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Some observations on the epidemiology of toxoplasmosis in Canada.

Between 1961 and 1974, 11934 samples of serum were tested by the Sabin-Feldman Dye test for the presence of antibodies to Toxoplasma gondii. Analysis of high-titred sera suggested that a 6-year cycle of high disease prevalence occurred across Canada. In addition, a decline in the percentage of positive reactions each year in the Fall. The suggestion that this decline was due to dry conditions during the summer months was supported by the observation that differences in the prevalence of toxoplasma infection in ten Canadian cities were related to their average summer rainfall. The significance of these observations in relation to the epidemiology of toxoplasmosis in this country is discussed. The influence of patient age on the prevalence of infection was also investigated; the results obtained suggested that at least 75% of infants with high antibody titres against T. gondii had obtained these antibodies by placental transfer from their mothers.

Adolescent↗

Value of lymph node biopsy in the diagnosis of acquired toxoplasmosis.

Toxoplasmic lymphadenitis generally involves a solitary lymph node in the head and neck regions, without systemic symptoms. In order to determine the frequency of toxoplasmic lymphadenitis, we reviewed the histological sections of 731 consecutive patients with reactive lymph node hyperplasia. Amongst 731 patients, 112 had histological features supporting a diagnosis of toxoplasmic lymphadenitis (15.3 per cent). In 80 of these patients (71 per cent), either Indirect Haemaglutination test (IHA), in 37 cases, or the Enzyme-Linked Immunosorbent Assay (ELISA) for detecting toxoplasmic IgG or IgM antibodies, in 43 cases, were performed. In 76 out of 80 patients (95 per cent), histological features correlated well with serological studies. The IHA test was positive in 30 patients with a titre of 1/64 or higher. The IgG-ELISA test was positive in 11 whereas the IgM-ELISA test was positive in 28 patients. These results provide further evidence of the distinctive nature of the histological changes in toxoplasmic lymphadenitis, which should enable the clinician to make a confident diagnosis of acute acquired toxoplasmosis.

Adolescent↗

A commercial vaccine for ovine toxoplasmosis.

This paper describes the development of the first commercial vaccine for toxoplasmosis. The vaccine comprises live tachyzoites of the S48 'incomplete' strain of Toxoplasma gondii and is deployed to control toxoplasma abortion in sheep. A discussion of protective immune mechanisms and recent studies on host responses to the vaccine is also included.

Animals↗

Studies on a murine model of congenital toxoplasmosis: vertical disease transmission only occurs in BALB/c mice infected for the first time during pregnancy.

The incidence of congenital toxoplasmosis was determined by an ELISA in the litters of BALB/c mice which had been infected 8 weeks before mating, on day 12 of pregnancy, or on both these occasions. Of those mice given the infection for the first time on day 12 of pregnancy, 5 out of 6 gave birth to infected litters with approximately 50% of the individuals in each litter being infected. BALB/c mice which had been infected 8 weeks before mating did not give birth to infected litters, even if they were reinfected on day 12 of pregnancy. Following infection BALB/c mice were found to harbour significantly fewer tissue cysts than the congenic H-2 derivative BALB/K strain. However, chronically infected BALB/K mice also failed to produce infected litters, indicating that tissue cyst burden in the dam did not influence congenital infection at least on the BALB background. This study demonstrates that BALB/c dams chronically infected with Toxoplasma gondii, have immunity capable of protecting their embryos from congenital infection, even if the dams are reinfected during pregnancy. Our results demonstrate that the BALB/c mouse can be used as a model of human or ovine congenital T. gondii infection suitable for testing putative vaccines.

Animals↗

Body height, body mass index, waist-hip ratio, fluctuating asymmetry and second to fourth digit ratio in subjects with latent toxoplasmosis.

Between 20% and 60% of the population of most countries are infected with the protozoan Toxoplasma gondii. Subjects with clinically asymptomatic life-long latent toxoplasmosis differ from those who are Toxoplasma free in several behavioural parameters. Case-control studies cannot decide whether these differences already existed before infection or whether they were induced by the presence of Toxoplasma in the brain of infected hosts. Here we searched for such morphological differences between Toxoplasma-infected and Toxoplasma-free subjects that could be induced by the parasite (body weight, body height, body mass index, waist-hip ratio), or could rather correlate with their natural resistance to parasitic infection (fluctuating asymmetry, 2D : 4D ratio). We found Toxoplasma-infected men to be taller and Toxoplasma-infected men and women to have lower 2D : 4D ratios previously reported to be associated with higher pre-natal testosterone levels. The 2D : 4D ratio negatively correlated with the level of specific anti-Toxoplasma antibodies in Toxoplasma-free subjects. These results suggest that some of the observed differences between infected and non-infected subjects may have existed before infection and could be caused by the lower natural resistance to Toxoplasma infection in subjects with higher pre-natal testosterone levels.

Body Height↗

Enzyme-linked immunosorbent assays for the measurement of specific antibodies in experimentally induced ovine toxoplasmosis.

Tachyzoites of the RH strain of Toxoplasma gondii were inoculated intravenously into sheep following which serum samples were collected at approximately weekly intervals for 9 months. The sera were examined by the toxoplasma dye test and two enzyme-linked immunosorbent assays (ELISA) specifically developed for investigations of ovine toxoplasmosis. One was an antibody class capture assay for the detection of anti-toxoplasma specific IgM, the other an indirect assay which detected anti-toxoplasma IgG. Some of the sheep had antibodies to toxoplasma prior to inoculation but none had specific IgM. Sera collected 17 days after inoculation showed that all had raised specific antibody levels but the only sheep that produced specific antitoxoplasma IgM were those that were initially without any antibody. Specific IgM could be detected in all these particular sheep for at least 1 month after infection and up to 3 months in some. Specific IgG persisted at high levels for at least 3 months and could still be detected at moderate levels for at least 9 months. The ELISA methods described are simple to perform and could clearly distinguish between previous infection and this experimental infection with Toxoplasma gondii.

Animals↗

Ecological comparison of the risks of mother-to-child transmission and clinical manifestations of congenital toxoplasmosis according to prenatal treatment protocol.

We compared the relative risks of mother-to-child transmission of Toxoplasma gondii and clinical manifestations due to congenital toxoplasmosis associated with intensive prenatal treatment in Lyon and Austria, short term treatment in 51% of Dutch women, and no treatment in Danish women. For each cohort, relative risks were standardized for gestation at seroconversion. In total, 856 mother-child pairs were studied: 549 in Lyon, 133 in Austria, 123 in Denmark and 51 in The Netherlands. The relative risk for mother-to-child transmission compared to Lyon was 1.24 (95% CI: 0.88, 1.59) in Austria; 0.59 (0.41, 0.81) in Denmark; and 0.65 (0.37, 1.01) in The Netherlands. Relative risks for clinical manifestations compared with Lyon (adjusted for follow-up to age 3 years) were: Austria 0.19 (0.04, 0.51); Denmark 0.60 (0.13, 1.08); and The Netherlands 1.46 (0.51, 2.72). There was no clear evidence that the risk of transmission or of clinical manifestations was lowest in centres with the most intensive prenatal treatment.

Anti-Bacterial Agents↗

Prognostic factors for the long-term development of ocular lesions in 327 children with congenital toxoplasmosis.

The aim of this study was to identify the high-risk factors associated with the development of ocular lesions in a large cohort of children with congenital toxoplasmosis (CT), irrespective of their gestational age at the time of maternal infection. Children were managed according to a standardized protocol and monitored for up to 14 years at the Croix-Rousse Hospital, Lyon, France. Cox model and a flexible regression, spline-based method were used for the analysis. During a median follow-up time of 6 years, 79 of the 327 children (24%) had at least one retinochoroidal lesion. No bilateral impairment of visual acuity was observed. The risk of a child developing ocular disease was higher not only when mothers were infected early during pregnancy, which was expected, but also when CT was diagnosed prior to or at the time of birth, when non-ocular manifestations were present at baseline and when birth was premature.

Adolescent↗

Incidence of congenital toxoplasmosis estimated by neonatal screening: relevance of diagnostic confirmation in asymptomatic newborn infants.

Congenital toxoplasmosis is rarely identified by routine clinical examination. The aim of this study was to estimate the incidence of the disease in the region of Ribeirão Preto, south-eastern Brazil. A definitive diagnosis was made on the basis of the persistence of anti-Toxoplasma IgG antibodies beyond 1 year of age. Blood samples obtained from 15,162 neonates and adsorbed onto filter paper were tested for anti-Toxoplasma IgM antibodies. Fifteen samples gave positive results. A definitive diagnosis was confirmed in five of the 13 infants (38.5%) who completed follow-up. These five infants presented with serum IgM and/or IgA antibodies, and clinical abnormalities. Disease incidence was estimated to be 3.3/10,000 (95% CI 1.0-7.7), indicating the need for preventive measures. Neonatal screening is feasible, but screening tests with a better performance are required; positive screening results must be carefully confirmed.

Animals↗

Sarcoidosis mimicking toxoplasmosis with severe hypercalcaemia and normal 1,25-dihydroxy vitamin D.

We report a case of a female patient with sarcoidosis who presented with a generalized lymphadenopathy and a strong IgG serological test of toxoplasmosis. Progressive lymphadenopathy with a rising plasma calcium (up to 15 mg dL-1) with a normal plasma 1,25-dihydroxy vitamin D concentration occurred later. Corticosteroid therapy resulted in prompt clinical and biochemical responses with normalization of plasma calcium and a significant reduction in 1,25-dihydroxy vitamin D concentration. This is an exceptional presentation of sarcoidosis with severe hypercalcaemia and normal vitamin D metabolites.

Adult↗

Clinical ocular toxoplasmosis in neonatal kittens.

OBJECTIVE: To describe ocular findings in kittens with congenital or early neonatal infection by Toxoplasma gondii and to determine if there are detectable differences in disease caused by three strains. ANIMALS STUDIED: Six adult female cats and the offspring from seven litters. METHODS: Four kittens from uninfected specific pathogen-free (SPF) queens and 21 kittens from SPF queens inoculated at various times late in gestation with Mozart, Maggie, or ME-49 strain of T. gondii were used. Ocular examinations were performed on queens prior to and after delivery, and on kittens weekly to bi-weekly for up to 27 weeks. Whole blood for serology was collected from all kittens at 5(1/2) to 8 weeks of age and again at 12 weeks of age or later. RESULTS: No kittens from noninfected queens developed ocular lesions or antibody to T. gondii. Three of the 24 kittens from infected queens died or were euthanized early in the study. Chorioretinitis was detected in 15 of 21 living kittens from infected queens. Two developed concurrent anterior uveitis that resolved within 1 week. Posterior segment lesions varied ophthalmoscopically between strains. Of 21 kittens from T. gondii-infected queens, six developed positive antibody titers to T. gondii during the study. All seropositive kittens were born to queens infected with Mozart strain of T. gondii. CONCLUSION: Results of this study suggest that ocular toxoplasmosis can occur without other evidence of clinical illness in kittens infected in utero or in the neonatal period, and that T. gondii strains may have varying degrees of ocular pathogenicity in cats.

Animals↗

Fetal cataract in congenital toxoplasmosis.

We report a case of the prenatal diagnosis of fetal cataract due to congenital toxoplasmosis. To the best of our knowledge, this is the first report of such a case. We discuss the long-term ocular sequelae of the condition and how they should affect prenatal counselling.

Adolescent↗

Toxoplasmosis transmitted by blood transfusions.

Blood from humans collected into heparin or citrate was inoculated with toxoplasma organisms. After storage at 4 C up to 28 days, samples were injected into the ear veins of rabbits. The test rabbits developed toxoplasmosis. Similar results were obtained by transfusing rabbits with blood obtained from rabbits subcutaneously injected with toxoplasma organisms.

Animals↗

[Sero-epidemiologic profile of toxoplasmosis in northern Tunisia].

Toxoplasma antibodies prevalence was studied in the north of Tunisia where a mild climate prevails. Two groups of individuals were investigated: 857 living in rural area and 564 living in urb town. Sera were analysed by ELISA and indirect immunofluorescence. The overall prevalence was 58.4%. It roses from 24.5% at ten years to 52.1% at 20 years of age. A maximum level, around 70%, was reached by about 30 years. The risk of acute infection after this age seemed low as judging by the proportion of high antibodies titers observed in this group (14.2% before 30 years vs 3.7% after). A significantly higher prevalence was detected in urban residents (67% vs 52.8%). In this group, the rate of seroconversion seems the highest between ten and 20 years of age and the majority of women are infected before reaching childbearing age. In the rural area, the seropositivity is lower between ten-20 years and many women at childbearing age still susceptible to toxoplasmosis. The risk of acute infection seems higher in the youngest ones as showed by the proportion of high antibodies titers observed in the 18-30 age group (9.2%) compared to the one observed after 30 years (1.9%).

Adolescent↗

Gastric toxoplasmosis in acquired immunodeficiency syndrome: antemortem diagnosis with histopathologic characterization.

Gastrointestinal symptoms attributable to Toxoplasma gondii infection are distinctly unusual, and antemortem diagnosis of gastrointestinal involvement is rarely documented, particularly in the absence of cerebral manifestations or disseminated disease. This case report describes a rare example of T. gondii infection of the stomach diagnosed antemortem in a 22-year-old Haitian woman with acquired immunodeficiency syndrome (AIDS) who presented with fever and abdominal pain. An abdominal computerized tomographic scan showed thickened gastric walls. Endoscopy showed diffusely thickened gastric folds and a fundic ulcer along the greater curvature. Light and electron-microscopic examination of gastric mucosal biopsy specimens showed active Toxoplasma infection with necrosis and intracellular trophozoites within the gastric epithelium, smooth muscle cells, macrophages, and endothelial cells. Both true cysts and pseudocysts were seen. Disseminated disease was documented by the growth of T. gondii in a tissue culture from a venous blood sample. It is concluded that some patients with AIDS, particularly those from areas endemic for Toxoplasma infection, can manifest disseminated disease in unusual locations such as the gastrointestinal tract. Documentation of active T. gondii infection based on tissue cultures of venous blood or on biopsy specimens of symptomatic extracerebral sites can lead to a rapid diagnosis of toxoplasmosis, a treatable disease.

Acquired Immunodeficiency Syndrome↗

Acute disseminated toxoplasmosis in a captive three-toed sloth (Bradypus tridactylus).

Fatal toxoplasmosis was diagnosed in a captive three-toed sloth (Bradypus tridactylus), an arboreal species of the tropical rainforests of South and Central America. In view of its specialized lifestyle and ecosystem and its low metabolic rate, B. tridactylus would seem to warrant further investigation in respect of its susceptibility to Toxoplasma gondii.

Acute Disease↗

[Toxoplasmosis transmission by blood transfusion? (author's transl)].

T-cells of the chicken tumour HPRS-1, mouse mastocytoma cells, Friend virus-transformed erythroleukaemia cells as well as normal human, mouse and chick erythrocytes were tested for their receptivity to toxoplasma infection. The studies indicate that T-cells and mastocytoma cells, which may be counted as part of the white blood cell series, have the highest invasion rate after incubation with toxoplasma. Friend-erythroleukaemia cells were less often affected; mature human, mouse and chick erythrocytes were refractory. The results suggest that cells of the white blood cell series are receptive to toxoplasma infection but that nucleated precursors of the red series may also be so, while mature erythrocytes cannot be infected. The possibility of transmission of toxoplasmosis by blood transfusion can no longer be doubted.

Animals↗

[Congenital ocular toxoplasmosis--ocular manifestations and prognosis after early diagnosis of infection].

BACKGROUND: Congenital toxoplasmosis (CT) is the most frequently encountered congenital infection. The aim of the present review is to report about the long-term outcome of functional and morphological manifestations after an early confirmation of the diagnosis. PATIENTS AND METHODS: We report on a cohort of patients with serologically confirmed CT, born between 1988 and 2001, who were followed up prospectively at a single centre (Institute of Parasitology, Hôpital de la Croix Rousse, University of Lyon). All patients underwent regular ophthalmological, parasitological and paediatric controls on a half-yearly or annual basis. Ocular manifestations were documented and visual acuity was assessed as far as was possible. RESULTS: 1,506 seroconversions were diagnosed during pregnancy, and 327 of the live-born offspring were seropositive for CT. At the end of the study period, ocular manifestations occurred in 79 of the children (24 %), and in 7 cases (9 %) they were discovered during the first month of life. In 72 of the patients (91 %), the ocular manifestations developed between 1 and 151 months (median follow-up time: 6.3 +/- 3.7 years; range: 0.5 - 14 years) under medical treatment for the first year of life. At the end of the study period, information regarding visual acuity was available for 66 patients. In 55 of these (83 %), visual acuity was normal in both eyes, and in 11 (17 %), it was reduced below 0.5. In 1 child, both eyes were functionally affected, one severely. CONCLUSION: CT may not become manifest ocularly until after a decade, which underlines the necessity for long-term ophthalmological monitoring of the infected individuals. In our patients, the prognostic outcome after therapy for the first year of life was better than that reported in the literature. This favourable outcome may serve as a basis for patient counselling.

Adolescent↗