Bilharzia ranks with malaria as one of the most widespread and serious parasitic diseases in the world, afflicting an estimated 250 million people in Asia, Africa, Latin America, and the Caribbean. It is transmitted through contact with contaminated water. So, unlike malaria with its more democratic vector, bilharzia is invariably a problem among poorer communities in the developing countries. It is a debilitating disease rather than a fatal one. It can take years for tissue damage caused by the parasite to manifest itself in the form of internal bleeding and malfunctions of the bladder, liver, and intestines. The disease saps energy and shortens the life span but it does not contribute obviously to mortality statistics.What is the main idea of this paragraph