Genetic Characterization of Toxoplasma gondii Isolates from Pigs in Jilin Province, Northeastern China

Molecular Detection and Genotyping of Toxoplasma gondii from Pigs for Human Consumption in Zhejiang and Jiangsu Provinces, Eastern China

Toxoplasma gondii infections are common in humans and animals worldwide. Ingestion of raw or undercooked meat containing tissue cysts of T. gondii is one major source of transmission of this parasite. It is important to guarantee the meat quality of China since our pork industry produces about half of the world's pork. In this study, a total of 746 pig samples were collected from Zhejiang and Jiangsu provinces in eastern China, and examined for T. gondii infection by PCR amplification targeting B1 gene. In this study, we found that 57 of 746 (7.6%) pigs were positive for B1 gene, with 8.5% (48/562) in Zhejiang province and 4.9% (9/184) in Jiangsu province, respectively. The positive DNA samples were further genotyped at 11 genetic markers, including SAG1, 5'-and 3'-SAG2, alternative SAG2, SAG3, BTUB, GRA6, L358, PK1, c22-8, c29-2, and an apicoplast locus Apico through PCR-restriction fragment length polymorphism (PCR-RFLP) technology. Two genotypes (ToxoDB 9 and ToxoDB 10) of T. gondii were identified by PCR-RFLP in Zhejiang province. However, both genotypes were not determined from Jiangsu province, which is speculated on the low DNA concentration and the small number of samples. These results indicate that T. gondii infection is endemic in pigs in eastern China and may raise public food safety concerns, suggesting more interventions for T. gondii-related risks are needed in the future.

Molecular detection and genetic characterization of Toxoplasma gondii in pork from Chongqing, southwest China

Raw or undercooked meat is an important source of Toxoplasma gondii infection in China, but there is little research data on these infections in Chongqing. This study determined the prevalence of T. gondii, and its genotypes, in pork. A total of 1,223 diaphragm muscle samples were collected from eight slaughterhouses and 79 markets and detected by PCR amplification of the ITS gene. All of the positive samples were used for genotype identification by PCR-RFLP with 11 genetic markers. The total positive rate of T. gondii in Chongqing pork was 8.7%, and differences in T. gondii infection rates were found between different districts (0%-23.3%), seasons (e.g., 4.3% from Spring, 7.3% from Summer, 11.4% from Autumn, 12.0% from Winter) and years (2.7%-14.3%). Six samples were successfully genotyped, of which one was identified as ToxoDB#9 and five were ToxoDB#9-like. This was the first continuous study about the prevalence of T. gondii in pork in Chongqing for several years. Slaughterhouses in different districts, pork source, farm scale, season and year were potential risk factors for T. gondii contamination by the univariate logistic regression, and using multivariate logistic regression districts, pork source and year were the independent risk factor. These data may help reducing the levels of toxoplasmosis in pigs and humans in Chongqing.

Lower seroprevalence of Toxoplasma gondii in swine from central China after an outbreak of African swine fever

Toxoplasma gondii is widespread worldwide and can infect swine. This study evaluated the seroprevalence of T. gondii in swine from central China after an outbreak of African swine fever (ASF). A total of 2683 swine serum samples were collected from farms in four provinces. Of the serum samples, 1.42% (38/2683) (95% CI, 1.03–1.94) tested positive for T. gondii IgG antibody by a modified agglutination test (MAT) (cut-off: 1:25). Comparing with the results of previous studies, specifically our survey from before the outbreak, the seroprevalence of T. gondii in swine from central China was significantly decreased after the occurrence of ASF (OR = 7.679, 2015–2017 vs. 2019–2020). In general, the proportion of seropositive animals increased with the age of the swine, indicating post-natal transmission of T. gondii. Furthermore, there was a significant difference in seroprevalence between suckling pigs and weaned pigs (p < 0.05). This is the first large-scale investigation of T. gondii infection in swine after an ASF outbreak in China. The lower seroprevalence of T. gondii in swine after ASF may be due to stricter biosecurity measures on the farms, but results indicated swine exposure to zoonotic parasites despite these measures. This highlights that pigs must be considered a potential source of human T. gondii infections.

All about Toxoplasma gondii infections in pigs: 2009-2020

Toxoplasma gondii infections are common in humans and animals worldwide. Toxoplasma gondii infection in pigs continues to be of public health concern. Pigs are important for the economy of many countries, particularly, USA, China, and European countries. Among the many food animals, pigs are considered the most important for T. gondii transmission in USA and China because viable parasites have rarely been isolated from beef or indoor raised chickens. Besides public health issues, T. gondii causes outbreaks of clinical toxoplasmosis in pigs in China, associated with a unique genotype of T. gondii (ToxoDB genotype #9 or Chinese 1), rarely found in other countries. The safety of ready to eat pork products with respect to T. gondii infection is a matter of recent debate. Here, we review in detail seroprevalence, prevalence of viable and nonviable T. gondii, epidemiology, risk assessment, diagnosis, and curing of pork products containing T. gondii for the past decade. This review will be of interest to biologists, parasitologists, veterinarians, and public health workers.

Bioinformatics of excretory/secretory proteins of Toxoplasma gondii strain ME49

Toxoplasma gondii is an obligate intracellular parasite that is globally distributed and can infect almost all warm-blooded animals, including humans. While vaccines are not available for prophylaxis, there are limited therapeutic options which often do not result in eradication of parasites from patients. ME49 is a cystogenic strain of T. gondii with a potential as a vaccine candidate. Excretory and secretory (ES) proteins are thought to play crucial roles in host-parasite interactions. Hence, we predicted and functionally annotated the ES proteins in T. gondii ME49 using public databases. ES proteins were further examined for the characteristics and possible functions through gene ontology (GO) term enrichment and analyses of metabolic pathways, enzyme code distribution (EC distributing) and protein domains. The potential antigenicity of T. gondii ME49 ES proteins was evaluated for the first time using Abundance of Antigenic Regions (AAR) value to predict the antigenic potential by measuring sequence length and number of antigenic regions. The results showed that the ES proteins have different AAR values at RNA and microarray level. Our studies provide valuable information for future experimental studies, including the identification of novel ES proteins of therapeutic, diagnostic and immunoprophylactic interests.

Toxoplasma gondii oocyst-driven infection in pigs, chickens and humans in northeastern China

Background

Toxoplasma gondii, an intracellular apicomplexan protozoan parasite, can infect almost all warm-blooded animals. The aim of the present study was to investigate T. gondii oocyst-driven infection in pigs, chickens and humans in Jilin province, northeastern China.

Results

The serum samples of pigs, chickens and humans were sampled and tested by indirect enzyme-linked immunosorbent assays (ELISAs) using dense granule antigen GRA7, oocyst-specific protein OWP8, and sporozoite-specific protein CCp5A, respectively. Results showed a prevalence of 16.7% by GRA7-ELISA, and 12.2% by OWP8- and CCp5A-ELISA in pigs; 10.4% by GRA7-ELISA, 13.5% by OWP8-ELISA, and 9.4% by CCp5A-ELISA in chickens; and 14.2% by GRA7-ELISA, 3.6% by OWP8-ELISA, and 3.0% by CCp5A-ELISA in humans. No significant differences were observed between T. gondii seroprevalence in pigs and chickens among the three antigens-based ELISAs (P > 0.05). However, there were significant differences between T. gondii seroprevalence rates in humans (P < 0.05). These findings demonstrated a low prevalence of T. gondii oocyst-driven infection in humans, a medium prevalence in pigs, and a high prevalence in chickens.

Conclusions

The present study demonstrated that different oocyst-driven infection rates in different animal species, which would help to design effective strategies to prevent T. gondii transmission. To our knowledge, this is the first study to differentiate T. gondii infective forms in pigs, chickens and humans in China.

First Report on Toxoplasma gondii Seroprevalence in Free-Ranging Pigs in Northeastern China

INTRODUCTION

Toxoplasma gondii is the pathogen of toxoplasmosis, which affects a wide range of animal species and humans.

MATERIALS AND METHODS

In the present study, a serological investigation was undertaken to determine the seroprevalence of T. gondii infection in free-ranging pigs in northeastern China. A total of 806 serum samples were collected from free-ranging pigs in 6 cities in Liaoning, Jilin, and Heilongjiang Provinces.

RESULTS

Among them, 163 serum samples (20.22%) were detected T. gondii positive by indirect hemagglutination test (IHA). In each administrative district, the prevalence ranges from 12.99 to 22.22%. It was found that sample collection year and season were associated with T. gondii infection. Samples collected in 2015 and 2016 had had higher positive rate compared to those collected in 2017. Samples collected in summer and autumn also have higher positive rate than those in winter.

CONCLUSION

This is the first report on T. gondii seroprevalence in free-ranging pigs in northeastern China, which adds the epidemiological data of T. gondii infection in free-ranging pigs in China. These results indicated that free-ranging pigs in Liaoning, Jilin, and Heilongjiang Provinces are exposed to T. gondii, which is a significant threat to local pig industry as well as public health. It is necessary to take relevant comprehensive measures to prevent and control T. gondii infection in free-ranging pigs in these regions.

Molecular Detection and Genotyping of Toxoplasma gondii in Pigs for Human Consumption in Hunan Province, China

Toxoplasma gondii is one of the most important sources of foodborne diseases. In this study, the molecular prevalence and genotypes of T. gondii were investigated in pigs in Hunan province, China. A total of 339 brain tissue samples of pigs were collected from April 2015 to December 2017 in Hunan province and were used to detect the T. gondii B1 gene. Of these, 34 (10%; 95% confidence interval: 8.7-12.6) samples were tested positive for the T. gondii B1 gene. Positive samples were genotyped at 10 genetic markers (SAG1, SAG2 [5' + 3' SAG2, alter. SAG2], SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico) using polymerase chain reaction-restriction fragment length polymorphism technology. Moreover, one sample was identified as genotype ToxoDB#10 (Type I), and another sample was suspected to be unusual genotype ToxoDB#61 that has never been reported in China. This study showed that T. gondii is prevalent in pigs in Hunan province, posing a food safety threat to the public health in the investigated areas. Our result has implications for better understanding the genetic diversity of T. gondii infections in animals in China.

Prevalence, Risk Factors, and Genotypes of Toxoplasma gondii in Food Animals and Humans (2000-2017) From China

Toxoplasma gondii as a food-borne pathogen, the infection of it in food animals has relation with human toxoplasmosis, but the trends and epidemiological features of T. gondii infections in food animals are rarely studied in China. The aimed of this study was to assess the epidemiology and risks of T. gondii in sheep, goats, swines, chickens, yaks, cattle and humans from 2000 to 2017 and to explore prevention and control strategies. The overall seroprevalence of T. gondii infections in food animals is 23.7% (39,194/165,417, 95%CI, 23.49-23.90%), which is significantly higher than that in humans (8.2%, 95%CI, 8.06-8.39%, 8,502/103,383) (P < 0.0001). Compared the prevalence of T. gondii infections in animals and humans sampled from 2000 to 2010, it was significantly increased in the period 2011 to 2017 (P < 0.0001). Compared the food animals from non-Yangtze River, animals from regions of the Yangtze River have high seroprevalence rates for T. gondii (P < 0.0001). Furthermore, samples from the western to eastern regions of the Yellow River showed an increase in seroprevalence for T. gondii (P < 0.0001). It was speculated that T. gondii oocysts may be transmitted by water and annual precipitation possible help the oocyst spread and retain accessible for potential hosts. Effective prevention and control strategies are including water filtration or water boiling, inactivating oocysts from feline's feces, monitoring birds and rodents. Chinese 1 (ToxoDB#9) is the predominant genotype in food animals from China.

Prevalence, risk factors and genetic characterization of Toxoplasma gondii in sick pigs and stray cats in Jiangsu Province, eastern China

Toxoplasma gondii is an obligate intracellular parasitic protozoan with a worldwide distribution. The parasites in edible tissues of pigs and oocysts from cats are the major sources of T. gondii infection in humans. However, there are no data from sick pigs in veterinary clinics or from stray cats in Jiangsu Province, eastern China. In total, biological samples from 141 sick pigs and 64 stray cats were collected from this region. The rate of T. gondii infection in sick pigs was 46.81% using a polymerase chain reaction (PCR), and the overall prevalence of toxoplasmosis in stray cats was 34.38% by PCR and an enzyme-linked immunosorbent assay (ELISA). T. gondii was significantly more prevalent in lungs and heart than in liver and spleen (P < 0.05). Age and geographic region were considered to be the main risk factors associated with T. gondii infection in these pigs. The DNA samples from 17 sick pigs and seven stray cats, were successfully genotyped by multilocus PCR-restriction fragment length polymorphism (PCR-RFLP) with 10 genetic markers [SAG1, SAG2 (5'-3'SAG2, alt. SAG2), SAG3, GRA6, PK1, c22-8, c29-2, BTUB, L358 and Apico]. Six distinct genotypes were found, which were designated ToxoDB PCR-RFLP genotypes #9 (Chinese I), #10 (Type I), #213, and #89, and New 1 and New 2. Chinese I is the most prevalent T. gondii genotype in this region. The two new genotypes (designated New 1 and New 2) are reported and the ToxoDB PCR-RFLP genotype #89 is found for the first time in China. Such information will be useful for the prevention, diagnosis and treatment of porcine toxoplasmosis in Jiangsu Province, eastern China.

Sixty Years (1957-2017) of Research on Toxoplasmosis in China-An Overview

Toxoplasma gondii is a ubiquitous zoonotic pathogen belonging to apicomplexan parasites. Infection in humans and animals may cause abortion and other severe symptoms under certain circumstances, leading to great economical losses and public health problems. T. gondii was first discovered in China in 1955 and the corresponding work was published in 1957. Since then, a lot of work has been done on this parasite and the diseases it causes. This review summarizes the major progress made by Chinese scientists over the last 60 years, and gives our perspectives on what should be done in the near future. A wide variety of diagnostic approaches were designed, including the ones to detect T. gondii specific antibodies in host sera, and T. gondii specific antigens or DNA in tissue and environmental samples. Further work will be needed to translate some of the laboratory assays into reliable products for clinic uses. Epidemiological studies were extensively done in China and the sero-prevalence in humans increased over the years, but is still below the world average, likely due to the unique eating and cooking habits. Infection rates were shown to be fairly high in meat producing animals such as, pigs, sheep, and chickens, as well as in the definitive host cats. Numerous subunit vaccines in the form of recombinant proteins or DNA vaccines were developed, but none of them is satisfactory in the current form. Live attenuated parasites using genetically modified strains may be a better option for vaccine design. The strains isolated from China are dominated by the ToxoDB #9 genotype, but it likely contains multiple subtypes since different ToxoDB #9 strains exhibited phenotypic differences. Further studies are needed to understand the general biology, as well as the unique features of strains prevalent in China.

Diagnosis of Swine Toxoplasmosis by PCR and Genotyping of Toxoplasma gondii from pigs in Henan, Central China

Background

Toxoplasma gondii, a widely prevalent protozoan parasite, causes serious toxoplasmosis infections in humans and other animals. Among livestock, pigs are susceptible to T. gondii infection. Despite Henan being one of the biggest pig-raising provinces in China, little information exists on the epidemiology of toxoplasmosis in this location. Therefore, we molecularly characterized DNA samples from pigs in Henan. A total of 1647 samples, including 952 from dead piglets, 478 from seriously sick fattening pigs and 217 from abortion sows, were collected from different animal hospitals or pig farms from 10 different cities in Henan (2006–2008). Each pig corresponded to a separate pig farm. DNA was extracted from 3 to 5 g of the most severely affected pig tissue (liver, spleen, lung, hilar lymph nodes and amniotic fluid) after postmortem examination. The presence of the T. gondii B1 gene was detected using nested polymerase chain reactions (PCR). Genotyping was performed directly on DNA from the PCR-positive tissue samples using 11 PCR restriction fragment length polymorphism markers (SAG1, 5′- and 3′-SAG2, alternative SAG2, SAG3, BTUB, GRA6, L358, PK1, c22–8, c29–2, and Apico).

Results

Of all samples, thirty-four were positive for the T. gondii B1 gene (2.06%, 95% CI: 1.86%–2.26%) from four cities, including 31 from NanYang city, one (PgXY 1) from Xinyang City, one (PgZZ 1) from Zhengzhou City and one (PgZK1) from Zhoukou City. The prevalence was found to be highest in piglets than in fattening pigs and sows. And the difference was statistically significant (P<0.01). The following 32 samples were genotyped with complete data: 13 hilar lymph node tissue samples, seven liver tissue samples, seven lung tissue samples, four spleen tissue samples, and one amniotic fluid sample. Only one genotype, belonging to ToxoDB Genotype #9, was identified.

Conclusions

This is the first large-scale survey molecularly characterizing T. gondii from pigs in Henan. The results of the present study revealed that T. gondii infection is present in swine in Henan and is a potential source of foodborne toxoplasmosis in the investigated areas. Implementation of effective control measures for T. gondii to reduce the chance of zoonotic toxoplasmosis spreading from pig farms may be warranted. The results show that the ToxoDB #9 genotype may be the dominant T. gondii lineage in mainland China. These findings strengthen the limited Chinese T. gondii epidemiology database.

Toxoplasma gondii Infection in Farmed Wild Boars (Sus scrofa) in Three Cities of Northeast China

The apicomplexan protozoan parasite Toxoplasma gondii is a widely distributed etiological agent of foodborne illness. This parasite can cause production losses in livestock and serious disease in humans through consumption of contaminated meat. Pig meat is the most likely source of human infection, and wild boars may play a role in the transmission of T. gondii by serving as a reservoir host. This study aimed to investigate the seroprevalence of antibodies to T. gondii among farmed wild boars in China. In an 11-month survey, a total of 882 serum samples were obtained from farmed wild boars from three cities (Jilin City, Siping City, and Baishan City) in Jilin province, Northeast China and were tested for antibodies specific for T. gondii. Using modified agglutination test and a cutoff titer of 1:25, the prevalence of T. gondii infection in the examined samples was 10.0% (88 of 882). The highest seroprevalence was observed in animals from Jilin city (15.3%, 43/281) and followed by Siping (11.4%, 30/263) and Baishan (4.4%, 15/338). Logistic regression analysis revealed a significant correlation between the investigated geographic region and T. gondii infection. In addition, prevalence was higher in females compared to males, and the highest prevalence was detected in piglets. These findings indicate that farmed wild boars may become a source of foodborne toxoplasmosis, posing a food safety threat to the public health in the investigated areas. Implementation of effective measures to control T. gondii infection in farmed wild boars in China may be warranted.

Seroprevalence and genetic characterization of Toxoplasma gondii in masked palm civet (Paguma larvata) in Hainan province, tropical China

In the present study, the seroprevalence, risk factors and genotyping of Toxoplasma gondii in masked palm civet were investigated in tropical China. A total of 500 serum were collected from five administrative farms in tropical China, and assayed for T. gondii antibodies by modified agglutination test (MAT). The brain samples of 20 aborted fetuses were examined by semi-nested-PCR, and positive aborted fetuses (50%) were necropsied to collect the brain tissue for molecular and bioassay examinations. Genomic DNA was extracted from the 29 brain tissues of infected mice and T. gondii B1 gene was amplified using multilocus PCR-RFLP. Overall, 27.6% (95% CI: 23.682-31.518) of the animals was positive for T. gondii antibodies. Ages of masked palm civet was considered as a main risk factor associated with T. gondii infection. 4 DNA samples (13.8%) were positive for the T. gondii B1 gene. Three samples belong to ToxoDB#9, and one belongs to genotype the type II variant (ToxoDB genotype#3). Our results indicated that ToxoDB Genotype#9 has a distribution in masked palm civet that could be potential reservoirs for T. gondii transmission, which may pose a threat to human health.

Seroprevalence and genotypes of Toxoplasma gondii isolated from pigs intended for human consumption in Liaoning province, northeastern China

Background

Genetic information for Toxoplasma gondii isolates from pigs in eastern, south, and southwestern regions of China has been reported previously. However, there are no data from pigs in the northeastern area of the country. To better understand the epidemiology of T. gondii, we determined the seroprevalence and genotypes of T. gondii from pigs slaughtered for human consumption in Liaoning province, northeastern China.

Findings

Out of 2063 pigs examined, 233 (11.26 %) were seropositive for T. gondii by the modified agglutination test (MAT), and viable parasites were isolated by bioassay in mice from 23 (9.87 %) of the 233 seropositive pigs. Fifteen out of 23 isolates were genotyped using 10 PCR-restriction fragment length polymorphism (RFLP) genetic markers including SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico. One isolate was identified as ToxoDB genotype #3 (type II-variant), and one was genotype #1 or #3. The other 13 isolates were ToxoDB #9 (type Chinese 1).

Conclusions

To our knowledge, this is the first report of T. gondii isolation and genotyping from pigs in northeastern China. This study indicates that pigs are a potential source for transmission of T. gondii to humans, therefore poses a potential public health concern. The genotyping results revealed the presence of genotype Chinese 1 in northeastern China, enriching the scope of T. gondii genotypes distribution in eastern Asia.