title: Development of Dose-Response Models to Predict the Relationship for Human Toxoplasma gondii Infection Associated with Meat Consumption.
abstract: Toxoplasma gondii is a protozoan parasite that is responsible for approximately 24% of deaths attributed to foodborne pathogens in the United States. It is thought that a substantial portion of human T. gondii infections is acquired through the consumption of meats. The dose-response relationship for human exposures to T. gondii-infected meat is unknown because no human data are available. The goal of this study was to develop and validate dose-response models based on animal studies, and to compute scaling factors so that animal-derived models can predict T. gondii infection in humans. Relevant studies in literature were collected and appropriate studies were selected based on animal species, stage, genotype of T. gondii, and route of infection. Data were pooled and fitted to four sigmoidal-shaped mathematical models, and model parameters were estimated using maximum likelihood estimation. Data from a mouse study were selected to develop the dose-response relationship. Exponential and beta-Poisson models, which predicted similar responses, were selected as reasonable dose-response models based on their simplicity, biological plausibility, and goodness fit. A confidence interval of the parameter was determined by constructing 10,000 bootstrap samples. Scaling factors were computed by matching the predicted infection cases with the epidemiological data. Mouse-derived models were validated against data for the dose-infection relationship in rats. A human dose-response model was developed as P (d) = 1-exp (-0.0015 × 0.005 × d) or P (d) = 1-(1 + d × 0.003 / 582.414)(-1.479) . Both models predict the human response after consuming T. gondii-infected meats, and provide an enhanced risk characterization in a quantitative microbial risk assessment model for this pathogen.
authors.affiliation: Department of Nutrition and Food Science, University of Maryland, College Park, MD, USA.
authors.forename: Miao
authors.initials: M
authors.lastname: Guo
authors.affiliation: Department of Nutrition and Food Science, University of Maryland, College Park, MD, USA.
authors.forename: Abhinav
authors.initials: A
authors.lastname: Mishra
authors.affiliation: Department of Nutrition and Food Science, University of Maryland, College Park, MD, USA.|Center for Food Safety and Security Systems, University of Maryland, College Park, Md, USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Buchanan
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, Beltsville Agriculture Research Center, Animal Parasitic Diseases Laboratory, Beltsville, MD, USA.
authors.forename: Jitender P
authors.initials: JP
authors.lastname: Dubey
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, Beltsville Agriculture Research Center, Animal Parasitic Diseases Laboratory, Beltsville, MD, USA.
authors.forename: Dolores E
authors.initials: DE
authors.lastname: Hill
authors.affiliation: National Academy of Sciences, Washington, DC, USA.
authors.forename: H Ray
authors.initials: HR
authors.lastname: Gamble
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Jones
authors.affiliation: Department of Electronic and Computer Engineering, University of Maryland, College Park, MD, USA.
authors.forename: Xianzhi
authors.initials: X
authors.lastname: Du
authors.affiliation: Department of Nutrition and Food Science, University of Maryland, College Park, MD, USA.|Center for Food Safety and Security Systems, University of Maryland, College Park, Md, USA.
authors.forename: Abani K
authors.initials: AK
authors.lastname: Pradhan
mesh_terms: D000818:Animals; D005506:Food Contamination; D006801:Humans; D016013:Likelihood Functions; D008460:Meat / Q000469:parasitology*; D051379:Mice; D008954:Models, Biological; D051381:Rats; D018570:Risk Assessment; D014122:Toxoplasma; D014123:Toxoplasmosis / Q000453:epidemiology*; D014124:Toxoplasmosis, Animal / Q000453:epidemiology
keywords: Dose-response; Toxoplasma gondii; human infection; meat; quantitative microbial risk assessment