João Luis Garcia

Background and Objectives: Toxoplasmosis is one of the most prevalent parasitic diseases in Brazil and occurs in healthy individuals with few or no symptoms. The aim of this study was to determine the prevalence of IgG and IgM antibodies to T. gondii in the serum of blood donors from Cuiabá, Mato Grosso. Methods: This was an observational cross-sectional study with 633 serum samples from blood donors at the Cuiabá Blood Center. A total of 633 serum samples from blood donors were obtained to investigate the prevalence of anti-T. gondii antibodies in Cuiabá, Mato Grosso. Results: The seroprevalence of T. gondii infection was 323/633 (51%). A total of 314/633 (49%) samples were seroreactive for IgG for T. gondii antibodies and nine (1.4%) samples with inconclusive results. In addition, 10/633 (1.57%) samples with IgM for T. gondii and 11 (0.1%) samples were inconclusive. Statistical analyses revealed significant differences for the presence of IgG for T. gondii in the stratifications by age, adults between 20-60 years of age, (p=0.000) and brown skin color (p=0.002). While for the presence of IgM for T. gondii, the variable geographic region of Cuiabá south (p=0.030) was also statistically significant. Conclusion: Based on the data obtained, it is inferred a relatively high prevalence of individuals with positive IgG antibodies for T. gondii in the blood samples of the tested donors, suggesting a chronic or past infection.

Toxoplasma gondii is an intracellular protozoan transmitted via environmentally resistant oocysts present in food and water, as well as through the consumption of meat containing infective bradyzoites. This study evaluated the inactivation of T. gondii oocysts and bradyzoites (ME-49 strain) by Pulsed Electric Field technology (PEF). Treatment efficacy was determined by mouse bioassay combining brain qPCR and indirect immunofluorescence (IFA), with complementary qPCR in Hs27 cells. The infectious dose (ID₅₀) of T. gondii was estimated at 34.6 oocysts. PEF-treated oocysts (15 kV/cm; 50 kJ/kg; 225 µs) showed a significant reduction in infectivity compared with untreated controls; accordingly, the dose required to establish infection increased to 85.3 oocysts after PEF treatment. Brain qPCR and IFA were highly correlated, whereas heart tissue was less sensitive. Bradyzoites recovered from PEF-treated meat (3.3 kV/cm; 27 kJ/kg; 1600 µs) showed a 50% infectivity reduction compared with untreated samples. In vitro assays confirmed an in vivo reduction in infectivity, indicating that cell cultures can serve as an ethical and efficient tool for preliminary viability assessment. This is the first evidence of T. gondii inactivation by PEF, highlighting its potential as a non-thermal strategy. Further studies are needed to optimize treatment parameters.

Purpose Toxoplasma gondii and Neospora caninum are protozoan that infect animals worldwide. Dogs act as sentinels of these infections, indicating potential risks to human health, particularly in the case of T. gondii due to its zoonotic nature. Therefore, we aimed to determine the seroprevalence and associated factors for T. gondii and N. caninum infections in dogs living in the Pantanal biome, Brazil. Methods This study evaluated the seroprevalence in 743 serum samples from dogs in Barão de Melgaço and Nossa Senhora do Livramento, municipalities endemic for canine visceral leishmaniasis located in the Pantanal biome of Mato Grosso, Brazil, by Indirect Immunofluorescence Assay. Results Overall, 66.4% (n = 493) were positive for T. gondii and 12.4% (n = 92) for N. caninum. Seropositivity was associated with dogs older than 3 years (T. gondii—p = 0.001; OR = 2.579; N. caninum—p = 0.004; OR = 7.621), living together with other dogs and/or cats (T. gondii—p = 0.04; N. caninum—p = 0.005), and absence of a public sewage system at home (T. gondii—p = 0.044; OR = 4.730; N. caninum—p = 0.035; OR = 1.376). For T. gondii, additional associations were found with street access (p = 0.015; OR = 3.966), contact with rodents (p = 0.025; OR = 1.539), and a diet including leftover food (p = 0.025; OR = 2.405). Infection by N. caninum was more frequent in rural dogs (p = 0.011; OR = 4.857) and in those coinfected with Leishmania infantum (p < 0.001; OR = 6.407). Conclusion The investigated regions are endemic for T. gondii and N. caninum, with increased risk associated with environmental conditions and dog management practices. Furthermore, dogs infected with L. infantum showed a higher likelihood of coinfection with N. caninum.

Toxoplasma gondii is a zoonotic parasite that can infect mammals and birds, posing a risk to human health. It can cause reproductive disorders in small ruminants. Neospora caninum affects ruminants, especially cattle, and causes abortions; however, studies have also reported reproductive alterations in sheep and goats. The aim of this study was to investigate the seroprevalence and epidemiological aspects of infection by T. gondii and N. caninum in goats in northern Paraná, Brazil. Blood samples were collected from 321 animals on eight goat farms in northern Paraná. IgG anti-T. gondii antibodies were analyzed using an indirect fluorescence antibody test (IFA), with cutoff points of 64 for T. gondii and 50 for N. caninum. Of the 321 animals analyzed, 110 (34.3%) were seropositive for T. gondii and 33 (10.3%) were seropositive for N. caninum. Eight farms (100%) were seropositive for T. gondii and seven (87.5%) were seropositive for N. caninum. Statistically significant associations were observed between seropositivity for T. gondii and a history of abortions and the presence of cats on the property. Investigation of the seroprevalence of T. gondii and N. caninum is essential for implementing measures to control and prevent toxoplasmosis and neosporosis in Northern Paraná.

Toxoplasmosis is a widely spread zoonosis worldwide, considered one of the most important parasitic infections that affect global public health, and usually, it is not correctly diagnosed. Serological tests for the diagnosis of Toxoplasma gondii infection have limitations in differentiating acute from chronic infection, which is important to determine the appropriate clinical management and treatment, mainly in pregnant women and immunocompromised individuals infected by this parasite. The present study aimed to characterize immunogenic epitopes from T. gondii immunodominant antigens, as SAG1(SRS29B), SAG2A (SRS34A), GRA1, GRA2, GRA3, GRA5, GRA6, GRA7, MAG1, BSR4, and CCp5A, by investigating if these parasite components might emerge as alternatives to improve the diagnosis of toxoplasmosis. A detailed comparative in silico analysis was used for this purpose. Once the protein sequences were retrieved from the ToxoDB database, different parameters were calculated, including physicochemical characteristics, accessibility values, and antigenicity. Multiple sequence alignment, 3D structures modeling, and the validation of 3D structures were also performed among all 11 peptides. Considering the results from the combination of all parameters analyzed, it can be hypothesized that the linear epitopes from SAG1, GRA3, and BSR4 proteins were found to be stable and hydrophilic, with a significant antigenicity score, and accessibility on the protein surface. Also, these three selected peptides were able to detect anti-T. gondii antibodies in serum samples from pigs infected by tachyzoites, when compared with control serum samples, obtained from the same naïve animals and tested by ELISA, demonstrating remarkable difference in terms of reactivity. Taken together, as our study addresses a critical challenge in the serodiagnosis of toxoplasmosis, particularly in gestational and congenital infections, where false-positive and false-negative results often arise from the use of native or recombinant antigens of T. gondii, our findings highlight the potential of synthetic peptides derived from novel epitopes of this parasite as alternative tools for the development of more accurate immunodiagnostic assays for toxoplasmosis.

Introduction: Toxoplasma gondii can infect all warm-blooded animals, including humans, which makes it a significant public health concern worldwide. Dogs can play a crucial role in the epidemiology of toxoplasmosis by acting as mechanical vectors and sentinel for environmental contamination. Objectives: This study aimed to assess the seroprevalence and spatial distribution of T. gondii in dogs from Ourinhos, São Paulo, Brazil. Methods: Blood samples from 602 dogs from different areas of Ourinhos municipality were collected during the rabies vaccination campaign. Information about the age, gender, breed of the dogs, and residential address of each tutor were collected. The indirect fluorescent antibody test (IFAT) was performed to evaluate the presence of antibodies against the parasite, while the spatial analysis was used to evaluate regions associated with seropositivity. Results: In total, 23.7% (143/602) of the samples tested positive, with no significant association observed between gender, age, or breed. Spatial analysis revealed a high concentration of positive cases in the municipality's most peripheral neighborhoods. Conclusions: These results indicate that dogs in Ourinhos, SP, Brazil, are exposed to T. gondii, and that peripheral neighborhoods likely have higher environmental contamination."

Introduction: Toxoplasmosis is caused by Toxoplasma gondii, an intracellular protozoan that can infect humans and all warm-blooded animals. Objective: The present study aimed to isolate and genetically characterize T. gondii in sheep meat. Methods: The study was conducted in a sheep slaughterhouse, and samples of masseter muscles, tongue, heart, diaphragm, and blood were collected from 50 sheep. The sheep sera were subjected to an indirect immunofluorescence assay (IFA) to detect anti-Toxoplasma gondii IgG antibodies. The cutoff point used was 1:64. Tissue samples from seropositive animals were subjected to mouse bioassay. Inoculating mice determined the virulence of isolated strains. Genotyping was performed using multilocus PCR-RFLP with 11 genetic markers. Kaplan-Meier was used to build a survival curve. Results: IFAT showed 12% (6/50) of seropositivity, and the antibody titers were 64 (4/50, 8%) and 256 (2/ 50, 4%). The isolates were named TgShBrPr01 and TgShBrPr02. Genetic characterization of the isolate TgShBrPr01 showed the genotype ToxoDB #183. The isolated TgShBrPr02 did not amplify all markers; however, the available typing data indicate a new genotype. The survival curve of TgShBrPr01 showed a high virulence strain and killed all the Swiss Webster mice infected with 102 and 103 T. gondii tachyzoites. Conclusion: This study isolated two new atypical (nonclonal) T. gondii strains from sheep, underscoring the potential risk of this transmission source to humans, especially when meat is consumed raw or undercooked.