Behavioral and Neuropathological Changes After Toxoplasma gondii Ocular Conjunctival Infection in BALB/c Mice.

Ocular infection with Toxoplasma gondii causes toxoplasmosis in mice. However, following ocular infection with tachyzoites, the cause of the accompanying progressive changes in hippocampal-dependent tasks, and their relationship with the morphology and number of microglia, is less well understood. Here, in 6-month-old, female BALB/c mice, 5 µl of a suspension containing 48.5 × 106 tachyzoites/ml was introduced into the conjunctival sac; control received an equal volume of saline. Before and after instillation, all mice were subject to an olfactory discrimination (OD) test, using predator (cat) feces, and to an open-field (OF) task. After the behavioral tests, the animals were culled at either 22 or 44 days post-instillation (dpi), and the brains and retinas were dissected and processed for immunohistochemistry. The total number of Iba-1-immunolabeled microglia in the molecular layer of the dentate gyrus was estimated, and three-dimensional reconstructions of the cells were evaluated. Immobility was increased in the infected group at 12, 22, and 43 dpi, but the greatest immobility was observed at 22 dpi and was associated with reduced line crossing in the OF and distance traveled. In the OD test, infected animals spent more time in the compartment with feline fecal material at 14 and at 43 dpi. No OD changes were observed in the control group. The number of microglia was increased at 22 dpi but returned to control levels by 44 dpi. These changes were associated with the differentiation of T. gondii tachyzoites into bradyzoite-enclosed cysts within the brain and retina. Thus, infection of mice with T. gondii alters exploratory behavior, gives rise to a loss in predator's odor avoidance from 2 weeks after infection, increased microglia number, and altered their morphology in the molecular layer of the dentate gyrus.

T. gondii Infection in Urban and Rural Areas in the Amazon: Where Is the Risk for Toxoplasmosis?

Toxoplasmosis, an infection caused by Toxoplasma gondii, which is found worldwide, can affect human and animal health in different ways. This study aimed to estimate the infection prevalence in humans and to determine risk factors related to urban and rural areas in a municipality in the Brazilian Amazon where an outbreak had been registered. Blood samples for serological analysis were obtained, and interviews were performed to fill out an epidemiological questionnaire. A total of 1140 individuals were included, of which 70.6% (804/1140; 95% CI: 67.9-73.2%) were positive for IgG anti-T. gondii antibodies. In rural areas, the prevalence was 62.6% (95% CI: 58.9-66.3%), while in urban areas, it was 81.9% (95% CI: 78.4-85.4%). The risk of becoming infected in urban areas was 2.7 times higher (95% CI = 2.0-3.6%) than that in rural areas. When comparing the prevalence in the age group from 1 to 10 years in both areas, the rate was 28.6% (42/147; 95% CI: 21.3-35.9%) for rural areas and 69.4% (61/88; CI 95%: 59.7-79.0%) for urban areas. Therefore, it is concluded that parasite exposure starts in the first years of life in urban areas and that disordered urban area expansion may cause an increase in exposure to the different strains of T. gondii present in the Amazon.

Anti-Toxoplasma gondii antibodies in beef cattle slaughtered in the metropolitan region of Belém, Brazilian Amazon.

The relevance of consuming raw or undercooked beef in the transmission of toxoplasmosis is unclear due to the high resistance of cattle to infection. However, this possibility needs to be considered in endemic areas, such as the Amazon, where the consumption of beef is frequent. The objective of this study was to determine the frequency of anti-Toxoplasma gondii IgG antibodies in beef cattle slaughtered in the metropolitan region of Belem, Pará state, Brazil. Blood samples were collected from 500 animals of both genders in a licensed slaughterhouse in Belém. Anti-T. gondii IgG antibodies were detected by an indirect immunofluorescence assay (IFA) with a cut-off titer of 1:64. Anti-T. gondii antibodies were found in 203 animals (40.6%), with a titer of 64 in 112 animals (55.2%), 128 in 68 animals (33.5%), 256 in 15 animals (7.4%), 512 in 5 animals (2.5%), and 1,024 in 3 animals (1.4%). No significant difference was observed between males and females (p > 0.05). The high frequency of anti-T. gondii antibodies observed in beef cattle slaughtered in Belém indicates that the meat of these animals may be an important source of infection for humans and carnivorous domestic animals when inadequately cooked beef is consumed.

Anti-Toxoplasma gondii antibodies in beef cattle slaughtered in the metropolitan region of Belém, Brazilian Amazon / Anticorpos anti-Toxoplasma gondii em bovinos de corte abatidos na região metropolitana de Belém, Amazônia brasileira

Abstract The relevance of consuming raw or undercooked beef in the transmission of toxoplasmosis is unclear due to the high resistance of cattle to infection. However, this possibility needs to be considered in endemic areas, such as the Amazon, where the consumption of beef is frequent. The objective of this study was to determine the frequency of anti-Toxoplasma gondii IgG antibodies in beef cattle slaughtered in the metropolitan region of Belem, Pará state, Brazil. Blood samples were collected from 500 animals of both genders in a licensed slaughterhouse in Belém. Anti-T. gondii IgG antibodies were detected by an indirect immunofluorescence assay (IFA) with a cut-off titer of 1:64. Anti-T. gondii antibodies were found in 203 animals (40.6%), with a titer of 64 in 112 animals (55.2%), 128 in 68 animals (33.5%), 256 in 15 animals (7.4%), 512 in 5 animals (2.5%), and 1,024 in 3 animals (1.4%). No significant difference was observed between males and females (p > 0.05). The high frequency of anti-T. gondii antibodies observed in beef cattle slaughtered in Belém indicates that the meat of these animals may be an important source of infection for humans and carnivorous domestic animals when inadequately cooked beef is consumed.

Resumo A importância do consumo de carne bovina crua ou mal passada na transmissão da toxoplasmose ainda é pouco definida, devido à alta resistência desses animais à infecção. Contudo, em áreas endêmicas, como da Amazônia, onde o consumo de carne bovina é frequente, essa possibilidade precisa ser considerada. O objetivo do presente estudo foi determinar a frequência de anticorpos IgG anti-T. gondii em bovinos de corte abatidos na região metropolitana de Belém, Estado do Pará. Foram coletadas amostras de sangue de 500 animais, de ambos os sexos, em um abatedouro oficial do município de Belém. A detecção de anticorpos IgG anti-T. gondii foi realizada pela reação de imunofluorescência indireta (RIFI), com ponto de corte de 1:64. Anticorpos anti-T. gondii foram encontrados em 203 animais (40,6%), com títulos de 64 em 112 animais (55,2%); 128 em 68 (33,5%); 256 em 15 (7,4%); 512 em 05 (2,5%); e 1.024 em 03 (1.4%). Não foi observada diferença estatisticamente significativa entre machos e fêmeas (p > 0,05). A alta frequência de anticorpos anti-T. gondii, observada nos bovinos de corte abatidos em Belém, indica que a carne desses animais pode ser importante fonte de infecção para humanos e animais domésticos carnívoros, caso venha a ser consumida de forma inadequada.