Detection of T. gondii in tissues of sheep and cattle following oral infection

In vitro assay to determine inactivation of Toxoplasma gondii in meat samples

Consumption of raw and undercooked meat is considered as an important source of Toxoplasma gondii infections. However, most non-heated meat products contain salt and additives, which affect T. gondii viability. It was our aim to develop an in vitro method to substitute the mouse bioassay for determining the effect of salting on T. gondii viability. Two sheep were experimentally infected by oral inoculation with 6.5 × 104 oocysts. Grinded meat samples of 50 g were prepared from heart, diaphragm, and four meat cuts. Also, pooled meat samples were either kept untreated (positive control), frozen (negative control) or supplemented with 0.6 %, 0.9 %, 1.2 % or 2.7 % NaCl. All samples were digested in pepsin-HCl solution, and digests were inoculated in duplicate onto monolayers of RK13 (a rabbit kidney cell line). Cells were maintained for up to four weeks and parasite growth was monitored by assessing Cq-values using the T. gondii qPCR on cell culture supernatant in intervals of one week and ΔCq-values determined. Additionally, 500 μL of each digest from the individual meat cuts, heart and diaphragm were inoculated in duplicate in IFNγ KO mice. Both sheep developed an antibody response and tissue samples contained similar concentrations of T. gondii DNA. From all untreated meat samples positive ΔCq-values were obtained in the in vitro assay, indicating presence and multiplication of viable parasites. This was in line with the mouse bioassay, with the exception of a negative mouse bioassay on one heart sample. Samples supplemented with 0.6 %-1.2 % NaCl showed positive ΔCq-values over time. The frozen sample and the sample supplemented with 2.7 % NaCl remained qPCR positive but with high Cq-values, which indicated no growth. In conclusion, the in vitro method has successfully been used to detect viable T. gondii in tissues of experimentally infected sheep, and a clear difference in T. gondii viability was observed between the samples supplemented with 2.7 % NaCl and those with 1.2 % NaCl or less.

Can cloning and sequencing help to genotype positive Toxoplasma gondii clinical samples? Results and validation using SAG3 as a model

Genotyping of T. gondii in human cases is relevant to understand the transmission patterns and epidemiology of this parasitosis. However, this genetic characterization can be hampered by the difficulty of isolating the parasite from mild or asymptomatic cases and by the detection efficiency of molecular assays such as the multilocus nested-polymerase chain reaction-restriction fragment length polymorphism (Mn-PCR-RLFP). To propose an alternative for the genotyping of positive clinical samples of T. gondii with a low amount of the parasite DNA mixed within the host DNA or mixed infections, we carried out this study to validate the sequences of the SAG3 gene of T. gondii obtained after two rounds of amplification cloned into a bacterial model, thereby achieving the separation and identification of more than one genotype of T. gondii. Also, the detection limit of the parasite DNA and the fidelity of the reagents used in the nested PCR-RFLP in artificial clinical samples by sequencing were determined. T. gondii DNA was detected from 6.25 ng of DNA and 200 parasites/mL of blood. The fidelity of the AmpliTaq Gold™ polymerase after 65 cycles of amplification was 100%. Denaturation of the products obtained after two rounds of nested PCR amplification showed no evidence of chimera or artifact production. The cloning efficiency was 97.5% (39/40 clones), and none of the experiments produced recombinant sequences. Thus, the generation of chimeras with this methodology could be ruled out. Genotyping of clinical samples is important because there is no strain selection bias, as can occur in the bioassay (where more virulent strains can be selected over nonvirulent strains), and therefore, mixed infections can be detected through cloning and sequencing. Furthermore, these two techniques could be useful tools to genotype weak amplicons of any T. gondii gene obtained during nested PCR.

Effect of Domestic Freezing on the Viability of Toxoplasma gondii in Raw and Dry-Cured Ham from Experimentally Infected Pigs

ABSTRACT

Toxoplasma gondii is the causative agent of the parasitic disease toxoplasmosis, which is an important foodborne zoonosis. Eating undercooked meat of infected animals has been considered the major transmission route of T. gondii to humans. The present study was conducted to evaluate the efficacy of domestic freezing for inactivation of T. gondii bradyzoites in ham. Raw and dry-cured ham from a pig experimentally inoculated orally with 4,000 oocysts of T. gondii VEG strain was subjected to domestic freezing at -20°C for up to 14 days. The effect was evaluated by bioassay in mice and a quantitative PCR assay. In raw and dry-cured ham, -20°C for 7 and 14 days, respectively, did not inactivate T. gondii. More studies are needed to find the correct temperature and time needed to render the bradyzoites noninfectious for humans. Meanwhile, the recommendations for freezing to inactivate T. gondii in raw or dry-cured meats must be revisited because domestic freezing conditions do not reduce the risk of infection.

HIGHLIGHTS

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.

Anatomical distribution of Toxoplasma gondii in naturally and experimentally infected lambs

Consumption of raw or undercooked meat containing Toxoplasma gondii tissue cysts is one of the main sources of infection for humans worldwide. Among the various species intended for human consumption, sheep appear to be a high risk for human infection. The present study focused on the detailed anatomical distribution of Toxoplasma gondii in naturally and experimentally infected lambs using fresh and frozen samples of various pieces of meat, from a public health perspective. The first objective was to rank the edible parts intended for human consumption according to the detectable parasite burden by real-time PCR targeting the 529-bp repeated element. The second objective was to evaluate the impact of freezing by comparing the detection efficiency of the quantitative PCR between fresh and frozen tissues, as imports of lamb carcasses/cuts may arrive frozen or chilled. The highest estimated parasite loads were observed in skeletal muscles, and more particularly in edible portions such as quadriceps femoris muscle, intercostal muscles, deltoid muscle and diaphragm, with a significant difference in detectable parasite burden between fresh and frozen samples (p < 0.0001) or natural and experimental infection (p < 0.0001). Thoracic and pelvic limbs (3278-1048 parasites/g muscle) were ranked at the top of the list. Toxoplasma gondii DNA was detected in all the edible parts of lamb studied. These results suggest that lamb meat represents a risk for consumers. Further investigations are needed in order to confirm these differences in larger numbers of animals and in different breeds.

Comparison of serological and molecular techniques to detect Toxoplasma gondii in free-range chickens (Gallus gallus domesticus)

The present study aimed to compare different indirect and direct diagnostic techniques to diagnose Toxoplasma gondii in free-range chickens. Samples of 386 chickens obtained from 24 Paraná properties were used for serological analysis by indirect fluorescent antibody test (IFAT), modified agglutination test (MAT), and enzyme-linked immunosorbent assay (ELISA). Animals positive by IFAT and/or MAT had their tissues submitted to the mouse bioassay, and those who were positive in this technique had their blood, tissues, and acidic pepsin tissue digestion submitted to PCR (conventional, nested, and quantitative-PCR (qPCR)). One hundred and nineteen chickens (30.8 %) were positive in at least one of the serological tests, being 102 (26.4 %) in the IFAT, 64 (16.6 %) in the MAT, and 62 (16.0 %) in the ELISA. The IFAT was used as a gold standard, and the MAT showed higher sensitivity (46.0 %) and specificity (94.0) compared to ELISA (43.5 % and 93.6 %, respectively). Ninety samples of eighteen chickens positive in the mouse bioassay were subjected to PCR, and according to molecular tests, the conventional PCR detected the T. gondii DNA in 30 % (27/90) of the samples, in 38.8 % (35/90) with nested-PCR and 40.0 % (36/90) with real-time. According to molecular analyzes, the sensitivity was higher in ITS1 nested-PCR (69.4 %) and specificity in conventional PCR-529bp (90.7 %), using the qPCR as the gold standard. MAT and ELISA had similarities in concordance analyzes. The IFAT was the serological technique with the highest agreement with the mouse bioassay, and serological tests in parallel showed to be a good screening option for the isolation of T. gondii in chick tissues. The PCR markers effectively detected the parasite DNA, and the heart was the tissue with the highest number of positives samples. The conventional PCR had sensitivity similar to nested-PCR and qPCR and could be a cheaper alternative to diagnose T. gondii infection in chicken tissues.

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.

<i>Toxoplasma gondii</i> Infection in Cattle Egret (<i>Bubulcus ibis</i>): First Report from Shebin El-Kom, Menoufia Governorate, Egypt

BACKGROUND AND OBJECTIVE

Toxoplasma gondii (T. gondii) is capable of infecting a broad range of intermediate hosts. Cattle egret (Bubulcus ibis) is a species of herons that is common in Egypt. This work aimed to study the prevalence of T. gondii in cattle egret which is an efficient tool of investigating environmental contamination with T. gondii.

MATERIALS AND METHODS

Serum, heart and brain tissues of 51 cattle egrets were collected from Shebin El-Kom, Menoufia, Egypt and tested using Modified Agglutination Test (MAT) and mice bioassay.

RESULTS

There was a detection rate of 13.7% (7/51) in these birds using MAT. By intraperitoneal injection of mice with heart and brain tissues digest of MAT positive birds, the parasite was isolated from two T. gondii sero-positive birds (28.6%). The mice bioassay was confirmed by MAT, Hematoxylin and Eosin (HAND E) staining of the brain of the infected mice, also by Polymerase Chain Reaction (PCR) and sequencing.

CONCLUSION

This is the first report of T. gondii infection in cattle egret from Egypt and more studies are needed on Egyptian wildlife to understand the sylvatic life cycle of the parasite.

Effect of Toxoplasma gondii on Ram Sperm Quality After Experimental Infection

The aim of this study was to investigate the effect of experimental Toxoplasma gondii infection on ram sperm quality. Five months old, pre-pubertal, rams were divided into four groups (n = 8 per group). Group A was the control group; the remaining animals received per os (p.o.) 5000 oocysts per ram. Group B did not receive treatment post-infection (p.i.). Group C received sulphadimidine (intermuscular injection (i.m.) 33 mg/kg for eight days; every 48 hrs) two months p.i. and Group D received the same drug twice (24 hours p.i. and two months later). Blood samples were collected every 15 days to detect serum immunoglobulin G (IgG). Epididymal sperm samples were analyzed for concentration, kinetics, morphology/viability, functional membrane integrity, DNA integrity, and the presence of parasite DNA. Histopathological examination was performed on the testes. The IgG titres in infected groups raised two weeks p.i. and remained high for four months. Higher values were noticed in viability and functional membrane integrity in positive spermatozoa in the control group compared to other groups, level of significance p < 0.05. Abnormal sperm was higher in groups C and D vs. A and C vs. B (p < 0.05). T. gondii DNA was detected in three sperm samples of the infected rams (12.5%). Histopathology revealed similar findings with little variation among all infected groups, characterized mostly by increased interstitial connective tissue, non-purulent inflammation, and presence of seminiferous tubules with spermatogenic cell depletion, which increased gradually from D to C and B groups. In conclusion Toxoplasmosis in pre-pubertal age negatively affected mature ram sperm quality, while sulphadimidine administration failed to alter this.

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.

Toxoplasma gondii in beef consumed in France: regional variation in seroprevalence and parasite isolation

In France, the consumption of cattle and sheep meat appears to be a risk factor for infection of pregnant women with Toxoplasma gondii. Several nation-wide surveys in France have investigated the prevalence of T. gondii in sheep and pig meat, but little is known at present about the prevalence of the parasite in beef. The main objective of the present cross-sectional survey was to estimate the seroprevalence of T. gondii infection in beef consumed in France. A secondary objective was to attempt to isolate T. gondii from cattle tissues and to study the geographical and age variations of this seroprevalence. The overall estimate of seroprevalence of T. gondii in bovine carcasses (n = 2912), for a threshold of 1:6 was 17.38%. A strong age effect was observed (p < 0.0001) with a seroprevalence of 5.34% for calves (<8 months) and 23.12% for adults (>8 months). Seroprevalence estimates given by area of birth and area of slaughtering for adults showed that the areas with the highest seroprevalence were not the same between these two variables. Only two strains, corresponding to genotype II, were isolated from heart samples, indicating that there is a limited risk of human infection with T. gondii, which needs to be correlated with the food habit of consuming raw or undercook (bleu or saignant) beef. However, new questions have emerged, especially concerning the isolation of parasites from beef and the precise role of bovines, generally described as poor hosts for T. gondii, in human infection.

Detection of Toxoplasma gondii infection in semen of rams used for natural mating in commercial sheep farms in Tunisia

Toxoplasmosis, a parasitic infection, disrupts sexual functions resulting in decline in reproductive and economic performance in sheep. Lacking discernible symptoms, toxoplasmosis is difficult to detect and diagnose in infected animals. Here, to estimate the prevalence of natural infection by Toxoplasma gondii, we used PCR to amplify and detect T. gondii DNA in semen from 92 rams of three breeds from four regions in Tunisia and seroprevalence was determined using a commercial ELISA kit. From the PCR amplifications, 51.09 ± 10.21% of the rams were tested positive for T. gondii with an overall seroprevalence of 39.13 ± 9.97%. Risk factors including ram location and number of accomplished mating seasons significantly (p < .05) affected the sero- and molecular prevalence of T. gondii in semen but, there was a fair concordance between sero- and molecular prevalence (Kappa = 0.33). Sequences of T. gondii from five positive samples were 100% identical (same haplotype). Comparison of these sequences with those archived at the GenBank showed a sequence similarity range between 95 and 100%. The haplotype defining the five Tunisian sequences was similar to the one observed in chicken, cats, European pole cat and humans from Brazil, St Kitts and Nevis, Great Britain and Tunisia, respectively. This indicates its wide geographic distribution and non-species specificity. Our findings suggest a high prevalence of toxoplasmosis in Tunisian matting rams; further studies concerning its venereal transmission capacity are needed prior to recommending a systematic screening of T. gondii DNA in rams' semen used for both natural breeding and artificial insemination.

Serological and molecular rapid diagnostic tests for Toxoplasma infection in humans and animals

Infection by Toxoplasma gondii is prevalent worldwide. The parasite can infect a broad spectrum of vertebrate hosts, but infection of fetuses and immunocompromised patients is of particular concern. Easy-to-perform, robust, and highly sensitive and specific methods to detect Toxoplasma infection are important for the treatment and management of patients. Rapid diagnostic methods that do not sacrifice the accuracy of the assay and give reproducible results in a short time are highly desirable. In this context, rapid diagnostic tests (RDTs), especially with point-of-care (POC) features, are promising diagnostic methods in clinical microbiology laboratories, especially in areas with minimal laboratory facilities. More advanced methods using microfluidics and sensor technology will be the future trend. In this review, we discuss serological and molecular-based rapid diagnostic tests for detecting Toxoplasma infection in humans as well as animals.

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.

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.

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.

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

Background

Although the detection of Toxoplasma gondii in bovine tissues is rare, beef might be an important source of human infection. The use of molecular techniques, such as magnetic capture qPCR (MC-qPCR), in combination with the gold standard method for isolating the parasite (mouse bioassay), may increase the sensitivity of T. gondii detection in infected cattle. The risk of transmission of the parasite to humans from undercooked/raw beef is not fully known and further knowledge about the predilection sites of T. gondii within cattle is needed. In the current study, six Holstein Friesian calves (Bos taurus) were experimentally infected with 10⁶ T. gondii oocysts of the M4 strain and, following euthanasia (42 dpi), pooled tissues were tested for presence of the parasite by mouse bioassay and MC-qPCR.

Results

Toxoplasma gondii was detected by both MC-qPCR and mouse bioassay from distinct pools (100 g) of tissues comprising: liver, tongue, heart, diaphragm, semitendinosus (hindlimb), longissimus dorsi muscle (sirloin) and psoas major muscle (fillet). When a selection of individual tissues which had been used for mouse bioassay were examined by MC-qPCR, parasite DNA could only be detected from two animals, despite all calves showing seroconversion after infection.

Conclusions

It is apparent that one individual test will not provide an answer as to whether a calf harbours T. gondii tissue cysts. Although the calves received a known number of infectious oocysts and highly sensitive methods for the detection of the parasite within bovine tissues were applied (mouse bioassay and MC-qPCR), the results confirm previous studies which report low presence of viable T. gondii in cattle and no clear predilection site within bovine tissues.

Species-Specific Transcriptional Regulation of Genes Involved in Nitric Oxide Production and Arginine Metabolism in Macrophages

Activated mouse macrophages metabolize arginine via NO synthase (NOS2) to produce NO as an antimicrobial effector. Published gene expression datasets provide little support for the activation of this pathway in human macrophages. Generation of NO requires the coordinated regulation of multiple genes. We have generated RNA-sequencing data from bone marrow-derived macrophages from representative rodent (rat), monogastric (pig and horse), and ruminant (sheep, goat, cattle, and water buffalo) species, and analyzed the expression of genes involved in arginine metabolism in response to stimulation with LPS. In rats, as in mice, LPS strongly induced Nos2, the arginine transporter Slc7a2, arginase 1 (Arg1), GTP cyclohydrolase (Gch1), and argininosuccinate synthase (Ass1). None of these responses was conserved across species. Only cattle and water buffalo showed substantial NOS2 induction. The species studied also differed in expression and regulation of arginase (ARG2, rather than ARG1), and amino acid transporters. Variation between species was associated with rapid promoter evolution. Differential induction of NOS2 and ARG2 between the ruminant species was associated with insertions of the Bov-A2 retrotransposon in the promoter region. Bov-A2 was shown to possess LPS-inducible enhancer activity in transfected RAW264.7 macrophages. Consistent with a function in innate immunity, NO production and arginine metabolism vary greatly between species and differences may contribute to pathogen host restriction.

SEROLOGICAL SURVEY OF TOXOPLASMOSIS, NEOSPOROSIS AND BRUCELLOSIS AMONG CATTLE HERDS IN OYO STATE, SOUTH-WESTERN NIGERIA

BACKGROUND

Several zoonotic diseases are known to constitute great impediment to livestock management and production worldwide, especially in developing countries where control measures are largely non-existent. This study sets out to investigate the occurrence of toxoplasmosis, neosporosis and brucellosis among cattle herds in Oyo State, southwest Nigeria.

MATERIALS AND METHODS

A cross-sectional survey to screen for antibodies to Toxoplasma gondii, Neospora caninum and Brucella abortus was conducted among 174 cattle in 17 herds. Sera obtained from the cattle were screened for antibodies to Toxoplasma gondii and Neospora caninum using enzyme-linked immunosorbent assay (ELISA) and for Brucella abortus antibodies using Rose Bengal test and Competitive Enzyme Linked Immunosorbent Assay (cELISA).

RESULTS

Overall, herd level prevalence of 52.9%, 23.5% and 23.5% as well as individual prevalence of 7.5%, 3.4% and 3.4% was obtained for toxoplasmosis, neosporosis and brucellosis, respectively. Antibodies to T. gondii, N. caninum and B. abortus were detected in 2 of the 17 herds, T. gondii and N. caninum in 4 herds, and T. gondii and B. abortus in 4 herds. Statistically significant association was only found between seropositivity to T. gondii antibodies and sex (p<0.05).

CONCLUSION

Our results showed that toxoplasmosis, neosporosis and brucellosis are prevalent among cattle herds screened in the study area. Considering the potential impact of these diseases on livestock management and production, extensive surveillance is necessary for development and implementation of effective control and prevention strategies.

Congenital Toxoplasmosis in Chronically Infected and Subsequently Challenged Ewes

This experiment studied congenital transmission in sheep experimentally infected with oocysts of Toxoplasma gondii and reinfected at one of three stages of pregnancy. Twenty ewes were experimentally infected with T. gondii strain ME49 (day 0). After the T. gondii infection became chronic (IFAT≤512), the ewes were allocated with rams for coverage. After the diagnosis of pregnancy, these ewes were allocated into four experimental groups (n = 5): I-reinfected with T. gondii on the 40^th day of gestation (DG); II-reinfected on DG 80; III-reinfected on DG 120; and IV-saline solution on DG 120 (not reinfected). Five ewes (IFAT<64) were kept as negative controls (uninfected, group V), therefore in groups I-III were infected prior to pregnancy and re-infected during pregnancy, group IV was only infected prior to pregnancy, and group V was not infected. Parasitism by T. gondii was investigated (histopathology, immunohistochemistry, mouse bioassay and PCR) in mothers and lambs tissue. All ewes produced lambs serologically positive for T. gondii. The results of the mouse bioassay, immunohistochemistry and PCR assays revealed the presence of T. gondii in all 20 sheep and their lambs. The congenital transmission of T. gondii was associated with fetal loss and abnormalities in persistently infected sheep and in ewes infected and subsequently reinfected by this protozoan. Therefore, congenital T. gondii infection was common when ewes were chronically infected prior to pregnancy, with or without reinfection during at various stages of gestation.

Factors associated with Toxoplasma gondii infection in confined farrow-to-finish pig herds in western France: an exploratory study in 60 herds

BACKGROUND

Infection by Toxoplasma gondii postnatally can occur after ingestion of contaminated meat or water (tissue cysts/oocysts). In Europe, percentage of meat borne infections is estimated between 30 and 63 %, out of which pork makes the most important source. The aim of this study was to (i) investigate the seroprevalence of T. gondii in intensive pig farms from western France; and (ii) identify the risk factors associated with seropositivity.

METHODS

Data were collected between November 2006 and February 2008 in 60 intensive farrow-to-finish farms, where sera were taken from 3595 fattening pigs, weaned and suckling piglets. Information about three classes of potential seropositivity risk factors were obtained through a questionnaire concerning: (i) breeding characteristics; (ii) farm management; and (iii) husbandry and hygiene. The modified agglutination test (MAT) was used for detection of specific anti T. gondii antibodies in pig sera, starting from 1/6 dilution.

RESULTS

The overall proportion of seropositive animals was 6.9 %, but the proportion of herds with at least one positive pig was 100 %. Multivariate logistic mixed model showed an increased seropositivity risk in weaned compared to suckling piglets, and a decreasing risk for mid-sized and large farms. The presence of a Danish entry facility, that clearly separates clean and dirty areas, had a protective effect on T. gondii seropositivity as well.

CONCLUSIONS

The observed proportion of herds with at least one T. gondii seropositive animal provides further evidence that even in confined conditions of pig breeding, infection occurs, and is common. The highest risk for acquiring T. gondii is at the end of weaning period. Smaller confined pig farms demonstrate higher T. gondii seropositivity levels. This study also showed that Danish entry on farm buildings provides effective protection against T. gondii.

Toxoplasma gondii infection in pork produced in France

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

Detection of Toxoplasma gondii in small ruminants in Chennai using PCR and modified direct agglutination test

A total of 193 sera samples, along with tissues (lung, heart, and brain) collected from 136 sheep and 57 goats from the Corporation slaughter house, Madras Veterinary College teaching hospital, and private mutton shops from Chennai were tested for Toxoplasma gondii. All the sera samples were tested using modified direct agglutination test. Of the 193 sera samples, 57 (29.5 %) had a minimum titre of 1:20, with 30.14 % (41/136) of sheep and 28.07 % (16/57) of goats being seropositive. Tissue samples from all 193 animals, when subjected to B1 based PCR to detect T. gondii DNA, showed 3.67 and 3.50 % to be positive in sheep and goats, respectively. In the present investigation B1 based PCR detected T. gondii in low numbers, possibly due to limitation of the sample size. The presence of T. gondii in tissues of sheep and goats slaughtered for human consumption in Chennai indicates the role of these food animals as potential sources of infection to human.

The utility of diversity profiling using Illumina 18S rRNA gene amplicon deep sequencing to detect and discriminate Toxoplasma gondii among the cyst-forming coccidia

Next-generation sequencing (NGS) has the capacity to screen a single DNA sample and detect pathogen DNA from thousands of host DNA sequence reads, making it a versatile and informative tool for investigation of pathogens in diseased animals. The technique is effective and labor saving in the initial identification of pathogens, and will complement conventional diagnostic tests to associate the candidate pathogen with a disease process. In this report, we investigated the utility of the diversity profiling NGS approach using Illumina small subunit ribosomal RNA (18S rRNA) gene amplicon deep sequencing to detect Toxoplasma gondii in previously confirmed cases of toxoplasmosis. We then tested the diagnostic approach with species-specific PCR genotyping, histopathology and immunohistochemistry of toxoplasmosis in a Risso's dolphin (Grampus griseus) to systematically characterise the disease and associate causality. We show that the Euk7A/Euk570R primer set targeting the V1-V3 hypervariable region of the 18S rRNA gene can be used as a species-specific assay for cyst-forming coccidia and discriminate T. gondii. Overall, the approach is cost-effective and improves diagnostic decision support by narrowing the differential diagnosis list with more certainty than was previously possible. Furthermore, it supplements the limitations of cryptic protozoan morphology and surpasses the need for species-specific PCR primer combinations.

Application of different techniques to detect Toxoplasma gondii in slaughtered sheep for human consumption

Abstract The aim of this study was to investigate occurrence of Toxoplasma gondii in sheep slaughtered in the state of Alagoas, Brazil, by means of different diagnosis techniques. Serum samples and tissues from 100 slaughtered sheep were used. To detect antibodies, the indirect immunofluorescence antibody test (IFAT) was used, and tissues from seropositive animals (cut-off ≥1:64) were submitted to Polymerase Chain Reaction (PCR) and immunohistochemistry (IHC). To assess the concordance between the direct techniques, the kappa test was used. In the IFAT, it was observed that 14% (14/100) of the ovine samples were serum-positive. In the PCR, 21.43% (3/14) of the animals were positive and in IHC, it was observed that 7.14% (1/14) were positively stained for T. gondii in cerebral tissue. Histopathologically, the predominant finding was the presence of mononuclear cell infiltrate in the heart and a perivascular cuff in the cerebrum and cerebellum. The concordance between the direct diagnosis techniques was moderate (k=0.44). Thus, it is important to use different direct techniques in diagnosing toxoplasmosis in naturally infected sheep.

Comparison of parasitological, immunological and molecular methods for evaluation of fecal samples of immunosuppressed rats experimentally infected with Strongyloides venezuelensis

Definitive diagnosis of strongyloidiasis in humans is typically achieved by detection of larvae in fecal samples. However, limitations on sensitivity of parasitological methods emphasize the need for more robust diagnostic methods. The aim of this study was to compare the diagnostic value of three methods: eggs per gram of feces (EPG), coproantigen detection by enzyme linked immunosorbent assay (ELISA), and DNA detection by conventional polymerase chain reaction (PCR). The assays were performed at 0 and 5, 8, 13, 21 and 39 days post-infection (dpi) using fecal samples from experimentally infected immunocompetent and immunosuppressed rats. In immunocompetent rats, eggs were detected in feces on days 5, 8 and 13 dpi; coproantigen detection and PCR amplification were successful at all post-infection time points (5, 8, 13, 21 and 39 dpi). In immunosuppressed rats, eggs were detected at 5, 8, 13 and 21; coproantigen detection and PCR amplification were successful at all post-infection time points. In conclusion, these results suggest that coproantigen detection and PCR may be more sensitive alternatives to traditional methods such as EPG for diagnosis of Strongyloides venezuelensis infection.

Predilection sites for Toxoplasma gondii in sheep tissues revealed by magnetic capture and real-time PCR detection

Undercooked lamb and mutton are common sources of Toxoplasma gondii infection for humans. A sequence specific magnetic capture technique in combination with quantitative real-time PCR targeting the 529 bp repeat element of T. gondii was used for estimation of the parasite burdens in various sheep tissues (n = 6) three months after peroral experimental inoculation with 10,000 T. gondii oocysts. Brain was the most frequently affected organ (positive in all 6 sheep) and showed the highest estimated parasite loads (0.5-30,913 parasites/g tissue). Lung samples were positive in three sheep, with load estimates of 36.3 to <1 parasite/g tissue. Heart tissue was positive in three sheep and kidney only in one animal with low parasite loads (<1 parasite/g tissue). Only few skeletal muscle samples in 2 animals showed positive results, with very low parasite burdens, while samples from further internal organs (i.e. liver and spleen) were negative in all animals. This study identified the brain as the most important predilection site and therefore the most appropriate tissue for T. gondii detection.

Vaccination of pigs with the S48 strain of Toxoplasma gondii--safer meat for human consumption

As clinical toxoplasmosis is not considered a problem in pigs, the main reason to implement a control strategy against Toxoplasma gondii (T. gondii) in this species is to reduce the establishment of T. gondii tissue cysts in pork, consequently reducing the risk of the parasite entering the human food chain. Consumption of T. gondii tissue cysts from raw or undercooked meat is one of the main sources of human infection, with infected pork being considered a high risk. This study incorporates a mouse bioassay with molecular detection of T. gondii DNA to study the effectiveness of vaccination (incomplete S48 strain) in its ability to reduce tissue cyst burden in pigs, following oocyst (M4 strain) challenge. Results from the mouse bioassay show that 100% of mice which had received porcine tissues from vaccinated and challenged pigs survived compared with 51.1% of mice which received tissues from non-vaccinated and challenged pigs. The presence (or absence) of T. gondii DNA from individual mouse brains also confirmed these results. This indicates a reduction in viable T. gondii tissue cysts within tissues from pigs which have been previously vaccinated with the S48 strain. In addition, the study demonstrated that the main predilection sites for the parasite were found to be brain and highly vascular muscles (such as tongue, diaphragm, heart and masseter) of pigs, while meat cuts used as human food such as chop, loin, left tricep and left semitendinosus, had a lower burden of T. gondii tissue cysts. These promising results highlight the potential of S48 strain tachyzoites for reducing the number of T. gondii tissues cysts in pork and thus improving food safety.

Seroprevalence of Toxoplasma gondii in Dairy Cattle with Reproductive Problems in Sudan

Toxoplasmosis, caused by Toxoplasma gondii, is one of the most common parasitic infections of humans and other warm-blooded animals in most parts of the world. The disease is common among sheep and goats and it is recognized as one of the major causes of reproductive failure in these animals. Cattle, on the other hand, can be infected, but abortion or perinatal mortality has not been recorded. This survey was carried out to study the prevalence of this disease in cattle in Khartoum and Gazira States (Sudan). 181 sera samples collected from dairy cattle with reproductive problems were assayed for antibodies to T. gondii by ELISA. The prevalence rate of T. gondii antibodies in cattle at herd level was 44.8% (13/29). Herd level infection rates were 50% and 33.3% in Khartoum and Gazira States, respectively. The overall prevalence of T. gondii at individual level in both states was 13.3% (24/181). The prevalence was 12.7% (17/134), was 14.9% (7/47) in Khartoum and Gazira State, respectively. There was significantly higher (P < 0.05) prevalence of T. gondii antibodies in the age group less than one year old (36.4%) than in other age groups and in males (30.8%) than in females (11.9%) while no significant relationship was discerned regarding breed, location, season, or signs of reproductive disease.

Seroprevalence and risk factors of toxoplasmosis in cattle from extensive and semi-intensive rearing systems at Zona da Mata, Minas Gerais state, Southern Brazil

BACKGROUND

Concerning the infection of humans by T. gondii, limited efforts have been directed to the elucidation of the role of horizontal transmission between hosts. One of the main routes of transmission from animals to humans occurs through the ingestion of raw or insufficiently cooked meat. However, even though the detection of T. gondii in meat constitutes an important short-term measure, control strategies can only be accomplished by a deeper understanding of the epidemiology of toxoplasmosis. The present study aimed to investigate the seroprevalence of toxoplasmosis in cattle from Zona da Mata, Minas Gerais, Brazil, and to identify associated risk factors, through an epidemiological investigation.

METHODS

The animals studied (Bos indicus, breed Nelore or Gir) were reared in the Zona da Mata micro-region and killed at a commercial slaughterhouse at Juiz de Fora, Minas Gerais state. The animals came from 53 cattle farms with extensive (predominantly pasture feeding management) or semi-intensive (food management based on grazing, salt mineral and feed supplementation) rearing systems. Blood samples were collected from 1200 animals, and assigned to Indirect Fluorescent Antibody Test.

RESULTS

When analyzing IgG anti-T.gondii we found an overall seroprevalence of 2.68%. In Brazil prevalences vary from 1.03% to 60%. Although in the present study, the seroprevalence per animal is considered low compared to those observed in other studies, we found out that of the 53 farms analyzed, 17 (34.69%) had one or more positive cattle. It is a considerable percentage, suggesting that the infection is well distributed through the Zona da Mata region. The results of the epidemiological investigation showed that the main risk factors of Toxoplasma gondii infection are related to animal management and to the definive host. There was a relationship between the number of seropositive cattle and the presence and number of resident cats, presence and number of stray cats, presence of cats walking freely, rat control by using cats and feed storage.

CONCLUSION

These results may contribute to the development of preventive strategies in Brazil and other developing countries were extensive and semi-intensive cattle rearing systems are very widespread and the efforts to control this important zoonotic disease have attained little success.

Evaluation of a commercial ELISA kit for detection of antibodies against Toxoplasma gondii in serum, plasma and meat juice from experimentally and naturally infected sheep

Background

Toxoplasmosis is one of the most common food borne zoonoses worldwide, and can be a serious life-threatening disease in the congenitally infected fetus and in immunosupressed patients. Among food animals, sheep along with goats and pigs possess the highest incidence of T. gondii cysts in meat, and play a major role as a source of human infection.

Methods

In this study, a new commercial ELISA kit (PrioCHECK® Toxoplasma Ab SR, Prionics Schlieren-Zurich, Switzerland) for the detection of anti-T. gondii antibodies in serum, plasma and meat juice of sheep, was evaluated by comparing it with the indirect fluorescent antibody test (IFAT), indirect haemagglutination test (IHA) and real-time PCR, on samples from experimentally inoculated and naturally exposed sheep.

Results

The commercial ELISA detected the infection status in 50% and 100% of sheep orally inoculated with 10,000 T. gondii oocysts (n = 6), from two or three weeks post infection (wpi), respectively, both on serum and plasma samples. Meat juice from all experimentally inoculated sheep collected at slaughter (12 wpi) showed positive ELISA values. In naturally exposed sheep (n = 396), the ELISA showed a very good agreement with IFAT (kappa = 0.91-1.0) and IHA (kappa = 0.96-1.0) performed on serum; and a positive correlation was observed between ELISA values and IFAT titers. By a Receiver Operating Characteristics (ROC) curve analysis, the commercial ELISA had relative sensitivities between 93.33% and 100%, and relative specificities between 96.87% and 100% respect to IFAT and IHA, depending on the considered cut-off value and animal groups tested. Furthermore, the ELISA correctly recognized all animals reacting positive in real-time PCR. The ELISA results on meat juice agreed with those on serum samples in all experimentally inoculated animals, and in 94 out of 96 (97.9%) naturally exposed sheep, when meat juice was tested at a 1:10 dilution.

Conclusion

The commercial ELISA kit evaluated in this study could represent a valuable tool to improve the surveillance and reporting system for T. gondii in sheep populations at the farm level or for diagnosis at the slaughterhouse, contributing to the control of this widespread zoonosis.

Toxoplasma gondii in wild and domestic animals from New Caledonia

Samples (serum or meat juice) collected from 205 animals in New Caledonia in April 2009 were tested for antibodies against Toxoplasma gondii by ELISA using the multi-species ID Screen^® Toxoplasmosis Indirect kit (IDVET, Montpellier). Antibodies to T. gondii were detected in 2% (1/49) of the pigs, in 3.3% (1/30) of the cattle, in 13.8% (4/29) of Rusa deers, in 16% (4/25) of the horses, in 32.8% (21/64) of the dogs, and in 50% (4/8) of cats. Statistically, no significant difference was observed between T. gondii seroprevalence and age or sex. No survey on the prevalence of T. gondii in animals has ever been conducted in New Caledonia and this is the first serological evidence of T. gondii in Rusa deer (Cervus timorensis russa). These results indicate an important circulation of T. gondii exists in the animal populations of New Caledonia. In view of humans being exposed, it is advisable to insist on sanitary education and on respect for good hygienic and food practice.

Increased Toxoplasma gondii positivity relative to age in 125 Scottish sheep flocks; evidence of frequent acquired infection

Toxoplasma gondii seroprevalence was determined in 3333 sheep sera from 125 distinct sheep flocks in Scotland, with the majority of flocks being represented by 27 samples, which were collected between July 2006 and August 2008. The selected farms give a representative sample of 14,400 sheep holdings identified in the Scottish Government census data from 2004. Overall T. gondii seroprevalence, at individual sheep level, was determined to be 56.6%; each flock tested, had at least a single positive animal and in four flocks all ewes tested positive. The seroprevalence of sheep increased from 37.7% in one year old stock to 73.8% in ewes that were older than six years, showing that acquired infections during the life of the animals is frequent and that environmental contamination by T. gondii oocysts must be significant. The median within-flock seroprevalence varied significantly across Scotland, with the lowest seroprevalence of 42.3% in the South and the highest seroprevalence of 69.2% in the far North of Scotland and the Scottish Islands, while the central part of Scotland had a seroprevalence of 57.7%. This distribution disequilibrium may be due to the spread and survival of oocysts on pasture and lambing areas. A questionnaire accompanying sampling of flocks identified farms that used Toxovax®, a commercial vaccine that protects sheep from abortion due to T. gondii infection. Only 24.7% of farmers used the vaccine and the vaccine did not significantly affect the within flock seroprevalence for T. gondii. The implications for food safety and human infection are discussed.

Distribution of Lesions in Fetal Brains Following Experimental Infection of Pregnant Sheep With Toxoplasma gondii

Six ovine fetal brains were harvested 33 to 35 days postchallenge from 5 ewes, each of which was given 3000 Toxoplasma gondii oocysts on day 90 of pregnancy. Histopathologic examination of transverse sections taken at 13 levels in the fetal brains revealed the presence of toxoplasmosis-related lesions in all 6 brains. However, lesions were not randomly distributed ( P = .007); they were most numerous at the level of the optic tract, the rostral margin of the pons, and 4 mm caudal to the ansate sulcus and were absent in all sections at the level of the caudal cerebellum. Lesion distribution may be due to hemodynamic factors, differences in the expression of endothelial surface receptor molecules at the level of the blood-brain barrier, or the presence of localized permissive/inhibitory factors within the brain. The results have implications for the selection of areas of brain from aborted ovine fetuses to be examined histopathologically for laboratory diagnosis.

Development of lesions and tissue distribution of parasite in lambs orally infected with sporulated oocysts of Toxoplasma gondii

The host-pathogen interaction is as a key feature during the formation of tissue cysts of Toxoplasma gondii within intermediate hosts. In this study, we investigated whether oral infection of lambs with T. gondii oocysts may be used as an experimental model in sheep to study this interaction, with the main objective being to detect the presence and distribution of lesions and parasite within different organs at different time points after oral infection. Lambs were infected with 5 × 10(3) and 5 × 10(5) sporulated T. gondii oocysts and culled at 2, 3, 5 and 6 weeks post-infection (WPI). During the infection, rectal temperature of the animals and serological antibodies against T. gondii were monitored. The presence of inflammatory lesions and parasite were evaluated through histological and immunohistochemical methods at different organs (brain, liver, lung, heart and lymph nodes). The lambs showed no clinical signs other than fever, and lesions appeared mainly in the brain, characterized by glial foci and perivascular cuffs, and in the heart, denoted by foci of interstitial myositis. Tissue cysts and tachyzoite-like structures were observed at all time points studied in the brain, where together with the glial foci they appeared mainly in the cerebral cortex of the forebrain and in the midbrain, but also in the heart, lung and lymph nodes. This study shows that oral infection with sporulated oocysts in lambs may provide a model for investigating the host-parasite interaction in situ during the development of tissue cysts.