Last data update: May 13, 2024. (Total: 46773 publications since 2009)
Records 1-5 (of 5 Records) |
Query Trace: Gamble HR[original query] |
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Quantifying the risk of human Toxoplasma gondii infection due to consumption of fresh pork in the United States
Guo M , Lambertini E , Buchanan RL , Dubey JP , Hill DE , Gamble HR , Jones JL , Pradhan AK . Food Control 2017 73 1210-1222 Toxoplasma gondii is one of the leading foodborne pathogens in the United States. The Centers for Disease Control and Prevention (CDC) reported that T. gondii accounts for 24% of deaths due to foodborne illness in the United States. Consumption of undercooked pork products in which T. gondii has encysted has been identified as an important route of human exposure. However, little quantitative evaluation of risk due to different pork products as a function of microbial quality at the abattoir, during the production process, and due to consumer handling practices is available to inform risk management actions. The goal of this study was to develop a farm-to-table quantitative microbial risk assessment (QMRA) model to predict the public health risk associated with consumption of fresh pork in the United States. T. gondii prevalence in pigs was derived through a meta-analysis of existing data, and the concentration of the infectious life stage (bradyzoites) was calculated for each pork cut from an infected pig. Logistic regression and log-linear regression models were developed to predict the reduction of T. gondii during further processing and consumer preparation, respectively. A mouse-derived exponential dose-response model was used to predict infection risk in humans. The estimated mean probability of infection per serving of fresh pork products ranges from 3.2 × 10−7 to 9.5 × 10−6, corresponding to a predicted approximately 94,600 new infections annually in the U.S. population due to fresh pork ingestion. Approximately 957 new infections per year were estimated to occur in pregnant women, corresponding to 277 cases of congenital toxoplasmosis per year due to fresh pork ingestion. In the context of available data, sensitivity analysis suggested that cooking is the most important parameter impacting human health risk. This study provides a scientific basis for risk management and also could serve as a baseline model to quantify infection risk from T. gondii and other parasites associated with meat products. |
A systematic meta-analysis of toxoplasma gondii prevalence in food animals in the United States
Guo M , Mishra A , Buchanan RL , Dubey JP , Hill DE , Gamble HR , Jones JL , Pradhan AK . Foodborne Pathog Dis 2016 13 (3) 109-18 Toxoplasma gondii is a widely distributed protozoan parasite. The Centers for Disease Control and Prevention reported that T. gondii is one of three pathogens (along with Salmonella and Listeria), that together account for >70% of all deaths due to foodborne illness in the United States. Food animals are reservoirs for T. gondii and act as one of the sources for parasite transmission to humans. Based on limited population-based data, the Food and Agriculture Organization/World Health Organization estimated that approximately 22% of human T. gondii infections are meatborne. The objective of the current study was to conduct a systematic meta-analysis to provide a precise estimation of T. gondii infection prevalence in food animals produced in the United States. Four databases were searched to collect eligible studies. Prevalence was estimated in six animal categories (confinement-raised market pigs, confinement-raised sows, non-confinement-raised pigs, lamb, goats, and non-confinement-raised chickens) by a quality-effects model. A wide variation in prevalence was observed in each animal category. Animals raised outdoors or that have outdoor access had a higher prevalence as compared with animals raised indoors. T. gondii prevalence in non-confinement-raised pigs ranked the highest (31.0%) followed by goats (30.7%), non-confinement-raised chickens (24.1%), lambs (22.0%), confinement-raised sows (16.7%), and confinement-raised market pigs (5.6%). These results indicate that T. gondii-infected animals are a food safety concern. The computed prevalence can be used as an important input in quantitative microbial risk assessment models to further predict public health burden. |
Qualitative assessment for Toxoplasma gondii exposure risk associated with meat products in the United States
Guo M , Buchanan RL , Dubey JP , Hill DE , Lambertini E , Ying Y , Gamble HR , Jones JL , Pradhan AK . J Food Prot 2015 78 (12) 2207-19 Toxoplasma gondii is a global protozoan parasite capable of infecting most warm-blooded animals. Although healthy adult humans generally have no symptoms, severe illness does occur in certain groups, including congenitally infected fetuses and newborns, immunocompromised individuals including transplant patients. Epidemiological studies have demonstrated that consumption of raw or undercooked meat products is one of the major sources of infection with T. gondii. The goal of this study was to develop a framework to qualitatively estimate the exposure risk to T. gondii from various meat products consumed in the United States. Risk estimates of various meats were analyzed by a farm-to-retail qualitative assessment that included evaluation of farm, abattoir, storage and transportation, meat processing, packaging, and retail modules. It was found that exposure risks associated with meats from free-range chickens, nonconfinement-raised pigs, goats, and lamb are higher than those from confinement-raised pigs, cattle, and caged chickens. For fresh meat products, risk at the retail level was similar to that at the farm level unless meats had been frozen or moisture enhanced. Our results showed that meat processing, such as salting, freezing, commercial hot air drying, long fermentation times, hot smoking, and cooking, are able to reduce T. gondii levels in meat products. whereas nitrite and/or nitrate, spice, low pH, and cold storage have no effect on the viability of T. gondii tissue cysts. Raw-fermented sausage, cured raw meat, meat that is not hot-air dried, and fresh processed meat were associated with higher exposure risks compared with cooked meat and frozen meat. This study provides a reference for meat management control programs to determine critical control points and serves as the foundation for future quantitative risk assessments. |
Development of dose-response models to predict the relationship for human toxoplasma gondii infection associated with meat consumption
Guo M , Mishra A , Buchanan RL , Dubey JP , EHill D , Gamble HR , Jones JL , Du X , Pradhan AK . Risk Anal 2015 36 (5) 926-38 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 x 0.005 x d) or P (d) = 1-(1 + d x 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. |
Toxoplasmosis in sentinel chickens (Gallus domesticus) in New England farms: seroconversion, distribution of tissue cysts in brain, heart, and skeletal muscle by bioassay in mice and cats
Dubey JP , Lehmann T , Lautner F , Kwok OC , Gamble HR . Vet Parasitol 2015 214 55-8 Free-range chickens are a good indicator of soil contamination with oocysts because they feed from the ground and they are also an important source of infection for cats that in turn shed oocysts after eating tissues of intermediate hosts. Little is known of the epidemiology of toxoplasmosis in chickens. In the present study 90 Toxoplasma gondii seronegative, sentinel chickens were placed on three (30 each) swine farms in New England in November, 2003. Chickens were bled monthly and their sera were tested for T. gondii antibodies by the modified agglutination test (MAT, cut-off 1:25). Chickens that seroconverted were euthanized and their tissues were bioassayed in mice, cats, or both. Over the course of the experiment (7 months), 31 of 71 chickens seroconverted (MAT 1:100 or higher). Tissues of 26 seropositive chickens were bioassayed in both cats and mice; viable T. gondii was isolated, by bioassay in mice, from hearts (whole) of all 26 chickens, brains (whole) of 3 chickens and leg muscles (25g) of 11 chickens; 21 of 26 cats fed 250g of muscle from seropositive chickens excreted T. gondii oocysts. Results indicated that the density of T. gondii in poultry muscle is low but heart is the tissue of choice for isolation of viable parasites. |
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