Giardia duodenalis imago and cystis (public domain - Centers for Disease Control and Prevention - CDC PHIL #3394)
These "happy" parasites are not as nice guys as they seem! Giardia duodenalis causes giardiasis, which affects millions of humans and many domestic and wild mammals. To discover contamination sources as food or water, high resolution genetic markers are valuable tools because they allow researchers, sanitation companies and diagnostic institutions to carry out fine-scale population genetics-based epidemiological studies. In a recently published paper, Mauricio Durigan (a former colleague at State University of Campinas, now an US Food and Drug Administration researcher - and a great friend) led a group of Brazilian researchers to develop these molecular tools.