Preface

During a time span of more than a century since its recognition, the protozoan parasite *Toxoplasma gondii* has never seized to fascinate researchers. A ubiquitous organism able to infect all mammals and birds, that has been estimated to infect one third of the global human population, deserves as much. Recognized in the early days as an agent affecting the fetus, the clinical focus has moved with the advent of AIDS and increased use of treatments with immunosuppressive effect, to toxoplasmosis as an opportunistic infection, and in the recent years back again to the long known ocular disease, this time as a consequence of acquired as much as congenital disease. Developments were always associated with the use of the leading methodologies of the times, currently embodied in the penetration of molecular biology methods into medicine and microbiology, which allowed for studies of *T. gondii* and the infection it induces at the genomic level. In addition, *T. gondii* owes part of its popularity to being a very desirable model of intracellular infection quite easy to grow in the lab, offering the possibility to study various immunological, biochemical, cell biology and other aspects and providing a wealth on data on immune control, host-parasite relationship, etc. It is thus not surprising that the centenary of *T. gondii* presented an inspiration for a number of texts and books overviewing both the biology of the organism and the clinics of the disease it causes. In this regard, it is hard to find a niche for yet another book on toxoplasmosis. However, any effort on compiling a series of essays stands witness to its moment in the history of knowledge development, and offers its readers, specialist or not, a view on the current achievements and research interests.

A current approach to this zoonosis is the concept of "one health", based on the understanding that a disease occurring between animals and man in a specific environment can only be dealt with at the interface of all "players" involved. The structure of this book follows this concept, in that it integrates human and animal data in its respective parts. The book is opened by a formidable chapter on factors affecting the dynamics of the *T. gondii* life cycle, in which Gilot-Fromont and colleagues describe how these elements shape the spatial and temporal variability of the epidemiological dynamics, and conclude on the evolutionary and medical implications of these variations.

In line with the "one health" concept, this part is continued by a review (Chapter 2) of both the epidemiology and the epizootiology of toxoplasmosis in South-East Europe.

#### X Preface

Bobić and colleagues review the data published in this region in the past two decades, showing that a prevention effort requires concerted action on the animal, human and environmental side, thereby illustrating on real facts the need for a complex and unified approach advocated in Chapter 1.

Preface XI

**Dr. Olgica Djurković-Djaković**

Serbia

Centre of Excellence in Biomedicine

National Reference Laboratory for Toxoplasmosis

Institute for Medical Research, University of Belgrade

The book is concluded by a text on so-called pseudo-toxoplasmosis (Chapter 9), in which Shimada overviews i.e. genetic disorders causing clinical symptoms that can be initially mis-diagnosed for toxoplasmosis and in which toxoplasmosis should be ruled out in the differential diagnosis. One such case published by the author is here discussed in the light of other entities that may mimick toxoplasmosis, focusing on

specific methods and examinations needed to distinguish between the two.

The issue of epizootiology introduced by Bobić and colleagues is subject of the following two contributions, which review the current data on *T. gondii* infection in animals in the Chech Republic and Slovakia, respectively. Whereas Bartova and colleagues (Chapter 3) offer a comprehensive review of *T. gondii* infection in farm, wild and zoo animals in the Chech Republic in the last decade, in Chapter 4 Luptakova and colleagues overview their own data on toxoplasmosis in animals in Slovakia, focusing on the diagnostic methods available and discussing their advantages and pitfalls.

Part 2 is devoted to molecular epidemiology. Chapter 5 involves a text by Ivović and colleagues on the use of molecular methods for the diagnosis of toxoplasmosis, focusing on their advantages and limitations, as well as for the genotyping of strains isolated from clinical samples, providing data on the molecular epidemiology of *T. gondii* in Serbia.

The next chapter (Chapter 6) is an interesting text by P. Jokelainen, who shows that *T. gondii* strains of the most common pan-European genotype II may be, and have been, fatal for some of their animal hosts including mountain hares and foxes, in Finland but elsewhere in Europe as well. This is a good reminder that whereas insight into the parasite genotypes is expected to provide answers to many clinical questions, it is not the parasite genotype but the interplay and balance between the parasite and its host, with its different immunological responses, genetics etc., that determines the outcome of infection.

Part 3 concerns important clinical issues of toxoplasmosis. Chapter 7 is an authoritative account by Jean Dupouy-Camet and colleagues on the epidemiology of ocular toxoplasmosis as the major *T. gondii* induced clinical entity, occurring as an early or late consequence of acquired as much as of congenital disease. This relatively novel concept changes our view of acquired infection, making a strong case for the prevention of acquired infection in the general population.

Ocular toxoplasmosis in the particular setting of Brazil is further explored in Chapter 8 by Bahia-Oliveira and colleagues. As known to those familiar with the current literature, toxoplasmosis seems to be an entirely different disease in Brazil. Initially recognized after hydric epidemics, insight into strain differences at the molecular level provided explanation for the significant clinical differences observed in Brazil vs. elsewhere. Bahia-Oliveira and colleagues further explore the multifactorial nature of ocular toxoplasmosis, and based on own research on clinical, immunological and genetic parameters in a large patient series in an endemic area, propose a novel clinical classification of retinochoroidal scars in epidemiological surveys.

The book is concluded by a text on so-called pseudo-toxoplasmosis (Chapter 9), in which Shimada overviews i.e. genetic disorders causing clinical symptoms that can be initially mis-diagnosed for toxoplasmosis and in which toxoplasmosis should be ruled out in the differential diagnosis. One such case published by the author is here discussed in the light of other entities that may mimick toxoplasmosis, focusing on specific methods and examinations needed to distinguish between the two.

X Preface

*gondii* in Serbia.

of infection.

unified approach advocated in Chapter 1.

Bobić and colleagues review the data published in this region in the past two decades, showing that a prevention effort requires concerted action on the animal, human and environmental side, thereby illustrating on real facts the need for a complex and

The issue of epizootiology introduced by Bobić and colleagues is subject of the following two contributions, which review the current data on *T. gondii* infection in animals in the Chech Republic and Slovakia, respectively. Whereas Bartova and colleagues (Chapter 3) offer a comprehensive review of *T. gondii* infection in farm, wild and zoo animals in the Chech Republic in the last decade, in Chapter 4 Luptakova and colleagues overview their own data on toxoplasmosis in animals in Slovakia, focusing on the diagnostic methods available and discussing their advantages and pitfalls.

Part 2 is devoted to molecular epidemiology. Chapter 5 involves a text by Ivović and colleagues on the use of molecular methods for the diagnosis of toxoplasmosis, focusing on their advantages and limitations, as well as for the genotyping of strains isolated from clinical samples, providing data on the molecular epidemiology of *T.* 

The next chapter (Chapter 6) is an interesting text by P. Jokelainen, who shows that *T. gondii* strains of the most common pan-European genotype II may be, and have been, fatal for some of their animal hosts including mountain hares and foxes, in Finland but elsewhere in Europe as well. This is a good reminder that whereas insight into the parasite genotypes is expected to provide answers to many clinical questions, it is not the parasite genotype but the interplay and balance between the parasite and its host, with its different immunological responses, genetics etc., that determines the outcome

Part 3 concerns important clinical issues of toxoplasmosis. Chapter 7 is an authoritative account by Jean Dupouy-Camet and colleagues on the epidemiology of ocular toxoplasmosis as the major *T. gondii* induced clinical entity, occurring as an early or late consequence of acquired as much as of congenital disease. This relatively novel concept changes our view of acquired infection, making a strong case for the

Ocular toxoplasmosis in the particular setting of Brazil is further explored in Chapter 8 by Bahia-Oliveira and colleagues. As known to those familiar with the current literature, toxoplasmosis seems to be an entirely different disease in Brazil. Initially recognized after hydric epidemics, insight into strain differences at the molecular level provided explanation for the significant clinical differences observed in Brazil vs. elsewhere. Bahia-Oliveira and colleagues further explore the multifactorial nature of ocular toxoplasmosis, and based on own research on clinical, immunological and genetic parameters in a large patient series in an endemic area, propose a novel clinical

prevention of acquired infection in the general population.

classification of retinochoroidal scars in epidemiological surveys.

#### **Dr. Olgica Djurković-Djaković**

National Reference Laboratory for Toxoplasmosis Centre of Excellence in Biomedicine Institute for Medical Research, University of Belgrade Serbia

**Section 1** 

**Epidemiology and Epizootiology** 

**Section 1** 

**Epidemiology and Epizootiology** 

**Chapter 1** 

© 2012 Gilot-Fromont et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2012 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution,

**The Life Cycle of** *Toxoplasma gondii*

Emmanuelle Gilot-Fromont, Maud Lélu, Marie-Laure Dardé,

*Toxoplasma gondii* (*T. gondii*) is considered as one of the most successful parasites in the world. This success is first illustrated by its worldwide distribution, from arctic to hot desert areas, including isolated islands and in cities [1]. *T. gondii* is also among the most prevalent parasites in the global human population, with around one third of the population being infected [2]. Finally, it is able to infect, or be present in, the highest number of host species: any warm-blooded animal may act as an intermediate host, and oocysts may be transported

Beyond this ubiquitous distribution lies a fascinating transmission pattern: simply saying that *T. gondii* has a complex life cycle does not encompass all transmission routes and modes that can be used by the parasite to pass from definitive hosts (DHs), where sexual reproduction occurs, to intermediate hosts (IHs). The "classical" complex life cycle uses felids (domestic and wild-living cats) as DHs and their prey as IHs (Figure 1). Felids are infected by eating infected prey and host the sexual multiplication of the parasite. They excrete millions of oocysts that sporulate in the environment. Sporulated oocysts may survive during several years and may disperse through water movements, soil movements and microfauna. Ingesting a single sporulated oocyst may be sufficient to infect an IH and begin the asexual reproduction phase [1]. This classical life cycle thus relies on a preypredator relationship and on environmental contamination, like other parasites, e.g.,

However, beside this classical cycle, *T. gondii* shows specific abilities that allow it to use "complementary" transmission routes (Figure 1). During the phase of asexual multiplication, tachyzoites may disseminate to virtually any organ within the IH, in

and reproduction in any medium, provided the original work is properly cited.

Céline Richomme, Dominique Aubert, Eve Afonso, Aurélien Mercier, Cécile Gotteland and Isabelle Villena

by invertebrates such as filtrating mussels and oysters [1, 3].

**in the Natural Environment** 

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/48233

*Echinococcus multilocularis* [4].

**1. Introduction** 

#### **Chapter 1**
