2010 Annual Report 1a.Objectives (from AD-416) Risk-based management systems for the control of zoonotic parasites in swine. 1b.Approach (from AD-416) Will determine genetic and antigenic variation among toxoplasma isolates from food animals. 3.Progress Report Toxoplasma gondii is a widespread parasitic infection that can cause severe disease in immunocompromised patients. Our studies seek to define the factors that contribute to the severity of disease caused by this parasite. By understanding the virulence determinants of the parasite that enable it to cause harm, it may be possible to develop new therapeutic approaches to combat human infection. Towards this goal we have successfully performed a genetic cross between the virulent type I GT-1 strain and avirulent type II ME49 strain. A total of ~ 50 recombinant progeny have been genotyped by hybridization using the Affymetrix array for T. gondii. We have measured the virulence of these recombinant progeny in mice and used this trait to map the genes that mediate the substantial difference in virulence between these lineages. Project plans, goals, and accomplishments were discussed via conference calls and e-mail; technical advice was provided to the Cooperator in writing and by teleconference.