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PubMed1993

Application of the polymerase chain reaction to the diagnosis of human toxoplasmosis.

Toxoplasmosis may cause significant damage to the developing fetus and is a life-threatening opportunistic infection in immunocompromised persons. Serological investigation is unreliable, while isolation of the parasite is time consuming and may lack sensitivity. We have developed a system for detecting Toxoplasma gondii based on the amplification of the P30 gene using sequential rounds of PCR and nested primers. The clinical value of this technique was assessed by the investigation of a range of tissues taken from pregnant women, fetuses, neonates, AIDS patients and organ graft recipients. The PCR assay produced more positive reactions than isolation of the parasite by means of cell culture or animal inoculation. Extended autoradiography was found to be more sensitive than stained agarose gels for detecting the PCR product. Systematic contamination of PCR reactions was avoided but it was not possible to exclude sporadic contamination in certain cases. Detection of specific DNA is of clinical value in the investigation of the pregnant woman in order to assess the risk of transplacental passage of infection and in the fetus and neonate to identify congenital toxoplasmosis. Even so, PCR findings must be interpreted with caution because of the risk of a sample being contaminated. PCR may be the investigation of choice when brain biopsy is performed on a patient with AIDS and when toxoplasmosis associated with bone marrow transplantation is suspected.

AIDS-Related Opportunistic Infections↗
PubMed2006

Toxoplasmosis: beyond animals to humans.

The parasitic zoonosis toxoplasmosis, which was poorly understood before the advent of the HIV epidemic, has become a major clinical problem worldwide. Humans acquire toxoplasmosis from cats, from consuming raw or undercooked meat and from vertical transmission to the foetus through the placenta during pregnancy. Studies of the unique environmental factors in various communities indicate the important roles that eating habits and culture have on the transmission of this infection. The socioepidemiological aspects of toxoplasmosis are thought to be important contributing factors for the spread of this disease. Preventative measures should consider the cultures and beliefs of people in various communities more than solving poverty and giving orthodox health education.

Animals↗
PubMed1950

Experimental congenital toxoplasmosis. I. The vagina as a portal of entry of toxoplasma in the mouse.

Toxoplasmosis can be transmitted to mice by the introduction of Toxoplasma into the vagina. Pregnant mice were more susceptible to infection than non-pregnant animals in the ratio of 3 to 1. Obvious signs of vaginitis were not observed. Many of the infected mice remained entirely free of external signs, while a minority showed neurological or respiratory disturbances. Pregnant animals, especially those infected 6 to 10 days following conception, often died in the terminal stages of pregnancy or shortly after parturition. The possibility that the vagina may serve as one of the portals of entry of Toxoplasma in the human being and that infection may occur by sexual contact or by contamination by feces or other Toxoplasma-containing materials is discussed. The high susceptibility of the pregnant mouse to toxoplasmosis under the conditions of these experiments suggests a possible explanation for the higher incidence of congenital as compared to postnatal human toxoplasmosis and for the associated asymptomatic maternal infection. The infected but clinically normal human mothers may be compared to some vaginally infected pregnant mice which remained symptom-free.

Animals↗
PubMed1997

Screening for active toxoplasmosis in patients by DNA hybridization with the ABGTg7 probe in blood samples.

We report the potential use of a specific Toxoplasma gondii DNA probe (ABGTg7). We applied a dot blot hybridization assay to blood samples for the diagnosis of cerebral toxoplasmosis (CT), acute toxoplasmic lymphadenopathy (ATL), and disseminated toxoplasmosis in transplant recipients (TRs). We studied a total of 84 individuals: 38 patients and 46 controls. We found positive hybridization signals for 12 (66.7%) of 18 patients with confirmed CT, 9 (52.9%) of 17 patients with ATL, and 2 (66.7%) of 3 TRs. PCR assays were performed in parallel for patients with ATL, resulting in T. gondii DNA detection for 10 patients (58.8%). A comparative study between dot blot and PCR assays performed with the blood of mice that had been experimentally infected with tachyzoites gave similar results: 60 and 70% positive results, respectively. Finally, the sum of positive values obtained by both DNA tests (dot blot assay plus PCR) increased the rate of positivity for ATL patients to 76.4%. These results demonstrate that the T. gondii ABGTg7 repetitive DNA element is an additional useful resource for diagnosing Toxoplasma parasitemia in patients with CT and ATL and in TRs. Thus, our ABGTg7-based dot blot test may lead to an improvement in T. gondii detection methods in patients with acute toxoplasmosis.

Animals↗
PubMed2006

Comparison between two amplification sets for molecular diagnosis of toxoplasmosis by real-time PCR.

PCR is now commonly applied to the diagnosis of toxoplasmosis. Although several methods are available, comparative studies are few, making it difficult to compare the performance of each technique. We compared the sensitivities of two real-time PCR assays through a prospective study on fetuses, neonates, and immunocompromised patients and on the ocular diagnosis of toxoplasmosis. The first system targeted the widely used B1 gene (GenBank accession number AF179871) while the second (RE) targeted a more recently described sequence repeated roughly 200 to 300 times (GenBank accession number AF146527). We demonstrated that molecular diagnosis requires the duplication of PCR assays, especially with the B1 system, as only one PCR was positive in 33.3% of cases. Our study showed that the RE target was more sensitive for all biological samples (amniotic fluid, placenta, aqueous humor, whole blood, and cerebrospinal and bronchoalveolar fluids) and significantly improved the performance of the diagnosis of toxoplasmosis. Taking into consideration all clinical samples, the mean gain in the crossing point value was 4.2 +/- 1.7 cycles and was even more significant for amniotic fluid (5.8 +/- 1.7 cycles).

Amniotic Fluid↗
PubMed2001

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.

Animals↗
PubMedDate not supplied

[Toxoplasmosis in AIDS].

Toxoplasmosis is one of the major opportunistic infections observed in France in 15 to 37 percent of HIV-infected patients. Its main manifestation is encephalitis. Other, less frequent manifestations are chorioretinitis, pneumonia or disseminated toxoplasmosis. The conventional treatment is a combination of pyrimethamine 50-75 mg/day and sulfadiazine 6-8 g/day. Acute therapy should be pursued for at least 3 weeks or until optimal response is achieved, i.e. 6 to 8 weeks in most cases. The pyrimethamine-clindamycin combination in doses of at least 2.4 g/day is a possible alternative. Other drugs are being studied, but there is still a need for new drugs active against the parasite, that could be used in humans. In HIV-infected patients treatment should be maintained lifelong to prevent relapses. Maintenance regimens use the same drugs as acute therapy but in lower doses. The main field of research is primary prophylaxis of toxoplasmosis in HIV-infected patients.

AIDS-Related Opportunistic Infections↗
PubMed1965

A SURVEY OF TOXOPLASMOSIS AMONG MENTALLY RETARDED CHILDREN.

To determine what role, if any, toxoplasmosis plays in the mental retardation of children, sera from 345 mentally retarded children were tested for the presence of antibodies to Toxoplasma gondii. The serological tests employed were the complement-fixation, the Sabin-Feldman dye test and the immunofluorescence test. The donors were also skin-tested with toxoplasmin.Of 345 mentally retarded donors nine gave a positive skin reaction, 15 possessed complement-fixing antibodies, 21 had immunofluorescent antibodies and 45 had dye test antibodies to T. gondii.The incidence of antibodies to T. gondii in the mentally retarded group was approximately the same as in the normal control group of the same age, and less than in the group suspected of having toxoplasmosis. It is concluded that in the children in this study toxoplasmosis played little or no role as a predisposing factor in the occurrence of congenital mental deficiency.

Adolescent↗
PubMed2004

Serodiagnosis of toxoplasmosis. The impact of measurement of IgG avidity.

The development of IgG avidity assays has revolutionised serological diagnosis of Toxoplasma infections. The measurement of IgG avidity has shown its power in various clinical settings, especially in situations where timing and differentiation of primary and secondary infections is crucial. However, no laboratory test performed alone is self-sustained, whereby the diagnostic strategy of choice is sequential (or combinatorial) use of high-quality IgG, IgM, IgA and IgG-avidity assays. The impact of IgG avidity measurement will be discussed in five clinical scenarios: acute acquired infection, primary infection during pregnancy, congenital toxoplasmosis, ocular toxoplasmosis and Toxoplasma infection in immunocompromised patients. All in all in toxoplasmosis, superior diagnostic performance is achieved by appropriate combinations of serological, culture-based and PCR techniques.

Acute Disease↗
PubMed1998

Feline ocular toxoplasmosis.

Ocular infection with Toxoplasma gondii is a well-recognized and important clinical entity in many animal species. In the cat, ocular toxoplasmosis is commonly associated with systemic infection, yet its role in causing anterior uveitis in an otherwise healthy cat is unclear. The purpose of this article is to review the salient epidemiological, clinical, and histopathologic features of systemic and ocular toxoplasmosis in the cat. Additionally, pathogenesis and possible immunopathogenic mechanisms of ocular toxoplasmosis, which may account for the higher prevalence of anterior uveitis in cats seropositive for T. gondii, are discussed. Finally, diagnosis, treatment and prevention of feline toxoplasmosis are reviewed.

Journal Article↗
PubMed1999

Serological diagnosis of toxoplasmosis: usefulness of IgA detection and IgG avidity determination in a patient with a persistent IgM antibody response to toxoplasma gondii

We report the detection of specific IgA antibodies and the determination of IgG avidity in sequential serum samples from a patient exhibiting significant levels of Toxoplasma-specific IgM antibodies for seven years after the onset of the clinical symptoms of toxoplasmosis. IgM antibodies were detected by an indirect immunofluorescence test and by three commercial enzyme-linked immunosorbent assays (ELISA). Anti-T. gondii IgA was quantified by the alpha-capture ELISA technique using a commercial kit. As defined by the manufacturer of the IgA ELISA test used, most patients with acute toxoplasmosis have antibody levels > 40 arbitrary units per ml (AU/mL). At this cut-off level, the patient still had a positive ELISA result (45 AU/mL) in a serum sample taken one year after the beginning of clinical manifestations. The IgG avidity-ELISA test was performed with the Falcon assay screening test (F.A.S.T.(R)) - ELISA system. Avidity indices compatible with a recent Toxoplasma infection were found only in serum samples taken during the first 5 months after the onset of the clinical symptoms of toxoplasmosis. These results show that the interpretation of positive IgM results as indicative of recently acquired toxoplasmosis requires additional laboratory confirmation either by other tests or by the demonstration of a significant rise in the antibody titers in sequential serum samples.

Journal Article↗
PubMed1999

[Acquired toxoplasmosis]

OBJECTIVE: The aim of this review is to present some important aspects of acquired toxoplasmosis to the pediatric practitioner. METHOD: All the articles about acquired toxoplasmosis published during the last decade and indexed in the Index Medicus were revised. From each one, interesting aspects were critically selected. RESULTS: We describe aspects of the epidemiology, pathogenesis, clinical manifestations, diagnosis, treatment and prevention related to acquired toxoplasmosis. CONCLUSION: The content of this article may facilitate the management of patients suspected of having acquired toxoplasmosis.

Journal Article↗
PubMed1977

The complement-fixation test in the diagnosis of congenital toxoplasmosis.

We present serologic results on 26 patients with congenital toxoplasmosis and on 22 of their mothers. The infection was severe (central nervous system involvement) in 12 patients, 12 had only ocular manifestations, and two were asymptomatic. The dye test results were positive on all specimens, and were positive at a titer of 1:1,024 or higher if collected from patients younger than 2 years of age. The complement-fixation test (CFT) results were positive on all specimens from patients younger than 2 years of age and on 69% of specimens collected from older patients. These serologic results are contrasted with those obtained on two control groups: (1) 46 uninfected infants followed up after birth because of substantial antibody titers in their mothers during pregnancy; and (2) 190 infants and children tested because toxoplasmosis was tentatively included in the differential diagnosis of the current illness. In both control groups the positive results on the CFT were limited almost exclusively to cord blood specimens or specimens collected during the first 2 weeks of life. Lower CFT titers in follow-up specimens suggested that the antibodies were maternal in origin. These two tests are valuable in providing laboratory support for the diagnosis of congenital toxoplasmosis, particularly the test for the comparatively short-lived complement-fixing antibody.

Antibodies↗
PubMed1977

Serological survey for congenital toxoplasmosis among 4,136 pregnant women.

A prospective seroepidemiological survey for latent congenital toxoplasmosis was carried out among 4,136 women and 3,787 of their offspring in and around Montreal. The indirect immunofluorescent antibody test was used to titrate specific IgG and IgM antibodies and results were standardized in international units. The prevalence of antibodies was 40-8% for the mothers and 36-4% for the babies. Mean annual seroconversion rate was 0-95%. Thus, 30 women would have been expected to acquire toxoplasmosis during pregnancy: two cases only were observed and the reasons for it are discussed. Four cases of congenital toxoplasmosis were diagnosed serologically (0-1%), none of them showed any signs of illness. Preventive treatment was administered to 12 of 52 pregnant women suspected of a recently acquired infection.

Adolescent↗
PubMed2005

A decade of discoveries in veterinary protozoology changes our concept of "subclinical" toxoplasmosis.

One of the most compelling topics to emerge from the last decade of veterinary protozoology is disease caused by a zoonotic pathogen, Toxoplasma gondii, in otherwise healthy people. These findings may catch the health professions by surprise, because veterinary and medical courses and textbooks typically emphasize that T. gondii infections are subclinical, unless acquired in utero or the patient has a serious immunosuppressive condition. Nevertheless, numerous reports in the last decade associate toxoplasmosis with lymphadenopathy, fever, weakness and debilitation, ophthalmitis, and severe multisystemic infections in people who do not have immunosuppressive conditions. Toxoplasmosis in rodents causes altered behavior, and similar mental aberrations are coming to light in humans; recent studies associate T. gondii infection with personality shifts and increased likelihood of reduced intelligence or schizophrenia. These conditions reduce the quality of life of individuals, and may exact a significant economic burden upon society. Of course, toxoplasmosis continues to cause serious conditions in AIDS patients and congenitally infected people, as well as abortions and encephalitis in domestic and wild animals. Environmental contamination is heavy enough to extend into marine wildlife. It is time for the health professions to amend teaching curricula regarding T. gondii. Veterinary parasitologists should lead the way in developing methods to reduce the prevalence of T. gondii in food animals. Public health policies should prohibit the practice of allowing pet cats to roam. Organizations and individuals that feed feral cats are unwittingly contributing to the dissemination of T. gondii, by sustaining artificially dense populations of a definitive host of this protozoal parasite.

Animals↗
PubMed2007

Effectiveness of prenatal treatment for congenital toxoplasmosis: a meta-analysis of individual patients' data.

BACKGROUND: Despite three decades of prenatal screening for congenital toxoplasmosis in some European countries, uncertainty remains about the effectiveness of prenatal treatment. METHODS: We did a systematic review of cohort studies based on universal screening for congenital toxoplasmosis. We did a meta-analysis using individual patients' data to assess the effect of timing and type of prenatal treatment on mother-to-child transmission of infection and clinical manifestations before age 1 year. Analyses were adjusted for gestational age at maternal seroconversion and other covariates. FINDINGS: We included 26 cohorts in the review. In 1438 treated mothers identified by prenatal screening, we found weak evidence that treatment started within 3 weeks of seroconversion reduced mother-to-child transmission compared with treatment started after 8 or more weeks (adjusted odds ratio [OR] 0.48, 95% CI 0.28-0.80; p=0.05). In 550 infected liveborn infants identified by prenatal or neonatal screening, we found no evidence that prenatal treatment significantly reduced the risk of clinical manifestations (adjusted OR for treated vs not treated 1.11, 95% CI 0.61-2.02). Increasing gestational age at seroconversion was strongly associated with increased risk of mother-to-child transmission (OR 1.15, 95% CI 1.12-1.17) and decreased risk of intracranial lesions (0.91, 0.87-0.95), but not with eye lesions (0.97, 0.93-1.00). INTERPRETATION: We found weak evidence for an association between early treatment and reduced risk of congenital toxoplasmosis. Further evidence from observational studies is unlikely to change these results and would not distinguish whether the association is due to treatment or to biases caused by confounding. Only a large randomised controlled clinical trial would provide clinicians and patients with valid evidence of the potential benefit of prenatal treatment.

Coccidiostats↗
PubMed1988

IgA antibodies against P30 as markers of congenital and acute toxoplasmosis.

Specific IgA antibodies against P30, a major surface protein of Toxoplasma gondii were sought in 198 serum samples (from 133 patients) by means of a double-sandwich enzyme-linked immunosorbent assay. These antibodies were detected in all cases of acute toxoplasmosis but in no cases of chronic toxoplasmosis nor in seronegative patients. They were not detected in samples from patients with "natural IgM antibodies" or in those containing rheumatoid factor or antinuclear antibodies. Among 26 infants whose mothers were infected during pregnancy, anti-P30 IgA antibodies were exclusively detected in the samples from the 8 infected infants, although anti-P30 IgM antibodies were detected in only 3 of the infected infants. No uninfected infant had IgA, though 5 had IgM at birth. Thus, the detection of IgA anti-P30 antibodies seems a better means than the detection of IgM antibodies of identifying infected infants, which is very important for treatment. In addition, the very early detection of IgA antibodies may be important for the diagnosis of acute toxoplasmosis, especially during pregnancy and perhaps also in patients infected by human immunodeficiency virus.

Acute Disease↗
PubMed1994

The diagnosis of toxoplasmosis using IgG avidity.

Current methods to establish the duration of toxoplasma infection in pregnant women and for the diagnosis of toxoplasmosis in the neonate or HIV infected patient have significant limitations. We assessed the precision of a commercial ELISA for the detection of toxoplasma specific IgG and adapted the assay to measure avidity using an elution agent washing step. The sensitivity and specificity of the ELISA were 100 and 75% respectively and optimal measurement of avidity was achieved using 6 M urea as the elution agent. Toxoplasma lymphadenopathy of less than 3 months duration was associated with low avidity specific IgG but some discordant findings were recorded. Serial measurement of IgG avidity assisted the distinction between actively produced antibody in infants with congenital toxoplasmosis and passively acquired antibody of maternal origin in uninfected babies. There was no significant difference between avidity levels in HIV infected patients with or without cerebral toxoplasmosis.

AIDS-Related Opportunistic Infections↗