Toxoplasma gondii prevalence in farm animals in the United States

Effects of Recombinant Toxoplasma gondii Citrate Synthase I on the Cellular Functions of Murine Macrophages In vitro

Toxoplasmosis, which is one of the most widespread zoonoses worldwide, has a high incidence and infection can result in severe disease in humans and livestock. Citrate synthase (CS) is a component of nearly all living cells that plays a vital role in the citric acid cycle, which is the central metabolic pathway of aerobic organisms. In the present study, the citrate synthase I gene of Toxoplasma gondii (T. gondii) (TgCSI) was cloned and characterized. The TgCSI gene had an open reading frame of 1665 bp nucleotides encoding a 555 amino acid protein with a molecular weight of 60 kDa. Using western blotting assay, the recombinant protein was successfully recognized by the sera of rats experimentally infected with T. gondii, while the native protein in the T. gondii tachyzoites was detected in sera from rats immunized with the recombinant protein of TgCSI. Binding of the protein to murine macrophages was confirmed by immuno fluorescence assay. Following incubation of macrophages with rTgCSI, the rTgCSI protein was found to have a dual function, with low concentrations (5-10 μg/mL) enhancing phagocytosis and high levels (80 μg/mL) inhibiting phagocytosis. Investigation of murine macrophage apoptosis illustrated that 5 μg/mL rTgCSI protein can significantly induce early apoptosis and late stage apoptosis (*p < 0.05), while 10 μg/mL rTgCSI protein significantly induced early apoptosis, but had no effect on late stage of apoptosis (**p < 0.01), and 80 μg/mL rTgCSI protein inhibited late stage apoptosis of macrophages (*p < 0.05). Cytokine detection revealed that the secretion of interleukin-10, interleukin-1β, transforming growth factor-β1 and tumor necrosis factor-α of macrophages increased after the cells were incubated with all concentration of rTgCSI, with the exception that 5 μg/mL rTgCSI had no effect on the secretion of interleukin-10 and interleukin-1β. However, secretion of NO and cell proliferation of the macrophages were substantially reduced. Taken together, these results suggested that TgCSI can affect the immune functions of murine macrophages by binding to the cells in vitro.

Risk factors associated with Toxoplasma gondii infection in free-range chickens in the semiarid region of Brazil

This study aimed to investigate the frequency of anti-Toxoplasma gondii antibodies in serum from 629 chickens on 39 family farms in seven municipalities in the semiarid region, Pernambuco, Brazil, and to identify risk factors associated with T. gondii infection. The risk factors were studied in 421 samples from 29 farms. Anti-T. gondii antibodies were investigated by indirect fluorescent antibody test with a 1:16 cutoff. The frequency of positive chickens was 27.9% (176/629) and 94.8% of the farms studied had chickens infected by T. gondii. Multivariate analysis showed variables significantly associated with anti-T. gondii antibodies in serum: slaughter of animals on the farm, reproductive disorders in sheep, consumption of fetal adnexa and placentas by chickens, presence of sheep in the property and birth of sheep the property. The results suggest that there is a complex relationship between general management practices for different animal species raised on the same farm and the prevalence of T. gondii infection in chickens. In addition, the results draw attention to the risk of human infection by T. gondii via consumption of infected chicken meat, because the farming conditions and the low human development indices observed in the region studied result in inappropriate meat preparation practices.

Immunization with a DNA vaccine encoding Toxoplasma gondii Superoxide dismutase (TgSOD) induces partial immune protection against acute toxoplasmosis in BALB/c mice

Background

Toxoplasma gondii (T. gondii) is an obligate intracellular protozoan parasite that infects all warm-blooded animals including humans and causes toxoplasmosis. An effective vaccine could be an ideal choice for preventing and controlling toxoplasmosis. T. gondii Superoxide dismutase (TgSOD) might participate in affecting the intracellular growth of both bradyzoite and tachyzoite forms. In the present study, the TgSOD gene was used to construct a DNA vaccine (pEGFP-SOD).

Methods

TgSOD gene was amplified and inserted into eukaryotic vector pEGFP-C1 and formed the DNA vaccine pEGFP-SOD. Then the BALB/c mice were immunized intramuscularly with the DNA vaccine and those injected with pEGFP-C1, PBS or nothing were treated as controls. Four weeks after the last immunization, all mouse groups followed by challenging intraperitoneally with tachyzoites of T. gondii ME49 strain.

Results

Results showed higher levels of total IgG, IgG2α in the sera and interferon gamma (IFN-γ) in the splenocytes from pEGFP-SOD inoculated mice than those unvaccinated, or inoculated with either empty plasmid vector or PBS. The proportions of CD4⁺ T cells and CD8⁺ T cells in the spleen from pEGFP-SOD inoculated mice were significantly (p < 0.05) increased compared to control groups. In addition, the survival time of mice immunized with pEGFP-SOD was significantly prolonged as compared to the controls (p < 0.05) although all the mice died.

Conclusion

The present study revealed that the DNA vaccine triggered strong humoral and cellular immune responses, and aroused partial protective immunity against acute T. gondii infection in BALB/c mice. The collective data suggests the SOD may be a potential vaccine candidate for further development.

Toxoplasma Gondii and Pre-treatment Protocols for Polymerase Chain Reaction Analysis of Milk Samples: A Field Trial in Sheep from Southern Italy

Toxoplasmosis is a zoonotic disease caused by the protozoan Toxoplasma gondii. Ingestion of raw milk has been suggested as a risk for transmission to humans. Here the authors evaluated pre-treatment protocols for DNA extraction on T. gondii tachyzoite-spiked sheep milk with the aim of identifying the method that resulted in the most rapid and reliable polymerase chain reaction (PCR) positivity. This protocol was then used to analyse milk samples from sheep of three different farms in Southern Italy, including real time PCR for DNA quantification and PCR-restriction fragment length polymorphism for genotyping. The pre-treatment protocol using ethylenediaminetetraacetic acid and Tris-HCl to remove casein gave the best results in the least amount of time compared to the others on spiked milk samples. One sample of 21 collected from sheep farms was positive on one-step PCR, real time PCR and resulted in a Type I genotype at one locus (SAG3). Milk usually contains a low number of tachyzoites and this could be a limiting factor for molecular identification. Our preliminary data has evaluated a rapid, cost-effective and sensitive protocol to treat milk before DNA extraction. The results of the present study also confirm the possibility of T. gondii transmission through consumption of raw milk and its unpasteurised derivatives.

A systematic review and meta-analysis of the seroprevalence of Toxoplasma gondii in cats in mainland China

BACKGROUND

Toxoplasmosis is caused by Toxoplasma gondii which can infect all warm-blooded animals. As the most common feline definitive host, cats play a vital role in the transmission of T. gondii. However, national estimates of the seroprevalence of T. gondii in cats in mainland China are lacking, and therefore a systematic review and meta-analysis were performed to provide insight into national environmental transmission levels and potential transmission to humans.

METHODS

Studies published up until July 1, 2016, on T. gondii seroprevalence in cats within mainland China were searched for in CNKI, WanFang, CBM, PubMed, Embase and through the reference lists of resulting articles. The seroprevalence with its 95% confidence interval (CI) for each individual study was presented, and then point estimates and their 95% confidence intervals (CIs) of pooled seroprevalence were calculated. Subgroup analyses were performed according to potential risk factors.

RESULTS

A total of 38 eligible studies, published between 1995 to 2016, covering fifteen provinces and municipalities, and involving 7,285 cats, were included. The seroprevalence in cats per study ranged from 3.9 to 79.4% with a median of 20.3%. As substantial heterogeneity existed among studies, a random-effects model was used to estimate the pooled seroprevalence. The value of the point estimate seroprevalence was 24.5% (95% CI: 20.1-29.0). Seroprevalence in stray cats was significantly higher than in pet cats (OR = 3.00, 95% CI: 1.60-5.64). The seroprevalence increased significantly with cat age (P = 0.018) with 17.4% (95% CI: 7.6-27.2) in the group of ≤ 1 year old, 19.5% (95% CI: 12.7-26.3) in the group of ≤ 3 year-old and 31.6% (95% CI: 22.9-40.3) in the group of > 3 year-old.

CONCLUSIONS

The seroprevalence of T. gondii in cats in mainland China was moderate and was associated with cat ownership and age. Due to the increasing prevalence of pet cats in China and the intimate relationship between these cats and humans, this might present a significant exposure risk, particularly for China's large susceptible population. Therefore, further research is needed into the links between cat ownership and human T. gondii infection and how to reduce T. gondii exposure in humans via cat contacts and the environmental contamination with T. gondii oocysts by cats.

Activation of chronic toxoplasmosis by transportation stress in a mouse model

Toxoplasma gondii is an obligate intracellular parasite infecting 25% of the world population and enormous number of animals. It can exist in two forms in intermediate hosts: the fast replicating tachyzoites responsible for acute infection and the slowly replicating bradyzoites responsible for life-long chronic infection. The interconversion between tachyzoites and bradyzoites plays critical roles in the transmission and pathogenesis of T. gondii. However, the molecular mechanisms that govern the interconversion are largely unknown. In this study, we established a chronic infection model in mice and examined the impact of transportation stress on the status of chronic infection. Our results demonstrated that, treating chronically infected mice with conditions mimicking transportation stress reduced the levels of several key cytokines that restrict the infection at chronic stage. Increased expression of the tachyzoite specific gene SAG1 (surface antigen 1) was detected in brain cysts of stress treated mice, indicating activation and conversion of bradyzoites to tachyzoites. Using this model, we identified fifteen toxoplasmic proteins that had significant abundance changes during stress induced cysts reactivation. These proteins serve as a basis for further investigation of the mechanisms governing bradyzoite conversion.

Seroprevalence of Toxoplasma gondii infection and risk factors in domestic sheep in Henan province, central China

Sheep are highly susceptible to infections with Toxoplasma gondii and play a major role in the transmission of toxoplasmosis to humans. In the present study, 779 serum samples from sheep were collected from Henan province, central China from March 2015 to May 2016, and antibodies to T. gondii were detected by modified agglutination test (MAT). The overall seroprevalence of T. gondii in sheep was 12.71% (99/779). The risk factors significantly associated with T. gondii seroprevalence were the geographical origin, age, presence of cats, and the rearing system. This is the first report of T. gondii infection in sheep in Henan province, central China, and of an association of seropositivity to T. gondii with risk factors.

Seroprevalence of Toxoplasma gondii in goats in Hunan province, China

Toxoplasma gondii infections are prevalent in animals and humans worldwide. In the present investigation, the seroprevalence of T. gondii in goats was investigated in Hunan province, subtropical China between March 2014 and December 2015. A total of 1,028 serum samples collected from 14 administrative regions of Hunan province were evaluated by the indirect hemagglutination test (IHAT) for the detection of specific antibodies. Antibodies to T. gondii were detected in 124 serum samples (12%). The T. gondii seroprevalence ranged from 1.7% to 19% among different regions in subtropical China, and the differences were statistically significant (p < 0.01). The results of the present survey indicated that T. gondii infection is prevalent in goats in Hunan, which poses a potential risk for human infection with T. gondii in this province.

Prevalence of Toxoplasma gondii in pet dogs in mainland China: A meta-analysis

Toxoplasmosis, caused by Toxoplasma gondii, is one of the most common zoonosis in the world, and can cause severe adverse consequences in pregnant women and immunosuppressed people. Throughout the world dogs are popular companion animals, however they are also important intermediate host of T. gondii and may play an instrumental role in mechanically transmitting Toxoplasma infection to humans. Therefore, an assessment of the level of T. gondii infection in pet dogs is of public health importance. To estimate the overall serological prevalence of toxoplasmosis in pet dogs in mainland China, we performed a meta-analysis using five bibliographic databases: CNKI, WanFang, VIP Chinese Journal Databases, PubMed and Google Scholar. A total of 60 articles, including data on 78719 pet dogs, published between 1998 and 2016 fulfilled the final eligibility criteria. The overall seroprevalence of T. gondii infection in pet dogs was 11.1% (95% CI: 10.1% to 12.1%). The seroprevalence of toxoplasmosis in >one-year-old dogs was 1.59 times more than that in ≤one-year-old group (RR=1.59, 95%CI=1.15, 2.21). There was no significant difference observed in pooled seroprevalence between male and female dogs (RR=1.02, 95%CI=0.91, 1.16). In terms of geographical regions, the lowest seroprevalence of toxoplasmosis infection (5.8%) was in North China and the highest (16.8%) was in Southwest of China. Results from this study showed that toxoplasmosis is common in pet dogs in mainland China, indicating that control measures by owners may reduce human exposure to T. gondii via dog contacts.

Toxoplasma infection in sheep from south of Iran monitored by serological and molecular methods; risk assessment to meat consumers

AIM

Toxoplasma gondii has a clinical and veterinary importance as it is known to cause congenital disease and abortion both in humans and livestock. Since the contaminated lamb is one of the sources of human infection, this study was performed to determine the prevalence of T. gondii in sheep in south of Iran.

MATERIALS AND METHODS

Sera and tissue samples (diaphragm and heart) were collected from 370 sheep from slaughterhouse of Jahrom. The samples were taken from both sexes and from 6 to 60 months age. Specific immunoglobulin G antibodies to T. gondii were examined with enzyme-linked immunosorbent assay, and B1 gene nested-polymerase chain reaction detection was done to survey the tissue samples.

RESULTS

The total prevalence of Toxoplasma infection among sheep was found to be 35.94% and 34.32% based on serological and molecular method, respectively. According to serologic and molecular findings, the females were more positive than males for Toxoplasma; maximum frequency of positive samples was observed in 24-36 months and the positive samples had been collected more in spring than in summer, but no statistical correlation was observed between prevalence rate and the age and sex of animals or season of sampling.

CONCLUSION

T. gondii is widely distributed in sheep in Jahrom with a rate comparable with other parts of Iran and the world. It suggested a widespread exposure of sheep in this region to T. gondii. Thus, consumption of undercooked or raw meat presents the transmission risk of the parasite and this might be considered as an important public health problem, mainly for high-risk groups such as the pregnant and the immunodeficient.

Blimp-1-mediated CD4 T cell exhaustion causes CD8 T cell dysfunction during chronic toxoplasmosis

CD8, but not CD4, T cells are considered critical for control of chronic toxoplasmosis. Although CD8 exhaustion has been previously reported in Toxoplasma encephalitis (TE)-susceptible model, our current work demonstrates that CD4 not only become exhausted during chronic toxoplasmosis but this dysfunction is more pronounced than CD8 T cells. Exhausted CD4 population expressed elevated levels of multiple inhibitory receptors concomitant with the reduced functionality and up-regulation of Blimp-1, a transcription factor. Our data demonstrates for the first time that Blimp-1 is a critical regulator for CD4 T cell exhaustion especially in the CD4 central memory cell subset. Using a tamoxifen-dependent conditional Blimp-1 knockout mixed bone marrow chimera as well as an adoptive transfer approach, we show that CD4 T cell-intrinsic deletion of Blimp-1 reversed CD8 T cell dysfunction and resulted in improved pathogen control. To the best of our knowledge, this is a novel finding, which demonstrates the role of Blimp-1 as a critical regulator of CD4 dysfunction and links it to the CD8 T cell dysfunctionality observed in infected mice. The critical role of CD4-intrinsic Blimp-1 expression in mediating CD4 and CD8 T cell exhaustion may provide a rational basis for designing novel therapeutic approaches.

Quantifying the Risk of Human Toxoplasma gondii Infection Due to Consumption of Domestically Produced Lamb in the United States

Toxoplasma gondii is a prevalent protozoan parasite worldwide. Human toxoplasmosis is responsible for considerable morbidity and mortality in the United States, and meat products have been identified as an important source of T. gondii infections in humans. The goal of this study was to develop a farm-to-table quantitative microbial risk assessment model to predict the public health burden in the United States associated with consumption of U.S. domestically produced lamb. T. gondii prevalence in market lambs was pooled from the 2011 National Animal Health Monitoring System survey, and the concentration of the infectious life stage (bradyzoites) was calculated in the developed model. A log-linear regression and an exponential doseresponse model were used to model the reduction of T. gondii during home cooking and to predict the probability of infection, respectively. The mean probability of infection per serving of lamb was estimated to be 1.5 cases per 100,000 servings, corresponding to ∼6,300 new infections per year in the U.S.

POPULATION

Based on the sensitivity analysis, we identified cooking as the most effective method to influence human health risk. This study provided a quantitative microbial risk assessment framework for T. gondii infection through consumption of lamb and quantified the infection risk and public health burden associated with lamb consumption.

Salivary IgA against sporozoite-specific embryogenesis-related protein (TgERP) in the study of horizontally transmitted toxoplasmosis via T. gondii oocysts in endemic settings

The aim of this study was to contribute to the better understanding of the relative epidemiological importance of different modes of infection with respect to horizontal transmission of Toxoplasma gondii in endemic settings. We investigated the prevalence of salivary IgA against a sporozoite-specific embryogenesis-related protein (TgERP) in a highly endemic area for toxoplasmosis in Brazil in order to pinpoint parasite transmission via oocysts. Prevalence calculated by salivary IgA specific to TgERP was compared to the prevalence calculated by serum IgG against both TgERP and tachyzoites (in conventional serological tests). Prevalence calculated by different serological and salivary parameters varied in the studied age groups. However, for the 15-21 years age group, values for T. gondii prevalence estimated by conventional serological tests and by anti-TgERP salivary IgA were similar; i.e. 68·7% and 66·6% or 66·7%, respectively, using two different cut-off parameters for salivary IgA anti-TgERP. Furthermore, salivary IgA anti-TgERP for this age group presented the highest specificity (93·33%), sensitivity (93·94%), and likelihood (14·09) compared to all the other age groups. These data demonstrate the importance of age for salivary IgA investigation against TgERP to estimate the mode of T. gondii transmission in endemic settings.

Molecular diagnosis of Toxoplasma gondii infection in Libya

Background

Toxoplasma gondii infections are prevalent in humans and animals throughout Libya. Current diagnosis is based on detection of Toxoplasma-specific IgM and IgG. In this study, we established and optimized a diagnostic PCR assay for molecular diagnosis of T. gondii in Libya.

Methods

From January to December, 2010, 177 blood and serum samples were collected from suspected patients. This includes: 140 women who have had spontaneous abortions, 26 HIV-positive patients, nine patients with leukemia and lymphoma, and two infants with ocular infection. Samples were screened for anti-Toxoplasma IgG and IgM antibodies before DNA extraction. The surface antigen gene 2 (SAG2) was targeted in a semi-nested PCR to amplify a 999 bp and a 614 bp fragment in the first and the second run respectively.

Results

A total of 54/140 (38.5 %) women who have had spontaneous abortions, 23/26 (88 %) HIV patients, 6/9 (66.6 %) of the leukaemia and lymphoma patients, and one child with ocular infection were seropositive for anti-Toxoplasma IgG and/or IgM. Genomic DNA was extracted from 38 selected seropositive samples. The PCR was sensitive enough to detect DNA concentration of 12 ng/μL. PCR analysis was performed for 38 selected seropositive patients (16 women who have had spontaneous abortions, 15 positive HIV patients, six leukaemia patients and one child with ocular infection). Our designed primers were successfully amplified in 22/38 (57.9 %) samples; 5/12 (35.7 %) from serum and 17/26 (65.8 %) from whole blood samples. All PCR positive samples were IgG-positive except two samples which were IgM and IgG & IgM-positive serum samples respectively. The semi-nested PCR confirmed five more samples. These included two leukaemia and two HIV-positive whole blood samples and one serum sample from an aborted woman.

Conclusion

The ability of PCR to diagnose active toxoplasmosis is needed in immunocompromised patients and congenital toxoplasmosis cases, especially when serological techniques fail. For the first time in Libya, we established and optimized semi-nested PCR of SAG2 gene. The developed PCR method was able to detect as little as 12 ng/μL of T. gondii DNA and was useful to diagnose the diseases in women who have had spontaneous abortions, HIV-positive patients, patients with leukemia and lymphoma, and infants with ocular infection.

Toxoplasma gondii infection in pork produced in France

The aim of this study was to assess the seroprevalence of the Toxoplasma gondii parasite in pork produced in France, and to determine infection risk factors. An innovative survey was designed based on annual numbers of slaughtered pigs from intensive and outdoor farms in France. A total of 1549 samples of cardiac fluids were collected from pig hearts to determine seroprevalence using a Modified Agglutination Test. Of those, 160 hearts were bio-assayed in mice to isolate live parasites. The overall seroprevalence among fattening pigs was 2·9%. The adjusted seroprevalence in pigs from intensive farms was 3·0%; the highest in sows (13·4%); 2·9% in fattening pigs and 2·6% in piglets. Adjusted seroprevalence in fattening animals from outdoor farms was 6·3%. Strains were isolated from 41 animals and all were genotyped by Restriction Fragment Length Polymorphism as type II. Risk-factor analysis showed that the risk of infection was more than three times higher for outdoor pigs, and that sows' risk was almost five times higher than that of fattening animals. This study provides further evidence of extensive pork infection with T. gondii regardless of breeding systems, indicating that farm conditions are still insufficient to guarantee 'Toxoplasma-free pork'.

Seroprevalence of Toxoplasma gondii among turkeys on family farms in the state of Northeastern Brazil

The aim of the present study was to investigate the prevalence of antibodies against Toxoplasma gondii in turkeys and chickens on family farms in the semi-arid region of the state of Pernambuco, Brazil. In order to do so, 204 sera samples from turkeys were analyzed using the Modified Agglutination Test (MAT) and 322 sera samples from chickens were assessed using the Immunofluorescence Assay (IFA). Twenty-eight properties contained turkeys and 23 of these properties also contained chickens. The relative frequency of positive turkeys was 11% (21/204), with 46.6% (13/28) of the properties containing at least one positive turkey. The frequency of positive chickens was 25.8% (83/322), with 95.6% (22/23) of the properties containing at least one positive chicken. Based on the results of the present study, it was possible to conclude that turkeys can serve as an indicator of environmental contamination by oocysts of T. gondii. However, they are less effective than chickens bred in the same conditions. The increasing demand from consumers for naturally produced products should worry local sanitary authorities due to the high prevalence of antibodies against T. gondii found in this type of rearing system, particularly among chickens.

A Systematic Meta-Analysis of Toxoplasma gondii Prevalence in Food Animals in the United States

Toxoplasma gondii is a widely distributed protozoan parasite. The Centers for Disease Control and Prevention reported that T. gondii is one of three pathogens (along with Salmonella and Listeria), that together account for >70% of all deaths due to foodborne illness in the United States. Food animals are reservoirs for T. gondii and act as one of the sources for parasite transmission to humans. Based on limited population-based data, the Food and Agriculture Organization/World Health Organization estimated that approximately 22% of human T. gondii infections are meatborne. The objective of the current study was to conduct a systematic meta-analysis to provide a precise estimation of T. gondii infection prevalence in food animals produced in the United States. Four databases were searched to collect eligible studies. Prevalence was estimated in six animal categories (confinement-raised market pigs, confinement-raised sows, non-confinement-raised pigs, lamb, goats, and non-confinement-raised chickens) by a quality-effects model. A wide variation in prevalence was observed in each animal category. Animals raised outdoors or that have outdoor access had a higher prevalence as compared with animals raised indoors. T. gondii prevalence in non-confinement-raised pigs ranked the highest (31.0%) followed by goats (30.7%), non-confinement-raised chickens (24.1%), lambs (22.0%), confinement-raised sows (16.7%), and confinement-raised market pigs (5.6%). These results indicate that T. gondii-infected animals are a food safety concern. The computed prevalence can be used as an important input in quantitative microbial risk assessment models to further predict public health burden.

Meat Juice Serology for Toxoplasma Gondii Infection in Chickens

Toxoplasma gondii is an important foodborne zoonosis. Free-range chickens are at particularly high risk of infection and are also excellent indicators of soil contamination by oocysts. In the present study, hearts of 77 free-range chickens were collected at slaughter. T. gondii meat juice enzyme-linked immunosorbent assay was performed with a commercial kit, following validation with positive controls, from experimentally infected chickens, and negative ones. Out of 77 samples, only 66 gave sufficient meat juice for serology. Of these, 24 (36.4%) were positive for T. gondii considering the 5*standard deviation values (calculated on the optical density of negative controls), while all the samples were negative considering sample/positive% values. Parasite-specific polymerase chain reaction was carried out on all samples obtained from heart tissue and none were positive for the presence of T. gondii DNA. Results would suggest that further study on the use of meat juice with a validated serological test to detect T. gondii in chickens could lead to widespread epidemiological studies in this important intermediate host. However, sample collection and test specificity require further evaluation.

Qualitative Assessment for Toxoplasma gondii Exposure Risk Associated with Meat Products in the United States

Toxoplasma gondii is a global protozoan parasite capable of infecting most warm-blooded animals. Although healthy adult humans generally have no symptoms, severe illness does occur in certain groups, including congenitally infected fetuses and newborns, immunocompromised individuals including transplant patients. Epidemiological studies have demonstrated that consumption of raw or undercooked meat products is one of the major sources of infection with T. gondii. The goal of this study was to develop a framework to qualitatively estimate the exposure risk to T. gondii from various meat products consumed in the United States. Risk estimates of various meats were analyzed by a farm-to-retail qualitative assessment that included evaluation of farm, abattoir, storage and transportation, meat processing, packaging, and retail modules. It was found that exposure risks associated with meats from free-range chickens, nonconfinement-raised pigs, goats, and lamb are higher than those from confinement-raised pigs, cattle, and caged chickens. For fresh meat products, risk at the retail level was similar to that at the farm level unless meats had been frozen or moisture enhanced. Our results showed that meat processing, such as salting, freezing, commercial hot air drying, long fermentation times, hot smoking, and cooking, are able to reduce T. gondii levels in meat products. whereas nitrite and/or nitrate, spice, low pH, and cold storage have no effect on the viability of T. gondii tissue cysts. Raw-fermented sausage, cured raw meat, meat that is not hot-air dried, and fresh processed meat were associated with higher exposure risks compared with cooked meat and frozen meat. This study provides a reference for meat management control programs to determine critical control points and serves as the foundation for future quantitative risk assessments.

Oral dependent-dose toxoplasmic infection model induced by oocysts in rats: Myenteric plexus and jejunal wall changes

Toxoplasmosis is a widely distributed disease caused by the protozoan Toxoplasma gondii that is mainly transmitted orally. Once ingested, the parasite crosses the intestinal barrier to reach the blood and lymph systems to migrate to other regions of the host. The objective of this study was to evaluate the changes in the myenteric plexus and the jejunal wall of Wistar rats caused by oral infection with T. gondii oocysts (ME-49 strain). Inocula of 10, 100, 500 and 5000 oocysts were used. The total population of myenteric neurons and the most metabolically active subpopulation (NADH-diaphorase positive - NADH-dp) exhibited a decrease proportional to the dose of T. gondii. There was also a quantitative increase in the subpopulation of NADPH-diaphorase-positive (NADPH-dp) myenteric neurons, indicating greater expression of the NOS enzyme. Neuronal atrophy was observed, and morphological and morphometric alterations such as jejunal atrophy were found in the infected groups. Hypertrophy of the external muscle with the presence of inflammatory foci was observed in the group infected with 5000 oocysts. The changes observed in the infected groups were proportional to the number of oocysts inoculated.

CD8+ T cell immunity in an encephalitis model of Toxoplasma gondii infection

Toxoplasma gondii infection induces a robust CD8 T cell immunity in the infected host, which is critical for keeping chronic infection under control. IFNγ production and cytolytic activity exhibited by CD8 T cells are critical functions needed to prevent the reactivation of latent infection. Paradoxically, the susceptible mice infected with the parasite develop encephalitis irrespective of the presence of vigorous CD8 T cell immunity. Recent studies from our laboratory have demonstrated that these animals have defect in the memory CD8 T cell population, which become dysfunctional due to exhibition of inhibitory receptors like PD-1. Although the blockade of PD-1-PDL-1 pathway rescues the CD8 response, PD-1(hi) expressing cells are refractory to the treatment. In this review, we discuss the development of CD8 memory response during chronic infection, mechanism responsible for their dysfunctionality, and possible therapeutic measures that can be taken to reverse the process.

Secreted effectors in Toxoplasma gondii and related species: determinants of host range and pathogenesis?

Recent years have witnessed the discovery of a number of secreted proteins in Toxoplasma gondii that play important roles in host-pathogen interactions and parasite virulence, particularly in the mouse model. However, the role that these proteins play in driving the unique features of T. gondii compared to some of its nearest apicomplexan relatives (Hammondia hammondi and Neospora caninum) is unknown. These unique features include distinct dissemination characteristics in vivo and a vast host range. In this review we comprehensively survey what is known about disease outcome, the host response and host range for T. gondii, H. hammondi, and N. caninum. We then review what is presently known about recently identified secreted virulence effectors in these three genetically related, but phenotypically distinct, species. Finally we exploit the existence of genome sequences for these three organisms and discuss what is known about the presence, and functionality, of key T. gondii effectors in these three species.

Seroprevalence and genotype of Toxoplasma gondii in pigs, dogs and cats from Guizhou province, Southwest China

BACKGROUND

Toxoplasma gondii is an obligate, intracellular protozoan that infects almost all warm-blooded animals, including humans, domesticated and wild animals. Recent studies of Toxoplasma gondii isolates from animals in different regions of China have shown a limited genetic diversity with the dominance of the ToxoDB PCR-RFLP genotype #9 named as "Chinese 1". However, there is not much published information regarding its prevalence in domestic animals from Guizhou province, a subtropical region in Southwest China. The objectives of this study were to determine seroprevalence and genetic diversity of T .gondii in pigs, dogs and cats in Guizhou province, Southwest China.

FINDINGS

The anti-T. gondii IgG were detected in 70.0%(49/70) pigs, 20.56%(22/107) dogs and 63.16(12/19) cats. The anti-T. gondii IgM were found in 0.93%(1/107) dogs, 21.53%(4/19) cats, but not in pigs. In addition, the toxoplasma circulating antigen (CAG) were detected in 16.9%18/70)pigs, 13.1% (14/107) dogs and 10.5%(2/19) cats. The T. gondii DNA were detected in 31.5%(22/70) pigs, 3.7%(4/107) dogs and 52.63%(10/19) cats. Five T. gondii isolates were obtained(3 from pigs and 2 from cats). The genotype of these five isolates belonged to the predominant genotype "Chinese 1".

CONCLUSIONS

The high prevalence of T. gondii infection in pigs,cats and dogs indicated that the T. gondii infection is common in Guizhou province. Additionally, the T. gondii genotype "Chinese 1" was dominant in Southwest China.

AMA1-deficient Toxoplasma gondii parasites transiently colonize mice and trigger an innate immune response that leads to long-lasting protective immunity

The apical membrane antigen 1 (AMA1) protein was believed to be essential for the perpetuation of two Apicomplexa parasite genera, Plasmodium and Toxoplasma, until we genetically engineered viable parasites lacking AMA1. The reduction in invasiveness of the Toxoplasma gondii RH-AMA1 knockout (RH-AMA1(KO)) tachyzoite population, in vitro, raised key questions about the outcome associated with these tachyzoites once inoculated in the peritoneal cavity of mice. In this study, we used AMNIS technology to simultaneously quantify and image the parasitic process driven by AMA1(KO) tachyzoites. We report their ability to colonize and multiply in mesothelial cells and in both resident and recruited leukocytes. While the RH-AMA1(KO) population amplification is rapidly lethal in immunocompromised mice, it is controlled in immunocompetent hosts, where immune cells in combination sense parasites and secrete proinflammatory cytokines. This innate response further leads to a long-lasting status immunoprotective against a secondary challenge by high inocula of the homologous type I or a distinct type II T. gondii genotypes. While AMA1 is definitively not an essential protein for tachyzoite entry and multiplication in host cells, it clearly assists the expansion of parasite population in vivo.

Serodiagnosis of Toxoplasma gondii infection in farm animals (horses, swine, and sheep) by enzyme-linked immunosorbent assay using chimeric antigens

Toxoplasma gondii infects all warm-blooded animals including humans, causing serious public health problems and great economic loss in the animal husbandry. Commonly used serological tests for diagnosis of toxoplasmosis involve preparation of whole Toxoplasma lysate antigen (TLA) from tachyzoites. The production of this antigen is associated with high costs and lengthy preparation and the possibility of staff infection. There are also some difficulties in the standardization of such tests. One approach in order to improve the diagnosis of T. gondii infection is to use recombinant chimeric antigens in place of the TLA, which was confirmed by studies in the serodiagnosis of toxoplasmosis in humans. In this paper, we assess, for the first time, the diagnostic utility of five T. gondii recombinant chimeric antigens (MIC1-MAG1-SAG1S, SAG1L-MIC1-MAG1, SAG2-GRA1-ROP1S, SAG2-GRA1-ROP1L, and GRA1-GRA2-GRA6) in immunoglobulin G (IgG) enzyme-linked immunosorbent assays (IgG ELISAs) with sera from three different groups of livestock animals (horses, pigs, and sheep). The reactivity of individual chimeric antigens was analyzed in relation to the results obtained in IgG ELISAs based on a mixture of three antigens (M1: rSAG1+rMIC1+rMAG1, M2: rSAG2+rGRA1+rROP1, and M3: rGRA1+rGRA2+rGRA6) and referenced to TLA. All chimeric antigens were characterized by high specificity (100%), and the sensitivity of the IgG ELISAs based on chimeric antigens was variable (between 28.4% and 100%) and mainly dependent on the animal species. The chimeric antigens were generally more reactive than mixtures of three antigens. The most effective for the diagnosis of toxoplasmosis was SAG2-GRA1-ROP1L, which can detect specific anti-T. gondii antibodies in 100%, 93.8%, and 100% of positive serum samples from horses, pigs, and sheep, respectively. The present study shows that recombinant chimeric antigens can be successfully used to diagnose T. gondii infection in farm animals, and can replace the commonly used TLA.

Toxoplasma gondii in livestock in St. Kitts and Nevis, West Indies

BACKGROUND

Toxoplasma gondii is a ubiquitous protozoan parasite capable of infecting all warm-blooded animals including livestock. In these animals, the parasite forms cysts in the tissues which may pose a risk to public health if infected meat is consumed undercooked or raw. The aim of this study was to determine the exposure of livestock to T. gondii in St. Kitts and Nevis.

METHODS

Sera and/or heart tissue and meat juice were collected from pigs (n = 124), sheep (n = 116) and goats (n = 66) at the St. Kitts Abattoir. Sera and meat juice were screened for reactive antibodies to T. gondii using an in-house ELISA. Heart tissue was screened for T. gondii DNA using quantitative PCR and positive samples were genotyped using RFLP.

RESULTS

Antibodies to T. gondii were detected in sera from 48% of pigs, 26% of sheep and 34% of goats tested. Antibodies were also detected in the meat juice from 55% of pig hearts, 22% of sheep hearts and 31% of goat hearts tested. There was a significant positive correlation between serology and meat juice results. T. gondii DNA was detected in heart tissue of 21% of pigs, 16% of sheep and 23% of goats tested. Preliminary PCR-RFLP analysis identified a predominance of the Type III genotype of T. gondii.

CONCLUSIONS

These results suggest widespread environmental contamination with T. gondii oocysts and that livestock could be a potentially important source of T. gondii infection if their infected meat is consumed (or handled) undercooked.

Prevalence and risk factors for Toxoplasma gondii infection in meat animals and meat products destined for human consumption

Toxoplasma gondii is a protozoan parasite that is responsible for approximately 24% of all estimated deaths attributed to foodborne pathogens in the United States. Human infection results from accidental ingestion of oocysts from the environment, in water, or on insufficiently washed produce or from consumption of raw or undercooked meat products that contain T. gondii tissue cysts. This review focused on studies of T. gondii in meat because many human T. gondii infections are acquired through consumption of raw or undercooked meat. Prevalence of T. gondii is higher in conventionally reared pigs, sheep, and poultry than in cattle and is greater in meat products from organic than from conventionally reared meat animals because of outdoor access, which poses substantially greater opportunities for exposure to infected rodents, wildlife, and oocyst-contaminated feed, water, or environmental surfaces. Risk factors related to T. gondii exposure for livestock include farm type, feed source, presence of cats, methods of rodent and bird control, methods of carcass handling, and water quality. This review serves as a useful resource and information repository for informing quantitative risk assessment studies for T. gondii infection in humans through meat consumption.

Seroprevalence and risk factors of Toxoplasma gondii and Neospora caninum infections in small ruminants in China

Little information is available about the seroprevalence of Toxoplasma gondii and Neospora caninum infections in sheep and goats in China. In the present investigation, the seroprevalence of T. gondii and N. caninum infections in sheep and goats were investigated in Qinghai province, China between January 2012 and June 2013. A total of 1250 serum samples (600 sheep and 650 goats) collected from 8 administrative regions of Qinghai province, China were evaluated by enzyme-linked immunosorbent assay for the detection of specific antibodies, and sera positive were subsequently confirmed with indirect fluorescent antibody test. Specific IgG against T. gondii were detected in 21.33% (95% confidence interval [CI]: 18.06-24.61%) (128/600) and 29.54% (95% CI: 26.03-33.05%) (192/650) and against N. caninum in 10.33% (95% CI: 7.9-12.77%) (62/600) and 7.23% (95% CI: 5.24-9.22%) (47/650) of the sheep and goats, respectively. The risk factors significantly associated with T. gondii and N. caninum seroprevalence were the presence of cats and dogs, the pasturing system, the herd size, the hygiene in the farms. The results of the present survey indicate that T. gondii and N. caninum infections are highly prevalent in sheep and goats in Qinghai province, China. This is the first time that antibodies to N. caninum have been detected in sheep and goats in China.

Xenozoonoses

Immunological and technical advances have led to tremendous increases in the number of people potentially able to benefit from allotransplantation. Ironically, it is the success of the field that has led to a renewed interest in xenotransplantation during the past several decades. To a large part, this has occurred because of the great scarcity of human organ and tissue donors. However, it has expanded to include the use of cells from animals into humans such as porcine islet cells for diabetes or extracorporeal perfusion of human blood through animal organs or cells. Similar to allotransplantation, issues regarding transmission of infections from the graft to the human recipient were brought up for consideration with these procedures in the 1990s (Michaels and Simmons, 1994; Chapman et al., 1995; Hammel et al., 1998; Fishman et al., 1998). A risk for infection exists with the use of any biologic agent regardless of whether it is from a human or an animal source. Accordingly, transmission of infections from human organs, tissues, or cells is a well-recognized cause of disease after allotransplantation (Ison and Grossi, 2013; Green and Michaels, 2012). As the human graft shortage continues, newer cellular therapies are explored. Thus, attention continues to be given to the potential use of xenogeneic organs, tissues, or cells for human maladies through xenotransplantation. The potential for novel zoonotic infections to emerge because of xenotransplantation (xenozoonoses or xenosis) led to a debate on whether the field should be permitted to progress. This chapter reviews the issues of xenotransplantation related to infections from animals to humans. Lessons learned from infections with prior nonhuman primate xenotransplantation and human allotransplantation are used to help inform about risks with newer xenogeneic procedures. In addition, information on known zoonoses is reviewed to better develop constructs to decrease the hazard of infection with these novel procedures.

Lack of association between Toxoplasma gondii infection and occupational exposure to animals

The association of infection with Toxoplasma gondii and occupational exposure to animals has been scantly determined. We performed a case-control study with 200 subjects from Durango Province, Mexico, occupationally exposed to animals and 200 age- and gender-matched subjects without this occupation. Sera from all participants were analyzed for anti-T. gondii IgG and IgM antibodies using enzyme-linked immunoassays. The association of seroprevalence with sociodemographic, work, clinical, and behavioral characteristics in cases was determined. Cases and controls had similar frequencies of anti-T. gondii IgG antibodies (12/200: 6.0% and 11/200: 5.5%, respectively) (OR = 3.0; 95% CI: 0.12-73.64; P = 1.0). The frequency of sera with high (>150 IU/ml) levels of anti-T. gondii IgG antibodies was comparable among cases and controls (P = 0.61). Seroprevalence of anti-T. gondii IgM antibodies was similar in cases (4, 2.0%) than in controls (4, 2.0%) (P = 1.0). Multivariate analysis showed that seropositivity was associated with eating while working (OR = 7.14; 95% CI: 1.91-26.72; P = 0.003) and consumption of duck meat (OR = 5.43; 95% CI: 1.43-20.54; P = 0.01). No association between seropositivity to T. gondii and occupational exposure to animals was found. However, risk factors for infection found should be taken into account to reduce the exposure to T. gondii.

Comparative study on Toxoplasma infection between Malaysian and Myanmar pregnant women

Background

Toxoplasma gondii, an obligate intracellular protozoan parasite, causes a disease called toxoplasmosis which can sometimes be acquired congenitally by a newborn from an infected mother. This study aimed to determine the seroprevalence of Toxoplasma infection and its associated risks among 219 and 215 pregnant women from Malaysia and Myanmar, respectively.

Methods

Anti-Toxoplasma IgG and IgM antibodies were screened by using standard commercial ELISA kits. The socio-demographic, obstetrics and risk factors associated with Toxoplasma infection data were compared between the two countries.

Results

The overall prevalence of Toxoplasma infection in Malaysian pregnant women (42.47%; 95% CI = 36.11-49.09) was significantly higher (p < 0.05) than Myanmar pregnant women (30.70%; 95% CI = 27.92-37.16). By univariate analysis, this study identified that age group, education, parity, awareness on toxoplasmosis and consumption of undercooked meat were significantly associated (p < 0.05) with Toxoplasma seropositive Malaysian pregnant women but none of these factors associated with Toxoplasma seropositive Myanmar pregnant women. In comparison using univariate analysis between the two countries, it was found that Toxoplasma seropositive Malaysian pregnant women was associated with aged 30 years and above, secondary or lower-secondary level of education, the third trimester of pregnancy, having one child or more, lacking awareness of toxoplasmosis, absence of bad obstetrics history, having no history of close contact with cats or soil, living on a farm and also consumption of undercooked meat, unpasterized milk or untreated water. Avidity measurement was used to confirm the stages of Toxoplasma infection in pregnant women who were positive for both IgG and IgM antibodies and found all were infected in the past.

Conclusion

From our study, Toxoplasma screening and its risk measurement in pregnant women is firmly recommended for monitoring purposes and assisting proper management, including diagnosis and treatment during antenatal period. Also, it is necessary to initiate preventive measures for Toxoplasma infection among reproductive-age women in general and seronegative pregnant women in particular. Avidity measurement should be incorporated in Toxoplasma routine screening, especially with the availability of a single serum sample to assist in the diagnosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-014-0564-9) contains supplementary material, which is available to authorized users.

Prevalence of Toxoplasma infection in veterinary laboratory sciences students comparing to ordinary people: a case-control study

Toxoplasma gondii causes the foremost widespread protozoan infection with a broad variety of host range, which consists of regarding of almost all warm-blooded vertebrates. There are some opinions concerning the probable occupational influence on infections to Toxoplasma in veterinary services personnel. The present study aimed to examine influence of studying in veterinary laboratory sciences as a risk factor on the prevalence rate of Toxoplasma infection in the students. In this case-control study, 80 blood samples were taken from veterinary laboratory sciences students (VLSS) as a case group and 80 blood samples from ordinary people of general population as a control group with the relatively same age, gender and health condition. Anti-Toxoplasma IgG levels in the serum samples were determined using quantitative ELISA method. According to the results, 27 (33.75 %) out of 80 samples of the cases group and also 29 (36.2 %) out of 80 samples of the control group were infected by the parasite. No statistically significant difference observed in the infection rate between the case and control groups (P = 0.740, OR 0.931; 95 % CI 0.61, 1.421). The mean serum antibody concentration in infected subjects of case and control groups showed no statistically significant difference (P = 0.618, t = 0.502). Normality of the data was assumed using Kolmogorov-Smirnov test (P = 0.806, Z = 0.641). Based on the results, in veterinary laboratory science students, toxoplasmosis is not related to their career and also the subjects of this group as the other people have the same risk to infect by this protozoan parasite.

Knowledge and practice on Toxoplasma infection in pregnant women from Malaysia, Philippines, and Thailand

Toxoplasma gondii, is one of the infectious agents of congenital TORCH infections, causes severe clinical outcomes in fetus and newborns. Nevertheless this life-threatening parasitic disease is preventable by simple preventive measures related to lifestyle during pregnancy. We aim to study on the knowledge about toxoplasmosis and practices that prevents this infection among the pregnant women. Total of 2598 pregnant women from Malaysia, Philippines, and Thailand were randomly surveyed to determine the knowledge and their practices on Toxoplasma infection. The questionnaire covered respondents' general information and knowledge on plausible risks factors, symptoms, timing of infection, prevention knowledge, and preventive behavior regarding Toxoplasma infection. Majority of these pregnant women were in their age group of 20-29 years (50.9%), completed secondary level of education (51.7%), in their second trimester of pregnancies (38.1%), non-parous (36.6%), and had no history of abortion (90.4%). Based on this survey, only 11% of these pregnant women had read, heard, or seen information regarding toxoplasmosis and 3.5% of them were aware of being tested for the infection. A small percentage of these pregnant women knew that T. gondii were shed in the feces of infected cats (19.4%) and sometimes found in the raw or undercooked meat (11.0%). There was 16.1% of responding women knew that toxoplasmosis is caused by an infection. Demographic profiles such as age group, level of education, pregnancy term, and number of children of the pregnant women showed significant association with their responses toward prevention knowledge and preventive behavior related questions (P < 0.05). Thus, it is suggested that health education on toxoplasmosis and primary behavioral practices should be consistently offered to reproductive age women in general and pregnant women in particular. This information could help to reduce vertical transmission of Toxoplasma infection during pregnancy.

Toxoplasma gondii seroprevalence in the United States 2009-2010 and comparison with the past two decades

Toxoplasma gondii is a ubiquitous parasite that can cause neurologic and ocular disease. We tested sera from 7,072 people ≥ 6 years of age in the 2009-2010 National Health and Nutrition Examination Survey (NHANES) for immunoglobulin G antibodies and compared these results with two previous NHANES studies. The overall T. gondii antibody seroprevalence among persons ≥ 6 years of age in 2009-2010 was 13.2% (95% confidence limit [CL] 11.8%, 14.5%) and age-adjusted seroprevalence was 12.4% (95% CL 11.1%, 13.7%); age-adjusted seroprevalence among women 15-44 years of age was 9.1% (95% CL 7.2%, 11.1%). In U.S. born persons 12-49 years of age, the age-adjusted T. gondii seroprevalence decreased from 14.1% (95% CL 12.7%, 15.5%) in NHANES III (1988-1994) to 9.0% (95% CL 7.6%, 10.5%) in NHANES 1999-2004 to 6.7% (95% CL 5.3%, 8.2%) in NHANES 2009-2010 (P < 0.001 linear trend). Although T. gondii antibody presence is still relatively common, the prevalence in the United States has continued to decline.

Toxoplasma infection in pregnant women: a current status in Songklanagarind hospital, southern Thailand

Background

Toxoplasmosis, being one of the TORCH’s infections in pregnant women, is caused by Toxoplasma gondii, an obligate intracellular protozoan parasite. This parasitic infection in pregnancy congenitally causes severe outcomes to their fetus and newborn. This study aimed to determine the seroprevalence and stages of Toxoplasma infection in pregnant women and its associated risks exposures.

Methods

The study was conducted within the pregnant women attending the antenatal clinic (ANC) at Songklanagarind hospital, Hat Yai, Songkhla province, Thailand. The sera of a total of 760 consecutive pregnant women were screened using standard commercial ELISA kits for detection of anti-Toxoplasma IgG and IgM antibodies. IgG avidity in the seropositive for both anti-Toxoplasma IgG and IgM antibodies were also assessed. The pregnant women’s socio-demographic, obstetrics and risk factors associated with Toxoplasma seropositivity data were analyzed using univariate and multivariate analyses.

Results

From the total 760 pregnant women, 190 (25%, 95% CI = 22.05-28.20) were positive for anti-Toxoplasma antibodies. Of these, 167 (22.0%, 95% CI = 19.0-25.0) were positive for only anti-Toxoplasma IgG antibody and 23 (3.0%, 95% CI = 2.0-4.0) were positive for both anti-Toxoplasma IgG and IgM antibodies. All these samples were high avidity, indicated the infection occured prior to four to five months. By applying statistical univariate analysis, age group, occupation and sources of drinking water showed a significant association with Toxoplasma seropositivity (p < 0.05). Multivariate logistic regression analysis further indicated that the significant factors associated with Toxoplasma seropositivity are age ≥26 (OR = 1.65, 95% CI = 1.11-2.44), working as laborer (OR = 1.57, 95% CI = 1.13-2.18) and drinking unclean (piped/tap/rain) water (OR = 1.75, 95% CI = 1.08-2.84).

Conclusion

The pregnant women in the active age group, working as laborers and exposure to unclean drinking water from various sources were at higher risk of Toxoplasma infection. Therefore, health education and the awareness of risk exposures regarding this parasitic disease are required to minimize the effects of this parasitic infection in pregnant women as well as in the general population.

Veterinary vaccines against toxoplasmosis

Toxoplasma gondii is a cosmopolitan protozoan parasite that infects a wide range of mammal and bird species. Common infection leads to high economic (e.g., abortions in sheep) and human (e.g., congenital toxoplasmosis or neurotoxoplasmosis in humans) losses. With one exception (Toxovax for sheep), there are no vaccines to prevent human or animal toxoplasmosis. The paper presents the current state and challenges in the development of a vaccine against toxoplasmosis, designed for farm animals either bred for consumption or commonly kept on farms and involved in parasite transmission. So far, the trials have mostly revolved around conventional vaccines and, compared with the research using laboratory animals (mainly mice), they have not been very numerous. However, the results obtained are promising and could be a good starting point for developing an effective vaccine to prevent toxoplasmosis.