Characterization of Toxoplasma gondii Isolates in Free-Range Chickens From Portugal

Molecular detection of Toxoplasma gondii in Tunisian free-range chicken meat and their offal

Free-range chickens are infected by Toxoplasma gondii (T. gondii) mainly when they pick-up their food from the ground. The present study was performed to estimate the molecular prevalence of T. gondii in free-range chicken meat (breast and thigh muscles) and their offal (heart and gizzard). The molecular characterization and the phylogeny of T. gondii amplicons were also investigated. Two PCRs were compared, the first targeting B1 gene and a nested PCR targeting the internal transcribed spacer ITS-1 gene. Among the 60 tested birds, 47 free-range chickens had at least one positive PCR, i.e., a prevalence of 78.3% (95% CI: 67.9-88.7%). The prevalence of T. gondii infection in muscles and organs analyzed by specific PCR targeting B1 gene (43.3%; 95% CI: 37-49.6%) was significantly higher than those analyzed for ITS-1 gene detection (15%; 95%CI: 10.4-19.5%) (p < 0.001). Heart samples had the highest T. gondii infection prevalence, as well as targeting either B1 gene (48.3%; 95% CI: 35.6-60.9%) or ITS-1 gene (21.6%; 95% CI: 11.2-32%). The present study showed that the consumption of undercooked free-range chicken meat represents a high risk for seronegative pregnant women. Our phylogenetic analysis revealed homology with wild and domestic birds and domestic mammals and a large geographic distribution.

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

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

Epidemiologic significance of Toxoplasma gondii infections in chickens (Gallus domesticus): the past decade

Toxoplasma gondii infections are common in humans and animals worldwide. Domestic free-range chickens (Gallus domesticus) are excellent sentinels of environmental contamination with T. gondii oocysts because they feed on the ground. Chickens can be easily infected with T. gondii; however, clinical toxoplasmosis is rare in these hosts. Chickens are comparatively inexpensive and thus are good sentinel animals for T. gondii infections on the farms. Here, the authors reviewed prevalence, the persistence of infection, clinical disease, epidemiology and genetic diversity of T. gondii strains isolated from chickens worldwide for the past decade. Data on phenotypic and molecular characteristics of 794 viable T. gondii strains from chickens are discussed, including new data on T. gondii isolates from chickens in Brazil. This paper will be of interest to biologists, epidemiologists, veterinarians and parasitologists.

Toxoplasma gondii genotypes circulating in domestic pigs in Serbia

Consumption of undercooked or raw pork is considered a significant risk factor for human infection with Toxoplasma gondii. In this study, we investigated the genetic structure of 18 T. gondii strains obtained from slaughter pigs from Northern Serbia (mainly Vojvodina). The examined samples originated from eight pigs from large commercial farms, six backyard pigs and four free-range Mangalica pigs, all found to be positive for either viable T. gondii or T. gondii DNA. Genotyping was attempted from both pig tissues and mouse brains from the bio-assays using a multiplex multilocus nested polymerase chain reaction-restriction fragment length polymorphism (Mn-PCR-RFLP) method with seven markers (GRA6, alt. SAG2, PK-1, BTUB, C22-8, CS3 and Apico). Identification was achieved for nine T. gondii isolates. Seven isolates were classified as type II and two as type III. These results are consistent with previous studies on animal isolates from Serbia as well as with previous reports that type III is more frequently found in samples from Southern Europe than in those from other parts of the continent.

Birds and poultries toxoplasmosis in Iran: A systematic review and meta-analysis

OBJECTIVE

To evaluate the overall prevalence of Toxoplasma gondii infection among birds and poultries in Iran.

METHODS

Data were systematically collected from 1983 to 2016 in Iran on the following electronic databases: PubMed, Google Scholar, Science Direct, Scopus, Web of Science, Magiran, Irandoc, IranMedex, and Scientific Information Database. Additionally, the abstracts of national scientific congresses and dissertations were included.

RESULTS

A total of 20 articles in the field of birds and poultries toxoplasmosis, totally examining 4563 cases with 754 positive results reporting the overall prevalence of infection from all parts of Iran could fulfill our eligibility criteria. The overall estimated prevalence included in chicken 20% (95% CI: 3%-38%) in chicken, pigeons 8% (95% CI: -17%-33%) and in sparrows 15% (95% CI: -25%-54%).

CONCLUSION

Although there is a lack in data about poultries and birds toxoplasmosis in Iran, our meta-analysis revealed that infection rate is high among birds and poultries in Iran. More studies are needed to manage controlling programs and prevention strategies among poultries in Iran.

The first isolation and molecular characterization of Toxoplasma gondii from horses in Serbia

Background

Consumption of undercooked or insufficiently cured meat is a major risk factor for human infection with Toxoplasma gondii. Although horsemeat is typically consumed rare or undercooked, information on the risk of T. gondii from infected horse meat to humans is scarce. Here, we present the results of a study to determine the presence of T. gondii infection in slaughter horses in Serbia, and to attempt to isolate viable parasites.

Methods

The study included horses from all regions of Serbia slaughtered at two abattoirs between June 2013 and June 2015. Blood sera were tested for the presence of specific IgG T. gondii antibodies by the modified agglutination test (MAT), and samples of trypsin-digested heart tissue were bioassayed in mice. Cyst-positive mouse brain homogenates were subjected to DNA extraction and T. gondii strains were genotyped using 15 microsatellite markers (MS).

Results

A total of 105 slaughter horses were sampled. At the 1:6 cut-off 48.6% of the examined horses were seropositive, with the highest titre being 1:400. Viable parasites were isolated from two grade type mares; both parasite isolates (RS-Eq39 and RS-Eq40) were T. gondii type III, and both displayed an increased lethality for mice with successive passages. These are the first cases of isolation of T. gondii from horses in Serbia. When compared with a worldwide collection of 61 type III and type III-like strains, isolate RS-Eq39 showed a combination of MS lengths similar to a strain isolated from a duck in Iran, and isolate RS-Eq40 was identical in all markers to three strains isolated from a goat from Gabon, a sheep from France and a pig from Portugal. Interestingly, the source horses were one seronegative and one weakly seropositive.

Conclusions

The isolation of viable T. gondii parasites from slaughter horses points to horsemeat as a potential source of human infection, but the fact that viable parasites were isolated from horses with only a serological trace of T. gondii infection presents further evidence that serology may not be adequate to assess the risk of toxoplasmosis from horsemeat consumption. Presence of T. gondii type III in Serbia sheds more light into the potential origin of this archetypal lineage in Europe.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2104-x) contains supplementary material, which is available to authorized users.

Predominance of atypical genotypes of Toxoplasma gondii in free-roaming chickens in St. Kitts, West Indies

Background

Toxoplasma gondii is a worldwide protozoan parasite of felids which can infect almost all warm-blooded animals, including humans. Free-roaming chickens are good indicators of environmental contamination with T. gondii oocysts because they feed from the ground. Previous research has demonstrated a high seroprevalence of T. gondii in domestic animals on St. Kitts but little is known about the genotypes circulating in the environment.

Methods

Hearts and brains from 81 free-roaming chickens in St. Kitts were digested and inoculated into 243 Swiss Webster mice in a bioassay. DNA was extracted from digested chicken tissues and the brains of all mice, and screened for T. gondii. Positive samples were genotyped using restriction fragment length polymorphism. Chicken sera were also screened for T. gondii antibodies using a modified agglutination test (MAT).

Results

Overall, 41% (33 out of 81) of chickens were positive for T. gondii either by serology and/or by PCR. Antibodies to T. gondii were detected by MAT in 32% (26 out of 81) of chickens, and T. gondii DNA was detected in mouse brains representing 26% (21 out of 81) of chickens. Genotyping of 21 DNA isolates, using polymorphisms at 10 loci, including SAG1, SAG2 (5′-3′ SAG2 and alt.SAG2), SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico, revealed that 7 were ToxoDB genotype #141, 6 were #1 (Type II), 3 were #13, 3 were #265, one was #264 and one was #2 (Type III). Genotypes #13 and #141 appear to be more virulent.

Conclusions

The results of this study highlight the greater genetic diversity of T. gondii circulating in the Caribbean region, with potentially different degrees of virulence to humans.

Validation of the modified agglutination test for the detection of Toxoplasma gondii in free-range chickens by using cat and mouse bioassay

The modified agglutination test (MAT) is one of the most commonly used tests for the detection of antibodies to Toxoplasma gondii in animal and human sera. The objective of the present study was to evaluate the diagnostic accuracy of the MAT and bioassay in free-range/backyard (FR) chickens (Gallus domesticus). Previously-published T. gondii test results from 2066 chickens from 19 countries were compiled for the present study. The frequency of isolation of T. gondii increased for MAT titres between 1:5 and 1:160, and ranged from 61 to 75% for antibody titres of 1:160, 1:320, and ⩾1:640. Twenty-three cats fed pooled hearts from a total of 802 FR seronegative (MAT, <1:5) chickens from several countries did not excrete oocysts, indicating a high negative predictive value of MAT because FR chickens would have been exposed to many microbes; cats are the most sensitive indicators of T. gondii infection in tissues and can excrete millions of oocysts after ingesting even a few bradyzoites. Of the 29 cats in this study, six cats, fed hearts pooled from 15–122 FR chickens, excreted oocysts; but these identifications were likely related to misidentification or prozone. Results of the present study support the validity of MAT for the detection of T. gondii infection in chickens.

Pathogenicity of Five Strains of Toxoplasma gondii from Different Animals to Chickens

Toxoplasma gondii is a protozoan parasite with a broad range of intermediate hosts. Chickens as important food-producing animals can also serve as intermediate hosts. To date, experimental studies on the pathogenicity of T. gondii in broiler chickens were rarely reported. The objective of the present study was to compare the pathogenicity of 5 different T. gondii strains (RH, CN, JS, CAT2, and CAT3) from various host species origin in 10-day-old chickens. Each group of chickens was infected intraperitoneally with 5×10⁸, 1×10⁸, 1×10⁷, and 1×10⁶ tachyzoites of the 5 strains, respectively. The negative control group was mockly inoculated with PBS alone. After infection, clinical symptoms and rectal temperatures of all the chickens were checked daily. Dead chickens during acute phage of the infection were checked for T. gondii tachyzoites by microscope, while living cases were checked for T. gondii infection at day 53 post-inoculation (PI) by PCR method. Histopathological sections were used to observe the pathological changes in the dead chickens and the living animals at day 53 PI. No significant differences were found in survival periods, histopathological findings, and clinical symptoms among the chickens infected with the RH, CN, CAT2, and CAT3 strains. Histopathological findings and clinical symptoms of the JS (chicken origin) group were similar to the others. However, average survival times of infected chickens of the JS group inoculated with 5×10⁸ and 1×10⁸ tachyzoites were 30.0 and 188.4 hr, respectively, significantly shorter than those of the other 4 mammalian isolates. Chickens exposed to 10⁸ of T. gondii tachyzoites and higher showed acute signs of toxoplasmosis, and the lesions were relatively more severe than those exposed to lower doses. The results indicated that the pathogenicity of JS strain was comparatively stronger to the chicken, and the pathogenicity was dose-dependent.

Genetic characterization of Toxoplasma gondii isolates from Portugal, Austria and Israel reveals higher genetic variability within the type II lineage

This study compared genetic diversity of Toxoplasma gondii isolates from Portugal, Austria and Israel. For this, we genotyped 90 T. gondii isolates (16 from Portugal, 67 from Austria and 7 from Israel) using 10 nested PCR-restriction length polymorphism (RFLP) genetic markers and 15 microsatellite (MS) markers. By PCR-RFLP typing, 7 isolates from Portugal chickens were identified as type II (ToxoDB #1 or #3), 4 were type III (ToxoDB #2) and the remaining 4 isolates have unique genotype pattern were designated as ToxoDB #254. One mouse virulent isolate from a bovine fetus (Bos taurus) in Portugal was type I (ToxoDB #10) at all loci and designated as TgCowPr1. All 67 isolates from Austria and 7 from Israel were type II (ToxoDB #1 or #3). By MS typing, many additional genetic variations were revealed among the type II and type III isolates. Phylogenetic analysis showed that isolates from the same geographical locations tend to cluster together, and there is little overlapping of genotypes among different locations. This study demonstrated that the MS markers can provide higher discriminatory power to reveal association of genotypes with geographical locations. Future studies of the type II strains in Europe by these MS markers will be useful to reveal transmission patterns of the parasite.

Epidemiological review of Toxoplasma gondii infection in humans and animals in Portugal

Toxoplasmosis is a worldwide zoonosis. However, data from Portugal are limited and a considerable part of the literature is in Portuguese. Currently, the rate of congenital infection in Portugal is unknown, and almost nothing is known of sequelae of congenital toxoplasmosis. There is no recent general population-based serological survey of Toxoplasma gondii in humans in Portugal. In addition, there is little information on genetic characteristics of T. gondii in animals and humans. In the present paper, we review prevalence, clinical spectrum and epidemiology of T. gondii in humans and animals in Portugal. This knowledge should be useful to biologists, public health workers, physicians and veterinarians.

Isolation and molecular characterization of Toxoplasma gondii isolated from pigeons and stray cats in Lisbon, Portugal

Cats and pigeons are important factors in the epidemiology of Toxoplasma gondii as felids are the only definitive hosts that can excrete environmentally resistant oocysts, and pigeons share the same places of cats and humans constituting a good model and indicator of the ground field contamination. We aimed to study the virulence and genotypes of T. gondii isolated from pigeons and stray cats in Lisbon, Portugal. Fresh samples of brain from 41 pigeons and 164 cats revealing antibodies to T. gondii were inoculated in mice. Three isolates (one isolated from a cat and two isolated from pigeons) were virulent in the mouse model. Sag2-based genotyping of T. gondii was achieved in 70.7% (29/41) of samples isolated from pigeons (26 samples were type II, two were type III, and one strain was type I). From the cat brain samples, 50% (82/164) yielded Sag2 positive results, where 72 belonged to genotype II and 10 were no type III (it was not possible to discriminate between type I and II). Further genotyping was obtained by multiplex PCR of 5 microsatellites (TUB2, TgM-A, W35, B17, B18), allowing the identification of two recombinant strains that had been previously identified as type II by Sag2 amplification (one isolated from cat brain and the other from pigeon brain). This is the first evidence of recombinant strains circulating in Portugal and the first report of T. gondii genotyping from cats in this country. This study also highlights the importance of environmental contamination in the synanthropic cycle constituting a potential source of human infection.

Pathogenicity of two Toxoplasma gondii strains in chickens of different ages infected via intraperitoneal injection

This experiment was conducted to investigate the pathogenicity of Toxoplasma gondii in broilers of different ages. Chickens at the ages of 7, 14, 21 and 28 days were injected intraperitoneally with 1 × 10(8) tachyzoites of RH and JS strains of T. gondii, respectively. The clinical signs and death of chickens were recorded daily post inoculation. Serum samples were collected at days 0, 4, 11, 18, 25, 32, 39, 46 and 53 post infection to screen T. gondii circulating antigens (TCA) and T. gondii circulating antibodies (TCAb). The results showed that T. gondii infection of 7-day-old chickens caused death, even though the mortality rate of the JS strain (100%) was significantly higher than that of the RH strain (70%). Chickens at 14 days old showed only mild clinical signs, but no death. Neither clinical signs nor death were recorded in 21-day-old and 28-day-old chickens. TCA and TCAb became positive at days 4 and 11, respectively. Both the TCA and the TCAb of groups 21 days old (RH strain) and 28 days old (both RH and JS strains) decreased to a negative level earlier than the other experimental groups. Specific T. gondii DNA was detected by polymerase chain reaction in chickens that survived in the 7-day-old group (RH strain) and in all infected chickens of groups 14 days old and 21 days old injected with both strains. In the groups injected at 28 days old, three samples (RH strain) and one sample (JS strain) were found negative. The results indicated that the age of the chicken was an important factor affecting the pathogenicity of T. gondii and that these two strains of T. gondii displayed different virulence for chickens.

Seroepidemiology of Toxoplasma gondii infection in women from the North of Portugal in their childbearing years

Seroprevalence of Toxoplasma gondii infection and associated risk factors were investigated in 401 women of childbearing age from the North of Portugal. Of the 98 (24·4%) seropositive women, 92 (93·9%) only had immunoglobulin (Ig)G, two (2·0%) only had IgM, and four (4·1%) others had both IgG and IgM. Risk factors for T. gondii infection in women were: engaging in soil-related activities without gloves [odds ratio (OR) 8·4], consumption of unwashed raw vegetables or fruit (OR 7·6), and consumption of smoked or cured (non-cooked) processed pork products (OR 2·5). Most women of childbearing age from the North Portugal are susceptible to primary infection with T. gondii and, therefore, the risk of congenital toxoplasmosis remains high.

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.

Infecção toxoplásmica causa hipertrofia da parede do cólon de frangos

Estudaram-se os efeitos da infecção toxoplásmica sobre a morfometria da parede intestinal, a distribuição de fibras colágenas e a dinâmica de mucinas secretadas no cólon de frangos. Foram utilizados 16 frangos machos de linhagem comercial, com 26 dias de idade. As aves foram distribuídas, aleatoriamente, em três grupos (G). As do G1 não receberam inóculo e se caracterizaram como grupo-controle; nas do G2, foram inoculados cistos teciduais da cepa ME49 de Toxoplasma gondii; e nos G3, oocistos da cepa M7741 de T. gondii. Após 60 dias da inoculação, os animais foram sacrificados para coleta do cólon, o qual foi submetido à rotina de processamento histológico. Em G2 e G3, observou-se hipertrofia da parede do cólon, contudo não houve alteração na proporção do número de células caliciformes e de enterócitos presentes no epitélio intestinal.

Self-mating in the definitive host potentiates clonal outbreaks of the apicomplexan parasites Sarcocystis neurona and Toxoplasma gondii

Tissue-encysting coccidia, including Toxoplasma gondii and Sarcocystis neurona, are heterogamous parasites with sexual and asexual life stages in definitive and intermediate hosts, respectively. During its sexual life stage, T. gondii reproduces either by genetic out-crossing or via clonal amplification of a single strain through self-mating. Out-crossing has been experimentally verified as a potent mechanism capable of producing offspring possessing a range of adaptive and virulence potentials. In contrast, selfing and other life history traits, such as asexual expansion of tissue-cysts by oral transmission among intermediate hosts, have been proposed to explain the genetic basis for the clonal population structure of T. gondii. In this study, we investigated the contributing roles self-mating and sexual recombination play in nature to maintain clonal population structures and produce or expand parasite clones capable of causing disease epidemics for two tissue encysting parasites. We applied high-resolution genotyping against strains isolated from a T. gondii waterborne outbreak that caused symptomatic disease in 155 immune-competent people in Brazil and a S. neurona outbreak that resulted in a mass mortality event in Southern sea otters. In both cases, a single, genetically distinct clone was found infecting outbreak-exposed individuals. Furthermore, the T. gondii outbreak clone was one of several apparently recombinant progeny recovered from the local environment. Since oocysts or sporocysts were the infectious form implicated in each outbreak, the expansion of the epidemic clone can be explained by self-mating. The results also show that out-crossing preceded selfing to produce the virulent T. gondii clone. For the tissue encysting coccidia, self-mating exists as a key adaptation potentiating the epidemic expansion and transmission of newly emerged parasite clones that can profoundly shape parasite population genetic structures or cause devastating disease outbreaks.

The parasites Toxoplasma gondii and Sarcocystis neurona have lifecycles that include a sexual stage in a definitive host and an asexual stage in intermediate hosts. For T. gondii, laboratory studies have demonstrated that the sexual stage can serve the dual purpose of producing new, virulent genotypes through recombination and promoting expansion of single clones via self-mating. Self-mating and other life history traits of T. gondii, including transmission of asexual stages among intermediate hosts, are assumed to account for the clonal population genetic structure of this organism. However, the relative contributions of sexual recombination and self-mating verses other life history traits in causing disease outbreaks or in shaping Toxoplasma's population genetic structure have not been verified in nature, nor have these traits been extensively examined in related parasites. To address this knowledge gap, we conducted population genetic analyses on T. gondii and S. neurona strains isolated from naturally occurring outbreaks affecting humans and sea otters, respectively. Our results identify self-mating as a key trait potentiating disease outbreaks through the rapid amplification of a single clone into millions of infectious units. Selfing is likely a key adaptation for enhancing transmission of recently emerged, recombinant clones and reshaping population genetic structures among the tissue-cyst coccidia.

Serotyping of naturally Toxoplasma gondii infected meat-producing animals

Serotyping was previously described as a promising method for typing strains of Toxoplasma gondii. The majority of precedent studies utilized serum samples collected from human patients with different T. gondii-associated pathologies. The aim of this work was to study the applicability of the same procedure for serotyping naturally infected meat-producing animals. An ELISA test based on GRA6 and GRA7 C-terminal polymorphic peptides was used. Peptide GRA6II has polymorphisms specific for the archetypal strains type II, GRA6I/III for strains type I and III, GRA7I for strains type I and GRA7III for strains type III. As reference material, and to validate this approach, serum samples from eleven free-range chickens and fifteen pigs used for Toxoplasma genotypes isolation were selected. These strains integrate the Biological Resource Centre (BRC) ToxoBS Bank. Three serum samples from chickens and two from pigs had serotyping results in agreement with genotyping. Thirty-five serum samples from chickens, twenty-nine from pigs and fifty from sheep, seropositive for T. gondii, from which no isolate was obtained, were also serotyped. Serotype III appeared significantly more frequent among sheep. Our results show that serotyping still need refinement, but may become a valuable tool for typing Toxoplasma strains from animal origin.

Toxoplasma gondii infections in chickens (Gallus domesticus): prevalence, clinical disease, diagnosis and public health significance

Chickens are considered one of the most important hosts in the epidemiology of Toxoplasma gondii infection because they are an efficient source of infection for cats that excrete the environmentally resistant oocysts and because humans may become infected with this parasite after eating undercooked infected chicken meat. The objective of this study is to review worldwide prevalence of T. gondii infection in chickens and to assess the role of infected chickens in the epidemiology of toxoplasmosis in humans. A very high prevalence of the parasite was found in chickens raised in backyards (up to 100%) and free-range organic (30-50%) establishments.

Direct high-resolution genotyping of Toxoplasma gondii in arctic foxes (Vulpes lagopus) in the remote arctic Svalbard archipelago reveals widespread clonal Type II lineage

Characterization of Toxoplasma gondii genotypes in hosts living in remote, isolated regions is important for elucidating the population structure and transmission mode of this parasite. Herein, we report the results of direct genotyping of T. gondii in brain tissue of arctic foxes (Vulpes lagopus) from the remote, virtually cat-free, high arctic islands of Svalbard. DNA extracts from brains of 167 seropositive arctic foxes (including four cases of fatal toxoplasmosis) and 11 seronegative arctic foxes were genotyped at 10 loci (SAG1, SAG2, SAG3, BTUB, GRA6, L358, c22-8, c29-2, PK1, and Apico) using the polymerase chain reaction-restriction fragment length polymorphism method. Of the 167 samples from seropositive foxes (including toxoplasmosis cases), 31 were genotyped at all 10 loci and 24 were genotyped at four to nine loci. To ensure confidence in T. gondii strain genotyping, samples for which less than four loci were genotyped were not considered positive. None of the 11 samples from seronegative foxes was positive for the 10 markers. Of the 55 samples that genotyped positively, 46 were of the Type II strain, 7 were of the Type III strain, and 2 were of atypical T. gondii strains. Five representative samples of the three genotypes were sequenced at loci SAG2, SAG3, GRA6, PK1, and UPRT-1. The DNA sequences confirmed the genotyping results. This study shows that the archetype Type II T. gondii strain, which is most widely distributed in North America and Europe, also predominates in arctic foxes on the Svalbard archipelago. This suggests that the T. gondii at this location originate from continental Europe and that transmission may be mediated by migrating birds. This study highlights the significance of long-distance transport of T. gondii and demonstrates that high-resolution genotyping protocols are useful for direct genetic studies of T. gondii when isolation of live parasites is infeasible.

Use of GRA6-derived synthetic polymorphic peptides in an immunoenzymatic assay to serotype Toxoplasma gondii in human serum samples collected from three continents

Serotyping is a simple typing method that consists of an immunoenzymatic assay (enzyme-linked immunosorbent assay [ELISA]) using synthetic polymorphic peptides derived from Toxoplasma gondii antigens. We developed a new ELISA based on GRA6 C-terminal polymorphic peptides. Serum samples from 41 human infections due to 23 archetypal (type I, II, or III) and 18 nonarchetypal strains were selected in order to validate this approach. For 20 out of the 23 archetypal infections, there was a clear correlation between microsatellite genotype and GRA6 serotyping. All infections due to nonarchetypal strains were misclassified as archetypal strain infections. The GRA6 C-terminal peptides from these strains were analyzed to explain this misclassification. A second group of 455 patients with acute and chronic toxoplasmosis due to unknown genotypes from different European, African, and Latin American countries were included in this study, and the strain type predicted by this method. The results suggest that serotyping is a promising method for typing strains, although limitations exist for African and South American strains as a consequence of higher peptide polymorphism. Other peptides from different markers must be studied in order to discriminate archetypal from nonarchetypal strains.

Epidemiological and genetic characterization of Toxoplasma gondii in urban pigeons from the area of Lisbon (Portugal)

Circumstantial evidence suggests that birds may be a good indicator of soil contamination, since they feed from the ground. Therefore a study was conducted to assess the prevalence of Toxoplasma gondii in urban pigeons (Columba livia) from different areas of the city of Lisbon and to genetically characterize T. gondii strains isolated from infected animals, in order to assess circulating genotypes. Sera from 695 pigeons captured at 33 different localities of the city of Lisbon were assayed by the direct agglutination test (DAT) showing a 4.6% prevalence. One third of flocks sampled revealed to be infected with T. gondii, with prevalence ranging between 5% and 62.5%. T. gondii DNA could be characterized directly from brain tissue from 12 of 23 seropositive pigeons. Microsatellite typing revealed that 9 strains belonged to type II, 2 were type III and one was type I. No recombinant or atypical genotypes were found. Attempts to recover viable T. gondii strains through bioassay in mice resulted in the isolation of 9 strains.

Isolation and genotyping of Toxoplasma gondii from Ugandan chickens reveals frequent multiple infections

The genetic make-up of an infecting Toxoplasma gondii strain may be important for the outcome of infection and the risk of reactivation of chronic disease. In order to survey the distribution of different genotypes within an area, free-range chickens act as a good model species. In this study 85 chickens were used to investigate the prevalence, genotype and mouse virulence of T. gondii in Kampala, Uganda. Antibodies were detected in 40 chickens, of which 20 had MAT-titres of 1:20 or higher and were also positive by PCR. Genotyping of 5 loci (SAG1, SAG2, SAG3, BTUB and GRA6) showed that 6 strains belonged to genotype I, 8 to Type II and 1 to Type III. Five chickens had multiple infections; 3 individuals with Type I plus Type II and a further 2 harbouring Types I, II and III. Isolates were obtained from 9 chickens via bioassay in mice, 6 were Type II strains and 3 were from animals with mixed infection. This is the first set of African T. gondii strains to be genotyped at multiple loci and in addition to the 3 predominant lineages we found a small number of new polymorphisms and a high frequency of multiple infections.

A new perspective on and re-assessment of SAG2 locus as the tool for genetic analysis of Toxoplasma gondii isolates

SAG2 locus, the coding gene of the P22 protein, has been widely used for the molecular epidemiology of Toxoplasma gondii and characterization of the parasite isolates with two separate polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) processes. To re-assess the resolution power and suitability of this genetic marker for molecular characterization of the parasite isolates, a number of 27 Toxoplasma strains from different zymodeme patterns were used in the present study. Both codon and non-codon regions of the SAG2 locus of all 27 strains were amplified and subjected to sequencing and nucleotide alignment. Nucleotide variations clustered the three major genotypes (I, II and III). Some minor genotypes, unidentifiable by SAG2-RFLP, could be identified by sequence comparison. However, there were other genotypes that could not be differentiated from the major types due to having identical sequences. This suggests that a remarkable number of field isolates representing several minor types will be miss-clustered with the major types by using the traditional SAG2-PCR-RFLP method. It was concluded that this technique seems not to be suitable for Toxoplasma population study. Thus, the utilization of more variable markers and other discriminatory methods are also recommended.

Biologic and genetic characteristics of Toxoplasma gondii isolates in free-range chickens from Nicaragua, Central America

The prevalence of Toxoplasma gondii in free-ranging chickens is a good indicator of the prevalence of T. gondii oocysts in the soil because chickens feed from the ground. The prevalence of T. gondii in 98 free-range chickens (Gallus domesticus) from Nicragua was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT), and found in 84 (85.7%) of 98 chickens with titers of 1:5 in 10, 1:10 in eight, 1:20 in seven, 1:40 in nine, 1:80 in 11, 1:160 in one, 1:200 in 27, 1:400 in six, 1:800 four, and 1:3200 in one bird. Hearts and brains of 32 chickens with titers of 1:10 or less were pooled and fed to three T. gondii-free cats. Hearts and brains of 66 chickens with titers of 1:20 or higher were bioassayed in mice. Feces of cats were examined for oocysts. The cat fed tissues from eight chickens with titers of 1:10 shed T. gondii oocysts. The two cats fed tissues of 24 chickens with titers of 1:5 or less did not shed oocysts. T. gondii was isolated by bioassay in mice from 47 chickens with MAT titers of 1:20 or higher. All infected mice from six isolates died of toxoplasmosis. Overall, 41 of 170 (24.1%) mice that became infected after inoculation with chicken tissues died of toxoplasmosis. Genotyping of these 48 isolates (47 from mice and 1 from pooled tissues) using polymorphisms at the loci SAG1, SAG2, SAG3, BTUB and GRA6 revealed eight genotypes. Six isolates had Type I alleles, three isolate had Type II alleles and six isolates had Type III alleles at all loci. Four isolates had mixed infections. Two isolates have a unique allele at SAG1 locus and combination of I and III alleles at other loci. The rest 27 isolates contained the combination of Type I and III alleles and were divided into four genotypes. More than one genotypes were often isolated in chickens from the same household, indicating multiple genotypes were circulating in the same environment. This may explain the high frequency of mixed infections observed. High rate of mixed infection in intermediate hosts such as chickens may facilitate genetic exchange between different parasite lineages in definitive feline hosts. This is the first report of genetic characterization of T. gondii isolates from Nicragua, Central America.

Characterization of Toxoplasma gondii isolates in free-range chickens from Chile, South America

The prevalence of Toxoplasma gondii in free-ranging chickens is a good indicator of the prevalence of T. gondii oocysts in the soil because chickens feed from the ground. The prevalence of T. gondii in 85 free-range chickens (Gallus domesticus) from Chile was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT), and found in 47 of 85 (55.3.9%) chickens with titers of 1:5 in six, 1:10 in four, 1:20 in four 1: 40 in three, 1: 80 in nine, 1: 160 in four 1:320 in nine, and 1: 640 or higher in eight. Hearts and brains of 47 chickens with titers of 1:5 or higher were pooled for each chicken and bioassayed in mice. Tissues from 16 seronegative (MAT<1:5) chickens were pooled and fed to one T. gondii-free cat. Feces of the cat were examined for oocysts but none was found based on bioassay of fecal floats in mice. Hearts and brains from seven seronegative (<1:5) were pooled and bioassayed in mice; T. gondii was not isolated. T. gondii was isolated by bioassay in mice from 22 chickens with MAT titers of 1:20 or higher. Genotyping of these 22 isolates using polymorphisms at the loci SAG1, SAG2, SAG3, BTUB and GRA6 revealed three genotypes. Seventeen isolates had type II alleles and four isolates had type III alleles at all loci. One isolate contained the combination of type I and III alleles. This is the first report of genetic characterization of T. gondii isolates from Chile, South America.

Biologic and genetic characteristics of Toxoplasma gondii isolates in free-range chickens from Costa Rica, Central America

The prevalence of Toxoplasma gondii in free-ranging chickens is a good indicator of the prevalence of T. gondii oocysts in the soil because chickens feed from the ground. The prevalence of T. gondii in 144 free-range chickens (Gallus domesticus) from Costa Rica was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT), and found in 60 (40.1%) of 144 chickens with titers of 1:5 in 16, 1:10 in 5, 1:20 in 2, 1:40 in 3, 1:80 in 5, and 1:160 or higher in 29. Tissues of all chickens were bioassayed for T. gondii in mice or cats. Hearts and brains of 52 chickens with titers of 1:5 or higher and 16 chickens with doubtful titers were pooled and bioassayed in mice. Tissues from 76 chickens with MAT titers of 1:10 or less were pooled and fed to three T. gondii-free cats. Fecal floats of cats were bioassayed orally in mice but were negative for T. gondii oocysts. T. gondii was isolated by bioassay in mice from 32 chickens with MAT titers of 1:10 or higher. All infected mice from 4 of the 32 isolates died of toxoplasmosis. Genotyping of these 32 isolates using polymorphisms at the loci SAG1, SAG2, SAG3, BTUB and GRA6 revealed five genotypes. Five isolates had type I alleles and one isolate had type III alleles at all loci. The rest 26 isolates contained the combination of type I and II or I and III alleles and were divided into three genotypes. None was found to have genotype II alleles at all five loci. This is the first report of genetic characterization of T. gondii isolates from Costa Rica, Central America.

Genetic and biologic characteristics of Toxoplasma gondii isolates in free-range chickens from Colombia, South America

The prevalence of Toxoplasma gondii in free-ranging chickens is a good indicator of the prevalence of T. gondii oocysts in the soil because chickens feed from the ground. The prevalence of T. gondii in 77 free-range chickens (Gallus domesticus) from Colombia, South America was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT), and found in 32 (44.4%) of 72 chickens with titers of 1:5 in 4, 1:10 in 3, 1:20 in 1, 1:40 in 1, 1:80 in 8, 1:160 in 8, 1:320 in 3, and 1:640 or higher in 4. Hearts and brains of 31 seropositive chickens were pooled and bioassayed in mice. Tissues from 32 (16+16) seronegative chickens were pooled and fed to two, T. gondii-free cats, and tissues from nine chickens without matching sera were fed to one T. gondii-free cat. Feces of cats were examined for oocysts. T. gondii oocysts were excreted by a cat that was fed tissues of 16 seronegative chickens. T. gondii was isolated by bioassay in mice from 23 chickens with MAT titers of 1:20 or higher. All infected mice from 16 of the 23 isolates died of toxoplasmosis. Overall, 82 (81.1%) of 101 mice that became infected after inoculation with chicken tissues died of toxoplasmosis. Genotyping of these 24 isolates using polymorphisms at the SAG2 locus indicated that seven T. gondii isolates were Type I, 17 were Type III, and none was Type II. Phenotypically, T. gondii isolates from chickens from Colombia were similar to isolates from Brazil but different from the isolates from North America; most isolates from chickens from Brazil and Colombia were lethal for mice whereas isolates from North America did not kill inoculated mice. Genetically, none of the T. gondii isolates from Colombia and Brazil was SAG2 Type II, whereas most isolates from chickens from North America were Type II. This is the first report of genetic characterization of T. gondii isolates from Colombia, South America.