Dynamics of a model of Toxoplasmosis disease in human and cat populations

AbstractA mathematical model for the transmission of Toxoplasmosis disease in human and cat populations is proposed and analyzed. We explore the dynamics of the Toxoplasmosis disease at the population level using an epidemiological type model. Discussion of the basic concepts of the Toxoplasmosis transmission dynamics on human and cat populations are presented. The cats in this model plays a role of infectious agents and host of the protozoan Toxoplasma Gondii parasite. Qualitative dynamics of the model is determined by the basic reproduction number, R0. If the threshold parameter R0<1, then the solution converges to the disease free equilibrium point. On the other hand if R0>1 the convergence is to the endemic equilibrium point. Numerical simulations of the model illustrates several different dynamics depending on the threshold parameter R0 and show the importance of this parameter

Bifurcation Analysis of Toxoplasmosis Epidemic Control on Increased Controlled Rate of Suppressing the Rate of Infected Births

The toxoplasmosis epidemic is an infectious disease caused by the parasitic Toxoplasma Gondii. This disease attacks the human immune system and other organs in the body, resulting in damage to tissues. The spread of the disease is carried out in various ways, one of them is eating foods that are less hygienic or not cooked properly, resulting in parasites remain active. Provision of controlled therapy is one solution in controlling the epidemic against suppression of the birth rate infected with toxoplasmosis. This study discusses the bifurcation analysis of a mathematical model for controlling the toxoplasmosis epidemic. Bifurcation analysis is carried out on the controlled rate and rate of birth control of toxoplasmosis. From the mathematical model of controlling the toxoplasmosis epidemic, stability and existence analysis are performed at each equilibrium point. Next, a function of two independent parameters is constructed which influences the spread of the disease, namely the controlled rate and the rate of infected births. Then, a bifurcation analysis of each region is obtained from each function of the two free parameters. From the bifurcation analysis, three regional conditions were obtained which showed the dynamics of the toxoplasmosis epidemic of two independent parameters with each interpretation of the bifurcation region

Mathematical modelling of Toxoplasma gondii transmission: A systematic review

Background: Toxoplasma gondii is a ubiquitous protozoan parasite that can infect virtually all warm-blooded animals. It is the causative agent of toxoplasmosis, a significant public health issue worldwide. Mathematical models are useful to study the transmission dynamics of T. gondii infection in different settings, and may be used to compare the effectiveness of prevention measures. Methods: To obtain an overview of existing mathematical models for transmission of T. gondii, a systematic review was undertaken. The review was conducted according to an a priori protocol and the results were reported according to the PRISMA guidelines. Specific search terms were developed and used in the search of three databases (Scopus, PubMed, and Embase). Results: In total, 484 unique records were retrieved from the systematic search. Among them, 15 studies that used mathematical models to study the transmission of T. gondii. These studies were categorized into four groups based on the primary aims: dynamics of transmission (n = 8), intervention (n = 5), spatial distribution (n = 1), and outbreak investigation (n = 1). Conclusions: Considering the high disease burden caused by T. gondii, the number of studies using mathematical models to understand the transmission dynamics of this parasite and to evaluate the effectiveness of intervention measures was only 15. This systematic review provides an overview of existing mathematical models and identifies the data gaps for model building. The results from this study can be helpful for further development of mathematical models and improved understanding of the transmission dynamics of T. gondii infection

Multiscale Modeling of Toxoplasma gondii

Toxoplasma gondii is a potentially deadly parasite that uses a very unique way of manipulating the cell and immune systems. To investigate the mechanics of how the parasite spreads within hosts, several interwoven topics related to the study of within-host dynamics of Toxoplasma gondii are presented here. Understanding the complicated methods of how the parasite grows, dies, invades, replicates, and evades the host immune response is the critical aim of this independent research. Understanding the processes of acute and chronic infection are studied independently, followed by modeling the two processes in the same model. Finally, the dynamic models are simulated within a 3D mesh representation of a mouse brain to visualize the infection spreading during the acute and chronic phase. The results presented shed light onto the effects of the immune response, cyst volume growth, and the dependence of multiple stages in the dissemination of the parasite within a host

Evaluation and Modeling of Food Safety Risk Factors Associated with Toxoplasma gondii Infection in the Farm-to-Fork Framework

Toxoplasma gondii is a widespread zoonotic parasite with a high seroprevalence in the human population and the ability to infect almost all warm blooded animals. Animal meat may contain viable T. gondii tissue cysts that can potentially cause infection if undercooked meat is consumed. The goal of this research is to estimate T. gondii distribution in animal meats by integrating experimental data with predictive modeling and statistical analyses to better understand the ecology of T. gondii infection and further evaluate mitigation methods to reduce the public health burden of toxoplasmosis. To understand the infectivity and transmission of T. gondii from the environment to animals and thereafter humans, the formation and distribution of T. gondii tissue cysts was estimated in varying sizes (5 g, 10 g and 50 g) of animal muscle tissues. Experimentally and naturally infected pigs, lambs and goats were evaluated. The sensitivity and specificity of different diagnostic tests for detecting T. gondii were also evaluated using logistic regression modeling and meta-analysis. Bootstrap and Gibbs statistical sampling techniques were used to assess the complete inactivation of T. gondii in pork through cooking and freezing. Dynamic compartmental modeling was used to simulate one year on a hypothetical pig farm to understand T. gondii infection transmission via the environment and in multiple hosts such as cats, rats, pigs and humans. Further, this modeled analyzed some of the dynamical behaviors of the T. gondii infection in the definite (cat) and intermediate (e.g. rat, pig and human) host populations. The results suggested that T. gondii tissue cysts can develop as early as 7 days after infection in experimentally infected pigs and are unevenly distributed in the muscle tissues of naturally infected lambs and goats based on bioassay in mice. Meat samples as small as 5 g have the potential to cause T. gondii infection if consumed raw or undercooked. The regression model predicted varying specificity and sensitivity for different sized meat samples with the highest sensitivity and lowest specificity for the largest samples (50 g). T. gondii tissue cysts in fresh pork were completely inactivated at or above 64°C (147.2°F) and below -18°C (0°F). Tissue cysts can remain viable in fresh meat for up to 30 days stored at 4°C (39°F). With the calculated predation rate of the hosts and the transmission rate of infection from environment, the T. gondii infection is expected to persist (R0 > 1) in all hosts over the simulation run of one year. This dissertation evaluated the T. gondii infection flow in different hosts, assessed mitigation strategies for food safety risks and estimated the distribution of the parasite in fresh cut meats of food animals

Evaluating food safety risk of Toxoplasma gondii in meat products consumed in the United States

Toxoplasma gondii is one of the leading foodborne pathogens in the United States. The main modes of T. gondii transmission are ingestion of food, soil or water contaminated with oocysts, or eating raw or undercooked meat containing tissue cysts. A substantial portion of human T. gondii infections is acquired through consumption of meats. The overall goal of this dissertation was to collect and summarize current knowledge and information of T. gondii infection, and estimate the risk of human T. gondii infection due to consumption of meat products that are potentially infected with T. gondii in the United States. A resource document was developed to collect relevant data of T. gondii prevalence in meat animals worldwide, and to identify risk factors associated with T. gondii prevalence. Furthermore, a quality-effects systematic meta-analysis was conducted to estimate T. gondii prevalence in meat animals raised in the United States. These results were used to define the risk level of meat category in a farm-to-retail qualitative assessment. Effects of meat processing on the survival of T. gondii were assessed, and critical steps for inactivating T. gondii were identified. An exponential and a beta-Poisson dose-response models were developed to estimate human infection by using scaling factors. Mouse-derived models were validated against data for the dose-infection relationship in rats. Two risk models were developed to quantitatively predict the risk of T. gondii infection in the United States due to consumption of fresh pork and domestically-produced lamb, respectively. The mean probability of infection per serving of fresh pork ranges from 3.2×10^-7 to 9.5×10^-6, corresponding to 94,606 and 957 new infections annually in the U.S. population and the pregnant women, respectively. The sensitivity analysis suggested that cooking is the most important parameter impacting human health risk. The mean probability of infection of lamb was estimated to be 1.5 cases per 100,000 servings, corresponding to approximately 6,300 new infections per year in the U.S. population. This project systematically evaluated food safety risk of T. gondii through meat consumption, and provided scientific evidence for risk managers that attention to T. gondii infection through meatborne routes is warranted