Tehran University of Medical Sciences Iranian Journal of Parasitology 1735-7020 11 3 2016 12 21 389 395 Fabiana Nabarro FERRAZ Dept. of Basic Health Sciences, Sector of Parasitology, State University of Maringa, Maringa, Brazil Denise Lessa ALEIXO Dept. of Basic Health Sciences, Sector of Parasitology, State University of Maringa, Maringa, Brazil Ana Paula GRUENDLING Dept. of Basic Health Sciences, Sector of Parasitology, State University of Maringa, Maringa, Brazil Mônica Lúcia GOMES Dept. of Basic Health Sciences, Sector of Parasitology, State University of Maringa, Maringa, Brazil Max Jean de Ornelas TOLEDO Dept. of Basic Health Sciences, Sector of Parasitology, State University of Maringa, Maringa, Brazil Silvana Marques DE ARAÚJO Dept. of Basic Health Sciences, Sector of Parasitology, State University of Maringa, Maringa, Brazil 2016 09 28 2016 09 28 Background: The study evaluated qualitative PCR, primers 121-122 as a tool to follow up evolution parasite load of Trypanosoma cruzi. Methods: The study was conducted at the State University of Maringa, in 2015. Step 1, dilutions 1/10 were performed from T. cruzi-Y strain to obtain preparations of 50,000-0.05 parasites/mL from which DNA were extracted, quantified, and amplified. Step 2, the extracted DNA in the dilutions 5-0.05 parasites/mL was re-diluted 1/10, 1/100, 1/1000, quantified, and amplified. Polyacrylamide gels were photographed and thicknesses of the 330 bp kDNA fragments were measured. Results: Step 1, in the dilutions 50,000-50 parasites/mL kDNA fragments had same thickness and, dilutions 5-0.05 parasites/mL showed progressive decrease in thicknesses and staining intensity of the 330 bp fragments. Step 2, demonstrated that dilutions of five (re-dilutions 1/10 and 1/100) and 0.5 (1/10) parasites/mL produced similar thicknesses of the 330 bp fragments obtained in Step 1. However, very dilute DNA samples make difficult to reproduce the fragments thicknesses. Conclusion: PCR, despite its limitations, was able to detect progressive decrease in thicknesses/staining intensity of kDNA fragments in the dilutions 5-0.05 parasites/mL. Hence, has the potential to be used to follow-up evolution of parasite load, not by quantifying the number of parasites, but by dynamic evolution of the fragments thicknesses during etiological treatment. https://ijpa.tums.ac.ir/index.php/ijpa/article/view/1219 https://ijpa.tums.ac.ir/index.php/ijpa/article/download/1219/720