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PubMed1982

Induced Toxoplasma gondii, Toxocara canis, and Isospora canis infections in coyotes.

Six littermate laboratory-raised coyotes (No. 1-6) were used to study the transmission of Toxoplasma gondii from cats and mice, and Toxocara canis and Isospora canis from dogs and mice. Coyotes 1 and 2 were inoculated orally with 1,000 infective oocysts of the TC-1 strain of T gondii; coyotes 3 and 4 were fed mice infected with tissue cysts of the TC-1 strain of T gondii. Eight days after inoculation with T gondii, the same 4 coyotes were exposed to Toxocara canis: coyotes 1 and 2 were inoculated orally with 500 embryonated eggs, and coyotes 3 and 4 were fed mice infected with Toxocara canis. Fifteen days after exposure to Toxocara canis, the same 4 coyotes were fed mice infected with I canis. Two coyotes (No. 5 and 6) did not receive any organism and they served as controls. All 4 inoculated coyotes remained clinically normal but became infected with all 3 organisms. Toxoplasma gondii was recovered from the brain, heart, diaphragm, and muscles of limbs of coyotes killed 49 and 66 days after inoculation with oocysts, but only from muscles of limbs of coyote 4, killed at 84 days, and from the brain and muscles of limbs of coyote 3, killed at 72 days after feeding infected mice. Control coyotes did not acquire any of the 3 infections.

Animals↗
PubMed1995

Seroprevalence of Toxoplasma gondii in domestic animals in Pakistan.

The seroprevalence of Toxoplasma gondii infections among food animals in South-West Pakistan was measured by serological examination using a commercial latex agglutination test (LAT). In all 262 blood samples, from 100 cattle, 40 sheep, 58 goats and 64 chickens, were collected from the city abattoir. Titers considered diagnostically significant (> or = 1:64) were detected in 25% of cattle and 2.5% of sheep. None of the goats and chickens presented seropositivity for anti-toxoplasma antibodies. The study suggests the need for further investigations to determine the impact of these findings on the human population.

Animals↗
PubMed1994

An ultrastructural study of the effect of treatment with atovaquone in brains of mice chronically infected with the ME49 strain of Toxoplasma gondii.

The morphological effects of drug treatment with atovaquone in the brains of mice chronically infected with Toxoplasma gondii was examined by light and electron microscopy. As early as 1 and 2 weeks of treatment there appeared to be fewer tissue cysts compared to untreated controls and this reduction was more significant after 4 weeks treatment. There also appeared to be a decrease in the number of inflammatory nodules and the severity of the meningitis. Ultrastructurally, the cysts of both treated and control animals were located within host cells. There was a marked increase in both the number of cysts with lysed bradyzoites and the number of degenerate bradyzoites after 4 weeks treatment. It is probable that the drug is more active against the metabolically active immature bradyzoites than the mature organisms. Drug treatment does not appear to result in rupture of tissue cysts or release of Toxoplasma antigens since there is a reduction rather than an increase in the inflammatory response. This drug may be useful in treating chronic toxoplasmosis since it appears to be active against the bradyzoites reducing the parasite burden (cyst number) without initiating a destructive inflammatory response.

Animals↗
PubMed1993

Expression of major histocompatibility complex class II antigens and levels of interferon-gamma, tumour necrosis factor, and interleukin-6 in cerebrospinal fluid and serum in Toxoplasma gondii-infected SCID and immunocompetent C.B-17 mice.

In order to investigate activation of the innate immune system in murine toxoplasmosis, T- and B-cell-deficient SCID mice and their co-isogenic immunocompetent C.B-17 counterparts were orally infected with a low-virulent strain of Toxoplasma gondii (DX strain). SCID mice developed a fatal necrotizing toxoplasmosis, whereas CD4+ and CD8+ T cells contributing to inflammatory infiltrates conferred resistance to immunocompetent mice. Significant amounts of interferon-gamma (IFN-gamma) were detectable in SCID mice. The most likely source for this cytokine is activated natural killer (NK) cells. In comparison to immunocompetent mice IFN-gamma levels were reduced in cerebrospinal fluid (CSF) and serum of SCID mice at days 7 and 14 of disease. Similar amounts of tumour necrosis factor (TNF) were detected in both strains of mice. In addition, immunohistochemistry showed major histocompatibility complex (MHC) class II antigen expression on SCID and C.B-17 microglial cells and macrophages demonstrating activation of these cells in both strains. However, the up-regulation of MHC class II antigen on microglia was less pronounced in SCID mice, presumably due to reduced levels of IFN-gamma. Interleukin-6 (IL-6) levels in CSF and serum were elevated in both strains and correlated with systemic and intracerebral disease activity. In conclusion, our results demonstrate activation of macrophages and NK cells as the predominant defence mechanisms of the comprised SCID immune system during toxoplasma infection. This implies a major role for the innate immune system during early stages of toxoplasmosis although T cells are necessary to control the infection efficiently.

Animals↗
PubMed1977

Kinetics of antibody mediated suppression of humoral immune response to Toxoplasma gondii at a cellular level.

The effect of passively transferred Toxoplasma gondii antiserum was examined at a cellular level by rosette forming cell response in NMRI mouse spleen. The initial number of responding rosette forming cells was decreased in antibody treated animals; However, their rate of proliferation in comparison to untreated group was not significantly affected. Almost similar response could be obtained by injecting low 5 x 10(4) Toxoplasma dose alone or a combination of passive antibody and higher antigen dose of 1 x 10(6) parasites.

Animals↗
PubMed1993

Skeletal muscle capillary ultrastructure in Toxoplasma gondii parasitized mice.

A light and transmission electron microscopic study was performed in skeletal muscles from mice experimentally infected with Toxoplasma gondii. Parasite cysts were not observed. Capillary endothelial cytoplasm abnormalities included proliferation of organelles, decrease of pynocytic vesicles, degenerative changes and necrosis. In some capillaries the lumen was reduced or absent. Pericytes also were altered. In all animals (n = 13), the basement membrane was normal. The cellular infiltrate consisted of macrophages, lymphocytes, mastocytes and eosinophils. The alterations observed in muscle microvasculature in absence of Toxoplasma gondii cysts, could be due to a host-immune response to the parasite.

Animals↗
PubMed1996

Immunobiological diagnosis of tropical ocular diseases: Toxocara, Pythium insidiosum, Pseudomonas (Burkholderia) pseudomallei, Mycobacterium chelonei and Toxoplasma gondii.

Of the sera obtained from 18 patients with ocular diseases comprising ocular larva migrans (OLM), Toxoplasma gondii, Mycobacterium chelonei, Pythium insidiosum bacteria and tumour, 3 sera were positive for Toxocara antibody at the titre over 1/1600 ELISA. All 3 of these sera came from males with unilateral grayish fundi. We demonstrated the value of the direct immunofluorescent assay (DIFA) on vitreous specimens from 7 cases of Toxoplasma retinitis. One vitreous specimen under electronmicroscopic examination revealed bradyzoites of T. gondii. In addition, a few cases of keratoconjunctivitis/ corneal ulcer with endophthalmitis, due to P. insidiosum, Ps. pseudomallei and Mycobacterium chelonei, were also diagnosed.

Adolescent↗
PubMed1997

Toxoplasma pneumonia.

Toxoplasma gondii, an obligate intracellular parasite, is the causal agent of significant morbidity and mortality worldwide. In the presence of a normal immune response, the pathogen becomes latent and the immunocompetent host remains chronically infected throughout life, often without clinical disease. In the case of the patient with the acquired immunodeficiency syndrome (AIDS) or other defects in cell-mediated immunity, the infection reactivates and is most often manifest as toxoplasmic encephalitis. Toxoplasmic pneumonitis follows the same pathogenetic mechanism, but occurs less frequently than either toxoplasmic encephalitis or other opportunistic pneumonias, such as a Pneumocystis carinii pneumonia (PCP). During the past decade the incidence of toxoplasma pneumonia has increased in immunocompromised patients and as a result, it has become essential that clinicians include this infectious agent in the diagnostic testing and differential diagnostic of pneumonia in T gondii seropositive patients. Most patients present with clinical and radiographic findings suggestive of PCP. The onset of disease tends to be more rapid, however. Diagnosis is based upon a high degree of clinical suspicion and demonstration of T gondii in bronchioalveolar lavage fluid and/or lung biopsy specimens. Effective therapy, pyrimethamine and sulfadiazine or trisulfapyrimidine with folinic acid, is available if initiated promptly.

Animals↗
PubMedDate not supplied

[Diversity in the clinical course of toxoplasma encephalitis in two patients infected with human immunodeficiency virus (HIV)].

The central nervous system (CNS) is the most common site of Toxoplasma gondii infection in HIV-positive patients, mainly due to reactivation of Toxoplasma cysts. The diagnosis is difficult since no sensitive and specific non-invasive diagnostic tests exist. The patient may present with rather unspecific signs and symptoms. We present atypical course of CNS-toxoplasmosis in two HIV-positive persons.

AIDS-Related Opportunistic Infections↗
PubMed1997

Increasing of Toxoplasma gondii (Coccidia, Sarcocystidae) infections by Trypanosoma lewisi (Kinetoplastida, Trypanosomatidae) in white rats.

To demonstrate that T. lewisi infection increases T. gondii multiplication in white rats, groups of five Wistar or Sprague Dawley rats were inoculated with 10(6) T. lewisi trypomastigotes and four or seven days later infected with Toxoplasma tachyzoites. Host survival time was monitored, and the presence of T. gondii was confirmed in all dead rats by studying peritoneal exudate smears and lung tissue sections stained with haematoxylin-eosin. The presence of Toxoplasma cysts or antibodies was checked in the brain of surviving rats. The increase is observed four days after trypanosome inoculation and is dependent on rat strain, but not on inoculum size or rat age. Humoral and cellular factors may have a role in the increase as has been reported for other experimental infections with African trypanosomes and T. cruzi.

Animals↗
PubMed2026

Toxoplasma gondii IgG seroprevalence in Mauritanian dromedary camels: First multi-regional survey.

Toxoplasma gondii is a globally distributed zoonotic parasite, and dromedary camels are important intermediate hosts in arid and semi-arid regions. However, information on T. gondii exposure in camels is lacking in Mauritania, which harbors one of the largest camel populations in West Africa. This study reports the first multi-regional seroepidemiological survey to estimate T. gondii seroprevalence and identify associated risk factors in Mauritanian dromedaries. Between 2023 and 2024, serum samples were collected from 953 camels across eight climatically distinct regions. Anti-T. gondii IgG antibodies were detected using the Modified Agglutination Test (MAT; cutoff≥1:20). Risk factors investigated included geographical region, sex, age group, and season of sampling, using multivariable logistic regression and a mixed-effects linear probability model accounting for regional clustering. The overall seroprevalence was 15.0% (143/953). Exposure varied markedly across regions, ranging from 0% in the hyper-arid northern regions of Adrar and Tagant to 41.7% in the southern Sahelian region of Guidimakha. This pronounced spatial gradient is consistent with contrasting climatic and ecological conditions, as higher rainfall and humidity in the south are hypothesized to favor environmental oocyst survival compared to the extreme aridity of the north. Geographical region and age were independent predictors of seropositivity. Compared with camels from Nouakchott, those from Guidimakha had higher odds of exposure (aOR = 2.63), whereas camels from Trarza had a markedly lower risk (aOR = 0.09). Camels older than 6 years were more than twice as likely to be seropositive as those aged 3-5 years, whereas sex and season were not associated with seropositivity. These findings indicate that T. gondii exposure is widespread in Mauritanian dromedaries and that ecological conditions may influence exposure patterns. The marked spatial heterogeneity supports targeted surveillance and One Health interventions to reduce the potential zoonotic risk associated with camel-derived food products.

Animals↗
PubMed2025

Multi-criteria decision making and its application to in silico discovery of vaccine candidates for Toxoplasma gondii.

Vaccine discovery against eukaryotic parasites is not trivial and few exist. Reverse vaccinology is an in silico vaccine discovery approach, designed to identify vaccine candidates from the thousands of protein sequences encoded by a target genome. Previously, we produced the Vacceed bioinformatics pipeline for identification of parasite membrane and excreted/secreted proteins that were likely be exposed to the hosts immune system. More recently, we improved upon machine learning as the final decision-making process to identify parasite proteins that induce a protective response in an animal model. Subsequently, we combined Vacceed with metrics on B and T cell epitope types to produce a new in silico discovery workflow. In this study we extend this in silico workflow to the developability of proteins as vaccines by the incorporation of metrics on the physicochemical properties of proteins. To demonstrate this process, every Toxoplasma gondii protein was ranked in its capacity to provide exposure to the immune system (Vacceed exposure score), presence of epitopes and solubility characteristics by several multicriteria decision making (MCDM) tools (such as TOPSIS, VIKOR and MABAC). A consensus rank was subsequently generated from the results of these tools using a variety of aggregate ranking methods. Levels of uncertainty in the aggregate protein rankings was assessed by conformal interval prediction in association with a machine learning model. Several of the top ranked proteins identified by this approach were novel, uncharacterized membrane transporters or proteins associated with RNA metabolism. In conclusion, MCDM automated the decision making using well known algorithms while conformal prediction intervals varied significantly across the 8000+ proteins of T. gondii. Highly ranked proteins (e.g. the top 100) typically generated low prediction intervals, providing high levels of confidence in their ranks.

Toxoplasma↗
PubMed2026

Serological and Molecular Prevalence of HCMV, HCV, HBV and Toxoplasma gondii Co-infection in Treatment-Naive HIV-Infected Individuals.

INTRODUCTION: Co-infections with human cytomegalovirus (HCMV), hepatitis B virus (HBV), hepatitis C virus (HCV), and Toxoplasma gondii (T. gondii) pose clinical challenges in human immunodeficiency virus-1 (HIV-1)-infected individuals by complicating disease progression and management. This study aimed to investigate the serological and molecular prevalence of HCMV, HBV, HCV, and T. gondii co-infections among treatment-naive HIV-infected individuals. METHODS: A cross-sectional study was conducted from March 2022 to August 2024 on 203 treatment- naive HIV-1-infected individuals. Plasma samples were analyzed using ELISA for serological markers and real-time PCR for molecular detection. Statistical analyses were performed to assess demographic and clinical variables associated with co-infections. RESULTS: Among the 203 participants, the prevalence of anti-HCV antibodies, HBsAg, HCMV IgM, and T. gondii IgM was 9.9%, 2.5%, 1.5%, and 0.5%, respectively. Molecular detection confirmed active HBV, HCV, and HCMV infections in 40%, 60%, and 66.7% of seropositive individuals, respectively, while T. gondii DNA was undetected. HCV genotyping revealed subtype 1a as the most common (50%), followed by 3a (37.5%) and 1b (12.5%). DISCUSSION: The findings indicate a moderate prevalence of HBV and HCV co-infections and a low prevalence of HCMV and T. gondii co-infections in treatment-naive HIV patients. CONCLUSION: These results highlight the need for targeted public health interventions, including vaccination and screening strategies, to reduce the risk of co-infections in HIV-infected individuals.

Humans↗
PubMed1983

Toxoplasma gondii and the compromised host. Antibody response in the absence of clinical manifestations of disease.

Toxoplasmosis is a well-described opportunistic infection in immunocompromised hosts. Meningoencephalitis, myocarditis, and pneumonitis are the most frequent clinical manifestations of disease. Because of difficulties both with isolation of the organism and with its identification in tissue, most laboratories rely on serological techniques for diagnosis of acute disease. The most widely available and commonly employed serological method is the indirect fluorescent antibody test (IFA). We recently encountered an immunocompromised patient with an undefined hematologic malignant neoplasm who had an IFA titer greater than 1:100,000 without clinical evidence of active toxoplasmosis. Although his dye test titer and direct agglutination titer were also elevated, he had negative double-sandwich-IgM enzyme-linked immunosorbent assay titers. Immunoperoxidase staining of the tissues failed to demonstrate trophozoites. This case demonstrates that elevated toxoplasma IFA titers may occur in patients at high risk for opportunistic infection but who do not manifest overt clinical toxoplasmosis.

Aged↗
PubMed1984

Acute Toxoplasma infection among family members of patients with acute lymphadenopathic toxoplasmosis.

Studies were performed to determine how frequently acute infections with Toxoplasma gondii occur among family members of patients with acute acquired lymphadenopathic toxoplasmosis. In five of the nine families studied, more than one family member had serologic evidence of recent acute infection with T gondii. In three of the families, the immunoglobulin M and immunoglobulin G antibody titers to T gondii among infected family members were similar irrespective of whether lymphadenopathy was present. Lymphadenopathy developed in one family member in each of two families (families VIII and IX) three and eight months after lymphadenopathy had developed in the index case (proband). These results suggest that common-source outbreaks occur with surprising frequency among family members of patients with lymphadenopathic toxoplasmosis and that the humoral response is similar with different manifestations of the infection.

Acute Disease↗
PubMed1996

Kinematic analysis of Toxoplasma gondii motility.

Toxoplasma gondii tachyzoites execute a complex and little understood combination of rapid movements to reach and penetrate human or other animals cells. In the present study, computer-assisted simulation was used to quantitatively analyze the motility of these parasites in three-dimensional space with spatial and temporal resolutions in the micrometer and subsecond ranges. A digital model based on electron-micrographs of a serially sectioned tachyzoite was animated according to a videomicrographed sequence of a characteristic repetitive movement. Keyframe animation defined over 150 frames by a total of 36 kinematic parameters for specific motions, of both the whole model and particular domains, resulted in a real-time life-like simulation of the videorecorded tachyzoite movement. The kinematic values indicate that a full revolution of the model is composed of three half-turns accomplished in nearly 5 s with two phases: a relatively slow 180 degrees tilting with regard to the substratum plane, followed by fast (over 200 degrees/s) spinning almost simultaneous with pivoting around the posterior end, each clockwise and for about 180 degrees. Maximal flexing of the body, as well as bowing and retraction of its anterior end, occur at midway during the tilting phase. An estimated 70 degrees. clockwise torsion of the body seems to precede the spinning-pivoting phase. The results suggest the operation of two basic forces in the motility of T. gondii tachyzoites: (1) a clockwise torque that causes torsion, spinning, and pivoting; and (2) a longitudinal pull that contracts, bends and tilts the parasite. We discuss the possibility that both of these forces might result from the action of an actin-myosin system enveloping the twisted framework of microtubules characteristic of these organisms.

Animals↗
PubMed1997

Actin in the parasite Toxoplasma gondii is encoded by a single copy gene, ACT1 and exists primarily in a globular form.

Actin is a highly conserved microfilament protein that plays an important role in the invasion of host cells by the protozoan parasite Toxoplasma gondii. We have characterized the ACT1 gene and localized the conventional isoform of actin that it encodes within T. gondii. The predicted amino acid sequence of ACT1 was most similar to two other parasite actins, Plasmodium falciparum Pfact-1 (93.1% identical) and Cryptosporidium parvum actin (88.1%): among vertebrate actins, ACT1 was most closely related to the mammalian beta and gamma (83%) actin isoforms. Actin-specific antibodies and fluorescently labeled DNAse I were used to localize actin in T. gondii tachyzoites by immunofluorescence and immunoelectron microscopy. Actin was detected beneath the parasite cell membrane and in clusters scattered within the cytosol of T. gondii tachyzoites. Actin filaments were not detected in detergent-solubilized parasites separated by high speed centrifugation, indicating that actin exists primarily in a globular form in T. gondii.

Actins↗