First report on seroprevalence and risk factors of Toxoplasma gondii infection in sheep and goats in North Lebanon.

INTRODUCTION: Toxoplasmosis is of dual importance in both public and veterinary health due to the respective risk of transplacental transmission in primo-infected pregnant women and economic losses caused by abortions in mammals. One of the main routes of Toxoplasma gondii transmission to humans is the consumption of raw or undercooked meats containing parasitic cysts. Here, we performed the first epidemiological study to determine the seroprevalence and the risk factors of toxoplasmosis in livestock in Lebanon. METHODOLOGY: Using a modified agglutination test with a cut-off of 1:40, we tested the positivity rate of Immunoglobulin G antibodies in the sera of 100 sheep and 80 goats collected from 18 different livestock farms located in North Lebanon between March and June 2018. RESULTS: Anti-Toxoplasma gondii IgG antibodies were detected in 42% of sheep and 34% of goats. Adults (> 1 year) were significantly more infected by T. gondii than the lambs (< 1 year) in both species (p < 0.05). CONCLUSIONS: These findings indicated that food animals are highly exposed to T. gondii in Lebanon and could be potentially a major risk factor of T. gondii infection to humans. Consequently, national prophylactic strategies should be implemented to control and to prevent T. gondii transmission between animals and humans.

Experimental Toxoplasmosis in Japanese Quails (Coturnix coturnix japonica).

OBJECTIVE: In this study, forming of experimental toxoplasmosis in quails; clinical, pathological, and serological determination of tissue lesions and bioassay techniques, which were aimed to compare them and determine pathogenesis. METHODS: A total of 120 one-year-old female quails (Coturnix coturnix japonica) were divided into oral infection, parenteral infection, and control groups. The oral group was infected with 0.5 ml inoculum suspension containing 106 tachyzoites of Toxoplasma gondii, whereas the control group was administered 0.5 ml of saline. The parenteral group was further divided into the following four subgroups: intraperitoneal, intramuscular, intravenous, and cloacal. The quails of the parenteral group were also divided into two groups and one by control group within itself for the 105 and 104 doses of the tachyzoite inoculums. RESULTS: Because of acute toxoplasmosis, death occurred in a quail that as intramuscularly infected with 105 tachyzoites; the quail exhibited neurological clinical symptoms such as torticollis, ataxia, and tremor. In histopathologic examination, T. gondii tissue cysts were detected in infected quails that were intramuscularly infected with 105 tachyzoites. Mouse trials were conducted using tissues of seropositive quails and isolated from peritoneal fluids infected mice. By Sabin-Feldman dye test and indirect hemagglutination test, seropositivity was observed in quails infected with 105 and 104 tachyzoites. CONCLUSION: Similar studies and subclinical cases, which may overlooked was concluded for diagnosis of toxoplasmosis with useful bioassay applications and serological tests.

Occurrence of Toxoplasma gondii and risk factors for infection in pigs raised and slaughtered in the Triângulo Mineiro region, Minas Gerais, Brazil / Ocorrência e fatores de risco da infecção por Toxoplasma gondii em suínos criados e abatidos na região do Triângulo Mineiro, Minas Gerais, Brasil

The Triângulo Mineiro region from Minas Gerais state, is an important meat-exporting region of Brazil and data about Toxoplasma gondii infection in pigs raised and slaughtered in this area are scarce. Therefore, the aim of this study was to evaluate the occurrence of T. gondii in swine and establish the risk factors associated with the infection. Samples were collected from 600 pigs raised under intensive system in farms located at three different counties (Carmo do Paranaíba, Patrocínio and Perdizes). The samples were submitted to indirect hemagglutination antibody test with dilution of 1:32 and to indirect immunofluorescence antibody test with a cutoff of 1:64. The occurrence of positive pig was 3.3% (n=20) and 51.8% (n=311) respectively. A significant difference was observed between toxoplasmatic infection and factors such as lineage, animal origin, size of the farm, collective raising with others species, presence of rodents and type of water offered (p≤0.05). There was no difference between gender and the farm goals. The results demonstrated an occurrence of anti-T.gondii antibodies higher than expected for intensive pig raising system on the studied area, which could indicate a possible sanitary management problem on the studied proprieties. Improvements on the raising techniques are necessary to reduce T. gondii infection sources.(AU)

A região do Triângulo Mineiro, no estado de Minas Gerais, é uma importante região exportadora de carne do Brasil e pesquisas sobre a infecção por Toxoplasma gondii em suínos criados e abatidos nesta região são escassos. Portanto, o objetivo deste estudo foi avaliar a ocorrência de T. gondii nesses animais e estabelecer os fatores de risco associados com a infecção. Foram coletadas amostras de 600 suínos criados sob sistema intensivo, em fazendas localizadas em três municípios diferentes (Carmo do Paranaíba, Patrocínio e Perdizes). As amostras foram submetidas à Hemaglutinação Indireta com diluição de 1:32 e à Reação de Imunofluorescência Indireta com ponto de corte 1:64. A ocorrência de suínos positivos foi de 3,3% (n=20) e 51,8% (n=311), respectivamente. Foi observada diferença significativa entre a infecção toxoplásmica e fatores como linhagem, procedência dos animais, tamanho das propriedades, criação em conjunto com outras espécies, presença de roedores e tipo de água consumida (p≤0,05). Não houve diferenças estatísticas entre o sexo e finalidade de produção em relação à infecção por T. gondii. Os resultados demonstraram uma ocorrência de anticorpos anti-T. gondii superior à esperada em criações intensivas de suínos na região estudada, o que poderia indicar uma possível falha no manejo sanitário das propriedades estudadas. Melhorias nas técnicas de criação são necessárias para redução das fontes de infecção por T. gondii nos rebanhos.(AU)

Risk factors associated with Toxoplasma gondii infection in free-range chickens in the semiarid region of Brazil / Fatores de riscos associados com a infecção de Toxoplasma gondii em galinhas de vida livre na região do semiárido do Brasil

Abstract This study aimed to investigate the frequency of anti-Toxoplasma gondii antibodies in serum from 629 chickens on 39 family farms in seven municipalities in the semiarid region, Pernambuco, Brazil, and to identify risk factors associated with T. gondii infection. The risk factors were studied in 421 samples from 29 farms. Anti-T. gondii antibodies were investigated by indirect fluorescent antibody test with a 1:16 cutoff. The frequency of positive chickens was 27.9% (176/629) and 94.8% of the farms studied had chickens infected by T. gondii. Multivariate analysis showed variables significantly associated with anti-T. gondii antibodies in serum: slaughter of animals on the farm, reproductive disorders in sheep, consumption of fetal adnexa and placentas by chickens, presence of sheep in the property and birth of sheep the property. The results suggest that there is a complex relationship between general management practices for different animal species raised on the same farm and the prevalence of T. gondii infection in chickens. In addition, the results draw attention to the risk of human infection by T. gondii via consumption of infected chicken meat, because the farming conditions and the low human development indices observed in the region studied result in inappropriate meat preparation practices.

Resumo Objetivou-se investigar a prevalência de anticorpos anti-Toxoplasma gondii em 629 soros de galinha em 39 propriedades da agricultura familiar em sete municípios de Pernambuco, Brasil e identificar os fatores de risco associados à infecção. Para a pesquisa de anticorpos anti-T. gondii empregou-se a reação de imunofluorescência indireta com ponto-de-corte 1:16. O estudo dos fatores de risco foi realizado em 29 propriedades, totalizando 421 amostras. A prevalência de aves positivas foi de 27,9% (176/629) e 94,8% das propriedades tinham galinhas infectadas por T. gondii. Na análise multivariada, obteve-se como variáveis significativas associadas com anticorpos anti-T. gondii a ocorrência de abate de animais na propriedade, relato de distúrbios reprodutivos em ovinos, ingestão de anexos fetais e placentas pelas galinhas, presença de ovinos na propriedade e nascimento de ovinos na propriedade. Os resultados sugerem relações complexas entre o manejo das espécies animais criados nas propriedades e a prevalência da infecção nas galinhas. Em adicional, chama-se atenção para o risco de infecção humana por T. gondii via consumo de carne de galinha infectada, uma vez que as condições de criação e os baixos índices de desenvolvimento observados na região resultam em inapropriada preparação da carne para consumo.

Risk factors for Toxoplasma gondii infection in sheep in the northeastern region of Brazil / Fatores de risco para a infecção de Toxoplasma gondii em ovinos da região nordeste do Brasil

Toxoplasma gondii is an infective parasite that causes reproductive disorders such as abortion, fetal mummification, birth of weak offspring, and stillbirth, thereby causing economic losses to sheep production. The northeastern region of Brazil has approximately 171 million small ruminants, of which 5.4% are sheep. The present study aimed at determining the rate of occurrence of T. gondii in sheep flocks on 60 farms in 19 municipalities in the three mesoregions (eastern, semi-arid, and sertão or backlands) of the state of Sergipe, Brazil, and the risk factors associated with this infection. Serum samples were collected between 2011 and 2012, from 60 farms located in 19 municipalities in the three mesoregions: 680 in the eastern region, 280 in the semi-arid region, and 240 in the backlands, totaling 1,200 samples (990 females and 210 males). Anti-T. gondii antibodies were detected by means of the indirect fluorescence antibody test (IFAT ≥ 64). The highest occurrence was detected in the eastern region (45.3%, p = 0.001). On farms with subsistence production, the risk of having animals infected by T. gondii was approximately twice as high as on breeding/rebreeding/fattening farms (OR: 3.03; CI: 1.97-4.68). There was a significant lack of sanitary care, such as absence of a dunghill (p = 0.000; OR: 1.60; CI: 1.26-2.03), quarantine (p = 0.000; OR: 1.87; CI: 1.45-2.41) and disinfection (p = 0.003; OR: 1.46; CI: 1.13-1.88). Regarding feeding, the risk of infection was 1.74 and 1.37 times higher in places that used a trough and/or that cats could access, respectively. The present study allows the conclusions that T. gondii is found on farms in the three mesoregions of the state of Sergipe and that environmental and management factors have an influence on sheep infection.(AU)

Toxoplasma gondii é um parasita cuja infecção leva a desordens reprodutivas como aborto, mumificação fetal, nascimento de cordeiros fracos e natimortos, provocando perdas econômicas na produção ovina. A região nordeste do Brasil possui aproximadamente 171 milhões de pequenos ruminantes, dos quais 5,4% são ovinos. Este estudo tem como objetivo determinar a ocorrência de T. gondii nos rebanhos ovinos de 60 propriedades de 19 municípios de três mesorregiões (leste, semiárido e sertão) do estado de Sergipe, Brasil, e os fatores de risco associados a essa infecção. Amostras de soro foram coletadas entre 2011 e 2012, em 60 propriedades localizadas em 19 municípios das três mesorregiões: 680 na região leste, 280 no semiárido e 240 no sertão, totalizando 1.200 amostras (990 fêmeas e 210 machos). Anticorpos anti-T.gondii foram detectados por reação de imunofluorescência indireta (RIF ≥ 64). A maior ocorrência foi detectada na região leste (45,3%, p = 0.001). Em propriedades com produção de subsistência, o risco de animais infectados por T. gondii é aproximadamente duas vezes maior que nas de cria/recria/engorda (OR = 3.03/ IC: 1.97-4.68). A ausência de cuidados sanitários, como ausência de esterqueira (p = 0.000/ OR: 1.60; CI: 1.26-2.03); quarentena (p = 0.000/ OR: 1.87; CI: 1.45-2.41) e desinfecção (p = 0.003/ OR: 1.46; CI: 1.13-1.88) foram significantes. Em relação à alimentação, o risco de infecção aumenta 1.74 e 1.37 em locais que utilizam cocho ou com presença de gatos, respectivamente. Este estudo permite concluir que o T. gondii é encontrado em propriedades das mesorregiões do estado de Sergipe e fatores ambientais e de manejo estão influenciando nas infecções em ovinos.(AU)

Risk factors for Toxoplasma gondii infection in sheep and cattle from Fernando de Noronha Island, Brazil / Fatores de risco para infecção por Toxoplasma gondii em ovinos e bovinos na Ilha de Fernando de Noronha, Brasil

Abstract Toxoplasmosis is a zoonotic disease of global distribution that affects all warm-blooded animals. The purpose of this investigation was to determine the prevalence of T. gondii infection and identify the risk factors associated with its occurrence in domestic ruminants raised on the island of Fernando de Noronha, Brazil, and to confirm that cattle and sheep raised in Fernando de Noronha Island present statistically different T. gondii prevalence rates. Serum samples were collected from sheep (n=240) and cattle (n=140) for the detection of antibodies by indirect immunofluorescence. Samples were collected from all the animals on all the farms. Risk factors were analyzed by univariate analysis and logistic regression. The prevalence rate of positive sheep was 85.0% while that of cattle was 10.7%. A multivariate analysis revealed that the site of contact of sheep with felines was a risk factor. For cattle, the risk factors identified in this study were: extensive farming system, water source, more than three cats per farm, and the presence of rats in feed storage locations. The findings revealed a significant difference in the prevalence rates in sheep and cattle raised in this insular environment.

Resumo A toxoplasmose é uma zoonose cosmopolita que acomete animais de sangue quente. Objetivou-se nessa investigação determinar a prevalência e identificar os fatores de risco associados à ocorrência da infecção por T. gondii em ruminantes domésticos criados na Ilha de Fernando de Noronha e demonstrar que bovinos e ovinos criados na ilha de Fernando de Noronha, Brasil, apresentam prevalências estatisticamente distintas. Foram obtidas amostras de soro sanguíneo de todos os ovinos (n=240) e bovinos (n=140) de todas as propriedades da ilha para a pesquisa de anticorpos na Reação de Imunofluorescência Indireta. Os fatores de risco foram analisados por meio da análise univariada e regressão logística. A prevalência de ovinos reagentes foi de 85,0% e 10,7% para bovinos, que foram significativamente diferentes. Na análise multivariada, local de contato de ovinos com outras espécies foi identificado como fator de risco. Para os bovinos, os fatores de risco foram: sistema extensivo, fonte de água, número de gatos nas propriedades e a presença de rato. Os resultados obtidos demonstram diferença significativa nas prevalências em ovinos e bovinos criados neste ambiente insular.

The expression of lactate dehydrogenase is important for the cell cycle of Toxoplasma gondii.

In Toxoplasma gondii, lactate dehydrogenase is encoded by two independent and developmentally regulated genes LDH1 and LDH2. These genes and their products have been implicated in the control of a metabolic flux during parasite differentiation. To investigate the significance of LDH1 and LDH2 in this process, we generated stable transgenic parasite lines in which the expression of these two expressed isoforms of lactate dehydrogenase was knocked down in a stage-specific manner. These LDH knockdown parasites exhibited variable growth rates in either the tachyzoite or the bradyzoite stage, as compared with the parental parasites. Their differentiation processes were impaired when the parasites were grown under in vitro conditions. In vivo studies in a murine model system revealed that tachyzoites of these parasite lines were unable to form significant numbers of tissue cysts and to establish a chronic infection. Most importantly, all mice that were initially infected with tachyzoites of either of the four LDH knockdown lines survived a subsequent challenge with tachyzoites of the parental parasites (10(4)), a dose that usually causes 100% mortality, suggesting that live vaccination of mice with the LDH knockdown tachyzoites can confer protection against T. gondii. Thus, we conclude that LDH expression is essential for parasite differentiation. The knockdown of LDH1 and LDH2 expression gave rise to virulence-attenuated parasites that were unable to exhibit a significant brain cyst burden in a murine model of chronic infection.

Toxopain-1 is critical for infection in a novel chicken embryo model of congenital toxoplasmosis.

We tested the hypothesis that cathepsins and specifically toxopain-1, a cathepsin B, play a critical role in the pathogenesis of toxoplasmosis. We found that inhibiting the expression of toxopain-1-specific mRNA and protein by >60% significantly decreased the capacity of the parasites to multiply and invade in vitro. To relate these in vitro results to the role of toxopain-1 in pathogenesis in vivo, we developed a novel chicken embryo model of congenital toxoplasmosis. Inhibiting either toxopain-1 expression or specific cysteine proteinase activity significantly reduced congenital infection of chicken embryos, as determined by histopathology and by the number of parasites quantified by real-time PCR. Our new model provides key in vivo validation for the hypothesis that toxopain-1 is a potential drug target in Toxoplasma gondii and also provides a new animal model for rapid, inexpensive screening of antiparasitic compounds.

STAT1 is essential for antimicrobial effector function but dispensable for gamma interferon production during Toxoplasma gondii infection.

The opportunistic protozoan Toxoplasma gondii is a prototypic Th1-inducing pathogen inducing strong gamma interferon (IFN-gamma) cytokine responses that are required to survive infection. Intracellular signaling intermediate STAT1 mediates many effects of IFN-gamma and is implicated in activation of T-bet, a master regulator of Th1 differentiation. Here, we show that T. gondii-infected STAT1-null mice fail to upregulate the IFN-gamma-dependent effector molecules inducible nitric oxide synthase (iNOS), IGTP, and LRG-47, which are required for mice to survive infection. Both T-bet and interleukin-12 receptor beta2 (IL-12Rbeta2) failed to undergo normal upregulation in response to T. gondii. Development of IFN-gamma-producing CD4(+) and CD8(+) T lymphocytes was severely curtailed in the absence of STAT1, but a substantial level of STAT1-independent non-T-cell-derived IFN-gamma was induced. Absence of STAT1 also resulted in increased IL-4, Arg1, Ym1, and Fizz1, markers of Th2 differentiation and alternative macrophage activation. Together, the results show that T. gondii induces STAT1-dependent T-lymphocyte and STAT1-independent non-T-cell IFN-gamma production, but that effector functions of this type 1 cytokine cannot operate in the absence of STAT1, resulting in extreme susceptibility to acute infection.

Toxoplasmosis in Indo-Pacific humpbacked dolphins (Sousa chinensis), from Queensland.

OBJECTIVE: To describe the clinical signs, gross pathology, serology, bacteriology, histopathology, electron microscopy and immunohistochemistry findings associated with toxoplasmosis in four Indo-Pacific humpbacked dolphins (Sousa chinensis) that stranded in Queensland in 2000 and 2001. DESIGN: Clinical assessment, gross necropsy, and laboratory examinations. PROCEDURE: Necropsies were performed on four S. chinensis to determine cause of death. Laboratory tests including serology, bacteriology, histopathology and transmission electron microscopy were done on the four dolphins. Immunohistochemistry was done on the brain, heart, liver, lung, spleen and adrenal gland from various dolphins to detect Toxoplasma gondii antigens. RESULTS: Necropsies showed all of four S. chinensis that stranded in Queensland in 2000 and 2001 had evidence of predatory shark attack and three were extremely emaciated. Histopathological examinations showed all four dolphins had toxoplasmosis with tissue cysts resembling T. gondii in the brain. Tachyzoite stages of T. gondii were detected in the lungs, heart, liver, spleen and adrenal gland, variously of all four dolphins. Electron microscopy studies and immunohistochemistry confirmed the tissues cysts were those of T. gondii. All four dolphins also had intercurrent disease including pneumonia, three had peritonitis and one had pancreatitis. CONCLUSION: Four S. chinensis necropsied in Queensland in 2000 and 2001 were found to be infected with toxoplasmosis. It is uncertain how these dolphins became infected and further studies are needed to determine how S. chinensis acquire toxoplasmosis. All four dolphins stranded after periods of heavy rainfall, and coastal freshwater runoff may be a risk factor for T. gondii infection in S. chinensis. This disease should be of concern to wildlife managers since S. chinensis is a rare species and its numbers appear to be declining.

Involvement of apoptosis and interferon-gamma in murine toxoplasmosis.

PURPOSE: A murine toxoplasmosis model has been developed that results in central nervous system (CNS) and ocular inflammation characterized by encephalitis with numerous brain tissue cysts and milder inflammation with rare tissue cysts in the eye after 4 weeks of Toxoplasma gondii infection. In this model IFN gamma and inducible nitric oxide (iNO) are protective against T. gondii infection. In this study, the role of apoptosis in the pathogenesis of toxoplasmosis was investigated. METHODS: C57BL/6 (wild-type mice), B6MRL/lpr, and B6MRL/gld (defective Fas or FasL expression, respectively) mice were infected intraperitoneally with 20 to 30 tissue cysts of the ME-49 strain of T. gondii. Mice were killed at days 0, 14, or 28 after infection. The eyes and brains were harvested for histologic, immunohistochemical, and molecular studies. Analysis included immunostaining for Fas, FasL, Bcl-2, and Bax; in situ apoptosis detection (TUNEL assay); RT-PCR amplification for IFN gamma; and measurement of ocular nitrite levels. The control mice were naïve mice of each strain that received no inoculation or injection. RESULTS: Wild-type mice appeared to constitutively express apoptotic molecules at higher levels in the eye than in the brain. Consequently, during T. gondii infection, apoptosis was greater in the eyes than in the brain. Untreated naïve lpr and gld mice showed no expression of Fas and FasL, respectively. After infection, a slightly higher number of tissue cysts (lpr, 11.8 +/- 2.4; gld, 10.3 +/- 3.4) were found in the brains of the mutants than in the control animals (8.8 +/- 2.9). However, no significant differences between the number of apoptotic cells, inflammatory scores, or number of tissue cysts were noted in the eyes. IFN gamma mRNA in control mice was detected at day 28 after infection, whereas in both mutants, mRNA production occurred earlier, at day 14. Ocular nitrite levels were higher in lpr and gld mice than in wild-type mice. CONCLUSIONS: No significant difference in the degree of ocular inflammation and apoptosis was detected between the wild-type and Fas or FasL mutant mice. However, there was an earlier and subjectively greater expression of IFN gamma in the brain and eye and a higher level of nitrite in the ocular tissue of mutant strains than in the wild type. Multiple factors are likely to be involved in the pathogenesis of ocular toxoplasmosis.

Identification of STAT4-dependent and independent mechanisms of resistance to Toxoplasma gondii.

The capacity of IL-12 to stimulate T and NK cell production of IFN-gamma is required for resistance to Toxoplasma gondii. To identify the transcription factors involved in this mechanism of resistance, mice deficient in STAT4, a protein involved in IL-12 signaling, were infected with T. gondii and their immune responses were analyzed. STAT4-/- mice were unable to control parasite replication and died during the acute phase of infection, whereas wild-type mice controlled parasite replication and survived this challenge. The susceptibility of STAT4-/- mice to toxoplasmosis correlated with a defect in their ability to produce IFN-gamma in response to infection, whereas administration of IFN-gamma to these mice inhibited parasite replication and delayed time to death. Interestingly, analysis of infected STAT4-/- mice revealed that these mice did produce low levels of IFN-gamma during infection, and the ability of splenocytes from infected or uninfected STAT4-/- mice to produce IFN-gamma was enhanced by the addition of IL-2 plus IL-18. Moreover, administration of IL-2 plus IL-18 to STAT4-/- mice resulted in elevated serum levels of IFN-gamma associated with a decreased parasite burden and delayed time to death. In vivo depletion studies demonstrated that the ability of IL-2 plus IL-18 to mediate STAT4-independent resistance to T. gondii is dependent on NK cell production of IFN-gamma. Together, these studies identify STAT4 as an important transcription factor required for development of the innate NK and adaptive T cell responses necessary for resistance to T. gondii. However, other signaling pathways can be used to bypass STAT4-dependent production of IFN-gamma and enhance innate resistance to T. gondii.

Increased susceptibility to Toxoplasma gondii infection in SAG-1 transgenic mice.

SAG-1, one of the major surface proteins of Toxoplasma gondii, has been reported to play an important role in immune and pathogenic mechanisms of the parasites but its exact function is still unclear. We investigated the time courses of T. gondii infection in B6C3F1 transgenic mice carrying the SAG-1 gene. SAG-1 transgenic mice were infected intraperitoneally with a high virulent RH strain or a low virulent Beverley strain of T. gondii. When infected with RH strain tachyzoites, no significant differences in time courses of survivals between SAG-1 transgenic and wild-type mice were observed. Both groups succumbed to an acute infection within 8 days after infection. However, a lower survival rate (20%) was observed in SAG-1 transgenic mice than in wild-type (80%), when infected with Beverley strain cysts. This result indicates that SAG-1 transgenic mice are more susceptible to T. gondii infection as compared with their wild-type counterpart. ELISA using recombinant SAG-1 protein indicates that SAG-1 transgenic mice do not produce antibodies to the SAG-1 molecule. These findings may provide a critical tool for analysing the molecular mechanisms of pathogenesis and host immune responses during toxoplasmosis.

Cold stress-induced modulation of inflammatory responses and intracerebral cytokine mRNA expression in acute murine toxoplasmosis.

The effects of a physical stressor, cold water stress (CWS), within the central nervous system were investigated in the acute phase of infection with Toxoplasma gondii. Female BALB/c mice were subjected to CWS for 5 min each day for 8 days prior to oral infection with 20 cysts of the low virulent ME 49 strain. Animals were killed at 10-day intervals to detect inflammation, gliosis, and expression of intracerebral cytokine mRNAs. Zones of inflammation were detected by Nissl staining and gliosis by immunoreactivity to glial fibrillary acidic protein. Larger zones of inflammation and reactive astrogliosis were consistently observed in mice subjected to CWS and infected (CWS +INF) compared to control infected (INF) mice. Expression of interleukin (IL)-1beta, IL-2, IL-12, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, and inducible nitric oxide synthase (iNOS) were decreased in CWS+INF mice at 10 days postinoculation (PI), followed by a gradual increase after day 20 PI. This was in contrast to increased expression of these cytokines at 10 days PI in INF mice with a gradual decline thereafter. Inflammation and astrogliosis in CWS+INF mice were associated with an increased expression of IL-1beta, IL-6, IL-12, and TNF-alpha between 20 and 30 days PI. These findings correlated with the continuous gene expression of tachyzoite surface antigen (SAG)-1 mRNA in CWS+INF mice compared to its sharp decline in INF mice after 20 days PI. These results suggest that CWS delays regulation and control of intracerebral Toxoplasma gondii during acute infection in BALB/c mice by decreasing the early expression of IFN-gamma, IL-2, TNF-alpha, iNOS, IL-1beta, and IL-12, while increasing the expression of IL-6, a counterregulatory cytokine.

Acute toxoplasmosis following renal transplantation in three cats and a dog.

Three cats and 1 dog that had undergone renal transplantation because of end-stage renal disease were examined because of complications 3 to 6 weeks after surgery. One cat died prior to treatment of the complications; Toxoplasma cysts were found in sections of the renal allograft, and Toxoplasma tachyzoites were found in other organs. The other 2 cats and the dog died despite treatment, and protozoal cysts, as well as tachyzoites, were identified in other organs but not within the allografts, suggesting that reactivation of latent infection following immunosuppression was the most likely cause of disseminated toxoplasmosis. These cases illustrate that toxoplasmosis can be a fatal complication in renal transplant recipients. We currently recommend that feline and canine donors and recipients undergo serologic testing for toxoplasmosis prior to surgery. In addition, we suggest that seropositive donors not be used for seronegative recipients and that seropositive recipients and that seropositive recipients be monitored closely after surgery for clinical signs of toxoplasmosis.

Toxoplasma gondii infection in sheep and cattle.

Toxoplasma gondii is a protozoan parasite that can infect all warm-blooded animals. Sheep and cattle show different susceptibilities to T. gondii infection. Primary infection in pregnant sheep can result in abortion or the birth of weak lambs but they are then protected against further challenge by the development of an effective immunity. Cattle on the other hand can be readily infected, but abortion or perinatal mortality have not been recorded. The evidence suggests that cattle develop a more effective immune response to T. gondii infection than sheep. Potential mechanisms to explain these differences are discussed in this paper.

Mycotoxin T-2 and aflatoxin B1 as immunosuppressors in mice chronically infected with Toxoplasma gondii.

The aim of this study was to determine whether repeated ingestion of mycotoxin T-2 (T2) or aflatoxin B1 (AFL) at low doses could contribute to the activation of toxoplasmosis in experimentally infected mice. Mice were divided into two groups: Control (C) and Infected (I). The cyst-forming Beverley strain of Toxoplasma gondii was used to produce the infection one month before treatment with mycotoxins. Mycotoxins were given intragastrically for a 50-day period. The average weight gain was reduced in the groups treated with mycotoxins. Mice developed specific IgG to T. gondii. Histopathological studies showed severe encephalitis in all groups infected. The number of unruptured and ruptured cysts was established and the severity of the lesions was evaluated, the groups treated with mycotoxins being the most severely affected. Immunohistochemical studies of the brain showed free antigen in tissues surrounding ruptured cysts. It is suggested that low and repeated doses of mycotoxins, necessary to produce a subclinical intoxication, precipitate Toxoplasma cyst rupture and consequently the activation of chronic toxoplasmosis.

Acquired retinochoroiditis in hamsters inoculated with ME 49 strain Toxoplasma.

PURPOSE: These studies were undertaken to establish an animal model for use in studies of ocular toxoplasmosis. An animal model is needed to examine the development, progression, and resolution of ocular Toxoplasma infections and to study the effects on the disease of currently used and experimental therapies. METHODS: Cysts of the ME 49 strain of Toxoplasma gondii were injected intraperitoneally into each of 60 golden hamsters. The hamsters' eyes were examined before inoculation and at intervals after inoculation, and fundus photographs were taken. Histologic sections were analyzed and photographed to document the ocular effects of the infection. RESULTS: Retinochoroiditis was found in both eyes of all hamsters within 2 to 3 weeks of inoculation. The disease resolved spontaneously without treatment and was quiescent in most cases at 12 weeks after inoculation. The animals remained in good general health, and those tested had high antibody titers to Toxoplasma (1:256 to 1:32,000) at 6 months after the infection. The discovery of cysts and lesions in the retina confirmed the diagnosis. CONCLUSIONS: Although the lesions were not identical to those of human disease, this animal model of ocular toxoplasmosis offers several advantages: reproducibility, short incubation time, spontaneous resolution without treatment, consistent production of cysts, and ease of inoculation intraperitoneally without intraocular injection.

Effects of swimming exercise on the pathogenesis of acute murine Toxoplasma gondii Me49 infection.

The effects of swimming exercise on the pathogenesis of acute murine toxoplasma infection were studied. Swimming (45 min/day) initiated on the day of inoculation with the avirulent Me49 strain of Toxoplasma gondii did not alter survival of infected mice. At a later stage of infection, daily swimming appeared to promote the recovery of appetite and weight gain. Immune activation was apparent in toxoplasma-infected mice, and swimming blunted splenic enlargement but not the respiratory burst activity of peritoneal exudate cells. Infection caused a significant elevation of serum tumor necrosis factor (TNF) levels which was attenuated by a daily swimming program. These data show that swimming exercise is not deleterious to mice acutely infected with T. gondii Me49 and that the more rapid recovery in exercised mice is associated with reduced serum TNF levels.

Pathogeny and immunological control of toxoplasmosis.

1. Toxoplasma gondii is a ubiquitous, obligate intracellular parasite of worldwide distribution. In humans, the parasite exists in two forms: the tachyzoite is the rapidly multiplying stage of the parasite which actively invades host cells and represents the principal pathogenic form at the acute phase of the disease; the bradyzoite is the form which multiplies slowly in host cells, resulting in the formation of cysts which persist in tissues. Several antigenic components have been identified, some of which are characteristic for each parasitic stage; particularly, in tachyzoites, the 30 kDa membrane protein represents up to 5% of the total protein content. 2. Toxoplasma infection in humans is usually asymptomatic because of effective immunity involving antibodies, T cells and cytokines. Activated macrophages, CD4 and CD8 lymphocytes and cytokines, such IFN gamma, play a major role in the control of acute infection and the maintenance of infection at the chronic stage. The alteration of immune functions, as observed in congenitally infected children and in HIV-infected patients, may induce the recrudescence of previously latent toxoplasmosis, in relation to disruption of the cyst form of the parasite. The resulting reactivation is responsible for life-threatening infections which are frequently manifested as toxoplasmic encephalitis. 3. In this review, the parasite and immunological factors participating in the pathogenesis of the lesions associated with acute, chronic and reactivated toxoplasmosis are presented.