SCHISTOSOME ADULTS, about a centimeter long, travel through the blood in pairs, with the smaller female (at bottom) held in a slit in the males body. The worms name derives from this slit: schisto means split, and some means body. Image: David Scharf: Photo Researchers, Inc.
- Parasitic worms known as schistosomes are a major cause of disability and death in many parts of the world, especially sub-Saharan Africa.
- Although a treatment exists, reinfection is the rule.
- A vaccine would make a world of difference, but none has yet proved effective. Genetic and other tools hold promise for generating new candidates.
Legend has it that vampires create no shadows, cast no reflection and—in more modern versions of the tale—cannot be captured on photographs, film or video. Of course, vampires are only myths. Unfortunately, schistosomes, which behave in some similar ways, are not. These infectious worms dwell in human veins and eat our blood. Among parasitic illnesses, the World Health Organization ranks schistosomiasis, the disease caused by the worms, second only to malaria in terms of the number of people it kills and chronically disables and the drag it imposes on the social and economic development of nations. And, in their own way, schistosomes have achieved invisibility. Cameras can capture these creatures, but our immune system does not.
Investigators have struggled for years against the schistosome’s evasiveness. They have been trying to create vaccines able to rally a defense that would pounce on the parasite quickly, thereby preventing disease, or that would help the body to clear existing infections. Vaccines are a necessary and missing component of a global effort to eradicate this illness. So far the results have been disappointing. But schistosome researchers like myself feel we may be at the start of a great leap forward. Genome projects are laying bare the DNA sequence of the parasite, and scientists are beginning to develop powerful new tools to probe its molecular secrets. These weapons may help make it possible to enhance immunity and accelerate vaccine efforts.
This article was originally published with the title Fighting Killer Worms.