Detection and dissemination of Toxoplasma gondii in experimentally infected calves, a single test does not tell the whole story

Prevalence and risk factors of Toxoplasma gondii infection in dairy cattle from the Western Region of Thailand

In total, 901 dairy cow sera and data were collected from 51 farms in Nakhon Pathom, Ratchaburi and Kanchanaburi provinces (Western Region of Thailand). Serum samples were processed via the multispecies ELISA method to detect IgG antibodies against Toxoplasma gondii infection. The results demonstrated that the calculated true prevalence was 1.48% (95% CI, 0.64-2.75%) for the individual-level and 29.41% (95% CI, 18.71-43%) for the farm-level. The univariate risk factor analysis showed that the number of total owned cats, the presence of stray cats, and the frequency of cleaning per day were significant factors (p < 0.2). These three factors were subjected to logistic regression analysis, and the results revealed that the frequency of cleaning farms per day was a potential risk factor for T. gondii-seropositive farms (OR = 2.745, 95% CI, 1.15-8.69, p = 0.02). The frequency of cleaning might increase the T. gondii oocyst distribution within the barn area, thus increasing the possibility of infection. Our findings show that T. gondii continues to circulate in the dairy cow population in the western part of Thailand. The presence of cats on farms was not found to be associated with T. gondii infection, but the high frequency of cleaning the floor was, and contributed to the potential risk of infection.

Evaluation of species-specific polyclonal antibodies to detect and differentiate between Neospora caninum and Toxoplasma gondii

Neosporosis and toxoplasmosis are major causes of abortion in livestock worldwide, leading to substantial economic losses. Detection tools are fundamental to the diagnosis and management of those diseases. Current immunohistochemistry (IHC) tests, using sera raised against whole parasite lysates, have not been able to distinguish between Toxoplasma gondii and Neospora caninum. We used T. gondii and N. caninum recombinant proteins, expressed in Escherichia coli and purified using insoluble conditions, to produce specific polyclonal rabbit antisera. We aimed to develop species-specific sera that could be used in IHC on formalin-fixed, paraffin-embedded (FFPE) tissue sections to improve the diagnosis of ruminant abortions caused by protozoa. Two polyclonal rabbit sera, raised against recombinant proteins, anti-Neospora-rNcSRS2 and anti-Toxoplasma-rTgSRS2, had specificity for the parasite they were raised against. We tested the specificity for each polyclonal serum using FFPE tissue sections known to be infected with T. gondii and N. caninum. The anti-Neospora-rNcSRS2 serum labeled specifically only N. caninum-infected tissue blocks, and the anti-Toxoplasma-rTgSRS2 serum was specific to only T. gondii-infected tissues. Moreover, tissues from 52 cattle and 19 sheep previously diagnosed by lesion profiles were tested using IHC with our polyclonal sera and PCR. The overall agreement between IHC and PCR was 90.1% for both polyclonal anti-rNcSRS2 and anti-rTgSRS2 sera. The polyclonal antisera were specific and allowed visual confirmation of protozoan parasites by IHC, but they were not as sensitive as PCR testing.

An abortion storm in a goat farm in the Northeast Region of Brazil was caused by the atypical Toxoplasma gondii genotype #13

The objective of this study was to characterise a Toxoplasma gondii-induced abortion outbreak on a goat farm in the State of Paraíba, Northeast Region of Brazil. From a herd of 10 does, seven experienced abortions and one gave birth to twins (one stillborn and the other weak and underdeveloped). Serum samples from all of the does were analysed by indirect fluorescent antibody test (IFAT). Samples of colostrum and placenta from two does, along with lung, heart, brain and umbilical cord samples from four of the foetuses, were screened by nested ITS1 PCR specific for T. gondii. The positive samples were then analysed by multiplex nested PCR-RFLP. All ten does tested positive by IFAT for anti-T. gondii IgG (titrations ranging from 1:4096 to 1:65,536). The ITS1 PCR screening revealed T. gondii DNA in the placenta (2/2), colostrum (2/2), umbilical cord (2/4), lung (1/4), heart (1/4), and brain (1/4). Four samples produced complete RFLP genotyping results, identifying a single genotype, ToxoDB #13. In conclusion, we demonstrated a high rate of abortion caused by T. gondii in a goat herd, highlighting the pathogenicity of genotype #13, one of the most prevalent genotypes of T. gondii in Brazil.

Reduced neural progenitor cell count and cortical neurogenesis in guinea pigs congenitally infected with Toxoplasma gondii

Toxoplasma (T.) gondii is an obligate intracellular parasite with a worldwide distribution. Congenital infection can lead to severe pathological alterations in the brain. To examine the effects of toxoplasmosis in the fetal brain, pregnant guinea pigs are infected with T. gondii oocysts on gestation day 23 and dissected 10, 17 and 25 days afterwards. We show the neocortex to represent a target region of T. gondii and the parasite to infect neural progenitor cells (NPCs), neurons and astrocytes in the fetal brain. Importantly, we observe a significant reduction in neuron number at end-neurogenesis and find a marked reduction in NPC count, indicating that impaired neurogenesis underlies the neuronal decrease in infected fetuses. Moreover, we observe focal microglioses to be associated with T. gondii in the fetal brain. Our findings expand the understanding of the pathophysiology of congenital toxoplasmosis, especially contributing to the development of cortical malformations.

Detection of Toxoplasma gondii Infection in Small Ruminants: Old Problems, and Current Solutions

Toxoplasmosis is a parasitic zoonosis of veterinary importance, with implications for public health. Toxoplasma gondii infection causes abortion or congenital disease in small ruminants. Moreover, the consumption of infected meat, cured meat products, or unpasteurized milk and dairy products can facilitate zoonotic transmission. Serological studies conducted in various European countries have shown the high seroprevalence of specific anti-T. gondii antibodies in sheep and goats related to the presence of oocysts in the environment, as well as climatic conditions. This article presents the current status of the detection possibilities for T. gondii infection in small ruminants and their milk. Serological testing is considered the most practical method for diagnosing toxoplasmosis; therefore, many studies have shown that recombinant antigens as single proteins, mixtures of various antigens, or chimeric proteins can be successfully used as an alternative to Toxoplasma lysate antigens (TLA). Several assays based on DNA amplification have been developed as alternative diagnostic methods, which are especially useful when serodiagnosis is not possible, e.g., the detection of intrauterine T. gondii infection when the fetus is not immunocompetent. These techniques employ multicopy sequences highly conserved among different strains of T. gondii in conventional, nested, competitive, and quantitative reverse transcriptase-PCR.

Modelling Neurological Diseases in Large Animals: Criteria for Model Selection and Clinical Assessment

Issue: The impact of neurological disorders is recognised globally, with one in six people affected in their lifetime and few treatments to slow or halt disease progression. This is due in part to the increasing ageing population, and is confounded by the high failure rate of translation from rodent-derived therapeutics to clinically effective human neurological interventions. Improved translation is demonstrated using higher order mammals with more complex/comparable neuroanatomy. These animals effectually span this translational disparity and increase confidence in factors including routes of administration/dosing and ability to scale, such that potential therapeutics will have successful outcomes when moving to patients. Coupled with advancements in genetic engineering to produce genetically tailored models, livestock are increasingly being used to bridge this translational gap. Approach: In order to aid in standardising characterisation of such models, we provide comprehensive neurological assessment protocols designed to inform on neuroanatomical dysfunction and/or lesion(s) for large animal species. We also describe the applicability of these exams in different large animals to help provide a better understanding of the practicalities of cross species neurological disease modelling. Recommendation: We would encourage the use of these assessments as a reference framework to help standardise neurological clinical scoring of large animal models.

Evidence of Hearing Loss and Unrelated Toxoplasmosis in a Free-Ranging Harbour Porpoise (Phocoena phocoena)

Simple Summary

Evidence of hearing impairment was identified in a female harbour porpoise (Phocoena phocoena) on the basis of inner ear analysis. The animal live stranded on the Dutch coast at Domburg in 2016 and died a few hours later. Ultrastructural examination of the inner ear revealed evidence of sensory cell loss, which is compatible with noise exposure. In addition, histopathology also revealed multifocal necrotising protozoal encephalitis. A diagnosis of toxoplasmosis was confirmed by positive staining of tissue with anti-Toxoplasma gondii antibodies; however, T. gondii tachyzoites were not observed histologically in any of the examined tissues. This is the first case of presumptive noise-induced hearing loss and demonstration of T. gondii cysts in the brain of a free-ranging harbour porpoise from the North Sea.

Abstract

Evidence of hearing impairment was identified in a harbour porpoise (Phocoena phocoena) on the basis of scanning electron microscopy. In addition, based on histopathology and immunohistochemistry, there were signs of unrelated cerebral toxoplasmosis. The six-year old individual live stranded on the Dutch coast at Domburg in 2016 and died a few hours later. The most significant gross lesion was multifocal necrosis and haemorrhage of the cerebrum. Histopathology of the brain revealed extensive necrosis and haemorrhage in the cerebrum with multifocal accumulations of degenerated neutrophils, lymphocytes and macrophages, and perivascular lymphocytic cuffing. The diagnosis of cerebral toxoplasmosis was confirmed by positive staining of protozoa with anti-Toxoplasma gondii antibodies. Tachyzoites were not observed histologically in any of the examined tissues. Ultrastructural evaluation of the inner ear revealed evidence of scattered loss of outer hair cells in a 290 µm long segment of the apical turn of the cochlea, and in a focal region of ~ 1.5 mm from the apex of the cochlea, which was compatible with noise-induced hearing loss. This is the first case of concurrent presumptive noise-induced hearing loss and toxoplasmosis in a free-ranging harbour porpoise from the North Sea.

Establishment and validation of a guinea pig model for human congenital toxoplasmosis

Background

Toxoplasma gondii is an obligate intracellular parasite with a worldwide distribution. Congenital infection in humans and animals may lead to severe symptoms in the offspring, especially in the brain. A suitable animal model for human congenital toxoplasmosis is currently lacking. The aim of this study is to establish and validate the guinea pig as a model for human congenital toxoplasmosis by investigating the impact of the T. gondii infection dose, the duration of infection and the gestational stage at infection on the seroconversion, survival rate of dams, fate of the offspring, T. gondii DNA loads in various offspring tissues and organs and the integrity of the offspring brain.

Methods

Pregnant guinea pigs were infected with three different doses (10, 100, 500 oocysts) of T. gondii strain ME49 at three different time points during gestation (15, 30, 48 days post-conception). Serum of dams was tested for the presence of T. gondii antibodies using immunoblotting. T. gondii DNA levels in the dam and offspring were determined by qPCR. Offspring brains were examined histologically.

Results

We found the survival rate of dams and fate of the offspring to be highly dependent on the T. gondii infection dose with an inoculation of 500 oocysts ending lethally for all respective offspring. Moreover, both parameters differ depending on the gestational stage at infection with infection in the first and third trimester of gestation resulting in a high offspring mortality rate. The duration of infection was found to substantially impact the seroconversion rate of dams with the probability of seroconversion exceeding 50% after day 20 post-infection. Furthermore, the infection duration of dams influenced the T. gondii DNA loads in the offspring and the integrity of offspring brain. Highest DNA levels were found in the offspring brain of dams infected for  ≥ 34 days.

Conclusion

This study contributes to establishing the guinea pig as a suitable model for human congenital toxoplasmosis and thus lays the foundation for using the guinea pig as a suitable animal model to study scientific questions of high topicality and clinical significance, which address the pathogenesis, diagnosis, therapy and prognosis of congenital toxoplasmosis.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04890-4.

Comparison of Direct and Indirect Toxoplasma gondii Detection and Genotyping in Game: Relationship and Challenges

The importance of game as a source of Toxoplasma gondii (T. gondii) infection in humans is largely unknown. New data on the presence of T. gondii in game hunted in the Federal State of Brandenburg, Germany, were obtained by direct and indirect detection (ELISA). DNA extracted either directly (5 g heart or foreleg muscle, DE) or after acid pepsin digestion (50 g heart, PD) or enriched by magnetic capture (50 g heart, MC) was examined by real-time PCR (qPCR). ELISA revealed seroprevalences of 20% in wild boar (Sus scrofa), 11% in roe deer (Capreolus capreolus) and 6% in red deer (Cervus elaphus). T. gondii DNA was detected by at least one direct detection method in 12% of wild boar, 6% of roe deer, 2% of fallow deer (Dama dama) and 2% of red deer. In both, positive wild boar and roe deer, T. gondii type II specific alleles were the most prevalent, as assessed by PCR-restriction fragment length polymorphism. The highest proportion of positive animals was detected by MC qPCR, followed by PD qPCR with a similar proportion of positive findings. Investigation of 50 g of heart muscle revealed a significantly higher proportion of positive qPCR results than analysis of 5 g (p = 0.048). An association between seropositivity and direct detection was evident in wild boar and roe deer (p < 0.001). Infectivity of T. gondii DNA–positive samples was confirmed by bioassay (4/4), providing evidence that game could represent a relevant source of viable T. gondii posing a risk for human infection.

Burden and regional distribution of Toxoplasma gondii cysts in the brain of COBB 500 broiler chickens following chronic infection with 76K strain

Toxoplasmosis is a worldwide zoonosis caused by the obligate intracellular apicomplexan parasite Toxoplasma gondii (T. gondii). Chickens are ground-feeders and represent, especially if free-range, important intermediate hosts in the epidemiology of toxoplasmosis and are used as sentinels of environmental contamination with T. gondii oocysts. Until now, little is known about the burden and regional distribution of T. gondii cysts in the chicken brain. It was therefore the aim of this study to investigate the abundance and specific distribution of T. gondii cysts within the chicken brain following chronic infection with a type II strain (76 K) of T. gondii. A total of 29 chickens were included in the study and divided into control group (n = 9) and two different infection groups, a low dose (n = 10) and a high dose (n = 10) group, which were orally inoculated with 1500 or 150,000 T. gondii oocysts per animal, respectively. Seroconversion was detected in the majority of chickens of the high dose group, but not in the animals of the low dose and the control group. Moreover, T. gondii DNA was detected most frequently in the brain and more frequently in the heart than in liver, spleen, thigh and pectoral muscle using qPCR analysis. The number of T. gondii cysts, quantified in the chicken brain using histological analysis, seems to be considerably lower as compared to studies in rodents, which might explain why T. gondii infected chickens very rarely, if at all, develop neurological deficits. Similar to observations in mice, in which no lateralisation for T. gondii cysts was reported, T. gondii cysts were distributed nearly equally between the left and right chicken brain hemispheres. When different brain regions (fore-, mid- and hindbrain) were compared, all T. gondii cysts were located in the forebrain with the overwhelming majority of these cysts being present in the telencephalic pallium and subpallium. More studies including different strains and higher doses of T. gondii are needed in order to precisely evaluate its cyst burden and regional distribution in the chicken brain. Together, our findings provide insights into the course of T. gondii infection in chickens and are important to understand the differences of chronic T. gondii infection in the chicken and mammalian brain.

Public Health Significance of Toxoplasma gondii Infections in Cattle: 2009-2020

Toxoplasma gondii infections are common in humans and animals worldwide. The ingestion of food or water contaminated with oocysts excreted by infected cats or ingesting uncooked or undercooked meat containing tissue cysts of T. gondii are the 2 major modes of transmission of T. gondii. Viable T. gondii is more prevalent in pork and lamb than in beef. In the past decade, there have been many articles on the high seroprevalence in cattle, particularly from China. There is a report of an outbreak of acute toxoplasmosis in humans suspected to be linked to the ingestion of Artisan fresh cheese from cow's milk. There are conflicting reports concerning the rate of congenital transmission of T. gondii in cattle, especially from Brazil. In a report from Brazil, viable T. gondii was isolated from the blood of 1 of 60 pregnant cows slaughtered at an abattoir and from 1 fetus. The role of beef in the epidemiology of T. gondii infections is still not clear. Here, we review prevalence, persistence of infection, clinical disease, epidemiology, and public health risks of T. gondii infections in cattle from beef and cow's milk worldwide for the past decade.

Spatial distribution of Toxoplasma gondii in cows and associated risk factors

The aim of the present study was to evaluate the spatial distribution of the prevalence of T. gondii in cows using the indirect immunofluorescence assay and determine associated risk factors. Serum samples were collected from 2970 cows on 263 rural farms in 223 municipalities. A questionnaire was administered to herd owners to collect data for the evaluation of risk factors associated with this disease. Mean seroprevalence of T. gondii in cows was 8.48% (95% CI: 7.48 to 9.49). The microregions with the greatest likelihood (p ≤ 0.05) of having infected animals were Anápolis, Ceres, São Miguel do Araguaia, the Federal District, Anicuns, and Vão do Paraná. The purchase of females or males for reproductive/breeding purposes was significantly associated (p ≤ 0.05) with the prevalence of T. gondii in these regions. A positive correlation (0.7618; p = 0.047) was found between the prevalence of T. gondii and total area in hectares of forests in these regions, suggesting that wild cats may be disseminating T. gondii at these sites. The present results highlight the importance of considering the meat from these animals to be an important infection route for humans who eat raw or undercooked food.

Foodborne transmission of Toxoplasma gondii infection in the last decade. An overview

Toxoplasmosis is a zoonotic disease of global distribution and importance. It is caused by the protozoan parasite Toxoplasma gondii, the only species in the Toxoplasma genus. This parasite can infect most warm-blooded animals, including humans and livestock. Main routes of transmission are by ingestion of tissue cysts in raw or undercooked meat of infected animals, ingestion of raw vegetables or water contaminated with T. gondii oocysts from cat feces, and transplacental. Around one-third of human beings are chronically infected with T. gondii. Most infections appear to be asymptomatic in immunocompetent persons, but toxoplasmosis can be fatal to the fetus and immunocompromised adults. Water and foodborne outbreaks have been caused by this parasite worldwide, but few are well documented. Importantly, T. gondii is a parasite of high importance in animal health, causing reproductive failure, particularly in small ruminants, and clinical toxoplasmosis in many species. This overview discusses the knowledge of T. gondii infections in the last decade focusing on the foodborne transmission of this parasite.

Detection of Toxoplasma gondii in retail meat samples in Scotland

Toxoplasma gondii is a globally important zoonotic parasite ranked as one of the most significant causes of disease burden among the major foodborne pathogens. Consumption of undercooked meat is a well-known risk factor for infection so the aim of this study was to investigate the presence of T. gondii in meat samples from retail outlets in Scotland. In Sampling Period 1, 300 meat samples (39 beef, 21 chicken, 87 lamb, 71 pork and 82 venison) were purchased from butchers', farmers' markets, farm shops and supermarkets, and in Sampling Period 2, 67 pure venison samples only were purchased from farmers' markets, farm shops and supermarkets. DNA was extracted and screened for T. gondii using a quantitative PCR targeting the 529 bp repeat element, and any positive samples were genotyped using PCR-RFLP targeting 10 markers. Meat juice was screened for T. gondii antibodies using a commercial ELISA or modified agglutination assay. Toxoplasma gondii DNA was detected in 0/39 (0%) beef samples, 1/21 (4.8%) chicken samples, 6/87 (6.9%) lamb samples, 3/71 (4.2%) pork samples and 29/82 (35.4%; Sampling Period 1) and 19/67 (28.4%; Sampling Period 2) venison samples. Partial PCR-RFLP genotyping revealed both clonal and non-clonal genotypes. Antibodies to T. gondii were detected in the meat juice of 2/38 (5.3%) beef samples, 3/21 (14.3%) chicken samples, 14/85 (16.5%) lamb samples, 2/68 (2.9%) pork samples and 11/78 (14.1%; Sampling Period 1) and 8/50 (16%; Sampling Period 2) venison samples. This is the first study to report the presence of T. gondii in retail meat products in Scotland and has highlighted venison as a potentially high risk meat. Further work is required to determine viability of parasites in this particular meat product.

Seroepidemiology of Toxoplasma gondii in Dairy Cows in Southeastern Brazil: Seropositive Cows on All Farms Investigated

PURPOSE

This study aimed to estimate the prevalence and identify the risk factors associated with the higher in-herd T. gondii seroprevalence in dairy cows in 37 farms in southern Minas Gerais, Southeastern Brazil.

METHODS

Serum samples from 1,105 dairy cows were subjected to an indirect fluorescence antibody test (IFAT 1:64) for anti-T. gondii IgG. The association existing between possible risk factors at the herd level and the seroprevalence were verified through Generalized Estimating Equation (GEE) multiple logistic regression models.

RESULTS

Anti-T. gondii antibodies were observed in 31.4% of the cows (347; 95% CI= 28.7-34.2) and on 100% of the farms (37; 95% CI= 90.6-100.0%), indicating that all properties possessed at least one seropositive animal. For univariate analysis, herds with seroprevalence were categorized as greater and less than 30% as the outcome. The "breeding of Holstein Friesian cows" (p= 0.016, OR= 6.667, 95% CI= 1.500-29.628) and in an "intensive system" (p= 0.013, OR= 6.120, 95% CI= 1.394-26.876) increased the chance of the herd seroprevalence being greater than 30% by approximately six-fold. However, these variables did not exhibit a significant association (p >0.05) in the Generalized Estimating Equations (GEE) logistic regression model.

CONCLUSIONS

The results demonstrate that T. gondii infection is widespread among dairy cows in the south of Minas Gerais, with a wide environmental dispersion of the parasite on farms in this region.

Seroprevalence and Risk Factors of Toxoplasma gondii in Ruminant Meats from Wet Markets in Klang Valley and Abattoirs in Selangor, Malaysia

Simple Summary

This study investigated the prevalence of Toxoplasma. gondii in meats of cattle, goat and sheep from wet markets and abattoirs in Selangor, Malaysia. Meat samples from wet markets in various districts and diaphragm samples from abattoirs were analyzed using ELISA to check for T. gondii IgG antibodies. Furthermore, attempts were made to detect T. gondii DNA from meat samples using the nested PCR technique. Twenty-five percent of the samples were positive for T. gondii antibodies, with the highest recorded in goat (55%), followed by sheep (35%) and cattle meat (9%). T. gondii DNA was not detected in any of the meat samples. Being the first report in Malaysia, the findings highlight the need for proper control in reducing exposure of ruminant meats to the parasite, especially those destined for human consumption.

Abstract

(1) Background: The objective of this study was to determine the prevalence of T. gondii in meats of cattle, goat and sheep from wet markets in Klang Valley, and abattoirs in Selangor, Malaysia; (2) Methods: A total of 192 meat samples were purchased from 51 wet markets in six districts in Klang Valley (Gombak, Klang, Kuala Lumpur, Hulu Langat, Petaling and Putrajaya). Meanwhile, a total of 200 diaphragm samples were collected from two government abattoirs located in Shah Alam and Banting, Selangor. All meat juices from samples were subjected to an indirect-ELISA kit for the presence of T. gondii IgG antibodies. Furthermore, all 184 meat samples of goat and sheep were subjected to conventional nested PCR (B1 genes) for the detection of T. gondii DNA; (3) Results: T. gondii antibodies were detected in 25% (n = 98/392) of the samples with seroprevalence of 9.1% (19/208, CI: 5.9%–13.8%) in cattle meat; 54.7% (41/75, 95% CI: 43.5%–65.4%) in goat meat and 34.9% (38/109, CI: 26.6%–44.2%) in sheep meat. No T. gondii DNA was detected in any of the meat samples of goat and sheep. T. gondii seropositivity in wet market samples was higher in goat (OR = 37.1 CI 12.4–110.3) and sheep meat (OR 9.03 CI: 3.28–24.8) compared to cattle meat (OR = 1.0) At univariate level, meat from non-licensed abattoirs (OR = 6.0 CI: 2.9–12.3) and female animals (OR = 6.7; CI 1.9–22.6) had higher risks of being seropositive for T. gondii antibodies than licensed abattoirs and male animals, respectively. (4) Conclusions: This is the first report of seroprevalence of T. gondii in ruminant meats for human consumption in Malaysia. The findings signified high exposure of meat samples from wet markets to T. gondii and the need for control measures to reduce the likelihood of infection when such raw or undercooked meats are consumed.

Toxoplasma gondii in cattle in Brazil: a review

Toxoplasma gondii is an apicomplexan protozoan that is frequently found in both humans and animals worldwide. The aim of this review was to list important aspects of Toxoplasma gondii infection in cattle in Brazil. The frequency of occurrence of T. gondii antibodies in Brazilian cattle ranges from 1 to 89.1%, depending on the region evaluated, based on data from 1978 to 2018. However, some characteristics of T. gondii infection in cattle remain uncertain, such as the role of meat intake in transmitting the parasite to humans. Most information regarding T. gondii infection among Brazilian cattle is limited to evaluations of the frequency of occurrence of antibodies. About 70% of the diagnoses of infection in these ruminants in Brazil are made via the indirect fluorescence antibody test (IFAT). Nevertheless, little is known about the population structure of this protozoan in cattle. It is necessary to expand the studies on toxoplasmosis in cattle, in order to better understand T. gondii infection in these animals and its implications for Brazilian public health.

Transfer Learning for Toxoplasma gondii Recognition

Toxoplasma gondii, one of the world's most common parasites, can infect all types of warm-blooded animals, including one-third of the world's human population. Most current routine diagnostic methods are costly, time-consuming, and labor-intensive. Although T. gondii can be directly observed under the microscope in tissue or spinal fluid samples, this form of identification is difficult and requires well-trained professionals. Nevertheless, the traditional identification of parasites under the microscope is still performed by a large number of laboratories. Novel, efficient, and reliable methods of T. gondii identification are therefore needed, particularly in developing countries. To this end, we developed a novel transfer learning-based microscopic image recognition method for T. gondii identification. This approach employs the fuzzy cycle generative adversarial network (FCGAN) with transfer learning utilizing knowledge gained by parasitologists that Toxoplasma is banana or crescent shaped. Our approach aims to build connections between microscopic and macroscopic associated objects by embedding the fuzzy C-means cluster algorithm into the cycle generative adversarial network (Cycle GAN). Our approach achieves 93.1% and 94.0% detection accuracy for ×400 and ×1,000 Toxoplasma microscopic images, respectively. We showed the high accuracy and effectiveness of our approach in newly collected unlabeled Toxoplasma microscopic images, compared to other currently available deep learning methods. This novel method for Toxoplasma microscopic image recognition will open a new window for developing cost-effective and scalable deep learning-based diagnostic solutions, potentially enabling broader clinical access in developing countries.IMPORTANCE Toxoplasma gondii, one of the world's most common parasites, can infect all types of warm-blooded animals, including one-third of the world's human population. Artificial intelligence (AI) could provide accurate and rapid diagnosis in fighting Toxoplasma So far, none of the previously reported deep learning methods have attempted to explore the advantages of transfer learning for Toxoplasma detection. The knowledge from parasitologists is that the Toxoplasma parasite is generally banana or crescent shaped. Based on this, we built connections between microscopic and macroscopic associated objects by embedding the fuzzy C-means cluster algorithm into the cycle generative adversarial network (Cycle GAN). Our approach achieves high accuracy and effectiveness in ×400 and ×1,000 Toxoplasma microscopic images.

Toxoplasma gondii in water buffaloes (Bubalus bubalis) from Romania: what is the importance for public health?

The purpose of our study was to evaluate the prevalence of Toxoplasma gondii infection in autochthonous Carpathian buffaloes from northwestern Romania by serology, PCR techniques, and mouse bioassay. Agreement between MAT and ELISA, correlation between indirect and direct detection methods, and risk factors were evaluated. The apparent overall seroprevalence of T. gondii was 8.1% by MAT and 6.6% by ELISA. The agreement between ELISA and MAT was fair. The apparent seroprevalence was significantly higher in adult buffaloes (12.5%) compared to calves (0.0%) and juveniles (1.9%) by MAT. Most of the positive adult buffaloes detected by MAT had antibodies at a low sera dilution and the highest dilution was 1:768 in a juvenile female (30 months). No viable T. gondii was detected by mouse bioassay, as no T. gondii cyst or DNA was found in the brain of mice and they did not seroconvert. However, T. gondii DNA was detected in two buffaloes: in a 30-month-old male buffalo by qPCR on the diaphragm digest and in a 252-month-old female buffalo by RE nPCR on the mesenteric lymph node. Both animals were negative in MAT and ELISA. The total prevalence of T. gondii by direct detection methods was 2.7%. There was no correlation between indirect and direct detection methods. Since no viable T. gondii was detected in buffaloes, the risk of human infection from buffalo meat is minimal. Buffaloes' biological response to a T. gondii infection appears to be very similar to the response of cattle.

Toxoplasma gondii infection and toxoplasmosis in farm animals: Risk factors and economic impact

The protozoan parasite Toxoplasma gondii is a zoonotic parasite that can be transmitted from animals to humans. Felids, including domestic cats, are definitive hosts that can shed oocysts with their feces. In addition to infections that occur by accidental oral uptake of food or water contaminated with oocysts, it is assumed that a large proportion of affected humans may have become infected by consuming meat or other animal products that contained infective parasitic stages of T. gondii. Since farm animals represent a direct source of infection for humans, but also a possible reservoir for the parasite, it is important to control T. gondii infections in livestock. Moreover, T. gondii may also be pathogenic to livestock where it could be responsible for considerable economic losses in some regions and particular farming systems, e.g. in areas where the small ruminant industry is relevant. This review aims to summarize actual knowledge on the prevalence and effects of infections with T. gondii in the most important livestock species and on the effects of toxoplasmosis on livestock. It also provides an overview on potential risk factors favoring infections of livestock with T. gondii. Knowledge on potential risk factors is prerequisite to implement effective biosecurity measures on farms to prevent T. gondii infections. Risk factors identified by many studies are cat-related, but also those associated with a potential contamination of fodder or water, and with access to a potentially contaminated environment. Published information on the costs T. gondii infections cause in livestock production, is scarce. The most recent peer reviewed reports from Great Britain and Uruguay suggest annual cost of about 5-15 million US $ per country. Since these estimates are outdated, future studies are needed to estimate the present costs due to toxoplasmosis in livestock. Further, the fact that T. gondii infections in livestock may affect human health needs to be considered and the respective costs should also be estimated, but this is beyond the scope of this article.

A one health approach to vaccines against Toxoplasma gondii

Toxoplasmosis is a serious disease with global impact, now recognised as one of the most important food borne diseases worldwide and a major cause of production loss in livestock. A one health approach to develop a vaccination programme to tackle toxoplasmosis is an attractive and realistic prospect. Knowledge of disease epidemiology, parasite transmission routes and main risk groups has helped to target key host species and outcomes for a vaccine programme and these would be to prevent/reduce congenital disease in women and sheep; prevent/reduce T. gondii tissue cysts in food animal species and to prevent/reduce T. gondii oocyst shedding in cats. Most animals, including humans, develop good protective immunity following infection, involving cell mediated immune responses, which may explain why live vaccines are generally more effective to protect against T. gondii. Recent advances in our knowledge of parasite genetics and gene manipulation, strain variation, key antigenic epitopes, delivery systems and induction of immune responses are all contributing to the prospects of developing new vaccines which may be more widely applicable. A key area in progressing vaccine development is to devise standard vaccine efficacy models in relevant animal hosts and this is where a one health approach bringing together researchers across different disciplines can be of major benefit. The tools and technologies are in place to make a real impact in tackling toxoplasmosis using vaccination and it just requires a collective will to make it happen.

The relationship between the presence of antibodies and direct detection of Toxoplasma gondii in slaughtered calves and cattle in four European countries

In cattle, antibodies to Toxoplasma gondii infection are frequently detected, but evidence for the presence of T. gondii tissue cysts in cattle is limited. To study the concordance between the presence of anti-T. gondii IgG and viable tissue cysts of T. gondii in cattle, serum, liver and diaphragm samples of 167 veal calves and 235 adult cattle were collected in Italy, the Netherlands, Romania and the United Kingdom. Serum samples were tested for anti-T. gondii IgG by the modified agglutination test and p30 immunoblot. Samples from liver were analyzed by mouse bioassay and PCR after trypsin digestion. In addition, all diaphragms of cattle that had tested T. gondii-positive (either in bioassay, by PCR on trypsin-digested liver or serologically by MAT) and a selection of diaphragms from cattle that had tested negative were analyzed by magnetic capture quantitative PCR (MC-PCR). Overall, 13 animals were considered positive by a direct detection method: seven out of 151 (4.6%) by MC-PCR and six out of 385 (1.6%) by bioassay, indicating the presence of viable parasites. As cattle that tested positive in the bioassay tested negative by MC-PCR and vice-versa, these results demonstrate a lack of concordance between the presence of viable parasites in liver and the detection of T. gondii DNA in diaphragm. In addition, the probability to detect T. gondii parasites or DNA in seropositive and seronegative cattle was comparable, demonstrating that serological testing by MAT or p30 immunoblot does not provide information about the presence of T. gondii parasites or DNA in cattle and therefore is not a reliable indicator of the risk for consumers.

Performance of three molecular methods for detection of Toxoplasma gondii in pork

Comparison of epidemiological data on the occurrence of Toxoplasma (T.) gondii tissue cysts in meat is hampered by the lack of standardization and a great variety of methods for molecular detection. Therefore, this study aimed to compare and validate three different polymerase chain reaction (PCR) methods for detection of T. gondii DNA in pork. Analytical performance characteristics of two real time PCRs (qPCRs; Tg-qPCR1, Tg-qPCR2) and one conventional endpoint PCR (cPCR), all targeting the 529 repeated element, were assessed using genomic DNA of three clonal T. gondii types prevailing in Europe and North America. qPCR efficiencies for all three clonal types ranged between 93.8 and 94.4% (Tg-qPCR1) and 94.3–95.6% (Tg-qPCR2). Tg-qPCR1 and Tg-qPCR2 showed an overall PCR performance score of 85% and displayed a similar 95% detection limit of 1.067 and 1.561 genome equivalents per PCR reaction (GE/PCR), respectively. However, T. gondii DNA could be detected at concentrations as low as 0.1 GE/PCR. Reliable quantification is possible over 4 log ranges from 10⁵ to 100 GE/PCR with mean repeatability relative standard deviations of ≤11% and reproducibility relative standard deviations of ≤12.7%. Presumably, both qPCRs are similarly suitable for sensitive and specific detection of T. gondii DNA in pork. In contrast, the cPCR using primer pair TOX5/Tox-8 proved to be highly sensitive with a detection limit of 1.41 GE/PCR, but not suitable for detection of T. gondii DNA in pork as unspecific amplification of porcine DNA was observed resulting in bands with similar size to the desired T. gondii-specific PCR product.

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Comparison of two real time PCRs and one conventional PCR targeting the 529 RE.

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Both real time PCRs show comparable performance and can be considered equivalent.

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qPCRs show 95% detection limits of 1.067 and 1.561 genome equivalents per PCR.

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Reliable quantification is possible over 4 log ranges from 10⁵ to 100 GE/PCR.

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cPCR using primer pair TOX5/Tox-8 showed non-specific amplification of porcine DNA.

Serological survey of cattle toxoplasmosis in Medea, Algeria

Toxoplasmosis is an important zoonotic disease transmitted to humans and warm-blooded animals by a ubiquitous parasite Toxoplasma gondii. One of the most common sources of human infection is the ingestion of tissue cysts through raw or undercooked meat. The present study was conducted to investigate a serological survey of Toxoplasma antibodies in cattle from Medea (North of Algeria). Serum samples were obtained from 295 clinically healthy cattle (261 females and 34 males). All cattle sera were tested for antibodies to T. gondii using the Modified Agglutination Test (MAT). According to MAT results, and taking 1:25 as the cut-off value, antibodies were found in 13 (4.4%) of 295 bovine sera. Five cattle had an antibody titer of 1:25; 6 of 1:50 and 2 of 1:100. More serological surveys are necessary to better understand the epidemiological status of toxoplasmosis in cattle and other ruminants.