Blood flukes (Schistosomes) are parasitic flatworms that cause disease in millions of people worldwide, mostly in the tropics. As part of their life cycle, newly-hatched flukes infect freshwater snails. Inside a snail’s body, the parasites grow and reproduce asexually to generate thousands of infectious progeny (the bright yellow dots in the image) in just a few weeks. Once the progeny are released from the snails, they can infect humans and other mammals that contact the water. In humans, flukes live for years in the blood capillaries, laying thousands of eggs each day, which are then released in the urine or feces. The eggs hatch on contact with water, starting a new life cycle. The eggs may also lodge themselves in human tissues, triggering an inflammatory response that produces extensive organ damage and can ultimately result in death.
To visualize the Schistosome parasites the infected snail was removed from its shell and treated with chemicals to render the tissues transparent and with a fluorescent molecule that binds strongly to the surface of the parasite. The snail was then viewed using a confocal microscope. This image is ~1.5 cm in width, 2 mm in thickness, and contains ~10 billion voxels.
Image courtesy of Bo Wang, PhD and HHMI Investigator Phillip Newmark, PhD, University of Illinois at Urbana-Champaign.