Genetic Characterization of Toxoplasma gondii DNA Samples Isolated From Humans Living in North America: An Unexpected High Prevalence of Atypical Genotypes

Early immune response to Toxoplasma gondii lineage III isolates of different virulence phenotype

Introduction

Toxoplasma gondii is an intracellular parasite of importance to human and veterinary health. The structure and diversity of the genotype population of T. gondii varies considerably with respect to geography, but three lineages, type I, II and III, are distributed globally. Lineage III genotypes are the least well characterized in terms of biology, host immunity and virulence. Once a host is infected with T.gondii, innate immune mechanisms are engaged to reduce the parasite burden in tissues and create a pro-inflammatory environment in which the TH1 response develops to ensure survival. This study investigated the early cellular immune response of Swiss-Webster mice post intraperitoneal infection with 10 tachyzoites of four distinct non-clonal genotypes of lineage III and a local isolate of ToxoDB#1. The virulence phenotype, cumulative mortality (CM) and allele profiles of ROP5, ROP16, ROP18 and GRA15 were published previously.

Methods

Parasite dissemination in different tissues was analyzed by real-time PCR and relative expression levels of IFNγ, IL12-p40, IL-10 and TBX21 in the cervical lymph nodes (CLN), brain and spleen were calculated using the ΔΔCt method. Stage conversion was determined by detection of the BAG1 transcript in the brain.

Results

Tissue dissemination depends on the virulence phenotype but not CM, while the TBX21 and cytokine levels and kinetics correlate better with CM than virulence phenotype. The earliest detection of BAG1 was seven days post infection. Only infection with the genotype of high CM (69.4%) was associated with high T-bet levels in the CLN 24 h and high systemic IFNγ expression which was sustained over the first week, while infection with genotypes of lower CM (38.8%, 10.7% and 6.8%) is characterized by down-regulation and/or low systemic levels of IFNγ. The response intensity, as assessed by cytokine levels, to the genotype of high CM wanes over time, while it increases gradually to genotypes of lower CM.

Discussion

The results point to the conclusion that the immune response is not correlated with the virulence phenotype and/or allele profile, but an early onset, intense pro-inflammatory response is characteristic of genotypes with high CM. Additionally, high IFNγ level in the brain may hamper stage conversion.

Serotyping, a challenging approach for Toxoplasma gondii typing

Genotype analysis has revealed a high genetic diversity in strains of Toxoplasma gondii, isolated from a wide range of intermediate hosts and different geographic origins. Diversity is notably striking for parasites from wild hosts in South America, generally referred as non-archetypal genotypes. Those genotypes are implicated in the etiology of severe clinical disease, multivisceral toxoplasmosis, associated with high rate of mortality in immunocompetent individuals. Can we accept specific antibodies produced during T. gondii infection as biomarkers to identify infecting genotypes? Scientific evidence supports a positive response to this question; however, the genetic diversity of T. gondii genotypes organized into 16 haplogroups and collectively defined in 6 major clades, provides a reminder of the complexity and difficulty for the purpose. This review discusses serological approaches to genotyping T. gondii.

A unique Toxoplasma gondii haplotype accompanied the global expansion of cats

Toxoplasma gondii is a cyst-forming apicomplexan parasite of virtually all warm-blooded species, with all true cats (Felidae) as definitive hosts. It is the etiologic agent of toxoplasmosis, a disease causing substantial public health burden worldwide. Few intercontinental clonal lineages represent the large majority of isolates worldwide. Little is known about the evolutionary forces driving the success of these lineages, the timing and the mechanisms of their global dispersal. In this study, we analyse a set of 156 genomes and we provide estimates of T. gondii mutation rate and generation time. We elucidate how the evolution of T. gondii populations is intimately linked to the major events that have punctuated the recent history of cats. We show that a unique haplotype, whose length represents only 0.16% of the whole T. gondii genome, is common to all intercontinental lineages and hybrid populations derived from these lineages. This haplotype has accompanied wildcats (Felis silvestris) during their emergence from the wild to domestic settlements, their dispersal in the Old World, and their expansion in the last five centuries to the Americas. The selection of this haplotype is most parsimoniously explained by its role in sexual reproduction of T. gondii in domestic cats.

Building Programs to Eradicate Toxoplasmosis Part I: Introduction and Overview

Purpose of Review

Review building of programs to eliminate Toxoplasma infections.

Recent Findings

Morbidity and mortality from toxoplasmosis led to programs in USA, Panama, and Colombia to facilitate understanding, treatment, prevention, and regional resources, incorporating student work.

Summary

Studies foundational for building recent, regional approaches/programs are reviewed. Introduction provides an overview/review of programs in Panamá, the United States, and other countries. High prevalence/risk of exposure led to laws mandating testing in gestation, reporting, and development of broad-based teaching materials about Toxoplasma. These were tested for efficacy as learning tools for high-school students, pregnant women, medical students, physicians, scientists, public health officials and general public. Digitized, free, smart phone application effectively taught pregnant women about toxoplasmosis prevention. Perinatal infection care programs, identifying true regional risk factors, and point-of-care gestational screening facilitate prevention and care. When implemented fully across all demographics, such programs present opportunities to save lives, sight, and cognition with considerable spillover benefits for individuals and societies.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40124-022-00269-w.

Assessment of selected molecular factors and 17-β estradiol dosage in response to Toxoplasma gondii infection in swine

Background and Aim:

Toxoplasma gondii is a global zoonotic parasite infecting virtually all warm-blooded species, although a species-specific variability is evident referring to symptoms frame. Both the success of T. gondii and the outcome of infection depend on a delicate balance between host cellular pathways and the evasion or modulation strategies elicited by the parasite. The hormonal and molecular mechanisms involved in this delicate host-parasite balance are still unclear, especially when considering intermediate host species other than mouse. This study aimed to assess any correlation between T. gondii infection and selected molecular and hormonal factors involved in responses to infection in susceptible species such as swine. Moreover, blood counts and hematochemical assays (glucose, total cholesterol, and triglycerides dosage) were performed to evaluate the overall health condition of animals.

Materials and Methods:

Toxoplasmosis was diagnosed by enzyme-linked immunosorbent assay for antibodies determination and real-time polymerase chain reaction (RT-PCR) for T. gondii DNA detection. Target genes coding for key factors of cell responses to T. gondii infection were selected, and their transcription was assessed in various tissues by quantitative RT-PCR. 17-β estradiol concentrations were assessed by fluorimetric enzyme-linked immunoassay and the AIA-360 automated immunoassay analyzer. Blood count and hematochemical analyses were performed by a blood cell counter and a spectrophotometer, respectively.

Results:

The present research highlighted significant differences among infected and uninfected swine (control group) for both transcription profiles of some of the molecular factors considered and 17-β estradiol concentrations. Referring to the assessed hematological and biochemical parameters, no statistically significant differences were observed in infected swine compared to the control group.

Conclusion:

Our results contribute to the enrichment of data available about the subject and could be useful for a deeper knowledge of the interaction between this parasite and its hosts. However, more aspects are still unclear, such as the effective response of downstream molecules from the same pathways to the variation of factors observed in this study either assessing how the same factors respond to Toxoplasma gondii infection in other host speciesand further analyses should be performed on other host species.

Toxoplasmosis in Human and Animals Around the World. Diagnosis and Perspectives in the One Health Approach

Toxoplasmosis is a unique health disease that significantly affects the health of humans, domestic animals, wildlife and is present in ecosystems, including water, soil and food. Toxoplasma gondii is one of the best-adapted parasites in the word. This parasite is able to persist for long periods in its hosts, in different geographic regions of the word. This review summarizes the current literature of these themes, focusing on: (1) toxoplasmosis, a zoonotic infection; (2) One health approach and toxoplasmosis; (3) human toxoplasmosis; (4) animal toxoplasmosis; (5) toxoplasmosis diagnosis, as immunological, parasitological and molecular diagnosis; (6) T. gondii outbreaks caused by infected meat, milk and dairy products, as well as, vegetables and water consume; (7) studies in experimental models; (8) genetic characterization of T. gondii strains; (9) extracellular vesicles and miRNA; and (10) future perspectives on T. gondii and toxoplasmosis. The vast prevalence of toxoplasmosis in both humans and animals and the dispersion and resistence of T. gondii parasites in environment highlight the importance of the one health approach in diagnostic and control of the disease. Here the different aspects of the one health approach are presented and discussed.

Seroprevalence and Genetic Characterization of Toxoplasma gondii among Children with Neurodevelopmental Disorders in Egypt

Toxoplasma gondii is a parasite with a special predilection for the central nervous system. Toxoplasmosis's contribution to the triggering of many neurodevelopmental disorders was established. This study aimed to detect the seroprevalence and genotypes of T. gondii strains in children with neurodevelopmental disorders. The study included 180 children with neurodevelopmental disorders and 180 children in the control group. Assessment of seropositivity of Toxoplasma IgM and IgG antibodies in patients and controls was carried out. Genetic characterization of T. gondii was obtained by nested polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) technique targeting dense granule gene (GRA6). Our results showed that the overall seroprevalence of T. gondii antibodies in the patient and controls was 35.6% and 11.7%, respectively. Nested PCR showed positivity in 11.1% of the patient group for T. gondii DNA. T. gondii seropositivity rate was significantly high in patients with hydrocephalus and also in patients with epilepsy. Positive nested PCR was significantly high in children with hydrocephalus only. Genotyping using nested PCR-RFLP showed genotype I (80%) followed by atypical strains (20%) with no association with any specific clinical presentation. In conclusion, among toxoplasmosis-positive children with neurodevelopmental disorders, analysis of T. gondii GRA6 locus revealed the predominance of type I genotype followed by atypical strains.

Toxoplasma gondii Genotypes Circulating in Serbia-Insight into the Population Structure and Diversity of the Species in Southeastern Europe, a Region of Intercontinental Strain Exchange

In Europe, Toxoplasma gondii lineage II is dominant, and ToxoDB#1 the most frequently occurring genotype. The abundance of lineage III genotypes varies geographically and lineage I are rare, yet present in several regions of the continent. Data on the T. gondii population structure in southeastern Europe (SEE) are scarce, yet necessary to appreciate the diversity of the species in Europe. To help fill this gap, we genotyped 67 strains from nine species of intermediate hosts in Serbia by MnPCR-RFLP, determined the population structure, and identified the genotypes using ToxoDB. A neighbor-joining tree was also constructed from the isolates genotyped on nine loci. While 42% of the total genotype population consisted of ToxoDB#1 and ToxoDB#2, variant genotypes of both lineages comprised 46% of the population in wildlife and 28% in domestic animals and humans. One genotype of Africa 4 lineage was detected in a human sample. Interestingly, the findings include one lineage III variant and one II/III recombinant isolate with intercontinental distribution, which appear to be moderately related to South American genotypes. Based on these findings, SEE is a region of underappreciated T. gondii genetic diversity and possible strain exchange between Europe and Africa.

Interaction Between the Complement System and Infectious Agents - A Potential Mechanistic Link to Neurodegeneration and Dementia

As part of the innate immune system, complement plays a critical role in the elimination of pathogens and mobilization of cellular immune responses. In the central nervous system (CNS), many complement proteins are locally produced and regulate nervous system development and physiological processes such as neural plasticity. However, aberrant complement activation has been implicated in neurodegeneration, including Alzheimer's disease. There is a growing list of pathogens that have been shown to interact with the complement system in the brain but the short- and long-term consequences of infection-induced complement activation for neuronal functioning are largely elusive. Available evidence suggests that the infection-induced complement activation could be protective or harmful, depending on the context. Here we summarize how various infectious agents, including bacteria (e.g., Streptococcus spp.), viruses (e.g., HIV and measles virus), fungi (e.g., Candida spp.), parasites (e.g., Toxoplasma gondii and Plasmodium spp.), and prion proteins activate and manipulate the complement system in the CNS. We also discuss the potential mechanisms by which the interaction between the infectious agents and the complement system can play a role in neurodegeneration and dementia.

Toxoplasmosis Outbreak Associated With Toxoplasma gondii-Contaminated Venison-High Attack Rate, Unusual Clinical Presentation, and Atypical Genotype

BACKGROUND

During 2017, in response to a physician's report, the Wisconsin Department of Health Services, Division of Public Health, began investigating an outbreak of febrile illness among attendees of a retreat where never frozen, intentionally undercooked, locally harvested venison was served. Preliminary testing tentatively identified the illness as toxoplasmosis.

METHODS

Confirmatory human serology panels and testing of the venison to confirm and categorize the presence and type of Toxoplasma gondii were completed by French and American national reference laboratories. All 12 retreat attendees were interviewed; medical records were reviewed.

RESULTS

All attendees were male; median age was 51 years (range: 22-75). After a median incubation period of 7 days, 9 (82%) of 11 exposed persons experienced illness lasting a median of 12 days. All 9 sought outpatient healthcare for symptoms including fever, chills, sweats, and headache (100%) and ocular disturbances (33%). Testing confirmed the illness as toxoplasmosis and venison as the infection source. Multiple laboratory results were atypical for toxoplasmosis, including transaminitis (86%), lymphocytopenia (88%), thrombocytopenia (38%), and leukopenia (63%). One exposed but asymptomatic person was seronegative; the other had immunity from prior infection. The T. gondii strain was identified as closely related to an atypical genotype (haplogroup 12, polymerase chain reaction restriction fragment length polymorphism genotype 5) common in North American wildlife but with previously uncharacterized human clinical manifestations.

CONCLUSIONS

The T. gondii strain contaminating the venison might explain the unusual clinical presentations. In North America, clinicians and venison consumers should be aware of risk for severe or unusual presentations of acute toxoplasmosis after consuming undercooked game meat.

Recent epidemiologic and clinical Toxoplasma gondii infections in wild canids and other carnivores: 2009-2020

Toxoplasma gondii infections are common in humans and animals worldwide. The present review summarizes worldwide information on the prevalence of clinical and subclinical infections, epidemiology, diagnosis, and genetic diversity of T. gondii in wild canids and other carnivores for the past decade. Seroprevalence estimates of T. gondii worldwide were tabulated for each host. Seroprevalence in wild foxes was very high compared with farmed Arctic foxes. Economic and public health aspects of some of the carnivore species raised for fur and meat (raccoon dogs, mink) are discussed. Diagnostic efficacies of different serological methods and PCR methods are discussed. Clinical toxoplasmosis was observed mainly in carnivores concurrently infected with immunosuppressive Canine Distemper Virus infection. Abortion and blindness were noted in mink. Genetic diversity of isolates using DNA derived from 162 (89 viable T. gondii isolates and 73 DNA extracted from tissues) of wild carnivores from several countries is discussed. However, 69 of the 162 T. gondii isolates were strains from USA and these were genetically diverse with predominance of ToxoDB genotypes #4 and #5 (haplogroup 12). Only limited information is available concerning genotyping of T. gondii isolates from other countries; none of the 93 T. gondii isolates from other countries (Brazil, China, France, Grenada) were haplogroup 12.

Approach to ocular toxoplasmosis including pregnant women

PURPOSE OF REVIEW

To discuss available information on the effectiveness of anti-toxoplasma therapy for ocular toxoplasmosis and to provide clinicians with a practical approach to the disease.

RECENT FINDINGS

Only eleven randomized studies were identified. In the three studies for acute retinitis, there was a clear trend in favor of treatment. In the two studies for the prevention of recurrences, trimethoprim-sulfamethoxazole prophylaxis was superior to placebo. In the six studies comparing different regimens, there was no statistically significant difference between the regimens. In the setting of acute posterior uveitis suspected to be caused by toxoplasma, serological testing should always be obtained, and anti-toxoplasma drug treatment, and corticosteroids should be instituted for at least 6 weeks. Toxoplasmic chorioretinitis during pregnancy represents a particular challenge.

SUMMARY

Treatment with at least two drugs and corticosteroids should be offered to patients with active toxoplasmic chorioretinitis. Pregnant women with confirmed acute infection and concomitant acute retinitis should be treated for the ocular lesion(s) and to prevent vertical transmission. Pregnant women with chronic Toxoplasma infection acquired prior to gestation and concomitant retinitis by reactivation should be treated for the retinitis and monitored for vertical transmission.

Pathogenesis of ocular toxoplasmosis

Ocular toxoplasmosis is a retinitis -almost always accompanied by vitritis and choroiditis- caused by intraocular infection with Toxoplasma gondii. Depending on retinal location, this condition may cause substantial vision impairment. T. gondii is an obligate intracellular protozoan parasite, with both sexual and asexual life cycles, and infection is typically contracted orally by consuming encysted bradyzoites in undercooked meat, or oocysts on unwashed garden produce or in contaminated water. Presently available anti-parasitic drugs cannot eliminate T. gondii from the body. In vitro studies using T. gondii tachyzoites, and human retinal cells and tissue have provided important insights into the pathogenesis of ocular toxoplasmosis. T. gondii may cross the vascular endothelium to access human retina by at least three routes: in leukocyte taxis; as a transmigrating tachyzoite; and after infecting endothelial cells. The parasite is capable of navigating the human neuroretina, gaining access to a range of cell populations. Retinal Müller glial cells are preferred initial host cells. T. gondii infection of the retinal pigment epithelial cells alters the secretion of growth factors and induces proliferation of adjacent uninfected epithelial cells. This increases susceptibility of the cells to parasite infection, and may be the basis of the characteristic hyperpigmented toxoplasmic retinal lesion. Infected epithelial cells also generate a vigorous immunologic response, and influence the activity of leukocytes that infiltrate the retina. A range of T. gondii genotypes are associated with human ocular toxoplasmosis, and individual immunogenetics -including polymorphisms in genes encoding innate immune receptors, human leukocyte antigens and cytokines- impacts the clinical manifestations. Research into basic pathogenic mechanisms of ocular toxoplasmosis highlights the importance of prevention and suggests new biological drug targets for established disease.

Economic and public health importance of Toxoplasma gondii infections in sheep: 2009-2020

Toxoplasma gondii infections are common in humans and animals worldwide. The present review summarizes worldwide information on the prevalence of clinical and subclinical infections, epidemiology, diagnosis, control, and genetic diversity of T. gondii in sheep in the past decade. There is debate and uncertainty concerning repeat congenital infection as evidenced by finding T. gondii DNA in progeny of chronically infected sheep. However, there is no concrete evidence that T. gondii is the cause of repeated abortions in sheep. Recent data concerning pathogenesis of abortion in acutely infected sheep are reviewed. PCR-RFLP typing of T. gondii DNA derived from viable T. gondii isolates or tissues of infected sheep revealed low genetic diversity in sheep in Europe, Africa, Asia and North America but high diversity in South America. This review will be of interest to biologists, parasitologists, veterinarians, and public health workers.

A decreasing trend in toxoplasma gondii seroprevalence among pregnant women in Romania - results of a large scale study

Toxoplasmosis is a zoonotic infection caused by the obligate intracellular apicomplexan parasite Toxoplasma gondii (T. gondii). T. gondii infection is a cause of congenital infection worldwide. Primary infection or the reactivation of latent infection during pregnancy may lead to fetal infection and to congenital toxoplasmosis syndrome. Seropositive pregnant women are generally protected from maternal-fetal transmission of T. gondii, although exceptions exist. The aim of our study was to analyze the dynamics of T. gondii seroprevalence during a 10-year period and to correlate it with age and demographic features of pregnant women. We tested 6,889 pregnant women in Timisoara, Romania, for IgG-anti-T. gondii antibodies, in two successive periods: i) 2008-2010 (group 1: 1,457 participants); and ii) 2015-2018 (group 2: 5,432 participants). For each participant, data on age and area of residence were collected. Our results showed that in the Western Region of Romania T. gondii seroprevalence in pregnant women declined from 43.79 to 38.81% in the last ten years. This trend was observed in both urban (40.53 vs. 34.85%) and rural areas (52.22 vs. 46.22%). A higher seroprevalence rate was found in rural than in urban areas. In addition, we found an increasing tendency of seroprevalence related to the age of pregnant women.

Public health and economic importance of Toxoplasma gondii infections in goats: The last decade

Toxoplasma gondii infections are common in humans and animals worldwide. Toxoplasmosis in goats continues to be of public health and economic concern. The present review summarizes worldwide information on the prevalence of clinical and subclinical infections, epidemiology, diagnosis, treatment, and genetic diversity of T. gondii in goats in the past decade. There is debate and uncertainty regarding excretion of T. gondii in milk and the ingestion of raw milk as sources of T. gondii infection for humans. Toxoplasmosis can cause abortion and deaths even in adult goats. PCR-RFLP typing of T. gondii DNA derived from viable T. gondii isolates has revealed genetic diversity in goats in North and South America. The significance of T. gondii isolates in domestic goats usually associated with wildlife in USA is discussed. This review will be of interest to biologists, parasitologists, veterinarians, and public health workers.

Detection of Toxoplasma gondii oocysts in fresh vegetables and berry fruits

BACKGROUND

Toxoplasma gondii is the third most important contributor to health burden caused by food-borne illness. Ingestion of tissue cysts from undercooked meat is an important source of horizontal transmission to humans. However, there is an increasing awareness of the consumption of fresh fruit and vegetables, as a possible source for oocyst transmission, since this stage of the parasite can persist and remain infective in soil and water for long time. Herein, we outline findings related with detection of T. gondii oocysts in vegetables and berry fruits, which are usually raw consumed. The procedure includes the estimation of the number of oocysts.

METHODS

Food samples were collected from local producers and supermarket suppliers. Toxoplasma gondii oocysts were concentrated after washing the samples by applying high resolution water filtration and immunomagnetic separation (method 1623.1: EPA 816-R-12-001-Jan 2012), in order to (i) remove potential Cryptosporidium spp. oocysts and Giardia spp. cysts present in the samples; and (ii) select T. gondii oocysts. Toxoplasma gondii oocyst detection and an estimation of their numbers was performed by conventional PCR and real time qPCR, using specific primers for a 183-bp sequence of the T. gondii repetitive DNA region. All PCR-positive DNA samples were purified and sequenced. Restriction enzyme digestion with EcoRV endonuclease confirmed the presence of the T. gondii DNA fragment. In addition, the presence of the parasite was observed by fluorescent microscopy, taking advantage of the oocysts autofluorescence under UV light.

RESULTS

Forty percent of the analysed samples (95% CI: 25.5-56.5%) presented the expected PCR and digested DNA fragments. These fragments were confirmed by sequencing. Microscopic autofluorescence supported the presence of T. gondii-like oocysts. The estimated mean (± SE) oocyst concentration was 23.5 ± 12.1 oocysts/g, with a range of 0.6-179.9 oocysts/g.

CONCLUSIONS

Our findings provide relevant evidence of contamination of fresh vegetables and berry fruits with T. gondii oocysts.

First isolation and genotyping of Toxoplasma gondii in a free-living giant anteater (Myrmecophaga tridactyla) revealed a unique non-archetypal genotype

The protozoan parasite Toxoplasma gondii can infect virtually all warm-blooded animals worldwide but little is known of its infection in the endangered giant anteaters (Myrmecophaga tridactyla). The present study found antibodies to T. gondii in 13 of 23 free-living M. tridactyla from the northwest region of São Paulo state, Brazil, by the Modified Agglutination Test (MAT, cut-off titer 1:25). Unfrozen tissues of seven M. tridactyla were bioassayed in mice and viable T. gondii (strain designated TgMytrBrSP1) isolated from one seropositive giant anteater. To our knowledge, this is a new host record for T. gondii. Genotyping using PCR-RFLP revealed the Brazilian clonal Type BrIII genotype, and a unique non-archetypal genotype was revealed by microsatellite analysis.

White-tailed deer (Odocoileus virginianus) are a reservoir of a diversity of Toxoplasma gondii strains in the USA and pose a risk to consumers of undercooked venison

To assess the role of white-tailed deer (Odocoileus virginianus, WTD) in the epidemiology of toxoplasmosis, we conducted a national survey of WTD across the USA for Toxoplasma gondii infection. To do this, we combined serology with parasite isolation to evaluate the prevalence and genetic diversity of T. gondii in this game species. From October 2012 to March 2019, serum and tissues were collected from 914 WTD across the USA. Serum samples were screened for antibodies to T. gondii, and then the tissues of seropositive WTD were bioassayed in mice. Antibodies were detected in 329 (36%) of 914 WTD tested by the modified agglutination test (positive reaction at 1:25 or higher). Viable T. gondii was isolated from the heart of 36 WTD from 11 states. Three of the 36 isolates were pathogenic but not highly virulent to outbred Swiss Webster mice and all 36 isolates could be propagated further in cell culture and were genotyped. For genotyping, DNA extracted from cell culture-derived tachyzoites was characterized by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) using the genetic markers SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico. Genotyping revealed seven ToxoDB PCR-RFLP genotypes, including 24 isolates for genotype #5 (haplogroup 12), four isolates for #2 (type III, haplogroup 3), three isolates for genotypes #1 (type II, haplogroup 2), two isolates for genotypes #3 (type II, haplogroup 2) and one isolate each for #39, #221 and #224. Genotype #5 was the most frequently isolated, accounting for 66.6% (24 of 36) of the isolates. Combining the 36 isolates from this study with previously reported 69 isolates from WTD, 15 genotypes have been identified. Among these, 50.4% (53/105) isolates belong to genotype #5. Our results indicate moderate genetic diversity of T. gondii in WTD. The results also indicate that undercooked venison should not be consumed by humans or fed to cats.

Is Real-Time PCR Targeting Rep 529 Suitable for Diagnosis of Toxoplasmosis in Patients Infected with Non-Type II Strains in North America?

Toxoplasma gondii DNA detection is essential to antenatally diagnose a congenital infection and reactivation of a past infection in an immunocompromised patient. Initially, PCR methods targeted the 35-fold repetitive B1 gene, and more recently, coding sequence Rep 529 has been preferred, as it was reported to be repeated 200- to 300-fold and yielded far better sensitivity than amplification of the B1 sequence. To date, few data are available in regard to the efficacy of Rep 529 for non-type II genotypes. In this study, we compared the results of B1 quantitative PCR (qPCR) with those of two different Rep 529 qPCRs performed on 111 samples in two different laboratories (Rep 529-1 and Rep 529-2). The performances of the 3 qPCRs were also compared according to the genotypes of the isolates for 13 type II and 21 non-type II samples. The performance of the Rep 529 target was superior to that of the B1 target regardless of the genotype (threshold cycle [C_T ] values for the Rep 529-1 and Rep 529-2 qPCRs were lower than those for the B1 qPCR [P < 0.001 and P < 0.01, respectively]). The same results were observed when a comparison was made according to the genotype of the strain (type II and non-type II genotypes). To our knowledge, these results provide the first relative quantitative data revealing that the efficiency of Rep 529 qPCR does not depend on the genotype of T. gondii isolates and that, in fact, it is superior to B1 qPCR.

Genotyping of viable Toxoplasma gondii from the first national survey of feral swine revealed evidence for sylvatic transmission cycle, and presence of highly virulent parasite genotypes

Feral swine are known reservoirs of various pathogens, including Toxoplasma gondii. Here, we report the first national survey of viable T. gondii in feral swine in the USA. We paired serological surveys with parasite isolation and bioassay to evaluate the prevalence and genetic diversity of these parasites. From 2012–2017, sera and tissues from 1517 feral swine across the USA were collected for the isolation of viable T. gondii. Serum samples were initially screened for antibodies to T. gondii, and then the tissues of seropositive feral swine were bioassayed in mice. Antibodies were detected in 27.7% of feral swine tested by the modified agglutination test (1:25 or higher). Antibody positive rates increased significantly with age, with 10.1% of juveniles, 16.0% of sub-adults and 38.4% of adults testing seropositive. Myocardium (50 g) from 232 seropositive feral swine was digested in pepsin and bioassayed in mice. Viable T. gondii was isolated from 78 feral swine from 21 states. Twelve of the 78 isolates were pathogenic to outbred Swiss Webster mice and 76 of the 78 isolates could be propagated further in cell culture and were genotyped. For genotyping, deoxyribonucleic acid extracted from cell culture-derived tachyzoites was characterized by polymerase chain reaction restriction fragment length polymorphism using the genetic markers SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico. Genotyping revealed 15 ToxoDB genotypes, including 43 isolates for genotype #5 (haplogroup 12), 11 isolates for #24, four isolates for #2 (haplogroup 3), two isolates for each of genotypes #3 (haplogroup 2), #4 (haplogroup 12), #216, #221, #289 and #297 and one isolate for each of genotypes #1 (haplogroup 2), #39, #66, #260, #261 and #299. Genotype #5 was the most frequently isolated, accounted for 57% (43/76) of the isolates, followed by #24, accounted for 14% (11/76). Genotypes #260, #289, #297 and #299 are new types. Genotype #289 was highly virulent to mice and originated from feral swine collected in Louisiana on the same day at the same location. Genotype #216 was previously demonstrated to be highly virulent to mice. Our results indicate moderate genetic diversity of T. gondii in feral swine in the USA, with the genotype #5 (haplogroup 12) dominant in the continental USA, whereas genotype #24 (10/14) was dominant in Hawaii, suggesting different population structures of the parasites among the two distinct geographical locations.

Are molecular tools clarifying or confusing our understanding of the public health threat from zoonotic enteric protozoa in wildlife?

Emerging infectious diseases are frequently zoonotic, often originating in wildlife, but enteric protozoa are considered relatively minor contributors. Opinions regarding whether pathogenic enteric protozoa may be transmitted between wildlife and humans have been shaped by our investigation tools, and have led to oscillations regarding whether particular species are zoonotic or have host-adapted life cycles. When the only approach for identifying enteric protozoa was morphology, it was assumed that many enteric protozoa colonized multiple hosts and were probably zoonotic. When molecular tools revealed genetic differences in morphologically identical species colonizing humans and other animals, host specificity seemed more likely. Parasites from animals found to be genetically identical - at the few genes investigated - to morphologically indistinguishable parasites from human hosts, were described as having zoonotic potential. More discriminatory molecular tools have now sub-divided some protozoa again. Meanwhile, some infection events indicate that, circumstances permitting, some "host-specific" protozoa, can actually infect various hosts. These repeated changes in our understanding are linked intrinsically to the investigative tools available. Here we review how molecular tools have assisted, or sometimes confused, our understanding of the public health threat from nine enteric protozoa and example wildlife hosts (Balantoides coli - wild boar; Blastocystis sp. - wild rodents; Cryptosporidium spp. - wild fish; Encephalitozoon spp. - wild birds; Entamoeba spp. - non-human primates; Enterocytozoon bieneusi - wild cervids; Giardia duodenalis - red foxes; Sarcocystis nesbitti - snakes; Toxoplasma gondii - bobcats). Molecular tools have provided evidence that some enteric protozoa in wildlife may infect humans, but due to limited discriminatory power, often only the zoonotic potential of the parasite is indicated. Molecular analyses, which should be as discriminatory as possible, are one, but not the only, component of the toolbox for investigating potential public health impacts from pathogenic enteric protozoa in wildlife.

Immunological Molecular Responses of Human Retinal Pigment Epithelial Cells to Infection With Toxoplasma gondii

Ocular toxoplasmosis is the commonest clinical manifestation of infection with obligate intracellular parasite, Toxoplasma gondii. Active ocular toxoplasmosis is characterized by replication of T. gondii tachyzoites in the retina, with reactive inflammation. The multifunctional retinal pigment epithelium is a key target cell population for T. gondii. Since the global gene expression profile is germane to understanding molecular involvements of retinal pigment epithelial cells in ocular toxoplasmosis, we performed RNA-Sequencing (RNA-Seq) of human cells following infection with T. gondii tachyzoites. Primary cell isolates from eyes of cadaveric donors (n = 3), and the ARPE-19 human retinal pigment epithelial cell line, were infected for 24 h with GT-1 strain T. gondii tachyzoites (multiplicity of infection = 5) or incubated uninfected as control. Total and small RNA were extracted from cells and sequenced on the Illumina NextSeq 500 platform; results were aligned to the human hg19 reference sequence. Multidimensional scaling showed good separation between transcriptomes of infected and uninfected primary cell isolates, which were compared in edgeR software. This differential expression analysis revealed a sizeable response in the total RNA transcriptome-with significantly differentially expressed genes totaling 7,234 (28.9% of assigned transcripts)-but very limited changes in the small RNA transcriptome-totaling 30 (0.35% of assigned transcripts) and including 8 microRNA. Gene ontology and pathway enrichment analyses of differentially expressed total RNA in CAMERA software, identified a strong immunologic transcriptomic signature. We conducted RT-qPCR for 26 immune response-related protein-coding and long non-coding transcripts in epithelial cell isolates from different cadaveric donors (n = 3), extracted by a different isolation protocol but similarly infected with T. gondii, to confirm immunological activity of infected cells. For microRNA, increases in miR-146b and miR-212 were detected by RT-qPCR in 2 and 3 of these independent cell isolates. Biological network analysis in the InnateDB platform, including 735 annotated differentially expressed genes plus 2,046 first-order interactors, identified 10 contextural hubs and 5 subnetworks in the transcriptomic immune response of cells to T. gondii. Our observations provide a solid base for future studies of molecular and cellular interactions between T. gondii and the human retinal pigment epithelium to illuminate mechanisms of ocular toxoplasmosis.

Diversity of Toxoplasma gondii strains at the global level and its determinants

The population structure of Toxoplasma gondii is characterized by contrasting geographic patterns of strain diversity at different spatial scales: global, regional and even local scales in some regions. The determinants of this diversity pattern and its possible evolutionary mechanisms are still largely unexplored. This review will focus on three main dichotomies observed in the population structure of the parasite: (1) domestic versus wild, (2) South America versus the rest of the world and (3) intercontinental clonal lineages versus regional or local clonal lineages. Here, the impact in terms of public health of this remarkably contrasting geographic diversity of T. gondii populations is discussed, with emphasis on the role of globalization of exchanges that could lead to rapid evolution of T. gondii population spatial structure and new challenges in a One Health context.

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Recombination events drive the evolution of population structure of Toxoplasma gondii.

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The population structure of Toxoplasma is different in wild and domestic environments.

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Virulence of Toxoplasma strains in reservoir hosts influences selection of local strains.

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Globalization of exchanges will impact the population structure of the parasite.

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Clinicians should be aware of more pathogenic strains imported from the wild environment or from South America.

High burden and low awareness of toxoplasmosis in the United States

Toxoplasmosis, a disease with diverse clinical manifestations, caused by infection with the Apicomplexan parasite, Toxoplasma gondii (T. gondii), is a major source of morbidity and mortality in the United States. Although toxoplasmosis prevalence and mortality have declined over the past two decades, the CDC considers this disease a neglected parasitic infection requiring public health action. Here, we overview the literature to bring attention to the prevalence of the disease in the United States, and high economic burden associated with the disease. The conclusions to be drawn are clear: there is low awareness and underestimation of the disease burden amongst healthcare professionals; a high economic burden associated with the disease; relapse rates to treatment represent additional mortality and morbidity and further costs for the healthcare system; and better treatments are necessary to combat this public health threat.

Dual-target, real-time PCR for the diagnosis of intraocular Toxoplasma gondii infections

BACKGROUND

Toxoplasma gondii is the most common infectious cause of posterior uveitis worldwide. Two multicopy targets (B1 and Rep529) are commonly used in T. gondii PCR assays, but studies evaluating these targets in ocular fluid samples are limited. Herein, we determine the analytical characteristics of a single-reaction, internally controlled, dual-target, real-time T. gondii PCR and evaluate the clinical performance of this assay in intraocular fluid samples obtained at a reference ophthalmologic centre in the USA.

METHODS

Lower limits of detection for the B1 and Rep529 components of the dual-target assay were determined using serial dilutions of cultured T. gondii strain Z185. The dual-target assay was then used to test 148 archived intraocular samples (132 vitreous,16 aqueous humour) collected at the Francis I. Proctor Foundation between January 2010 and December 2015 for testing by a nested, conventional PCR targeting the B1 gene.

RESULTS

The 95% lower limits of detection for the dual-target assay was determined to be 1.05 tachyzoites/mL for B1 and 0.83 tachyzoites/mL for Rep529. Using archived clinical intraocular specimens, the dual-target assay demonstrated 97.2% positive per cent agreement (n=35/36; 95% CI 83.7% to 99.9%) and 99.1% negative per cent agreement (n=111/112; 95% CI 94.4% to 100%) compared with the nested, conventional B1 PCR.

CONCLUSION

This single-reaction, internally controlled, dual-target (B1, Rep529) real-time PCR for the detection of T. gondii DNA in intraocular specimens demonstrated excellent agreement with nested, conventional, B1 PCR. The dual-target design may ensure T. gondii detection when variation is present in one of two target regions.