysis and convulsions. ) in the Atacama Desert over the past 9,000 years. The researchers analyzed ancient DNA to identify kinetoplast kinetoplast /ki·ne·to·plast/ (ki-net´o-plast) a structure associated with the basal body in many protozoa, primarily the Mastigophora; it is rich in DNA and, like the basal body, it replicates independently. DNA DNA: see nucleic acid. DNA or deoxyribonucleic acid One of two types of nucleic acid (the other is RNA); a complex organic compound found in all living cells and many viruses. It is the chemical substance of genes. of Trypanosoma cruzi Trypanosoma cru·zi n. A protozoan that is the causative agent of South American trypanosomiasis. , the disease's infectious agent transmitted by the insect vector, a triatomid bug. Specimens analyzed were from muscle and visceral tissues in excavated, naturally mummified mum·mi·fy v. mum·mi·fied, mum·mi·fy·ing, mum·mi·fies v.tr. 1. To make into a mummy by embalming and drying. 2. To cause to shrivel and dry up. v.intr. human bodies buried in that hyperarid desert during the past 9 millennia. Results indicated that 41% of these bodies were infected by T. cruzi at the time of death. Among the 11 represented populations, no statistically significant differences in prevalence rates could be demonstrated when studied by the time period, sex, or age, except for lower rates (28%) for infants. Such prevalence rates are similar to those of modern T. cruzi-endemic areas. These results demonstrated the well-established presence of Chagas disease in this region among wild forest animals when the first humans (the Chinchorro) arrived. By settling this region, the new arrivals initially and inadvertently exposed themselves to the triatomid bug transmitting this disease, and joined the wild animals as part of the disease's reservoir. At some undetermined time during this 9,000-year interval, a few of the vector species became adapted to the thatched roof and other features of the region's human dwellings and initiated the independent domestic cycle involving only humans and their domesticated animals. The study also suggests that, given available specimens, the history of other infectious diseases can be similarly reconstructed. Aufderheide AC, Salo W, Madden M, Streitz J, Buikstra J, Guhl F, et al. A 9,000-year record of Chagas' disease. Proc Natl Acad Sci U S A. 2004;101:2034-9. Epub 2004 Feb 06. |
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