Genetic diversity of Toxoplasma gondii isolates obtained from free-living wild birds rescued in Southeastern Brazil

Genetic diversity of Toxoplasma gondii in South America: occurrence, immunity, and fate of infection

Toxoplasma gondii is an intracellular parasite with a worldwide distribution. Toxoplasma gondii infections are of great concern for public health, and their impact is usually most severe in pregnant women and their foetuses, and in immunocompromised individuals. Displaying considerable genetic diversity, T. gondii strains differ widely according to geographical location, with archetypal strains predominantly found in the Northern Hemisphere and non-archetypal (atypical) strains, with highly diverse genotypes, found mainly in South America. In this review, we present an overview of the identification and distribution of non-archetypal strains of T. gondii. Special attention is paid to the strains that have been isolated in Brazil, their interaction with the host immunological response, and their impact on disease outcomes. The genetic differences among the strains are pivotal to the distinct immunological responses that they elicit. These differences arise from polymorphisms of key proteins released by the parasite, which represent important virulence factors. Infection with divergent non-archetypal strains can lead to unusual manifestations of the disease, even in immunocompetent individuals.

In vitro and in vivo susceptibility to sulfadiazine and pyrimethamine of Toxoplasma gondii strains isolated from Brazilian free wild birds

Little is known about the existence of drug-resistant Toxoplasma gondii strains and their possible impact on clinic outcomes. To expand our knowledge about the existence of natural variations on drug susceptibility of T. gondii strains in Brazil, we evaluated the in vitro and in vivo susceptibility to sulfadiazine (SDZ) and pyrimethamine (PYR) of three atypical strains (Wild2, Wild3, and Wild4) isolated from free-living wild birds. In vitro susceptibility assay showed that the three strains were equally susceptible to SDZ and PYR but variations in the susceptibility were observed to SDZ plus PYR treatment. Variations in the proliferation rates in vitro and spontaneous conversion to bradyzoites were also accessed for all strains. Wild2 showed a lower cystogenesis capacity compared to Wild3 and Wild4. The in vivo analysis showed that while Wild3 was highly susceptible to all SDZ and PYR doses, and their combination, Wild2 and Wild4 showed low susceptibility to the lower doses of SDZ or PYR. Interestingly, Wild2 presented low susceptibility to the higher doses of SDZ, PYR and their combination. Our results suggest that the variability in treatment response by T. gondii isolates could possibly be related not only to drug resistance but also to the strain cystogenesis capacity.

Genetic diversity of Toxoplasma gondii isolates from birds in the world: A systematic review

Toxoplasma gondii (T. gondii) is one of the most important foodborne pathogens that infects a large number of vertebrate species and has a cosmopolitan distribution. Birds as intermediate hosts are very important in the life cycle of T. gondii and they can be a main source of infection for humans and felids, as well as other animals. Most species of birds feed from the ground and are the best indicator for soil contamination with T. gondii oocysts. Hence, T. gondii strains isolated from birds can represent different genotypes circulating in the environment and their main predators and consumers. The recent systematic review tries to represent the population structure of T. gondii in birds around the world. Six English language databases were searched from 1990 to 2020 to find the related studies and overall, 1275 isolates of T. gondii were separated from the analyzed samples in birds. The results of our study revealed that atypical genotypes were predominant (58.8%, 750 out of 1275). Types II, III, and I had less frequency with prevalence rates of 23.4%, 13.8%, and 2%, respectively. No isolates of Type I were reported from Africa. Summarizing ToxoDB genotypes circulating in birds around the world manifested that ToxoDB #2 was the most common (101/875), followed by ToxoDB #1 (80/875), and #3 (63/875). Totally, the results of our review represented the high genetic diversity of T. gondii with circulating non-clonal strains in birds from South and North America, while clonal parasites with low genetic diversity were predominant in Europe, Asia, and Africa.

Molecular screening for Sarcocystidae in muscles of wild birds from Brazil suggests a plethora of intermediate hosts for Sarcocystis falcatula

The genus Sarcocystis and the species Toxoplasma gondii are the most prevalent sarcocystid organisms found in birds. Molecular phylogenies based on the first internal transcribed spacer of the ribosomal coding DNA (ITS1) have been widely used to identify them. Here, pectoral muscles from 400 wild birds from Brazil were screened by means of molecular methods using nested PCR, and Sanger sequencing yielded amplicons. A pan-sarcocystid ITS1-directed nested PCR revealed 28 birds infected by Sarcocystis falcatula (ten Piciformes, eight Psittaciformes, five Columbiformes, two Accipitriformes, one Anseriformes, one Passeriformes and one Strigiformes); one infected by Sarcocystis halieti (one Accipitriformes); nine infected by unknown or undescribed Sarcocystis (six Passeriformes, one Piciformes, one Cathartiformes and one Cuculiformes); and six harboring Toxoplasma gondii DNA (three Pelecaniformes, two Falconiformes and one Columbiformes). Samples harboring S. falcatula-related ITS1 sequences were further characterized by means of PCR and sequencing of genetic sequences of three surface antigen coding genes (SAGs). From this, 10 new allelic combinations of SAGs (SAG2, SAG3 and SAG4) were identified, in addition to 11 SAG allelic combinations already found in Brazil. Samples with S. falcatula-unrelated ITS1 sequences were further characterized by means of PCR and sequencing of cytochrome c oxidase subunit I coding sequences (CO1) and 18S ribosomal DNA gene (18S rDNA). This study was the first extensive survey of wild birds in Brazil for Sarcocystidae species. It provides the first molecular evidence of natural S. falcatula infection in 14 species, including in the order Piciformes, and shows the high genetic diversity of S. falcatula in intermediate hosts in South America. Evidence of occurrence of at least three non-described species of Sarcocystis was also presented in this study. This survey corroborated the ubiquity of T. gondii infection but revealed surprisingly low prevalence of this parasite (1.5%).

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Extensive survey of free-living wild birds in Brazil for Sarcocystidae species.

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Sarcocystis falcatula was detected in Piciformes birds for the first time.

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Sarcocystis falcatula has an extensive genetic diversity in Brazil.

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Three non-described species of Sarcocystis were detected.

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Sarcocystis halieti was detected for the first time in the Americas.

Prevalence of Antibodies to Toxoplasma gondii in Different Wild Bird Species Admitted to Rehabilitation Centres in Portugal

Toxoplasma gondii is a worldwide zoonotic parasite. According to the “One Health” approach, studies on toxoplasmosis are essential since it affects humans and domestic and wild animals. In the present study, antibodies to T. gondii were determined in serum samples from 263 wild birds located in five wildlife rehabilitation centres in mainland Portugal by using the modified agglutination test (MAT) with a cut-off titre of 20. An overall seroprevalence of 36.5% (95% confidence interval [CI]: 30.7–42.6) was observed. For the first time, antibodies to T. gondii were detected in some avian species, including pallid swift (Apus pallidus) (33.3%), black-backed gull (Larus fuscus) (39.3%), European turtle-dove (Streptopelia turtur) (100%), bee-eater (Merops apiaster) (50.0%), carrion crow (Corvus corone) (33.3%), and Egyptian vulture (Neophron percnopterus) (100%), which expands the list of intermediate hosts of T. gondii. A lower seroprevalence was found in juvenile birds (31.9%) compared to adults (48.7%) (p = 0.016). The central region of Portugal was considered a risk factor for T. gondii infection in wild birds (odds ratio: 3.61; 95% CI: 1.09–11.91). This pioneer study calls attention to the need for further studies, to provide a clearer understanding of T. gondii epidemiology in Portugal, because it reflects wide dispersion of T. gondii oocysts in the environment.

Toxoplasma gondii in South America: a differentiated pattern of spread, population structure and clinical manifestations

Toxoplasma gondii is an obligate intracellular parasite belonging to the phylum Apicomplexa. It has a worldwide distribution and can infect a wide variety of intermediate hosts, including humans. In South America, toxoplasmosis shows high health impacts, and the incidence of the disease is frequently reported and more severe than in other regions, such as Europe. Although most T. gondii infections are asymptomatic, severe manifestations can occur in cases of congenital toxoplasmosis and immunocompromised individuals. In South America, the ocular disease in immunocompetent individuals is also frequently reported. Treatment for any clinical manifestation of toxoplasmosis consists of the combination of sulfadiazine (SDZ) and pyrimethamine (PYR). However, failures in the treatment of toxoplasmosis have been reported, especially in South America, suggesting the acquisition of resistance against SDZ and PYR. Another paradigm present in the literature is that once infected with T. gondii, the host is immunologically protected from further reinfections. However, some studies indicate cases of congenital transmission of T. gondii from immunocompetent pregnant women with chronic infection, suggesting the possibility of reinfection in humans. Thus, in this review, we will cover several aspects of South American T. gondii isolates, such as genetic characterization, disease manifestation, host reinfection and drug resistance.

Sarcocystidae in wild birds of southeastern Brazil

This study aimed to identify members of the Sarcocystidae family in naturally infected wild birds at a rescue center in the state of Minas Gerais, southeastern Brazil. The heart and brain of 44 wild birds were evaluated by bioassay in mice to detect T. gondii, and extracted DNA was used for nested PCR of the 18S ribosomal DNA gene to detect members of the Sarcocystidae family. The positive samples were sequenced, assembled, edited and compared with sequences deposited in GenBank. Toxoplasma gondii was isolated from six (13.6%) out of 44 birds. Toxoplasma gondii DNA was identified in 10/44 (22.7%) of the birds. The amplified sequences exhibited 100% similarity with the DNA of the ME49 strain of T. gondii. Sarcocystis DNA (99% similarity) was identified in 5/44 (11.4%) of the birds. T. gondii and Sarcocystis spp. are common in wild birds in Minas Gerais, Brazil.

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

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

Genotyping of Toxoplasma gondii in a lethal toxoplasmosis outbreak affecting captive howler monkeys (Alouatta sp.)

BACKGROUND

Toxoplasmosis is a zoonotic disease that affects humans and warm-blooded animals. This study describes an outbreak of toxoplasmosis in howler monkeys (Alouatta sp.) and survival of capuchins (Sapajus apella), under the same environmental conditions.

METHODS

Howler monkeys were submitted to post-mortem examination. Tissue samples were processed to histopathology and immunohistochemistry to detect lesions and tachyzoites of Toxoplasma gondii. Tissue samples were also frozen and submitted to PCR and genotyping of T. gondii.

RESULTS

Typical lesions were observed in several organs including the liver, lymph node, and brain, with intralesional cysts and tachyzoites of T. gondii demonstrated by immunohistochemistry. T. gondii genomic sequences were amplified by PCR, and genotyping characterized the same T. gondii clone in all howler monkeys.

CONCLUSIONS

Our results support the notion that some species of neotropical primates are highly susceptible to toxoplasmosis and the hypothesis that capuchins (S. apella) may be resistant.

Isolation and genotyping of Toxoplasma gondii in the Midwestern Brazil revealed high genetic diversity and new genotypes

We aimed to describe the genetic diversity of Toxoplasma gondii strains isolated from domestic animals, wildlife and humans in the Midwestern Brazil. For this purpose, fragments of tissue samples (heart, brain and lung) from 35 dogs, four cats, 105 wildlife, and amniotic fluids from eight pregnant women were collected and submitted to mouse bioassay test. In a total, 22 isolates from nine dogs, one cat, ten wild animals and two women were obtained. The DNA was extracted from T. gondii isolates (lungs and brains of infected mice) and from "primary samples" (aliquots of tissue homogenate from wild animals and amniotic fluids from pregnant women) in order to screen using a Polymerase Chain Reaction (PCR) targeting a repeated 529-base pairs fragment of the T. gondii genome. All positive PCR samples were genotyped using restriction fragment length polymorphism (RFLP) analysis. To the best of our knowledge, this was the first study to report isolates of T. gondii from Leopardus pardalis, Crax fasciolata, and Dasyprocta azarae. Moreover, multilocus PCR-RFLP revealed 11 T. gondii RFLP genotypes, comprising nine previously described, including the archetypal lineage #2 type III (n = 1); two clonal Brazilian lineages, #6 type BrI (n = 1) and #8 type BrIII (n = 5); #14 (n = 2), #41 (n = 1), #108 (n = 1), #140 (n = 2), #166 (n = 4), #190 (n = 1), one potentially mixed, and two new described genotypes in two isolates. Our results confirmed the high diversity of T. gondii strains in Brazil, including identical genotypes circulating among humans, domestic dogs and wildlife.

Environmental factors associated With Toxoplasma gondii Exposure in Neotropical Primates of Costa Rica

The apicomplexan parasite Toxoplasma gondii (T. gondii) has been found in more than 350 species of homoeothermic vertebrates in diverse climates and geographic areas. In most animals, T. gondii produces mild or asymptomatic infection. However, acute and hyperacute toxoplasmosis is associated with high mortality rates observed in Neotropical primates (NP) in captivity. These primates are distributed in 20 countries across the Americas, and although infection has been reported in certain countries and species, toxoplasmosis in the wild and its impact on NP population survival is unknown. Differences among species in exposure rates and disease susceptibility may be due in part to differences in host behavior and ecology. Four species of NP are found in Costa Rica, i.e., howler (Alouatta palliata), spider (Ateles geoffroyi), capuchin (Cebus imitator), and squirrel monkeys (Saimiri oerstedii). This study reports NP exposure to T. gondii using the modified agglutination test in 245 serum samples of NP (198 wild and 47 from captivity) from Costa Rica. Associations of serostatus with environmental (forest cover, annual mean temperature), anthropogenic (human population density), and biological (sex) variables in howler and capuchin monkeys were evaluated. The seroprevalence among wild NP was 11.6% (95% CI = 7.7–17.34), compared with 60% in captive monkeys (95% CI = 44.27–73.63), with significant differences between species (X² = 20.072; df = 3, p = 0.000164), suggesting an effect of behavior and ecology. In general, antibody titers were low for wild NP (<1:128) and high for captive NP (>1:8192), suggesting higher exposure due to management factors and increased life span in captivity. Seropositivity in howler monkeys was positively related to forest cover and inversely related to annual rainfall. For capuchins, annual rainfall was inversely related to seropositivity. Surveillance of T. gondii exposure in NP in captivity and in the wild is required to understand drivers of the infection and develop novel strategies to protect them.