To support FSIS in a risk assessment for food security we will determine and compare bioavailability and toxicity for purified and crude ricin in food using a mouse model.
Approach: 1. We will develop a mouse bioassay to measure toxicity of crude and purified ricin preparations. We will report LD50 and time-to-death data. By comparing intraperitoneal (ip) and intragastric (ig) routes of administration we will determine the bioavailability (ig) of pure and crude ricin in ground beef and liquid egg. 2. We will determine toxicity (LD50 and time-to-death) for crude ricin from several strains of castor, including at least the commercial cultivar Hale and a low-ricin line P1257654. We will bioassay high-ricin cultivars, if they are made available. 3. We will perform time-temperature studies on pure and crude ricin in ground beef and liquid egg, to measure inactivation of toxicity (LD50 and time-to-death). If inactivation is difficult we will report bioavailability as well as toxicity of heat-treated toxin. We will compare bioassay results to ELISA. 4. The study will be completed and final report submitted by September 30, 2006.