Toxoplasma Infection: Current Problems, Progress and New Challenges

Toxoplasmosis caused by Toxoplasma gondii is an important zoonosis of human and animal health significance. Current chemical therapeutics have side effects, and no commercially available vaccine is licensed for the prevention of toxoplasmosis in humans and most animals. Developing a safe and effective vaccine with long-term protection against T. gondii infection is necessary to control toxoplasmosis. HAD2a is a key member of the haloacid dehalogenase (HAD) phosphatase family, which is essential for T. gondii daughter budding. However, the role of HAD2a in T. gondii virulence remains unknown. In this study, we successfully constructed the had2a gene knockout strain in the T. gondii-type I RH strain (RHΔhad2a) and determined its role in virulence and vaccination. These results demonstrate that HAD2a played an important role in parasite daughter budding and in vitro replication. Knockout of the had2a gene attenuated the virulence of the T. gondii-type I RH strain. Vaccination with RHΔhad2a tachyzoites induced a Th1-biased immune response, provided partial protection against acute T. gondii infection in mice by highly virulent tachyzoites of RH and PYS (ToxoDB#9, Chinese I) strains, and conferred strong protection against challenge infection by cysts and oocysts of the less virulent type II Pru strain. These results demonstrate that T. gondii had2a is important for its in vitro proliferation and virulence in mice and that RHΔhad2a may be used as a candidate strain to generate a multiple gene knockout live-attenuated strain or be collaboratively applied with other live-attenuated strains to confer more effective protection against T. gondii infection. Full article

Toxoplasma gondii is a widespread protozoan parasite that infects most warm-blooded animals, and felids can serve as intermediate and definitive hosts. Pathological diagnosis and serological and etiological investigations were conducted on a captive caracal (Caracal caracal) carcass collected from China in 2022. Pathological diagnosis revealed that cardiac insufficiency, pulmonary edema, hepatic failure, and renal insufficiency were the causes of the caracal’s death. A modified agglutination test (cut-off: 1:25) revealed that IgG antibodies against T. gondii were present in the myocardium juice (1:1600), ascitic fluid (1:3200), and hydropericardium (1:800). A viable T. gondii (TgCaracalCHn2) strain was isolated from the tissue samples (heart, brain, spleen, and skeletal muscle) of this caracal using a mouse bioassay. The genotype of TgCaracalCHn2 was ToxoDB#5 (Type II variant), as determined via RFLP-PCR. The strain was avirulent in Swiss mice and matched the prediction of ROP18 and ROP5 gene alleles of TgCaracalCHn2 (2/2). Mild tissue cysts (203 ± 265) were observed in mice brains after inoculation with TgCaracalCHn2 tachyzoites. ToxoDB#5 is the dominant genotype in North American wildlife, and this is the first documented isolation of T. gondii ToxoDB#5 from China. This indicates that caracal plays an important role in the transmission of this T. gondii genotype. Full article

The aim of our study was to evaluate the impact of T. gondii status on eosinophils count (EOS), the eosinophil-to-lymphocyte ratio (ELR), and the eosinophil-to-neutrophil-to-lymphocytes ratio (ENLR) before and after cannabis cessation in patients with psychiatric disorders. One hundred and eighty-eight patients were included in the study. T. gondii, EOS, ELR, ENLR, and urinary cannabis were measured at baseline and after 4 weeks of cannabis cessation. Highest levels and increase of PNE (p = 0.02), ENLR levels (p = 0.031) and highest level of ELR (p = 0.03) were found in patients after cannabis cessation only in patients positive for T. gondii serology (Toxo+ group). At four weeks, significant interactions between cannabis and T. gondii status for EOS (p = 0.038), and for ENLR (p = 0.043) levels were found, as well as for the evolution between baseline and 4 weeks for ENLR level (p = 0.049). After cannabis cessation, we found a positive correlation between negative symptoms and EOS levels at 4 weeks in the Toxo+ group. This study shows that the increase of inflammation after cannabis cessation might be modulated by T. gondii seropositivity status in patients after cannabis cessation. Full article

Toxoplasma gondii is an opportunistic pathogenic protozoan that can infect all nucleated cells in almost all warm-blooded animals, including humans. T. gondii infection has been reported in many food animals worldwide. However, the prevalence and genotypes of T. gondii in chickens from farmers’ markets in Fujian province in southeastern China remain unreported. In the present study, four tissue samples from each of the 577 chickens (namely, the heart, liver, lungs, and muscles) were collected from farmers’ markets in five regions of Fujian province (Zhangzhou, Sanming, Quanzhou, Fuzhou, and Longyan). We first analyzed the prevalence and genotypes of T. gondii using PCR targeting of the B1 gene of T. gondii. Of the 577 chickens, thirty-two (5.5%) tested positive for the B1 gene. Among the five regions, Sanming had the highest infection rate (16.8%, 16/95), followed by Quanzhou (8.0%, 8/100), Longyan (5.0%, 5/100), Zhangzhou (1.1%, 2/182), and Fuzhou (1.0%, 1/100). Among these thirty-two T. gondii-positive chickens, the infection rates of the lungs, heart, liver, and muscles were 68.8% (22/32), 34.4% (11/32), 28.1% (9/32), and 9.4% (3/32), respectively. Significant differences in prevalence were found among the different regions (χ² = 35.164, p < 0.05) and tissues (χ² = 25.874, p < 0.05). A total of 128 tissue and organ samples of the thirty-two T. gondii-positive chickens from the different regions were analyzed using PCR–restriction fragment length polymorphism (PCR–RFLP) on the basis of 10 genetic markers. Seven tissue samples (lung samples from five chickens, heart samples from one chicken, and liver samples from one chicken) underwent successful amplification at all the genetic markers, and all the T. gondii genotypes were identified as genotype I (ToxoDB #10). These findings serve as a foundation for evaluating the risk of T. gondii contamination in chicken products intended for human consumption and offer insight into preventing the transmission of the parasite from chickens to humans. Full article

Toxoplasmosis, caused by the cosmopolitan protozoan Toxoplasma gondii, has particular implications during pregnancy due to the possible transmission of infection to the fetus. Very few studies have assessed seroprevalence and the risk factors for toxoplasmosis in healthy pregnant women. The aim of this study was to examine the seroprevalence of T. gondii infection in healthy pregnant women and to identify the associated risk factors for toxoplasmosis. The cross-sectional study involved 300 healthy pregnant women who came to the Institute for Blood Transfusion in Belgrade between November 2018 and February 2019 for routine blood group and Rh factor testing before delivery, who were also tested using serological screening for the presence of specific antibodies. Positives were further examined using enzyme immunoassay. Of the total sera of participants analyzed, 38 were positive for specific IgG, resulting in a seroprevalence rate of 12.7% (95% Confidence Interval (CI) 9.1–17.0%). All pregnant women presented negative anti-T. gondii IgM antibodies. The multivariate logistic regression analysis revealed that living in a house with a garden was independently associated with the risk of T. gondii infections, while eating chicken meat was connected with a lower risk compared to eating other types of meat with an odds ratio (OR) of 2.5 (95% CI 1.21–5.02) and an OR of 0.3 (95% CI 0.09–0.83), respectively. Although the prevalence of anti-T. gondii IgG antibodies is relatively low, it is essential to maintain and adapt evidence-based preventive measures for toxoplasmosis continually. Full article

The Zinc finger protein (ZFP) family is widely distributed in eukaryotes and interacts with DNA, RNA, and various proteins to participate in many molecular processes. In the present study, the biological functions of eight ZFP genes in the lytic cycle and the pathogenicity of Toxoplasma gondii were examined using the CRISPR-Cas9 system. Immunofluorescence showed that four ZFPs (RH248270-HA, RH255310-HA, RH309200-HA, and RH236640-HA) were localized in the cytoplasm, and one ZFP (RH273150-HA) was located in the nucleus, while the expression level of RH285190-HA, RH260870-HA, and RH248450-HA was undetectable. No significant differences were detected between seven RHΔzfp strains (RHΔ285190, RHΔ248270, RHΔ260870, RHΔ255310, RHΔ309200, RHΔ248450, and RHΔ236640) and the wild-type (WT) strain in the T. gondii lytic cycle, including plaque formation, invasion, intracellular replication, and egress, as well as in vitro virulence (p > 0.05). However, the RHΔ273150 strain exhibited significantly lower replication efficiency compared to the other seven RHΔzfp strains and the WT strain, while in vivo virulence in mice was not significantly affected. Comparative expression analysis of the eight zfp genes indicates that certain genes may have essential functions in the sexual reproductive stage of T. gondii. Taken together, these findings expand our current understanding of the roles of ZFPs in T. gondii. Full article

Sheep are highly susceptible to Toxoplasma gondii, and miscarriage is the main clinical feature. This study investigated 227 sheep samples (210 myocardial tissues from slaughterhouses, 6 ewe serum samples, 3 aborted fetuses, and 8 dead lambs from veterinary clinics) from central China for T. gondii infection. Antibodies against T. gondii were detected using the modified agglutination test (MAT). PCR was performed to detect T. gondii DNA in the tissue samples. The results showed that four samples were seropositive (MAT titer ≥ 1:100), with a seroprevalence of 1.8% (4/227). The seropositive samples included two myocardial samples from a slaughterhouse, one ewe and its aborted fetus from a veterinary clinic. The results revealed that 7 out of 207 (3.4%) sheep tissue samples were PCR-positive, including two myocardial tissue samples from slaughterhouses, three aborted fetuses, and two lambs from veterinary clinics. Toxoplasma gondii vertical transmission had occurred in two of three pairs of ewes and her pups. One viable T. gondii strain (TgSheepCHn14) was isolated from the myocardial tissues of sheep from a slaughterhouse. Tachyzoites were obtained from cell cultures at 70 days following seeding in the brains and lungs of mice. This strain was non-lethal to Swiss mice. The number of parasite brain cysts in mice decreased with time post-infection (p < 0.05). Overall, the prevalence of T. gondii in the sheep samples was low. Although the samples were scattered, and not from planned collections, the current study detected T. gondii antibodies and DNA in aborted fetuses, indicating that vertical transmission could occur and maintain the parasites in sheep herds without exogenous infection. Full article

Toxoplasma gondii is an obligatory intracellular protozoan in the family Apicomplexa. It infects almost one-third of the world’s population and causes toxoplasmosis, a prevalent disease. The parasite’s egress from infected cells is a key step in the pathology caused by T. gondii. Moreover, T. gondii’s continuous infection relies heavily on its capacity to migrate from one cell to another. Many pathways are involved in T. gondii egress. Individual routes may be modified to respond to various environmental stimuli, and many paths can converge. Regardless of the stimuli, the relevance of Ca²⁺ as a second messenger in transducing these signals, and the convergence of various signaling pathways in the control of motility and, ultimately, egress, is well recognized. This review attempts to outline intra- and extra-parasitic regulators that mediate T. gondii egress, and provides insight into potential clinical interventions and research. Full article

Background: The protozoan parasite Toxoplasma gondii may cause serious illness in the immunocompromised. The Toxoplasma gondii seropositive prevalence in pregnant women in WHO Eastern Mediterranean Region countries is inconsistent in the literature and it is associated with outcomes that have not be fully elucidated, hence the need for a better understanding of the pooled seroprevalence and associated maternal and fetal outcomes. Objective: The objective was to conduct a systematic literature review and determine the pooled prevalence of WHO Eastern Mediterranean Regional countries’ pregnant women’s seroprevalence of Toxoplasma gondii and the maternal–fetal outcomes. Methods: This quantitative study examined WHO Eastern Mediterranean countries’ maternal–fetal outcomes and Toxoplasma gondii prevalence in pregnant women. The targeted population was pregnant women, while the primary outcome was seropositivity of Toxoplasma gondii, while other outcomes such as maternal and fetal associations and risk factors were determined PubMed, SCOPUS, MEDLINE, and Index Medicus for the Eastern Mediterranean Region (IMEMR) databases were searched up until 30 January 2023. The search terms used were “Toxoplasma gondii” OR “Toxoplasma infection” AND “Pregnant woman” or pregnan* OR Antenatal OR Prenatal OR Gravidity OR Parturition OR Maternal AND WHO Eastern Mediterranean Region). OpenMeta-Analyst and Jamovi were used to analyze the generated data. Results: In total, 95 of 2947 articles meeting the inclusion criteria examined Toxoplasma gondii prevalence in pregnant women from WHO Eastern Mediterranean countries. The pooled prevalence of Toxoplasma gondii in pregnant women was 36.5% (95%CI: 32.6–40.4) with a median value of 35.64%, range values of 1.38–75.30%, with 99.61% heterogeneity. The pooled seroprevalence of IgG of Toxoplasma gondii was 33.5% (95%CI: 29.8–37.2) with a median value of 33.51%, and a range values of 1.38–69.92%; the pooled seroprevalence of IgM was 3.6% (95%CI: 3.1–4.1)) with a median value of 3.62 and range values of 0.20–17.47%, while cases of pooled seroprevalence of both IgG and IgM positivity was 3.0% (95%CI: 1.9–4.4) with a median value of 2.05 and a range values of 0.05–16.62%. Of the Toxoplasma gondii seropositive women, 1281/3389 (34.8%) 174/1765 (32.9%), 1311/3101 (43.7%), and 715/1683 (40.8%) of them had contact with cats, drank unprocessed milk, ate raw or undercooked meat and ate unwashed raw vegetables, respectively. The maternal–fetal outcomes associated with Toxoplasma gondii seropositivity were a history of abortions, miscarriage, stillbirth, intrauterine fetal death, and premature birth, which were found in 868/2990 (32.5%), 112/300 (36.1%), 111/375 (25.7%), 3/157 (1.9%) and 96/362 (20.1%) of women who tested positive for Toxoplasma gondii antibodies. Conclusion: The study found a high proportion of Toxoplasma gondii seroprevalence in pregnant women in the WHO Eastern Mediterranean Region, which may be linked to poor outcomes for mothers and their babies. Thus, pregnant women require monitoring and comprehensive prevention strategies for Toxoplasma gondii infection. Full article

Background: Accumulating evidence suggests that toxoplasmosis in immunocompetent hosts can be severe and life-threatening. Methods: We performed a systematic review of severe toxoplasmosis cases in immunocompetent patients to gain insight into the epidemiology, clinical characteristics, radiological findings, and outcomes of these cases. We classified severe toxoplasmosis as cases with the symptomatic involvement of target organs (the lungs, central nervous system (CNS), and heart), disseminated disease, prolonged disease (>3 months), or a fatal outcome. Our primary analysis focused on cases published from 1985–2022 to avoid confounding with cases in AIDS patients. Results: We identified 82 pertinent articles (1985–2022) with a total of 117 eligible cases; the top five countries for these cases were French Guiana (20%), France (15%), Colombia (9%), India (9%), and Brazil (7%). Overall, 44% (51/117) of cases had pulmonary involvement, 39% (46/117) CNS, 31% (36/117) cardiac, 24% (28/117) disseminated disease, 2% (2/117) had prolonged disease, and 8% (9/117) of patients died. More than one organ was involved in 26% (31/117) of cases. Eighty-four percent (98/117) of cases occurred in the context of a recent acute primary Toxoplasma infection; for the remaining, the exact timing of infection was unclear. Genotyping data were very sparse. Among those reporting genotyping data, 96% (22/23) were caused by atypical non-type II strains; one case was caused by a type-II strain. Only half of the cases reported risk factors. The most common risk factors were eating raw/undercooked meat or eating game meat (47% (28/60)), drinking untreated water (37% (22/60)), or living in a toxoplasmosis high-prevalence area (38% (23/60)). For the 51 pulmonary cases, the main clinical presentation was pneumonia or pleural effusions in 94% (48/51) and respiratory failure in 47% (24/51). For the 46 CNS cases, the main clinical presentation was encephalitis in 54% (25/46), meningitis in 13% (6/46), focal neurologic findings in 24% (11/46), cranial nerve palsies in 17% (8/46), Guillain–Barre syndrome or Miller Fisher syndrome in 7% (3/46), and Brown–Sequard syndrome in 2% (1/46) of cases; more than one clinical manifestation could also be present. Among the 41 CNS cases reporting the CNS imaging findings, 68% (28/41) had focal supratentorial lesions and 7% (3/41) had focal infratentorial lesions. Brain abscess-like/mass-like lesions were seen in 51% (21/41) of cases. For the 36 cardiac cases, the main clinical presentation was myocarditis in 75% (27/36), pericarditis in 50% (18/36), heart failure and/or cardiogenic shock in 19% (7/36), and cardiac arrhythmias in 22% (8/36); more than one manifestation could also be present. Illness was critical in 49% (44/90) of cases intensive care unit care was needed in 54% (29/54) of cases among those reporting this information, and 9 patients died. Conclusion: The diagnosis of severe toxoplasmosis in immunocompetent hosts can be challenging. Toxoplasmosis should be considered in the differential diagnosis of immunocompetent patients presenting with severe illness of unclear etiology with pulmonary, cardiac, CNS, or multiorgan involvement/failure, or prolonged febrile illness, even in the absence of common exposure risk factors or common manifestations of toxoplasmosis (e.g., fever, mononucleosis-like illness, lymphadenopathy, and chorioretinitis). Fatal outcomes can also rarely occur in immunocompetent patients. Prompt initiation of anti-Toxoplasma treatment can be lifesaving. Full article