Systematic Review and Modelling of Age-Dependent Prevalence of Toxoplasma gondii in Livestock, Wildlife and Felids in Europe

Toxoplasma gondii infection in European brown hares (Lepus europaeus) in Brazil

Toxoplasmosis is a worldwide zoonosis that affects warm-blooded animals, including humans. Wild animals can act as intermediate hosts of this pathogen; thus, this study aims to detect Toxoplasma gondii infection in invasive European brown hares in Brazil. For this, 72 wild European brown hares were captured from July 2020 to June 2022 in three Brazilian states: São Paulo, Paraná, and Rio Grande do Sul. The diagnostic of Toxoplasma gondii infection was performed by bioassay in mouse, histopathology in Hematoxylin-Eosin-stained tissue sections (brain, liver, lungs, kidneys, and small intestine), serology by IFAT, and molecular techniques by conventional PCR and qPCR. The combined prevalence of the different diagnostic methods was 51.4% (37/72, CI= 40.1 - 62.6 %), and there was no statistical difference between sexes, age range, or geographical region of the hosts. Mouse bioassay was the technique that detected more positive hares. To our knowledge, this is the first confirmation of Toxoplasma gondii infection in invasive European brown hares in Brazil. These animals act as reservoirs and potential infection source for carnivores and other wild and domestic animals, including humans, thus contributing to perpetuate the disease cycle in São Paulo, Paraná, and Rio Grande do Sul States. Research such as the present study is necessary to raise awareness about the role of animals in the disease cycle.

Comparison of Direct and Indirect Detection of Toxoplasma gondii in Ovine Using Real-Time PCR, Serological and Histological Techniques

Toxoplasma gondii is a zoonotic pathogen and the ingestion of tissue cysts by consumption of lamb or mutton has been identified as a possible cause of infection in humans. Many serological surveys in sheep have been performed, showing relevant serological rates; however, while the detection of antibodies indicates an exposure to T. gondii, this does not necessarily imply the presence of tissue cysts in edible tissue. The current study aims to provide further understanding on the occurrence of T. gondii in sheep muscles and the strength of correlation between serological positivity and presence of the parasite in sheep. From 349 sheep, samples (i.e., blood, heart and diaphragm) were collected and subjected to ELISA tests, real-time PCR and histological tests. Despite the high seroprevalence, T. gondii DNA was detected in the heart and/or the diaphragm from 13 out of the 349 tested sheep (3.7%); all were adults (13/191). Furthermore, the histological tests did not reveal the presence of T. gondii tissue cysts in any of the examined portions of interventricular septum. It should be considered that the likelihood of detecting genetic material of the parasite is probably influenced by the uneven distribution of the tissue cysts in the carcass as well as the methodology applied. The findings of this study support the importance of describing the uncertainty associated with the data used for risk assessment to reduce inaccurate estimation or risk overestimation.

Seroprevalence and molecular detection of Toxoplasma gondii and Neospora caninum in beef cattle and goats in Hunan province, China

BACKGROUND

Toxoplasma gondii and Neospora caninum are closely related protozoan parasites that are considered important causes of abortion in livestock, causing huge economic losses. Hunan Province ranks 12th in the production of beef and mutton in China. However, limited data are available on the seroprevalence, risk factors and molecular characterization of T. gondii and N. caninum in beef cattle and goats in Hunan province, China.

METHODS

Sera of 985 beef cattle and 1147 goats were examined for the presence of specific antibodies against T. gondii using indirect hemagglutination test (IHAT) and anti-N. caninum IgG using competitive-inhibition enzyme-linked immunoassay assay (cELISA). Statistical analysis of possible risk factors was performed using PASW Statistics. Muscle samples of 160 beef cattle and 160 goats were examined for the presence of T. gondii DNA (B1 gene) and N. caninum DNA (Nc-5 gene) by nested PCR. The B1 gene-positive samples were genotyped at 10 genetic markers using the multilocus nested PCR-RFLP (Mn-PCR-RFLP).

RESULTS

Specific IgG against T. gondii were detected in 8.3% (82/985) and 13.3% (153/1147) and against N. caninum in 2.1% (21/985) and 2.0% (23/1147) of the beef cattle and goats, respectively. Based on statistical analysis, the presence of cats, semi-intensive management mode and gender were identified as significant risk factors for T. gondii infection in beef cattle. Age was a significant risk factor for T. gondii infection in goats (P < 0.05), and age > 3 years was a significant risk factor for N. caninum infection in beef cattle (P < 0.05). PCR positivity for T. gondii was observed in three beef samples (1.9%; 3/160) and seven chevon samples (4.4%; 7/160). Genotyping of PCR positive samples identified one to be ToxoDB#10. The N. caninum DNA was observed in one beef sample (0.6%; 1/160) but was negative in all chevon samples.

CONCLUSIONS

To our knowledge, this is the first large-scale serological and molecular investigation of T. gondii and N. caninum and assessment of related risk factors in beef cattle and goats in Hunan Province, China. The findings provide baseline data for executing prevention and control of these two important parasites in beef cattle and goats in China.

Seroprevalence of Toxoplasma gondii in wild boars (Sus scrofa) hunted in Ukraine

Toxoplasma gondii is an important zoonotic parasite worldwide, but it has received limited attention in Ukraine. A seroepidemiological study was conducted and samples from 452 wild boars that had been hunted in 2006-2011 in 23 of the 25 regions of Ukraine were tested to estimate T. gondii seroprevalence. A locally available commercial enzyme-linked immunosorbent assay (ELISA) was used for the investigation. Additionally, we tested 92 of the sera using a widely used commercial multi-species ELISA and an indirect immunofluorescence antibody test (IFAT). With the locally available ELISA, 35 of the 452 wild boars tested positive, yielding a seroprevalence estimate of 7.7% (95% confidence interval 5.5-10.5). The seropositive wild boars originated from eight of the regions. Using the majority criteria, 10/92 samples tested using both ELISAs and the IFAT were considered positive, yielding an estimated seroprevalence of 10.9% within the subset of samples. The highest seroprevalence was observed in wild boars hunted in Luhans'k (30.0%), Odesa (17.7%) and Kharkiv (12.7%). Seroprevalence was higher in older animals (13.3% for age group >12 months and 7.7% for age group ≤12 months). This is the first seroepidemiological study of T. gondii in wild boars in Ukraine. Assuming that seropositivity indicates presence of infectious parasites in the tissues, eating undercooked meat of wild boars hunted in Ukraine could be a potential source of infection to other hosts, including humans.

Observational longitudinal study on Toxoplasma gondii infection in fattening beef cattle: serology and associated haematological findings

Toxoplasmosis, caused by the protozoan parasite Toxoplasma gondii, is a globally distributed zoonotic infection with significant implications for human and animal health. This study investigated the prevalence of T. gondii infection in a population of beef cattle at three different stages of their productive lifespan and examined the impact of T. gondii serological status on blood parameters. A commercial beef fattening unit in Italy was the setting for this research, which involved a biosecurity assessment upon cattle arrival, blood sampling at three time points and Toxoplasma-specific serological testing using indirect fluorescent antibody tests (IFAT). Results revealed a dynamic pattern of T. gondii seropositivity in cattle, with an initial prevalence of 30.6% at arrival (T0) that increased to 44.6% at 14 days (T1) and then decreased slightly to 39.3% at slaughter after 5 months (T2). Interestingly, seroconversion was observed during the study, indicating ongoing infections, and antibody waning occurred in some animals. In terms of blood parameters, seropositive cattle exhibited significantly lower mean corpuscular volume (MCV) and a higher neutrophil-lymphocyte (N/L) ratio, suggesting an activation of the innate immune response. Furthermore, cattle with higher antibody titres displayed higher neutrophil counts. However, all blood parameters with a statistical significance were within the reference range. This study provides for the first time a longitudinal investigation on the serological status for T. gondii in naturally exposed beef cattle. These findings provide valuable insights into the clinico-pathological aspects of natural T. gondii exposure in cattle and underscore the importance of monitoring and managing T. gondii infection in livestock production systems.

Genotyping of European Toxoplasma gondii strains by a new high-resolution next-generation sequencing-based method

PURPOSE

A new high-resolution next-generation sequencing (NGS)-based method was established to type closely related European type II Toxoplasma gondii strains.

METHODS

T. gondii field isolates were collected from different parts of Europe and assessed by whole genome sequencing (WGS). In comparison to ME49 (a type II reference strain), highly polymorphic regions (HPRs) were identified, showing a considerable number of single nucleotide polymorphisms (SNPs). After confirmation by Sanger sequencing, 18 HPRs were used to design a primer panel for multiplex PCR to establish a multilocus Ion AmpliSeq typing method. Toxoplasma gondii isolates and T. gondii present in clinical samples were typed with the new method. The sensitivity of the method was tested with serially diluted reference DNA samples.

RESULTS

Among type II specimens, the method could differentiate the same number of haplotypes as the reference standard, microsatellite (MS) typing. Passages of the same isolates and specimens originating from abortion outbreaks were identified as identical. In addition, seven different genotypes, two atypical and two recombinant specimens were clearly distinguished from each other by the method. Furthermore, almost all SNPs detected by the Ion AmpliSeq method corresponded to those expected based on WGS. By testing serially diluted DNA samples, the method exhibited a similar analytical sensitivity as MS typing.

CONCLUSION

The new method can distinguish different T. gondii genotypes and detect intra-genotype variability among European type II T. gondii strains. Furthermore, with WGS data additional target regions can be added to the method to potentially increase typing resolution.

Proteomics analysis of Toxoplasma gondii merozoites reveals regulatory proteins involved in sexual reproduction

Sexual reproduction plays a crucial role in the transmission and life cycle of toxoplasmosis. The merozoites are the only developmental stage capable of differentiation into male and female gametes, thereby initiating sexual reproduction to form oocysts that are excreted into the environment. Hence, our study aimed to perform proteomic analyses of T. gondii Pru strain merozoites, a pre-sexual developmental stage in cat IECs, and tachyzoites, an asexual developmental stage, using the tandem mass tag (TMT) method in order to identify the differentially expressed proteins (DEPs) of merozoites. Proteins functions were subjected to cluster analysis, and DEPs were validated through the qPCR method. The results showed that a total of 106 proteins were identified, out of which 85 proteins had quantitative data. Among these, 15 proteins were differentially expressed within merozoites, with four exhibiting up-regulation and being closely associated with the material and energy metabolism as well as the cell division of T. gondii. Two novel DEPs, namely S8GHL5 and A0A125YP41, were identified, and their homologous family members have been demonstrated to play regulatory roles in oocyte maturation and spermatogenesis in other species. Therefore, they may potentially exhibit regulatory functions during the differentiation of micro- and macro-gametophytes at the initiation stage of sexual reproduction in T. gondii. In conclusion, our results showed that the metabolic and divisional activities in the merozoites surpass those in the tachyzoites, thereby providing structural, material, and energetic support for gametophytes development. The discovery of two novel DEPs associated with sexual reproduction represents a significant advancement in understanding Toxoplasma sexual reproduction initiation and oocyst formation.

Anti-Toxoplasma gondii Antibodies in European Residents: A Systematic Review and Meta-Analysis of Studies Published between 2000 and 2020

Toxoplasmosis has a major impact on animal and public health. Information regarding the seroprevalence of human Toxoplasma gondii infections from a European perspective has not yet been compiled to date. Thus, the present review summarized available resident data from the period 2000-2020. The overall seroprevalence of anti-T. gondii IgG was 32.1%, with great variability between countries (n = 30). The subgroup analysis identified different pooled prevalence data depending on the geographic area (p < 0.0001), target population (p = 0.0147), and serological diagnosis assays used (p = 0.0059). A high heterogeneity (I2 = 100%, p < 0.001; Q = 3.5e+05, d.f. = 135, p < 0.001) and degree of publication bias (Egger's test = 6.14, p < 0.001) were observed among the 134 studies considered. The occurrence of anti-T. gondii IgM, which was reported in 64.7% of studies, reached a pooled seroprevalence of 0.6%. In addition, among the eight main risk factors identified, "contact with soil", "consumption of undercooked beef", and "intake of unwashed vegetables" were the most significantly associated with infections. The fact that one-third of the European population has been exposed to T. gondii justifies extra efforts to harmonize surveillance systems and develop additional risk-factor analyses based on detailed source attribution assessment.

Past and present seroprevalence and disease burden estimates of Toxoplasma gondii infections in Germany: An appreciation of the role of serodiagnostics

Toxoplasmosis is one of the major foodborne parasitic diseases in Germany, with 49% of its population chronically infected with its causative agent, Toxoplasma gondii. Although the acute disease is usually benign in immunocompetent individuals, it is a threat for immunocompromised patients as well as for fetuses of seronegative mothers. As a result of infection, congenital and ocular toxoplasmosis can have serious lifelong consequences. Here I will highlight the epidemiologic situation, from its past in the two separate parts of Germany, to its unification 30 years ago and up to the present day. The main identified risk factor for infection in Germany is thought to be the consumption of undercooked or raw meat or sausages. However, the relative impact of this risky eating habit as well as that of other risk factors are changing and are discussed and compared to the situation in the Netherlands. Finally, the importance of robust and efficient high-throughput serological assays for obtaining reliable epidemiological data, on which public health decisions can be made, is highlighted. The potential of bead-based multiplex assays, which allow the incorporation of multiple antigens with different analytical properties and thus yield additional information, are described in this context. It illustrates the interdependence of new analytic assay developments and sound epidemiology, a foundation that decades-old data from Germany did not have.

The interplay between toxoplasmosis and host miRNAs: Mechanisms and consequences

Toxoplasmosis is one of the highly prevalent zoonotic diseases worldwide caused by the parasite Toxoplasma gondii (T. gondii). The infection with T. gondii could pass unidentified in immunocompetent individuals; however, latent cysts remain dormant in their digestive tract, but they could be shed and excreted with feces infesting the environment. However, active toxoplasmosis can create serious consequences, particularly in newborns and infected persons with compromised immunity. These complications include ocular toxoplasmosis, in which most cases cannot be treated. Additionally, it caused many stillbirths and miscarriages. Circulating miRNAs are important regulatory molecules ensuring that the normal physiological role of various organs is harmonious. Upon infection with T. gondii, the tightly regulated miRNA profile is disrupted to favor the parasite's survival and further participate in the disease pathogenesis. Interestingly, this dysregulated profile could be useful in acute and chronic disease discrimination and in providing insights into the pathomechanisms of the disease. Thus, this review sheds light on the various roles of miRNAs in signaling pathways regulation involved in the pathogenesis of T. gondii and provides insights into the application of miRNAs clinically for its diagnosis and prognosis.

First application of a droplet digital PCR to detect Toxoplasma gondii in mussels

Toxoplasmosis, caused by the protozoan Toxoplasma gondii, is one of the main food-, water- and soil-borne zoonotic disease worldwide. Over the past 20 years many papers were published on the transmission of T. gondii by marine animals, including mollusks, which can concentrate the oocysts and release them. Sporulated oocysts may remain viable and infective for 18 months in seawater. Therefore, raw or undercooked bivalve mollusks pose a risk to humans. This study aimed to apply and validate for the first time a very sensitive digital droplet polymerase chain reaction (ddPCR) protocol to detect and quantify T. gondii DNA in mussels. Four concentration levels: 8000 genomic copies (gc)/μL, 800 gc/μL, 80 gc/μL, 8 gc/μL of a T. gondii reference DNA were tested. DNA was extracted from 80 pools of mussels (Mytilus galloprovincialis). Forty pools were contaminated with T. gondii reference DNA and used as positive controls, while 40 pools were used as negative controls. DdPCR reaction was prepared using a protocol, previously developed by the authors, for detection of T. gondii in meat. Amplification was obtained up 8 gc/μL. All infected replicates resulted positive, as well as no droplets were detected in negative controls. The droplets produced in the reaction ranged from 8,828 to 14,075 (average 12,627 droplets). The sensitivity and specificity of ddPCR were 100% (95%CI = 94.3-99.9). In addition, 100 pools of mussels collected in the Gulf of Naples were used to validate the protocol. Of these 16% were positive (95% CI = 9.7-25.0) for T. gondii. Samples were also tested by real-time PCR and no positive samples were found. Data obtained from ddPCR showed good identification of negative and positive samples with higher specificity and efficiency than real-time PCR. This tool could be very useful for a rapid sensitive detection of low DNA concentrations of T. gondii in mussels, reducing the risk of toxoplasmosis in humans.

An Antibody-Based Survey of Toxoplasma gondii and Neospora caninum Infection in Client-Owned Cats from Portugal

Toxoplasma gondii and Neospora caninum are obligate intracellular protozoan parasites infecting a wide range of hosts worldwide. However, information on the epidemiology of toxoplasmosis and neosporosis in cats from Portugal is limited. Thus, this study aims to evaluate anti-T. gondii and anti-N. caninum seroprevalence in client-owned cats from Portugal and to identify risk factors using a panel of well-characterized sera. A total of 183 domestic cats were sampled and screened for antibodies against T. gondii and N. caninum using commercial ELISA assays, and their owners answered an online questionnaire designed to obtain background information. The overall anti-T. gondii and anti-N. caninum seroprevalences were 13.1% (CI: 8.97-18.77) and 3.8% (CI: 1.87-7.68), respectively. Univariate analysis revealed that living strictly indoors was a significant protection factor (cOR: 0.053; CI: 0.005-0.627), and the presence of a chronic disease a significant risk factor (cOR: 3.106; CI: 1.062-9.082) to T. gondii seroprevalence. When performing multivariate analysis, only chronic disease (aOR: 57.527; CI: 1.7-1976.7) and seropositivity to N. caninum (aOR: 7.929; CI:0.8-82.9) were found to be a significant risk factor to anti-T. gondii antibodies. To the best of our knowledge, this is the first report of N. caninum seropositivity in cats from Portugal.

Toxoplasma gondii Investigation of Home-Reared Pigs through Real-Time PCR and Digital Droplet PCR: A Very Low Prevalence

Toxoplasma gondii is a widespread protozoon that can infect both animals and humans. The main route of human infection is the consumption of the raw or undercooked meat of several animal species, including pigs. Although T. gondii represents a public health concern, control during slaughter is not mandatory, leading to a lack of information on the impact on human contagion as well as poor data availability in domestic animals intended for human consumption. We studied the presence of T. gondii in home-reared pigs, an unconventional type of farming subjected to stringent breeding conditions dictated by Italian regulation. Thus, the diaphragms, livers and masseter muscles from 480 pigs in Napoli Province (Italy) were analyzed using real-time PCR and digital droplet PCR. The results showed four matrices that tested positive for T. gondii with very low protozoan loads (0.62%), belonging to three different animals. The low density of the animals (the maximum was four animals per farm) and the biosafety farming features decisively contributed to the bioexclusion of this pathogen. Comparing these results to intensive and extensive farm data, lower exposure to the parasite was revealed, suggesting that this farming method might mitigate the risk of human exposure through meat consumption.

Migratory Wild Birds as Potential Long-Distance Transmitters of Toxoplasma gondii Infection

Toxoplasma gondii is a worldwide distributed zoonotic protozoan capable of infecting a wide range of mammals (including humans) and birds as intermediate hosts. Migratory wild birds, through interconnecting countries along their flyways, can play a role in the spatial spread of T. gondii and could contribute to its sylvatic cycle. Additionally, hunted wild birds used for meat consumption could represent a further source of human infection. To determine the presence of T. gondii in wild birds, a total of 50 individuals belonging to the Anseriformes and Charadriiformes orders were sampled during the 2021–2022 hunting season in Northern Italy. Cardiac muscle samples of three Northern shovelers (Anas clypeata), two wild mallards (A. platyrhynchos), one Eurasian teal (A. crecca), and one Northern lapwing (Vanellus vanellus) were positive for the molecular detection of T. gondii based on a targeted amplification of the B1 gene. A 14% (7/50) overall positivity was observed in the sampled population. Results from this study suggest a moderate exposure of wild aquatic birds to T. gondii, highlighting the importance of a further characterization of T. gondii in its wildlife hosts.