Multi-locus DNA sequencing of Toxoplasma gondii isolated from Brazilian pigs identifies genetically divergent strains

The Low Genetic Diversity of Dientamoeba fragilis Isolates in Southwest Turkey and Analysis of Clinical Findings

PURPOSE

Dientamoeba fragilis (D. fragilis) is a common intestinal protozoan with a global distribution. In the present study, we aimed to determine genetic diversity of D. fragilis isolates with multilocus sequence typing (MLST) in the southwest of Turkey and analyse the clinical findings.

MATERIALS AND METHODS

The study included faecal samples from 200 individuals in Aydin, Turkey. The positivity of D. fragilis was determined with 18 S rRNA gene-based PCR assay. Six nested-PCR reactions were set to amplify partial D. fragilis housekeeping genes in the positive samples. The sequences were aligned with the references from GenBank to detect nucleotide polymorphisms and haplotypes. Additionally, the clinical findings and demographic characteristics of patients were statistically analysed between D. fragilis-infected and non-infected cases.

RESULTS

The positivity of D. fragilis was 16% (32 out of 200 cases) with 18 S rRNA based-PCR, and all were classified as "genotype 1". The analysis of six MLST loci revealed different haplotypes only at one locus; the remaining five loci exhibited no polymorphisms. The haplotypes in the present study were identical to at least one previously reported reference, except the locus "large subunit of RNA polymerase II" locus. There were no significant differences in any of the clinical findings or demographic characteristics between the infected and non-infected groups.

CONCLUSIONS

Our study revealed a low genetic diversity of D. fragilis isolates from Turkey, like other countries including Italy, Denmark, the UK, Australia, and Brazil. The high degree of sequence similarity in housekeeping genes indicated the clonal distribution of D. fragilis.

CRISPR/Cas12a combined with RPA for detection of T. gondii in mouse whole blood

BACKGROUND

Toxoplasma gondii is an opportunistic protozoan that is ubiquitous in humans and animals. It can invade any human organ and cause severe diseases, including toxoplasma ophthalmopathy, meningoencephalitis, and liver necrosis. Porcine toxoplasmosis is prevalent in China. CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and Cas (CRISPR-Associated Protein) systems are widely used for gene editing and pathogen detection. CRISPR-based diagnostics are molecular assays that have been developed to detect parasites with high sensitivity and specificity.

METHODS

This study aimed to establish a combined CRISPR/Cas12a and RPA rapid detection method for T. gondii by targeting the B1 gene and 529 bp repeat element (529 RE). The detection results could be visualized by the fluorescence or lateral flow strips (LFS). The sensitivity and specificity of the method were evaluated, and T. gondii-infected mouse blood was used for detection.

RESULTS

The results indicated that the established method for T. gondii detection was satisfactory, with a detection limit of 1.5 cp/μl for the two loci. Moreover, the B1 gene could detect 1 tachyzoite per reaction, and the 529 RE could detect 0.1 tachyzoite per reaction, consistently with the highly sensitive nested polymerase chain reaction (PCR) results. The method was suitable for strains, including RH, and did not cross-react with other protozoa DNA with similar habits. The T. gondii-infected mouse blood samples were all positive for T. gondii at 1, 3, and 5 days post infection (dpi).

CONCLUSIONS

This study established a rapid, sensitive, and time-saving DNA detection method for T. gondii that has the potential to be an alternative tool for T. gondii detection in the field.

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

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

Toxoplasma gondii in tissues of sheep slaughtered for human consumption in a highly endemic area for toxoplasmosis in Brazil

Toxoplasma gondii infects warm-blooded animals, including humans, and the ingestion of undercooked meat of infected animals is an important source of infection. We investigated the presence of T. gondii by PCR and histopathology in tissues of 25 seropositive sheep slaughtered for human consumption in Rio de Janeiro and assessed the suitability of different tissues for molecular detection of the parasite. The animals were first screened for T. gondii antibodies by MAT (Modified Agglutination Test), and tissues of seropositive sheep (brain, heart, lungs, kidneys, liver and diaphragm) were subjected to molecular and histological examination. A nested-PCR targeting the P43 gene of T. gondii was performed, and kappa Coefficient was used to assess PCR results among tissues. DNA of the parasite was detected in 60 % (9 of 15) of the animals. and tissue pairs of lungs/heart, lungs/diaphragm or heart/diaphragm had substantial agreement with the global status of the animals. The combination between these three tissues leads to an almost perfect agreement with global status results. Sheep slaughtered for human consumption in Rio de Janeiro, Brazil are infected with T. gondii, and pairs of fragments of lungs and heart, lungs and diaphragm or heart and diaphragm could be used for molecular identification of T. gondii in sheep with substantial agreement with the global status of the animals.

Genetic and histopathological characterization of Toxoplasma gondii genotypes isolated from free-range chickens reared in the metropolitan region of Rio de Janeiro state, Brazil

This study aimed to genetically characterize Toxoplasma gondii isolates obtained from free-range chickens reared in the metropolitan region of the state of Rio de Janeiro, Brazil, and to evaluate the morbidity and histological changes associated with these isolates in mice. A mouse bioassay was used to isolate T. gondii from a pool of tissue samples (brain, heart, and thigh muscles) collected from 163 chickens. The 36 isolates obtained were genetically characterized by restriction fragment polymorphism (PCR-RFLP) analysis of the SAG1, 5'-3'SAG2, aSAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, Apico, and CS3 genomic regions. Seventeen atypical genotypes were identified and nine of them were reported for the first time. All identified genotypes caused clinical signs and histological changes in mice, with the majority being associated with high cumulative morbidity (65%) and severe or very severe histological changes (76%). The exclusive identification of atypical genotypes, with a predominance of new genotypes, indicates great genetic diversity of T. gondii in the region studied. In addition, the finding that all identified genotypes caused clinical signs and often severe histological changes in mice suggests potentially relevant virulence of these strains.

Molecular characterisation of Trichomonas vaginalis isolates in Southwest Turkey with multilocus sequence typing and genetic structure analysis in relation to different countries

Trichomonas vaginalis, a flagellated protozoan parasite, is among the most common sexually transmitted pathogens in the world. The present study aimed to identify the genetic profiles of T. vaginalis in the southwest of Turkey with multilocus sequence typing (MLST) and to analyse the genetic structure of the parasite in a collection of isolates from different countries. The study included 27 T. vaginalis isolates from symptomatic females in Aydin, Turkey. Seven housekeeping genes of T. vaginalis were partially amplified and sequenced after genomic DNA extraction from in vitro cultures. The allele profiles and sequence types (STs) of the isolates were determined by using the MLST database (https://pubmlst.org/tvaginalis). The genetic structure and differentiation of the parasite were analysed in relation to findings from other countries by assembling the available MLST sequences. When referred to the database, a total of 22 STs, including 18 new STs were found; besides, there were two new allele types. The genetic analysis of MLST data demonstrated the presence of two main genetic structures: Type I and Type II. In addition, the neighbor-joining method also revealed that the isolates were clustered into two groups. The genetic types distributed almost equally in the Netherlands and the USA, however, the predominance of Type I was noted in Turkey and the UK. The genetic differentiation among four countries was significant (p < .05), the gene flow was relatively high between the Netherlands and the USA, in contrast to Turkey. Finally, genetic variations were originated within populations (93.8%) rather than among populations (6.2%). In conclusion, we studied the genetic diversity of T. vaginalis isolates with MLST in the southwest of Turkey and showed the origin of genetic differentiation of the parasite among different countries. The presentation of MLST profiles and genetic variance of T. vaginalis isolates will contribute to the development of new diagnostic and treatment options for the parasite.

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.

Public health risks associated with food-borne parasites

Parasites are important food‐borne pathogens. Their complex lifecycles, varied transmission routes, and prolonged periods between infection and symptoms mean that the public health burden and relative importance of different transmission routes are often difficult to assess. Furthermore, there are challenges in detection and diagnostics, and variations in reporting. A Europe‐focused ranking exercise, using multicriteria decision analysis, identified potentially food‐borne parasites of importance, and that are currently not routinely controlled in food. These are Cryptosporidium spp., Toxoplasma gondii and Echinococcus spp. Infection with these parasites in humans and animals, or their occurrence in food, is not notifiable in all Member States. This Opinion reviews current methods for detection, identification and tracing of these parasites in relevant foods, reviews literature on food‐borne pathways, examines information on their occurrence and persistence in foods, and investigates possible control measures along the food chain. The differences between these three parasites are substantial, but for all there is a paucity of well‐established, standardised, validated methods that can be applied across the range of relevant foods. Furthermore, the prolonged period between infection and clinical symptoms (from several days for Cryptosporidium to years for Echinococcus spp.) means that source attribution studies are very difficult. Nevertheless, our knowledge of the domestic animal lifecycle (involving dogs and livestock) for Echinoccocus granulosus means that this parasite is controllable. For Echinococcus multilocularis, for which the lifecycle involves wildlife (foxes and rodents), control would be expensive and complicated, but could be achieved in targeted areas with sufficient commitment and resources. Quantitative risk assessments have been described for Toxoplasma in meat. However, for T. gondii and Cryptosporidium as faecal contaminants, development of validated detection methods, including survival/infectivity assays and consensus molecular typing protocols, are required for the development of quantitative risk assessments and efficient control measures.

Genotyping of Toxoplasma gondii from pigs in Yucatan, Mexico

Toxoplasmosis is a zoonotic disease of worldwide distribution. The parasite exhibits strong geographical patterns of strain variation with contrasting high levels of diversity across South America and restricted variation across North America. Little is known about the diversity of strains in the transitional area between the two continents. Here we present data on the prevalance and diversity of Toxoplasma gondii in the Yucatan peninsula of Mexico, through a study in commercially reared pigs. A survey of 12 farms found evidence of circulating T. gondii DNA in 125 of 632 blood samples (19.8%, CI: 16.7%-23%). In addition, 46 tongue samples were collected from culled animals and 16 of these were positive for T. gondii DNA and 3 were positive in mouse bioassay. PCR-sequencing was used to generate genotyping data from blood and tissue samples. Four loci (SAG1, 2, 3 and GRA6) were reliably amplified and revealed a high diversity among Yucatan strains with evidence of recombination and novel alleles. Sequencing data from the four loci was achieved in eight samples each of which had a different genotype. The predominant allelic type was atypical, in relation to the dominant strain types (I, II, III), the number of allelic variants being 27 (I, II-III, u-1-25), 20 (I, III, u1-18), 6 (I, III, u1-4) and 11 (I, II, u1-9) for the SAG1, SAG2, SAG3 and GRA6 loci respectively. Phylogenetic analysis showed that T. gondii strains from Yucatan shared alleles with strains originating from both North and South America. Our findings are consistent with data from other regions of Central America and suggest the genetic population structure of the parasite, with significant levels of allelic variation and recombination, constitutes a reservoir from which new strains may emerge. Positive bioassay results (7.5%) indicate that consumption of undercooked pork could be a potential T. gondii infection risk to humans.

Genotyping of Toxoplasma gondii isolates from naturally infected Gallus domesticus in Santa Catarina state, Brazil

ABSTRACT Toxoplasmosis is a widespread zoonosis that can infect warm-blooded animals including birds and humans, and chickens are considered to be indicators of environmental contamination. In Brazil, Toxoplasma gondii has a non-clonal population structure composed of three lineages (I, II, and III), presenting high recombination, and resulting in wide genetic diversity. This study aimed to genetically characterize T. gondii isolates from naturally infected chickens (Gallus domesticus) in Santa Catarina state, southern Brazil region. Sera from 133 free-range chickens were analyzed by an immunofluorescence assay (IFA) to detect IgG antibodies against T. gondii. Brain and heart from 30 positive animals, based on IFA (≥ 1:64), were used to isolate the parasite using a mouse bioassay. Strain genotyping was performed by PCR-RFLP using 12 genetic markers (SAG1, 5´-3´SAG2, alt. SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, Apico, and CS3). The results were classified according to the genotypes based on the ToxoDB (http://toxodb.org/toxo/). Of 133 chicken sera analyzed, 84 (63.16%) were positive, with antibody titers ranging from 16 to 1024. Eleven isolates were obtained from mouse bioassay (Ck3, Ck32, Ck35, Ck56, Ck63, Ck89, Ck102, Ck103, Ck125, Ck127, and Ck128). Genotyping revealed six genotypes; three were classified as #26, #53, and #120, and three (NEO1, NEO2, and NEO3) were had not been previously described. No clonal lineages of type I, II, or III were identified. The present study confirms the high genetic diversity of T. gondii in Brazil.

Investigating the Determinants of Toxoplasma gondii Prevalence in Meat: A Systematic Review and Meta-Regression

BACKGROUND

Toxoplasma gondii is one of the most widespread parasites in humans and can cause severe illness in immunocompromised individuals. However, its role in healthy people is probably under-appreciated. The complex epidemiology of this protozoan recognizes several infection routes but consumption of contaminated food is likely to be the predominant one. Among food, consumption of raw and undercooked meat is a relevant route of transmission, but the role of different meat producing animal species and meats thereof is controversial.

OBJECTIVES

The aim of the present work is to summarize and analyse literature data reporting prevalence estimates of T. gondii in meat animals/meats.

DATA SOURCES

We searched Medline, Web of Science, Science Direct (last update 31/03/2015).

ELIGIBILITY CRITERIA

Relevant papers should report data from primary studies dealing with the prevalence of T. gondii in meat from livestock species as obtained through direct detection methods. Meta-analysis and meta-regression were performed.

RESULTS

Of 1915 papers screened, 69 papers were included, dealing mainly with cattle, pigs and sheep. Pooled prevalences, based on random-effect models, were 2.6% (CI95 [0.5-5.8]) for cattle, 12.3% (CI95 [7.6-17.8]) for pigs and 14.7% (CI95 [8.9-21.5]) for sheep. Due to the high heterogeneity observed, univariable and multivariable meta-regression models were fitted showing that the geographic area for cattle (p = 0.032), the farming type for pigs (p = 0.0004) and the sample composition for sheep (p = 0.03) had significant effects on the prevalences of Toxoplasma detected/estimated. Moreover, the role of different animal species was dependent on the geographic location of animals' origin.

LIMITATIONS

Limitations were due mainly to a possible publication bias.

CONCLUSIONS AND IMPLICATIONS

The present work confirms the role of meat, including beef, as T. gondii sources, and highlights the need for a control system for this parasite to be implemented along the meat production chain. Moreover, consumer knowledge should be strengthened in order to reduce the impact of disease.

First report of genotype #65 of Toxoplasma gondii in pigs

The aim of the present study was to isolate and genotype Toxoplasma gondii from pigs slaughtered for human consumption in northeastern Brazil. Indirect immunofluorescence antibody test (IFAT) was used to screen positive pigs. Tissues samples of animals with antibody titers ≥64 were submitted to bioassay in mice. One isolate of T. gondii was obtained, and the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique, using 11 markers (SAG1, SAG2, altSAG2, SAG3, BTUB, GRA6, c228, c292, L358, PK1, and APICO), was applied to evaluate the genetic variability. DNA from reference strains was used as a positive control. By means of genetic analysis, genotype ToxoDB #65 was identified, which is considered an atypical strain. This is the first record of genotype #65 in pigs. Thus, further studies in this region are necessary to determine the genetic variability of T. gondii in pigs and possible impact on public health.

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.

Overlapping Toxoplasma gondii genotypes circulating in domestic animals and humans in Southeastern Brazil

Although several Toxoplasma gondii genotyping studies have been performed in Brazil, studies of isolates from animals in the state of Minas Gerais are rare. The objective of this study was to conduct a genotypic characterization of T. gondii isolates obtained from dogs, free-range chickens, and humans in Minas Gerais and to verify whether the T. gondii genotypes circulating in domestic animals correspond to the genotypes detected in humans. Genetic variability was assessed by restricted fragment length polymorphism at 11 loci (SAG1, 5′+3′SAG2, SAG2 alt, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico). Twelve different genotypes were identified among the 24 isolates studied, including 8 previously identified genotypes and 4 new genotypes. The genetic relationship of the 24 T. gondii isolates, together with the genotypes previously described from 24 human newborns with congenital toxoplasmosis, revealed a high degree of similarity among the genotypes circulating in humans and animals in Minas Gerais. The most common genotypes among these species were BrII, BrIII, ToxoDB #108, and ToxoDB #206. Restricted fragment length polymorphism at the CS3 locus of these 48 isolates showed that the majority of isolates presented alleles I (50%) or II (27%). Isolates harboring allele III at the CS3 locus presented low virulence for mice, whereas those harboring alleles I or II presented higher virulence. These results confirm the utility of marker CS3 for predicting the virulence of Brazilian isolates of T. gondii in mice. No association was found between the allele type and clinical manifestations of human congenital toxoplasmosis. This is the first report of T. gondii genotyping that verifies the overlapping genotypes of T. gondii from humans and animals in the same geographic region of Brazil. Our results suggest that there is a common source of infection to the species studied, most likely oocysts contaminating the environment.

Genetic characterization of Toxoplasma gondii revealed highly diverse genotypes for isolates from newborns with congenital toxoplasmosis in southeastern Brazil

Recent studies of Toxoplasma gondii isolates from animals in Brazil have revealed high genetic diversity. Many of these isolates are virulent to mice. It is speculated that these isolates may also be virulent to humans. However, there is very limited data regarding T. gondii strains from human infection. Therefore, it is not clear whether there is any association between parasite genotypes and disease phenotypes. In this study, a total of 27 T. gondii strains were isolated from humans with congenital toxoplasmosis in Minas Gerais state, Brazil. The genetic variability was assessed by restricted fragment length polymorphism in 11 loci (SAG1, 5' plus 3' SAG2, alternative [alt.] SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico). Genetic analysis of 24 strains revealed 14 different genotypes, including 7 previously identified from animals and 7 new types. The widespread genotype BrII accounted for 29% (7/24) of the isolates and was the dominant genotype involved in this study. This is the first report of genotyping of T. gondii isolates obtained from blood samples from newborns with congenital toxoplasmosis. Genotypic characterization of these isolates suggests high genetic diversity of T. gondii in this human population in Brazil. Future studies are needed to determine the source of contamination of this human population.

Toxoplasmosis in humans and animals in Brazil: high prevalence, high burden of disease, and epidemiology

Infections by the protozoan parasite Toxoplasma gondii are widely prevalent in humans and animals in Brazil. The burden of clinical toxoplasmosis in humans is considered to be very high. The high prevalence and encouragement of the Brazilian Government provides a unique opportunity for international groups to study the epidemiology and control of toxoplasmosis in Brazil. Many early papers on toxoplasmosis in Brazil were published in Portuguese and often not available to scientists in English-speaking countries. In the present paper we review prevalence, clinical spectrum, molecular epidemiology, and control of T. gondii in humans and animals in Brazil. This knowledge should be useful to biologists, public health workers, veterinarians, and physicians. Brazil has a very high rate of T. gondii infection in humans. Up to 50% of elementary school children and 50-80% of women of child-bearing age have antibodies to T. gondii. The risks for uninfected women to acquire toxoplasmosis during pregnancy and fetal transmission are high because the environment is highly contaminated with oocysts. The burden of toxoplasmosis in congenitally infected children is also very high. From limited data on screening of infants for T. gondii IgM at birth, 5-23 children are born infected per 10 000 live births in Brazil. Based on an estimate of 1 infected child per 1000 births, 2649 children with congenital toxoplasmosis are likely to be born annually in Brazil. Most of these infected children are likely to develop symptoms or signs of clinical toxoplasmosis. Among the congenitally infected children whose clinical data are described in this review, several died soon after birth, 35% had neurological disease including hydrocephalus, microcephaly and mental retardation, 80% had ocular lesions, and in one report 40% of children had hearing loss. The severity of clinical toxoplasmosis in Brazilian children may be associated with the genetic characteristics of T. gondii isolates prevailing in animals and humans in Brazil.

Evidence for a recent population bottleneck in an Apicomplexan parasite of caribou and reindeer, Besnoitia tarandi

The evolutionary history and epidemiology of parasites may be reflected in the extent and geographic distribution of their genetic variation. Among coccidian parasites, the population structure of only Toxoplasma gondii has been extensively examined. Intraspecific variation in other coccidia, for example, those assigned to the genus Besnoitia, remains poorly defined. Here, we characterize the extent of genetic variation among populations of Besnoitia tarandi, a parasite whose intermediate hosts include reindeer/caribou (Rangifer tarandus). Isolates from the Canadian Arctic and Finnish sub-Arctic were genotyped at six microsatellite loci, the first internal transcribed spacer region of nuclear rDNA, and the RNA polymerase β subunit (rpoB) encoded in the plastid genome. Remarkably, all isolates exhibited the same multilocus genotype, regardless of the isolate's geographic origin. This absolute monomorphism occurred despite the capacity of these loci to vary, as established by evident differentiation between B. tarandi and two other species of Besnoitia, and variation among four isolates of B. besnoiti. The surprising lack of genetic variation across the sampled range suggests that B. tarandi may have experienced a recent population bottleneck.

Isolation and genotyping of Toxoplasma gondii from pregnant dairy cows (Bos taurus) slaughtered

The current study aimed to evaluate serology, and isolate and genotype Toxoplasma gondii strains from pregnant dairy cows, slaughtered in an abattoir for human consumption, and their fetuses. Blood from 60 pregnant dairy cows and blood and tissue samples (brain, lung, heart, and liver) from their fetuses were collected and analyzed in a mouse bioassay. Antibodies against T. gondii were observed in 48.3% of cows and 3.7% of fetuses (IFAT, titers ≥ 50 for cows and 25 for fetuses were considered positive). Fourteen fetuses (23.3%) and six cows (10.0%) were identified as positive in the bioassay. T. gondii was isolated from a blood sample of a cow older than 4 years old in the 6th month of pregnancy, and from a blood sample of a fetus in the 6th month of gestation. These isolates were identified by polymerase chain reaction (PCR) as being of T. gondii and both strains showed type II alleles for all PCR-restriction fragment length polymorphism (PCR-RFLP) markers tested. T. gondii type II strain from cattle was isolated for the first time in Brazil. The current study also showed that transplacental transmission of T. gondii naturally occurs in dairy cows (23.3%) from Southern Brazil.

Population genetics of Toxoplasma gondii: new perspectives from parasite genotypes in wildlife

Toxoplasma gondii, a zoonotic protozoal parasite, is well-known for its global distribution and its ability to infect virtually all warm-blooded vertebrates. Nonetheless, attempts to describe the population structure of T. gondii have been primarily limited to samples isolated from humans and domesticated animals. More recent studies, however, have made efforts to characterize T. gondii isolates from a wider range of host species and geographic locales. These findings have dramatically changed our perception of the extent of genetic diversity in T. gondii and the relative roles of sexual recombination and clonal propagation in the parasite's lifecycle. In particular, identification of novel, disease-causing T. gondii strains in wildlife has raised concerns from both a conservation and public health perspective as to whether distinct domestic and sylvatic parasite gene pools exist. If so, overlap of these cycles may represent regions of high probability of disease emergence. Here, we attempt to answer these key questions by reviewing recent studies of T. gondii infections in wildlife, highlighting those which have advanced our understanding of the genetic diversity and population biology of this important zoonotic pathogen.

Oral oocyst-induced mouse model of toxoplasmosis: effect of infection with Toxoplasma gondii strains of different genotypes, dose, and mouse strains (transgenic, out-bred, in-bred) on pathogenesis and mortality

Humans and other hosts acquire Toxoplasma gondii infection by ingesting tissue cysts in undercooked meat, or by food or drink contaminated with oocysts. Currently, there is no vaccine to prevent clinical disease due this parasite in humans, although, various T. gondii vaccine candidates are being developed. Mice are generally used to test the protective efficacy of vaccines because they are susceptible, reagents are available to measure immune parameters in mice, and they are easily managed in the laboratory. In the present study, pathogenesis of toxoplasmosis was studied in mice of different strains, including Human Leukocyte Antigen (HLA) transgenic mice infected with different doses of T. gondii strains of different genotypes derived from several countries. Based on many experiments, the decreasing order of infectivity and pathogenicity of oocysts was: C57BL/6 background interferon gamma gene knock out (KO), HLA-A*1101, HLA-A*0201, HLA-B*0702, Swiss Webster, C57/black, and BALB/c. Mice fed as few as 1 oocyst of Type I and several atypical strains died of acute toxoplasmosis within 21 days p.i. Some Type II, and III strains were less virulent. The model developed herein should prove to be extremely useful for testing vaccines because it is possible to accurately quantitate a challenge inoculum, test the response to different strains of T. gondii using the same preparations of oocysts which are stable for up to a year, and to have highly reproducible responses to the infection.

Genotyping of Toxoplasma gondii isolates from cats in different geographic regions of China

Fourteen isolates of Toxoplasma gondii were isolated from cats from 4 different geographic provinces (Anhui, Hubei, Shanxi and Guangdong) in China and their genetic diversity with 8 nuclear loci SAG2, SAG3, BTUB, GRA6, L358, PK1, c22-8, c29-2, and an apicoplast locus Apico, was analysed by restriction fragment length polymorphisms (RFLPs). Two genotypes from these 14 isolates were identified but none of them belongs to the typical genetic types (types I, II and III). It is unexpected that such high similarity was observed in these 14 isolates although their original regions are significantly distant. Our results strongly indicate that the three traditional clonal lineages of types I, II and III of this parasite may not be preponderant in China. In addition, our results show that the genotypes of T. gondii in China may be highly clonal with atypical genotypes and higher virulence.

CD8 T Cells and Toxoplasma gondii: A New Paradigm

CD8 T cells are essential for control of Toxoplasma gondii infection. Once activated they undergo differentiation into short-lived effector and memory precursor effector cells. As effector cells, CD8 T cells exert immune pressure on the parasite via production of inflammatory cytokines and through their cytolytic activity. Once immune control has been established, the parasite encysts and develops into chronic infection regulated by the memory CD8 T-cell population. Several signals are needed for this process to be initiated and for development of fully differentiated memory CD8 T cells. With newly developed tools including CD8 T-cell tetramers and TCR transgenic mice, dissecting the biology behind T. gondii-specific CD8 T-cell responses can now be more effectively addressed. In this paper, we discuss what is known about the signals required for effective T. gondii-specific CD8 T-cell development, their differentiation, and effector function.