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

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

Serum samples of 930 sheep were tested by ELISA to assess the prevalence of anti-Toxoplasma gondii antibodies and to identify risk factors associated with the presence of toxoplasmosis in two regions of Rio Grande do Norte (Northeast Brazil), with different climatic conditions. The overall estimated prevalence was 22.1%, with 26.3% and 17.8% positive sheep in Leste Potiguar and Central Potiguar regions, respectively. Among the positive sheep, 18.1% had low-avidity IgG antibodies, suggesting the occurrence of recent toxoplasmosis. The risk factors for toxoplasmosis in sheep were: presence of cats (odds ratio (OR) = 1.55; confidence interval (CI) 95% = 1.11-2.16), age of the animals, with adults presenting a greater chance of infection (OR = 2.44; CI 95% = 1.58-3.75), and the use of running water (OR = 1.61; CI 95% = 1.25-2.09), characterizing the existence of transmission by sporulated oocysts of T. gondii in the environment.

In order to identify possible risk factors for T. gondii infection in goat herds in Ceará, Brazil, 2362 serum samples were tested by ELISA. The serological prevalence was 25.1%. The risk factors identified for Toxoplasma gondii infection in goat herds were age, number of cats, use of wooden feeding troughs and absence of feeding troughs. Goats older than 37 months had 2.01 (CI 95%; 1.55 - 2.61) higher risk of infection than younger animals. Greater risk of infection was observed in farms with more than 10 cats (OR = 1.73; CI 95%; 1.01 - 3.33). The use of wooden feeding troughs represented a high probability of infection (OR = 7.81; CI 95%; 1.66 - 36.67). The lack of feeding troughs also represented a high probability of infection (OR = 5.50; CI 95%; 1.24 - 24.39).

In an attempt to isolate and characterize Toxoplasma gondii from the State of Minas Gerais, Brazil, musculature samples from 72 pigs, 25 dogs, 28 free-range chickens and 50 chickens produced in industrialized farms were collected. Antibodies to T. gondii have not been detected in pigs, but were found in nine (40.9 %) out of 22 dogs, and in 15 (53.6 %) of 28 free range chickens. T. gondii was not isolated from pigs and industrialized chickens, but from eight dogs and 11 free range chickens. In order to determine T. gondii virulence, female BALB/c mice were inoculated with 103, 102, 101 and 100 tachyzoites of the 19 isolates. The strains RH (virulent) and ME49 (non-virulent) were used as references. Isolates were divided into three groups according to the virulence phenotype: five isolates were classified into virulent in mice, one into non-virulent and 13 into intermediate virulent. Nested-PCR of T. gondii SAG2 locus amplified DNA from 21 out of 22 DNA samples directly extracted from heart of free range chickens. These samples were genotyped through a PCR-RFLP assay. Seventeen (80.9 %) were classified into type I; one (4.8 %) into type III and three (14.3 %) into type I or II. Pour isoler et caractériser des isolats de Toxoplasma gondii au Minas Gerais, Brésil, des échantillons de muscle de 72 porcs, 25 chiens, 28 poulets d’élevage fermier et de 50 poulets d’élevage industriel ont été examinés. Il n’a pas décelé d’anticorps anti T. gondii chez les porcs, par contre, ils ont été détectés dans le sérum de neuf chiens sur 22 (40,9 %) et de 15 poulets fermiers sur 28 (53,6 %). T. gondii n’a été isolé, ni chez les porcs, ni chez les poulets d’élevage industriel. Il a été isolé sur huit chiens et 11 poulets fermiers. Pour déterminer la virulence des isolats de T. gondii, des souris BALB/c ont été inoculées avec 103, 102, 101 et 100 tachyzoïtes de 19 isolats et avec des souches RH (virulente), outre avec la souche ME49 (non-virulente). Les isolats de T. gondii ont été classés en trois groupes selon le phénotype de virulence: cinq classifiés comme virulents pour des souris, un non-virulent, et treize de virulence intermédiaire. À l’aide du Nested-PCR – pour extraire des produits d’amplification du locus SAG2 de T. gondii –, on a identifié le parasite dans 21 échantillons d’ADN extraits à partir du coeur de 22 poulets fermiers. Ces échantillons ont été génotypés par PCR-RFLP ; 17 (80,9 %) ont été classés de type I, un (4,8 %) de type III et trois (14,3 %) de type I ou II.

Real-time PCR (qPCR) was positive in 72/150 (48%) blood samples of newborns with congenital toxoplasmosis. Among infants with active retinochoroiditis, 68% had positive qPCR results, while positivity was 29% ( P = 0.009) in the absence of ocular involvement. Positive qPCR was associated with the presence of retinochoroidal lesions, with an odds ratio of 2.8.