A non-technical overview of water-borne microbial diseases that can be transmitted to humans by livestock is now available from the UC Davis-based UC Agricultural Issues Center. The report, written by Dr. Rob Atwill, a UC Davis veterinarian and environmental animal health specialist based at the Veterinary Medicine Teaching and Research Center in Tulare, deals with diseases caused by bacteria and protozoa such as Cryptosporidium parvum, Giardia duodenalis, Campylobacter, Salmonella and E. coli. Four conditions are necessary for these disease-causing agents to be transmitted from livestock to humans, according to Atwill. They must be shed by livestock, reach a water source such as a lake or stream, remain alive until ingested by a human and be in concentrations high enough to cause an infection in the human. While bacteria and protozoa carried by livestock can be a source of human infection, none of the viruses shed by livestock seem to pose a threat to human health in the United States, notes Atwill. Copies of the report, "Pathogens Excreted by Livestock and Transmitted to Humans Through Water" may obtained for $10 each from the UC Agricultural Issues Center.