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Mesocestoides vogae is a cestode of the order Cyclophyllidea, and its second intermediate hosts are mammals, birds, amphibians, and reptiles. The parasite forms a tetrathyridium in the second intermediate host and multiplies asexually, sometimes to the point of filling the host's abdominal cavity. Proliferated tetrathyridium may cause lethal conditions in the host. During the asexual multiplication period, the scolex first replicates into two and then divides into two worms. In this study, to investigate the factors that promote the replication, tetrathyridia were cultured under various in vitro conditions. When several worms which already had two scolexes were cultured together, the division into two worm bodies was complete, but when single worm was cultured, the division hardly proceeded. The result indicates that the division progression of tetrathyridia with two scolexes requires the presence of other worms. In contrast, tetrathyridia with only one scolex did not initiate the division process, whether cultured together or alone. Then, the necessity of direct contact between the bodies of the worms to promote the division of tetrathyridia with two scolexes was assessed. For this, the well of the culture plate was partitioned into upper and lower parts using a mesh, and 20 worms in the upper part and single worm in the lower part were cultured. In all examined wells, worms in the upper part showed complete division, whereas the worms in the lower part rarely completed the division. Thus, direct contact between tetrathyridium promotes the division of tetrathyridia bearing two scolexes., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Toxoplasma gondii is a protozoan parasite that infects almost all species of mammals and birds, including fur-bearing animals. However, the prevalence of T. gondii among Russian fur-bearing animals is unknown. In this study, the seroprevalence of T. gondii in European mink in Russia was investigated. In total, 100, 119 and 61 serum samples were collected from a fur farm, located in the Republic of Tatarstan, Russia, in autumn 2016, 2017 and 2018, respectively. The seroprevalence of T. gondii in 2016, 2017 and 2018 was 32% (23.2%-42.2%, 95% confidence interval [CI]), 31.1% (23.1%-40.3%, 95% CI) and 41.0% (28.8%-54.3%, 95% CI), respectively. In total, 50 brain samples from 100 animals whose blood was sampled in 2016 were analyzed by PCR to detect T. gondii DNA. T. gondii DNA was detected in 14% (7/50) of the mink brain samples. To examine single nucleotide polymorphisms (SNPs) in the partial B1 gene, we sequenced an 836-bp fragment, which contains a few SNPs, from the detected T. gondii DNA. The sequences of the fragments were identical to those of two of the major lineages, Type II and Type III, but differed from that of the Type I lineage., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Toxoplasma gondii strains have been isolated all over the world and their virulence has been examined mainly using laboratory mice. However, T. gondii differs in virulence depending on the host animal species. Therefore, to evaluate the virulence of each strain in domestic animals, it is necessary to examine using not only mice but also the concerned animals. We have shown that TgCatJpOk4, a T. gondii strain recently isolated in Okinawa, Japan, has a high virulence against laboratory mice, comparable to highest virulent RH strain in mice; however, the virulence to domestic animals remains unknown. In this study, we examined the virulence using the Microminipig. After infection, four out of five infected pigs showed severe clinical symptoms: inappetence, hypoactivity and tachypnea. Eventually, three out of the five infected pigs succumbed before the end of the observation. Among the three dead pigs, histological analysis revealed that interstitial pneumonia and spotty necrosis in the liver indicating that the TgCatJpOk4 strain has a high virulence not only in laboratory mice, but in pigs as well., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Toxoplasma gondii can infect almost all mammals and birds, including chickens. The aim of this study was to identify an appropriate immunogenic antigen for serodiagnosis of T. gondii infections in chickens. We examined serum samples from chickens that were intravenously or intraperitoneally infected with 10 6 -10 8 tachyzoites of T. gondii strains PLK, RH, CTG, ME49 or TgCatJpGi1/TaJ using enzyme-linked immunosorbent assays (ELISAs), latex agglutination tests (LATs) and western blotting. Regardless of parasite strain or infection dose and route, the commercial LAT was positive for almost all sera collected 1 week post-infection. However, at 2 weeks post-infection, LATs were negative in the same birds. ELISAs using the Escherichia coli-produced recombinant T. gondii antigens SAG1 and GRA7 showed strong signals at 1-2 weeks post infection, but thereafter diminished for the majority of serum samples. In contrast, western blotting against crude tachyzoite antigens showed a persistent band up to 4 weeks post-infection. Sera from these chickens reacted much more strongly with SAG1 from crude tachyzoite antigens than with recombinant SAG1. Even in experimentally-infected birds whose parasite burdens in tissue were undetectable, sera still reacted with native SAG1. We tested sera from free-range chickens on a small farm in Ghana, Africa, using western blotting and found that the serum of one bird reacted with a single band of approximately 27 kDa, the putative molecular weight of SAG1. Thus we conclude that native SAG1, but not E. coli-produced recombinant SAG1, is suitable for serodiagnosis of T. gondii infections in chickens., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The virulence of a type III Toxoplasma gondii strain isolated in Japan and designated here as TgCatJpGi1/TaJ was examined in mice and micro minipigs in this study. Despite its type III genotype, oral or intraperitoneal inoculation of cysts from it resulted in severe virulence in C57BL/6J and BALB/c mice. In contrast, mice inoculated with a high dose of TgCatJpGi1/TaJ tachyzoites showed no obvious clinical signs of infection, and all of them survived for >21 days post-inoculation. Furthermore, no clinical signs of infection were seen when micro minipigs were inoculated with 900 cysts. Interestingly, our allelic type screening of the virulence-related rop5, rop16, rop17, and rop18 genes, as based on restriction fragment length polymorphism analysis (RFLP), revealed that the RFLP patterns for TgCatJpGi1/TaJ were identical to those from nonvirulent type III parasites. These results suggest that TgCatJpGi1/TaJ possesses an unknown virulence factor or factors., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Toxoplasmosis, a most common zoonosis, is caused by the protozoan parasite Toxoplasma gondii. However, there is little epidemiological information on T. gondii infections in humans and livestock animals in Russia. Therefore, in this study, the seroprevalence of T. gondii in goats in Russia was investigated. A total of 216 goats from 32 farms were investigated and 95 of them were seropositive for T. gondii. The difference in seroprevalence between the examined regions was not statistically significant. We next collected serum samples from 99 cats and 181 humans in Kazan city, the state capital of the Republic of Tatarstan, Russia, and examined their T. gondii seroprevalences. Thirty-nine of the 99 cat samples and 56 of the 181 human samples showed seropositivity. Logistical regression analysis revealed that the cat breeding history of the human subjects, but not their sex or age is a significant risk factor for T. gondii seropositivity. These findings suggest that the natural environment in Russia may be widely polluted with T. gondii oocysts shed by cats, and ingestion of these oocysts provides a major route for human infection with this parasite., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Tachyzoites of Toxoplasma gondii, an obligate intracellular parasite, actively invade a broad spectrum of cell types. T. gondii infects leukocytes and spreads to distant organs such as the brain, lungs and muscles. However, the mechanism of T. gondii transmission from infected leukocytes to peripheral organs is unknown. To show the dynamics of infected leukocytes and intracellular parasites in vivo, previous studies have prepared T. gondii-infected leukocytes and injected them into circulation in experimental animals. However, when the infected leukocytes are prepared in vitro, some extracellular tachyzoites remain in the leukocyte cell culture because it is almost impossible to wash out these extracellular tachyzoites. These extracellular tachyzoites may distort experimental results. In this study, we report a method for removing extracellular tachyzoites from leukocyte culture suspension using antibody-conjugated magnetic beads. Using this method, extracellular tachyzoites in suspension cell culture can be effectively eliminated., (Copyright © 2016. Published by Elsevier Ireland Ltd.)

We investigated the presence of antibodies against Toxoplasma gondii in domesticated goats intended for human consumption in a rural suburb of Rajshahi, Bangladesh. Antibodies to T. gondii were found in 55.1% (80/145) of the goats tested in our sample. The seroprevalence among goats aged <1 year, 1-2 years, 2-3 years and ≥3 years were 36.7%, 66.0%, 59.1% and 100%, respectively. Our results demonstrated that seroprevalence increased with age. Among the seropositive goats, a subsample of eight free-ranging female goats with access to male goats was placed under continuous observation. During the observation period, these seropositive female goats delivered 11 kids, all of which were found to be seronegative before suckling colostrum. This finding strongly suggested that trans-placental infection rarely occurs in female goats that have acquired an infection before pregnancy. Our results indicate that infection via ingestion of oocysts plays a more important role than endogenous trans-placental infection in maintaining the endemicity of T. gondii among goats in Bangladesh., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Toxoplasma gondii is an obligate intracellular apicomplexan parasite that infects humans and animals. Ingested parasites cross the intestinal epithelium, invade leukocytes and are then disseminated to peripheral organs. However, the mechanism of extravasation of the infected leukocytes remains poorly understood. In this study, we demonstrate that T. gondii-invaded human and mouse leukocytes express higher level of CD44, a ligand of hyaluronan (HA), and its expression on myeloid and non-myeloid leukocytes causes T. gondii-invaded human and mouse leukocyte to adhere to HA more effectively than non-invaded leukocytes. The specific adherence of parasite-invaded leukocytes was inhibited by anti CD44 antibody. Leukocytes of CD44 knockout mice did not show parasite-invaded leukocyte specific adhesion. Our results indicate that parasite-invaded leukocytes, regardless of whether myeloid or not, gain higher ability to adhere to HA than non-invaded leukocytes, via upregulation of CD44 expression and/or selective invasion to CD44 highly expressing cells. The difference in ability to adhere to HA between parasite-invaded cells and non-invaded neighboring cells might facilitate effective delivery of parasite-invaded leukocytes to the HA-producing endothelial cell surface and/or HA-rich extra cellular matrix., (© 2013.)

The apicomplexan, obligate intracellular parasite Toxoplasma gondii orally infects humans and animals. The parasites cross the intestinal epithelium, invade leukocytes in the general circulation and then disseminate into the peripheral organs. The mechanism of extravasation of the infected leukocytes, however, remains poorly understood. It is known that adhesion of leukocytes to extracellular matrix (ECM) is an important factor in extravasation, and CD44 and ICAM-1 on the leukocyte surface are known receptors for hyaluronan (HA), an ECM component. In this study, we demonstrated up-regulation of CD44 and ICAM-1 expression on the surface of T. gondii-infected human monocytic THP-1 cells and fresh isolated human monocyte. T. gondii-infected THP-1 cells adhered more efficiently to immobilized HA than did non-infected cells. T. gondii-infected monocytes in the general circulation might preferentially adhere to the ECM and migrate out from blood vessels, so transporting parasites into the peripheral organs., (Copyright 2009 Elsevier Inc. All rights reserved.)

Toxoplasma gondii is an intracellular parasite. It has been thought that T. gondii can disseminate throughout the body by circulation of tachyzoite-infected leukocytes (intracellular parasite) in the blood flow. However, a small number of parasites exist as free extracellular tachyzoites in the blood flow (extracellular parasite). It is still controversial whether the extracellular parasites in the blood flow disseminate into the peripheral tissues. In this study, we evaluated the dissemination efficiency of the extracellular and intracellular parasites in the blood flow using GFP-expressing transgenic parasite (PLK/GFP) and DsRed Express-expressing transgenic parasite (PLK/RED). When PLK/GFP and PLK/RED tachyzoites were injected, as intracellular and extracellular forms respectively, at the same time into the tail vein of a mouse, many disseminated green fluorescent PLK/GFP tachyzoites were observed in the lung, the spleen, the liver and the brain. However, only a few red fluorescent PLK/RED tachyzoites were detected in these organs. When PLK/GFP and PLK/RED tachyzoites were injected in the opposite manner, that is, as extracellular and intracellular forms respectively, the majority of tachyzoites in these tissues were PLK/RED tachyzoites. Collectively, these results indicate that intracellular tachyzoites mainly disseminate throughout the body and that extracellular tachyzoites hardly contribute to parasite dissemination.