Waterborne Microbes




		Helminths, or parasitic worms, are sometimes not considered "microbes" in the strict sense since the adults are often large enough to be seen with the naked eye. They range from the barely visible round worms (0.3 mm) to huge tapeworms that can grow as long as 25 meters. Eggs and larvae are as small as 0.01 mm. Although individuals from all societies and regions play host to worms at some time in their lives, the highest case rates occur among children in rural areas of the tropics and subtropics. The most prevalent worms spread by the ingestion of water are certain nematodes (roundworms), including Guinea worm (Dracunculus medinensis), blood flukes (Schistosoma spp.), sheep liver flukes (Fasciola hepatica), and a variety of intestinal nematodes (round worms), including stomach worm (Ascaris lumbricoides), whip worm (Trichuris trichiura), hookworm (Ancylostoma duodenale and Necator americanus) and threadworm (Strongyloides stercoralis). Nematodes can ingest bacteria and protect them from disinfection. Filtration to one micron provides protection against helminthes, including their eggs and larvae.