Review

Authors: Florence Robert-Gangneux, Marie-Laure Dardé

The apicomplexan parasite Toxoplasma gondii was discovered a little over 100 years ago, but knowledge of its biological life cycle and its medical importance has grown in the last 40 years. This obligate intracellular parasite was identified early as a pathogen responsible for congenital infection, but its clinical expression and the importance of reactivations of infections in immunocompromised patients were recognized later, in the era of organ transplantation and HIV infection. Recent knowledge of host cell-parasite interactions and of parasite virulence has brought new insights into the comprehension of the pathophysiology of infection. In this review, we focus on epidemiological and diagnostic aspects, putting them in perspective with current knowledge of parasite genotypes. In particular, we provide critical information on diagnostic methods according to the patient's background and discuss the implementation of screening tools for congenital toxoplasmosis according to health policies.

Topics: Humans; Prevalence; Toxoplasma; Toxoplasmosis

PubMed: 22491772
DOI: 10.1128/CMR.05013-11

Review

Authors: Márcia Attias, Dirceu E Teixeira, Marlene Benchimol...

Toxoplasma gondii is a protozoan parasite that is the causative agent of toxoplasmosis, an infection with high prevalence worldwide. Most of the infected individuals are either asymptomatic or have mild symptoms, but T. gondii can cause severe neurologic damage and even death of the fetus when acquired during pregnancy. It is also a serious condition in immunodeficient patients. The life-cycle of T. gondii is complex, with more than one infective form and several transmission pathways. In two animated videos, we describe the main aspects of this cycle, raising questions about poorly or unknown issues of T. gondii biology. Original plates, based on electron microscope observations, are also available for teachers, students and researchers. The main goal of this review is to provide a source of learning on the fundamental aspects of T. gondii biology to students and teachers contributing for better knowledge and control on this important parasite, and unique cell model. In addition, drawings and videos point to still unclear aspects of T. gondii lytic cycle that may stimulate further studies.

Topics: Animals; Female; Humans; Life Cycle Stages; Pregnancy; Prevalence; Toxoplasma; Toxoplasmosis; Video Recording

PubMed: 33228743
DOI: 10.1186/s13071-020-04445-z

Review

Authors: J P Dubey, F H A Murata, C K Cerqueira-Cézar...

The morbidity due to congenital toxoplasmosis in humans is very high. Most of these infected children are likely to develop symptoms of clinical toxoplasmosis. Sequelae in fetus resulting from Toxoplasma gondii infections in women who become infected with this parasite during pregnancy can be devastating and enormous efforts are directed in some countries to prevent these consequences. Here, an update on congenital toxoplasmosis in humans, especially the rate of congenital infections in humans worldwide, is provided. Although several countries have surveillance programmes, most information on the rate of congenital transmission is from France and Brazil. Because of compulsory national screening programme in France to detect and treat women with recently acquired T. gondii infection with anti-toxoplasma therapy, the rate of congenital transmission and the severity of disease in children are declining. Infections by this parasite are widely prevalent in Brazil. The severity of clinical toxoplasmosis in Brazilian children is very high and may be associated with the genetic characteristics of T. gondii isolates prevailing in animals and humans in Brazil. Virtually little or no information is available on this topic from China, India and other countries in Asia.

Topics: Animals; Communicable Diseases; Female; Humans; India; Pregnancy; Toxoplasma; Toxoplasmosis; Toxoplasmosis, Congenital

PubMed: 34254575
DOI: 10.1017/S0031182021001013

Review

Authors: Gregory Milne, Joanne P Webster, Martin Walker...

Traditionally, the protozoan parasite Toxoplasma gondii has been thought of as relevant to public health primarily within the context of congenital toxoplasmosis or postnatally acquired disease in immunocompromised patients. However, latent T.gondii infection has been increasingly associated with a wide variety of neuropsychiatric disorders and, more recently, causal frameworks for these epidemiological associations have been proposed. We present assimilated evidence on the associations between T.gondii and various human neuropsychiatric disorders and outline how these may be explained within a unifying causal framework. We argue that the occult effects of latent T.gondii infection likely outweigh the recognised overt morbidity caused by toxoplasmosis, substantially raising the public health importance of this parasite.

Topics: Humans; Immunocompromised Host; Latent Infection; Mental Disorders; Toxoplasma; Toxoplasmosis

PubMed: 33012669
DOI: 10.1016/j.pt.2020.08.005

Review

Authors: A Alonso Aguirre, Travis Longcore, Michelle Barbieri...

One Health is a collaborative, interdisciplinary effort that seeks optimal health for people, animals, plants, and the environment. Toxoplasmosis, caused by Toxoplasma gondii, is an intracellular protozoan infection distributed worldwide, with a heteroxenous life cycle that practically affects all homeotherms and in which felines act as definitive reservoirs. Herein, we review the natural history of T. gondii, its transmission and impacts in humans, domestic animals, wildlife both terrestrial and aquatic, and ecosystems. The epidemiology, prevention, and control strategies are reviewed, with the objective of facilitating awareness of this disease and promoting transdisciplinary collaborations, integrative research, and capacity building among universities, government agencies, NGOs, policy makers, practicing physicians, veterinarians, and the general public.

Topics: Animals; Animals, Wild; Ecosystem; Humans; One Health; Toxoplasma; Toxoplasmosis; Toxoplasmosis, Animal

PubMed: 30945159
DOI: 10.1007/s10393-019-01405-7

Authors: Sandra K Halonen, Louis M Weiss

Toxoplasma gondii, an Apicomplexan, is a pathogic protozoan that can infect the central nervous system. Infection during pregnancy can result in a congenial infection with severe neurological sequelae. In immunocompromised individuals reactivation of latent neurological foci can result in encephalitis. Immunocompetent individuals infected with T. gondii are typically asymptomatic and maintain this infection for life. However, recent studies suggest that these asymptomatic infections may have effects on behavior and other physiological processes. Toxoplasma gondii infects approximately one-third of the world population, making it one of the most successful parasitic organisms. Cats and other felidae serve as the definite host producing oocysts, an environmentally resistant life cycle stage found in cat feces, which can transmit the infection when ingested orally. A wide variety of warm-blooded animals, including humans, can serve as the intermediate host in which tissue cysts (containing bradyzoites) develop. Transmission also occurs due to ingestion of the tissue cysts. There are three predominant clonal lineages, termed Types I, II and III, and an association with higher pathogenicity with the Type I strains in humans has emerged. This chapter presents a review of the biology of this infection including the life cycle, transmission, epidemiology, parasite strains, and the host immune response. The major clinical outcomes of congenital infection, chorioretinitis and encephalitis, and the possible association of infection of toxoplasmosis with neuropsychiatric disorders such as schizophrenia, are reviewed.

Topics: Animals; Central Nervous System Diseases; Humans; Toxoplasma; Toxoplasmosis

PubMed: 23829904
DOI: 10.1016/B978-0-444-53490-3.00008-X

Review

Authors: A M Tenter, A R Heckeroth, L M Weiss...

Toxoplasmosis is one of the more common parasitic zoonoses world-wide. Its causative agent, Toxoplasma gondii, is a facultatively heteroxenous, polyxenous protozoon that has developed several potential routes of transmission within and between different host species. If first contracted during pregnancy, T. gondii may be transmitted vertically by tachyzoites that are passed to the foetus via the placenta. Horizontal transmission of T. gondii may involve three life-cycle stages, i.e. ingesting infectious oocysts from the environment or ingesting tissue cysts or tachyzoites which are contained in meat or primary offal (viscera) of many different animals. Transmission may also occur via tachyzoites contained in blood products, tissue transplants, or unpasteurised milk. However, it is not known which of these routes is more important epidemiologically. In the past, the consumption of raw or undercooked meat, in particular of pigs and sheep, has been regarded as a major route of transmission to humans. However, recent studies showed that the prevalence of T. gondii in meat-producing animals decreased considerably over the past 20 years in areas with intensive farm management. For example, in several countries of the European Union prevalences of T. gondii in fattening pigs are now <1%. Considering these data it is unlikely that pork is still a major source of infection for humans in these countries. However, it is likely that the major routes of transmission are different in human populations with differences in culture and eating habits. In the Americas, recent outbreaks of acute toxoplasmosis in humans have been associated with oocyst contamination of the environment. Therefore, future epidemiological studies on T. gondii infections should consider the role of oocysts as potential sources of infection for humans, and methods to monitor these are currently being developed. This review presents recent epidemiological data on T. gondii, hypotheses on the major routes of transmission to humans in different populations, and preventive measures that may reduce the risk of contracting a primary infection during pregnancy.

Topics: Animals; Female; Humans; Life Cycle Stages; Male; Pregnancy; Toxoplasma; Toxoplasmosis; Zoonoses

PubMed: 11113252
DOI: 10.1016/s0020-7519(00)00124-7

Review

Authors: Xiao-Yu Zhao, Sarah E Ewald

Toxoplasma gondii is an incredibly successful parasite owing in part to its ability to persist within cells for the life of the host. Remarkably, at least 350 host species of T. gondii have been described to date, and it is estimated that 30% of the global human population is chronically infected. The importance of T. gondii in human health was made clear with the first reports of congenital toxoplasmosis in the 1940s. However, the AIDS crisis in the 1980s revealed the prevalence of chronic infection, as patients presented with reactivated chronic toxoplasmosis, underscoring the importance of an intact immune system for parasite control. In the last 40 years, there has been tremendous progress toward understanding the biology of T. gondii infection using rodent models, human cell experimental systems, and clinical data. However, there are still major holes in our understanding of T. gondii biology, including the genes controlling parasite development, the mechanisms of cell-intrinsic immunity to T. gondii in the brain and muscle, and the long-term effects of infection on host homeostasis. The need to better understand the biology of chronic infection is underscored by the recent rise in ocular disease associated with emerging haplotypes of T. gondii and our lack of effective treatments to sterilize chronic infection. This Review discusses the cell types and molecular mediators, both host and parasite, that facilitate persistent T. gondii infection. We highlight the consequences of chronic infection for tissue-specific pathology and identify open questions in this area of host-Toxoplasma interactions.

Topics: Animals; Disease Models, Animal; History, 20th Century; History, 21st Century; Humans; Toxoplasma; Toxoplasmosis

PubMed: 32609097
DOI: 10.1172/JCI136226

Review

Authors: Melodi Inceboz, Tonay Inceboz

is an intracellular protozoan parasite. Approximately 30% of the global population is infected by . In chronically infected individuals, the parasite resides in tissue cysts, especially in the brain. There is a growing interest in the role of parasitologic agents in the causation of neuropsychological disorders. In this review, we have explained the interactions between and its host, mechanisms, and consequences on neural and psychological diseases.

Topics: Brain; Chronic Disease; Host-Parasite Interactions; Humans; Neurocognitive Disorders; Toxoplasma; Toxoplasmosis; Toxoplasmosis, Cerebral

PubMed: 33685069
DOI: 10.4274/tpd.galenos.2020.6973

Authors: Shahnaz Akhtar Chaudhry, Nanette Gad, Gideon Koren...

Question Congenital toxoplasmosis is a dangerous fetal infection. Why is routine screening for Toxoplasma gondii infection during pregnancy not available for most Canadians? Answer Low prevalence of the infection, high cost associated with testing, low sensitivity of screening tests, false-positive test results, and limitations of treatment effectiveness are all cited as reasons for not routinely screening for T gondii infection in Canada. Currently, screening for the detection of T gondii is only performed in Nunavik and other parts of northern Quebec owing to the high prevalence of infection in this region. Congenital toxoplasmosis causes neurologic or ocular disease (leading to blindness), as well as cardiac and cerebral anomalies.

Topics: Anti-Bacterial Agents; Antiprotozoal Agents; Female; Humans; Infant, Newborn; Infectious Disease Transmission, Vertical; Mass Screening; Pregnancy; Pregnancy Complications, Infectious; Pyrimethamine; Spiramycin; Sulfadiazine; Toxoplasmosis; Toxoplasmosis, Congenital

PubMed: 24733322
DOI: No ID Found