Friday, March 13, 2009

TC II Strain of Chagas Disease Found in Guatemala

Using a method of identification more precise than those used until now, a group of scientists in Guatemala found a genetic variant of the causative agent of Chagas disease, which until now was believed to be found only in South America.

According to the article published in the February issue of the American Journal of Tropical Medicine and Hygiene, Trypanosoma cruzi (T. cruzi), the causative agent of this parasitic disease is divided into two genetically and biologically different lineages: T . cruzi I (TCI) and T. cruzi II (TCII). Until now it was known that the TCI was in both domestic and wild environments of South America and Central America, but it was believed that TCII only occurred in South America.

However, scientists at the Center for Health Studies at the Universidad del Valle in Guatemala felt that the lack of detection of TCII might be a limitation of the screening tests used so far. To confirm this hypothesis, the researchers collected samples of Triatoma dimidiata, the main vector of Chagas disease in Central America, commonly called chinches or chinch bugs, from houses in five departments where the disease is considered endemic.

These samples underwent a genetic analysis by polymerase chain reaction (PCR), which amplifies a copy of a gene billions of times and identifies the gene by electrophoresis. The researchers found that 84 percent of the sample bugs tested carried both lineages of the parasite.

Pamela Pennington, leader of the study, said that finding the genetic markers for both TCI and TCII raises another research question since the two strains show different sensitivities to drugs. It will be interesting to see whether the strains in Guatemala have more or less drug resistance than those found elsewhere.

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