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

Toxoplasma gondii Serotypes in Italian and Foreign Populations: A Cross-Sectional Study Using a Homemade ELISA Test

Toxoplasma gondii is a protozoan parasite responsible for human toxoplasmosis. The three major clonal lineages and different recombinant strains of T. gondii have a varied global distribution. This study aimed at evaluating the epidemiological distribution of types II and I–III and recombinant or mixed T. gondii in Italians and foreigners residing in Italy, establishing an association between serotypes and demographic characteristics. We collected the sera of 188 subjects who had tested positive for specific T. gondii antibodies. The population was differentiated into groups based on sex, nationality, and place of birth (Italy, Africa, South America, Asia, or Europe (except Italy)). We then performed a homemade ELISA test that detected both the antibodies against the amino acid sequences of the three main genotype antigens (I–III) in human sera and discerned the T. gondii strains. Serotype II of T. gondii was the most prevalent in the Italian population, whereas type I–III was the most prevalent in the foreign group. Surprisingly, we observed a notable amount of recombinant or mixed serotypes in European and Italian subjects. Moreover, we showed a significant difference in the prevalence of T. gondii serotypes between men and women, Italians, and foreigners. This descriptive study is the first to investigate the epidemiological distribution of T. gondii serotypes in humans in Italy using a homemade ELISA. We considered this technique suitable for discriminating between serotypes II and I–III and, consequently, for an epidemiological study focusing on the observation of circulating T. gondii strains and clinical correlations.

Syngamus trachea in free-ranging white stork (Ciconia ciconia) nestlings in Switzerland

Syngamosis is a disease caused by the strongylid nematode Syngamus trachea, which infects the respiratory tract of various bird species around the world. The parasite appears to be harmful for a wide variety of avian orders, occasionally leading to a fatal outcome, particularly in young birds.

The aim of this study was to examine the parasitic fauna in deceased or euthanized, free-ranging white storks nesting at the Zoo Basel in 2019 and 2020; and to assess the extent to which these parasites contributed to the wild birds' death.

In five out of 24 necropsied white storks, an infection with S. trachea was diagnosed based on morphological analysis of adult nematode stages and eggs, in combination with PCR amplification and sequencing of DNA extracted from female worms. The main pathological changes affected the white storks’ respiratory tract and a mixed cell tracheitis was diagnosed in the histopathological examination of three of the five infected birds. Some birds displayed additional lesions compatible with syngamosis, namely partially degenerated parasitic structures with concurrent granulomatous inflammation in the lung and multifocal acute hemorrhages in the bronchi and parabronchi. Coprological examinations (fecal flotation technique, fecal sedimentation technique, sodium acetate acetic acid formalin procedure and Ziehl-Neelsen staining) from the intestinal content as well as a PCR for Toxoplasma gondii on brain, lung, heart, liver, and spleen tissue yielded negative results in all examined individuals. In the absence of further major pathological findings, S. trachea was assumed to have significantly contributed to the death of the infected birds.

•

5 out of 24 dead, free-ranging white storks were infected with S. trachea.

•

All infected white storks were nestlings.

•

3 of the 5 infected nestlings displayed a mixed cell tracheitis.

•

120 tissue samples from 24 free-ranging white storks were negative for T. gondii.

The expressive identification and localization of bicoid-interacting protein 3 in the toxoplasma gondii Chinese I genotype Wh3 strain

Toxoplasma gondii is an important intracellular parasite that is distributed worldwide and can infect almost all warm-blooded animals. The Chinese I genotype Wh3 strain is the most common in China and has unique pathogenicity compared with other strains of T. gondii. Bicoid-interacting protein (Bin3) is predicted to be involved in the development and polarity of T. gondii, and the localization of this protein is necessary for studying the biological characteristics of the Chinese I genotypeWh3 strain of T. gondii. In this study, we established an in vitro the method of transforming the tachyzoites into bradyzoites to lay the foundations for further experimental studies. Parasites were induced by culturing in alkaline conditions, then the changes in parasites morphology were evaluated. SAG2C, BAG1 and SAG1 were used to identify parasites. The results show that the Chinese I genotype Wh3 strain exhibited pseudocysts and cysts in the alkaline conditions after being induced, and the bradyzoite stage expressed specific proteins at the same time. Bradyzoites, induced using an alkaline medium (pH = 8.2), had higher expression levels of the Bin3 protein than tachyzoites. The results of indirect immunofluorescence, using a Bin3 monoclonal antibody showed that the Bin3 protein is expressed in both free-state and pseudocysts tachyzoites, and in the cysts of the Chinese I genotype Wh3 strain. The Bin3 protein is located in the cytoplasm of free-state tachyzoites, secreted between the parasite and the pseudocyst membrane in pseudocysts, and distributed inside the cyst wall of cysts. These findings provide a basis for further study on the biological characteristics of the Chinese I genotype Wh3 strain.

Serosurvey of Toxoplasma gondii, Sarcocystis sp. and Neospora caninum in geese (Anser sp.) from urban parks and captivity

Geese, ducks, mallards, and swans are birds of the order Anseriformes, which are found in the wild, in zoos and parks, and raised for meat consumption. Toxoplasma gondii, Sarcocystis sp., and Neospora caninum are protozoans of several species of animals. Wild and domestic birds can serve as intermediate hosts, disseminators and potential sources of infection of these protozoa to humans through contaminated meat. The aims of this study were: (i) to perform a serological survey of T. gondii, Sarcocystis sp. and N. caninum in geese (Anser sp.) from public parks and from captivity and (ii) to compare seroprevalence between these two locations. Antibodies were detected by Immunofluorescence antibody test using the serum of 149 geese. Antibodies to Sarcocystis sp., T. gondii, and N. caninum were detected in 28.18%, 18% and 0.67% of geese, respectively; 57% of geese from urban parks and 26.53% of geese from captivity were seropositive for at least one protozoa. The results indicate environmental contamination, particularly for the occurrence of antibodies against T. gondii - a zoonosis that causes toxoplasmosis and is transmitted through oocyte ingestion. This is the first serological survey of T. gondii, Sarcocystis sp. and N. caninum in geese from urban parks in Curitiba, Brazil.

Molecular and virulence characterization of Toxoplasma gondii strains isolated from humans in Portugal

Toxoplasma gondii is an apicomplexan parasite responsible for toxoplasmosis which infects all warm-blooded vertebrates, including mammals and birds. The majority of studies conducted in Europe have revealed that more than 80 % of strains isolated from human infections belong to genotype II, whereas genotypes I and III are responsible for a small number of cases. Atypical and recombinant strains are generally associated with more severe infections. In Portugal, there is a lack of data concerning genetic diversity as the classical typing studies in humans have never been performed. We aimed to determine the Sag2 and microsatellite-based (TUB2, TgM-A, W35, B17, B18) genotypes of T. gondii isolated from humans in Portugal, as well as to study their virulence in mice. We analyzed 48 strains from congenital and acquired toxoplasmosis collected during the last two decades. Sag2-based genotyping of T. gondii was achieved in all 48 strains where 35 (73 %) were classified as type II and 13 (27 %) were type I. The multilocus PCR of five microsatellites allowed the classification of 10 strains (21 %) as recombinant strains that had been previously identified as type II or I by Sag2 typing. Seven out of the 48 strains, including three type I, three recombinant, and one type I, were virulent in mice. This study constitutes the first evidence of recombinant strains circulating in Portugal in humans from congenital infection, highlighting the need for a better evaluation of these strains as their phenotype is still barely understood.

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.

Animals are key to human toxoplasmosis

Toxoplasma gondii is an extremely sucessfull protozoal parasite which infects almost all mamalian species including humans. Approximately 30% of the human population worldwide is chronically infected with T. gondii. In general, human infection is asymptomatic but the parasite may induce severe disease in fetuses and immunocompromised patients. In addition, T. gondii may cause sight-threatening posterior uveitis in immunocompetent patients. Apart from few exceptions, humans acquire T. gondii from animals. Both, the oral uptake of T. gondii oocysts released by specific hosts, i.e. felidae, and of cysts persisting in muscle cells of animals result in human toxoplasmosis. In the present review, we discuss recent new data on the cell biology of T. gondii and parasite diversity in animals. In addition, we focus on the impact of these various parasite strains and their different virulence on the clinical outcome of human congenital toxoplasmosis and T. gondii uveitis.

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.

Evidence of the three main clonalToxoplasma gondiilineages from wild mammalian carnivores in the UK

Toxoplasma gondiiis a zoonotic pathogen defined by three main clonal lineages (types I, II, III), of which type II is most common in Europe. Very few data exist on the prevalence and genotypes ofT. gondiiin the UK. Wildlife can act as sentinel species forT. gondiigenotypes present in the environment, which may subsequently be transmitted to livestock and humans. DNA was extracted from tissue samples of wild British carnivores, including 99 ferrets, 83 red foxes, 70 polecats, 65 mink, 64 badgers and 9 stoats. Parasite DNA was detected using a nested ITS1 PCR specific forT. gondii, PCR positive samples were subsequently genotyped using five PCR–RFLP markers.Toxoplasma gondiiDNA was detected within all these mammal species and prevalence varied from 6·0 to 44·4% depending on the host. PCR–RFLP genotyping identified type II as the predominant lineage, but type III and type I alleles were also identified. No atypical or mixed genotypes were identified within these animals. This study demonstrates the presence of alleles for all three clonal lineages with potential for transmission to cats and livestock. This is the first DNA-based study ofT. gondiiprevalence and genotypes across a broad range of wild British carnivores.

Toxoplasma gondii sexual cross in a single naturally infected feline host: generation of highly mouse-virulent and avirulent clones, genotypically different from clonal types I, II and III

Tachyzoite clones obtained from a single Toxoplasma gondii oocyst field sample were genotyped and characterized regarding mouse virulence. PCR-RFLP genotyping of tachyzoites initially isolated from interferon-γ-knockout (GKO) mice, BALB/c mice and VERO cell culture using the nine independent, unlinked genetic markers nSAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico revealed mixed T. gondii infections showing combinations of type II and type III alleles at different loci. Forty-five individual clones were obtained from all mixed T. gondii tachyzoite cell cultures by limiting dilution. Sixteen T. gondii clones showed type III alleles at all loci and 29 clones displayed a combination of type II and type III alleles at different loci. Five clone groups were identified in total, four of which include T. gondii clones that showed a non-canonical allele pattern and have never been described in natural infections before. All tested clones, except two, were highly virulent in BALB/c mice. The isolation of different non-canonical T. gondii clones originating from an oocyst sample of a single naturally infected cat demonstrate that sexual recombination as well as re-assortment of chromosomes via a sexual cross of T. gondii occur under natural conditions and result in the emergence of clones with increased virulence in mice.

Epidemiology of and diagnostic strategies for toxoplasmosis

The apicomplexan parasite Toxoplasma gondii was discovered a little over 100 years ago, but knowledge of its biological life cycle and its medical importance has grown in the last 40 years. This obligate intracellular parasite was identified early as a pathogen responsible for congenital infection, but its clinical expression and the importance of reactivations of infections in immunocompromised patients were recognized later, in the era of organ transplantation and HIV infection. Recent knowledge of host cell-parasite interactions and of parasite virulence has brought new insights into the comprehension of the pathophysiology of infection. In this review, we focus on epidemiological and diagnostic aspects, putting them in perspective with current knowledge of parasite genotypes. In particular, we provide critical information on diagnostic methods according to the patient's background and discuss the implementation of screening tools for congenital toxoplasmosis according to health policies.

Toxoplasma gondii: diagnosis of experimental and natural infection in pigeons (Columba livia) by serological, biological and molecular techniques

This study aimed to diagnose experimental and natural Toxoplasma gondii infection in pigeons (Columba livia) by serological, biological and molecular techniques. Twelve pigeons, free of infection, were inoculated with 50 sporulated oocysts of T. gondii (VEG sample) and four remained uninfected controls. Four birds (three infected and one control) were euthanized at 15, 30, 45 and 60 days post-infection (dpi), and their tissues were used to perform a bioassay in mice and nested-PCR using B1 gene as target. Blood was obtained weekly and it was tested for the presence of anti-T. gondii antibodies by the indirect fluorescent antibody test (IFAT) and modified agglutination test (MAT). Seven (58.3%) out of 12 inoculated pigeons were positive by serological techniques and titers ranged between 1:40 and 1:5120 by MAT and between 1:512 and 1:4096 by IFAT. Complete agreement was seen between the results obtained by serological techniques and nested-PCR in seven positive birds. In the bioassay in mice, five (41.7%) out of 12 pigeons inoculated were positive to T. gondii. Only one pigeon died at 23 dpi due to toxoplasmosis. A second study with free-living pigeons was performed for detection of anti-T. gondii antibodies. Birds were captured in the municipalities of São Paulo, Ibiúna and Sorocaba, São Paulo State, Southeastern Brazil. All 126 free-living birds were negative to anti-T. gondii antibodies by MAT (titer < 1:5). Bioassays were performed in mice with tissues from all captured birds and T. gondii was not isolated in any pigeon.

Atypical Toxoplasma gondii genotypes identified in oocysts shed by cats in Germany

A total of 18,259 feline faecal samples from cats in Germany were collected and analysed for the presence of Toxoplasma gondii oocysts between June 2007 and December 2008. The proportion of T. gondii-positive samples collected between January and June was significantly lower than between July and December. The age of cats shedding T. gondii oocysts was not significantly different from the age of negative control cats. Forty-six T. gondii-positive samples were genetically characterised using nine PCR-restriction fragment length polymorphism (RFLP) markers which included newSAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico. In addition, 22 isolates that had already been partially characterised in a previous study were further typed using PCR-RFLP markers c22-8, c29-2, L358, PK1 and Apico. Genotyping of the 68 isolates revealed that the majority of T. gondii isolates (n=54) had Type II patterns at all loci but displayed a Type I pattern at the Apico locus. Three isolates displayed Type II patterns at all loci, including the Apico locus. In addition, we detected one isolate with clonal Type III patterns at all loci and three isolates with atypical and mixed genotypes. Seven isolates could not be fully genotyped. One of those isolates displayed alleles of both Types I and II at the Apico locus. To our knowledge this is the first description of the presence of T. gondii genotypes different from the clonal Types I, II and III in the faeces of naturally infected cats.