<i>Toxoplasma gondii</i>infection, from predation to schizophrenia: can animal behaviour help us understand human behaviour?

Webster, Joanne P.; Kaushik, Maya; Bristow, Greg C.; McConkey, Glenn A.

doi:10.1242/jeb.074716

Cited by 149 publications

(112 citation statements)

References 188 publications

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“…In particular, parasites commonly use the potent monoamine neurotransmitters dopamine (DA), serotonin and octopamine with conservation in structure and function across the vast range of host taxa that parasites manipulate (Pflüger and Stevenson, 2005;Shaw et al, 2009;Helluy, 2013;Libersat and Gal, 2013;McConkey et al, 2013;Vyas, 2013;Webster et al, 2013). These monoamines are also used by hosts to regulate a wide variety of brain functions from stress to reproduction (Libersat and Pflueger, 2004;Nelson and Trainor, 2007;Øverli et al, 2007).…”

Section: Neuropharmacological Host Manipulation Monoamines and Hormonesmentioning

confidence: 99%

Lessons in Mind Control: Trends in Research on the Molecular Mechanisms behind Parasite-Host Behavioral Manipulation

Herbison

2017

Front. Ecol. Evol.

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Scientific and public interest in host manipulation by parasites has surged over the past few decades, resulting in an exponential growth of cases where potential behavioral manipulation has been identified. However, these studies dwarf the number of genuine attempts to elucidate the mechanistic processes behind this behavioral manipulation. Ultimately, this imbalance has slowed progress in the study of the mechanisms underlying host manipulation. As it stands, research suggests that the mechanisms of host manipulation fall into three categories: immunological, genomic/proteomic and neuropharmacological, and forth potential category: symbioant-mediated manipulation. After exploration of the literature pertaining to these four pathways, four major trends become evident. First and foremost, there is a severe disconnect between the observed molecular and behavioral shifts in a parasitized host. Indeed, very rarely a study demonstrates that molecular changes observed in a host are the result of active manipulation by the resident parasite, or that these molecular changes directly result in behavioral manipulation that increases the parasite's fitness. Secondly, parasites may often employ multiple pathways in unison to achieve control over their hosts. Despite this, current scientific approaches usually focus on each manipulation pathway in isolation rather than integrating them. Thirdly, the relative amount of host-parasite systems yet to be investigated in terms of molecular manipulation is staggering. Finally, as a result of the aforementioned trends, guiding mechanisms or principles for the multiple types of behavioral manipulation are yet to be found. Researchers should look to identify the manipulative factors required to generate the molecular changes seen in hosts, while also considering the "multi-pronged" approach parasites are taking to manipulate behavior. Assessing gene expression and its products during transitional periods in parasites may be a key methodological approach for tackling these recent trends in the host manipulation literature.

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Section: Neuropharmacological Host Manipulation Monoamines and Hormonesmentioning

confidence: 99%

Lessons in Mind Control: Trends in Research on the Molecular Mechanisms behind Parasite-Host Behavioral Manipulation

Herbison

2017

Front. Ecol. Evol.

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“…T. gondii can persist in brain and muscle throughout the host's life, and chronic infection is asymptomatic in immunocompetent humans (2). However, recent studies have suggested that T. gondii infection is a risk factor for developing mental diseases, such as schizophrenia and depression, as well as human behavior and personality changes and suicide (3,4). Interestingly, T. gondii infection increases the risk of schizophrenia roughly 2.7 times, which is higher than that for genes associated with schizophrenia (5).…”

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confidence: 99%

Toxoplasma gondii Infection in Mice Impairs Long-Term Fear Memory Consolidation through Dysfunction of the Cortex and Amygdala

et al. 2016

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cChronic infection with Toxoplasma gondii becomes established in tissues of the central nervous system, where parasites may directly or indirectly modulate neuronal function. Epidemiological studies have revealed that chronic infection in humans is a risk factor for developing mental diseases. However, the mechanisms underlying parasite-induced neuronal dysfunction in the brain remain unclear. Here, we examined memory associated with conditioned fear in mice and found that T. gondii infection impairs consolidation of conditioned fear memory. To examine the brain pathology induced by T. gondii infection, we analyzed the parasite load and histopathological changes. T. gondii infects all brain areas, yet the cortex exhibits more severe tissue damage than other regions. We measured neurotransmitter levels in the cortex and amygdala because these regions are involved in fear memory expression. The levels of dopamine metabolites but not those of dopamine were increased in the cortex of infected mice compared with those in the cortex of uninfected mice. In contrast, serotonin levels were decreased in the amygdala and norepinephrine levels were decreased in the cortex and amygdala of infected mice. The levels of cortical dopamine metabolites were associated with the time spent freezing in the fear-conditioning test. These results suggest that T. gondii infection affects fear memory through dysfunction of the cortex and amygdala. Our findings provide insight into the mechanisms underlying the neurological changes seen during T. gondii infection.T oxoplasma gondii is one of the most successful brain parasites, infecting approximately one-third of the human population (1). T. gondii can persist in brain and muscle throughout the host's life, and chronic infection is asymptomatic in immunocompetent humans (2). However, recent studies have suggested that T. gondii infection is a risk factor for developing mental diseases, such as schizophrenia and depression, as well as human behavior and personality changes and suicide (3, 4). Interestingly, T. gondii infection increases the risk of schizophrenia roughly 2.7 times, which is higher than that for genes associated with schizophrenia (5). Several studies have also suggested that rodents infected with T. gondii exhibit decreased avoidance behavior in response to cat odors, indicating manipulation of the host's behavior by T. gondii to facilitate the parasite's transmission and complete sexual replication in the definitive host (6-11).To date, research on the mechanism(s) underlying behavioral changes following T. gondii infection has been conducted primarily from two points of view. First, the relationship between parasite localization in the brain and behavioral changes has been investigated, with a previous study reporting that T. gondii has no obvious tropism in the brain (12-15). However, another study found that tissue cyst density in amygdalar areas (the medial and basolateral amygdala) is 2-fold higher than that in nonamygdalar areas (9), whereas the presence of tissue cy...

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“…Characteristics of the infection also play a role, including its source (oocysts or tissue cysts), possible interactions with other infectious agents, and the genotype; thus, genotypes II and III more frequently establish chronic infections and show a greater expression of tyrosine hydroxylase genes in comparison with genotype I, and they may be more strongly related to behavioral changes [205].…”

Section: Is There An Etiological Association Between Toxoplasma Gondimentioning

confidence: 99%

Toxoplasma gondii and Schizophrenia: A Relationship That Is Not Ruled Out

Sorlózano-Puerto¹,

Gutiérrez‐Fernández²

2016

Schizophrenia Treatment - The New Facets

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Over recent years, it has been proposed that some diseases of unknown origin, such as schizophrenia, may be caused by persistent chronic infections coupled with a genetic component and may be perpetuated by the immune system. This hypothesis is supported by epidemiological and biological evidence on the exposure of schizophrenics to infectious diseases during prenatal or postnatal periods, including Toxoplasma gondii, chlamydia, human herpes virus, human endogenous retroviruses, parvovirus B19, mumps, and flu viruses. This growing list of microbes will undoubtedly continue to increase in the future. Linking infection to schizophrenia is a complex challenge that requires further experimental and epidemiological research. T. gondii is the infectious agent that has most frequently been related to neuropsychiatric disorders, including schizophrenia, and it is considered to represent a highly useful model to analyze the influence of a microorganism on human behavior and the development of psychiatric disease. It may also help to detect patient subpopulations susceptible to treatment with specific antimicrobials by improving definition of the differential phenotype of the disease, and it offers the possibility of a preventive approach.

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Toxoplasma gondiiinfection, from predation to schizophrenia: can animal behaviour help us understand human behaviour?

Cited by 149 publications

References 188 publications

Lessons in Mind Control: Trends in Research on the Molecular Mechanisms behind Parasite-Host Behavioral Manipulation

Lessons in Mind Control: Trends in Research on the Molecular Mechanisms behind Parasite-Host Behavioral Manipulation

Toxoplasma gondii Infection in Mice Impairs Long-Term Fear Memory Consolidation through Dysfunction of the Cortex and Amygdala

Toxoplasma gondii and Schizophrenia: A Relationship That Is Not Ruled Out

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