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PubMed2005

Toxoplasma gondii: partial cross-protection among several strains of the parasite against congenital transmission in a rat model.

Rats were immunized with cysts of two Toxoplasma strains or with RH strain tachyzoites prior to pregnancy. The litters of the 13 rats that received homologous challenges with cysts during pregnancy, were all protected, whereas of 173 rats that received heterologous challenges with cysts or oocysts, only 21 protected their litters. 38.3 and 17% of rats immunized with the RH and with complete strains respectively, and 57% of control rats challenged with cysts, transmitted the infection congenitally. The percentages when similar groups were challenged with oocysts, were 33.3, 48.2, and 56.2%, respectively. Immunization with cysts did not completely protect against challenge with oocysts, even if the same strain was used. The divergence of these results from the complete protection against congenital toxoplasmosis observed in immune women and ewes, might be due to the use of excessive challenge doses in the model.

Animals↗

PubMed2006

A human origin type II strain of Toxoplasma gondii causing severe encephalitis in mice.

Despite its capacity for sexual reproduction and global distribution, Toxoplasma gondii has a highly clonal structure, with the majority of isolates belonging to three distinct clonal types. Congenital toxoplasmosis has been associated with type I and type II strains. We here present the first characterization of a T. gondii strain (BGD1) from South-East Europe, isolated from the umbilical blood of a 24-week-old fetus in Serbia. Genotyping, performed by PCR-RFLP using a set of nested PCR markers (5'SAG2, 3'SAG2, BTUB, SAG3, and GRA6), showed that the BGD1 strain possessed a type II genotype. The cytokine patterns in Swiss-Webster mice inoculated with brain cysts of BGD1 and the prototype type II ME49 strain were similar until 180 days post-infection, with highly elevated IFN-gamma, IL-12 and IL-10 by d7 and decreasing thereafter. While both strains induced pneumonia and hepatitis in acute infection (d14), chronic infection (d56) was characterized, in addition to hepatitis, by severe meningoencephalitis, associated with numerous brain cysts. Thus, the BGD1 strain of T. gondii has type II genotypic and immunologic characteristics, but unlike other type II strains of human origin, induces severe encephalitis, making it an alternative to the sheep-derived ME49 strain for experimental models of infection.

Adult↗

PubMed1985

Detection of toxoplasmic immunity by multipuncture skin test with excretory-secretory antigen.

In 414 volunteers the sensitivity and specificity of a multipuncture skin test with excretory-secretory (ES) toxoplasma antigen was compared with serological detection by an indirect fluorescent antibody (IFA) test. The ES antigen was extracted from supernatants of cell cultures infected with Toxoplasma gondii, purified, and standardised, and the antigen used met current safety standards. The correlation between the skin test and IFA result was 94.2% (97.8% when the skin test was repeated 30 days later). No false-positive skin tests were noted. The skin test did not transform an originally negative serological test into a positive one. In programmes to prevent congenital toxoplasmosis, this sensitive, specific, and inexpensive skin test can be widely used for the detection of immunity to toxoplasma in women before their first pregnancy.

Adult↗

PubMed1998

Detection of Toxoplasma gondii in cured meats.

Congenital toxoplasmosis is associated with acute maternal infection acquired during or shortly before the pregnancy. The mother's infection is initiated by the ingestion of one of the life forms of the parasite but the relative importance of the different sources of toxoplasmosis are not established. Recent epidemiological studies have confirmed ingestion of raw meats as a risk factor but also identified consumption of cured meats as being associated with acute toxoplasmosis in pregnancy. There is little existing information concerning the efficiency of commercial curing processes for inactivating Toxoplasma gondii. We sought to detect the presence of T. gondii in ready-to-eat cured meat samples by amplification of the parasite's P30 gene using the polymerase chain reaction (PCR). In addition, tissue culture was used in order to isolate viable parasites. Laboratory inoculated specimens were used to assess the sensitivity of each method. PCR was able to detect parasite contamination down to a level of 5 x 10(3) trophozoites/g while viable toxoplasma could be detected in tissue culture at a level of 10(3) trophozoites/g cured meat. The high salt content of some cured meats limited sensitivity of the PCR assay by inhibition of the polymerase enzyme and reduced the sensitivity of tissue culture due to osmotic pressure causing cytopathic effect. However viable T. gondii was detected in one out of 67 ready-to-eat cured meat samples. Our results highlight the need for improved methods for detecting toxoplasma contamination of food. Health implications of consuming cured meats in pregnancy require careful consideration.

Animals↗

PubMed2002

Congenital infections.

Despite major medical advances, such as the introduction of the rubella vaccine and prolonged postnatal therapy of infants with congenital toxoplasmosis, intrauterine infections remain important causes of deafness, vision loss, and behavioral or neurologic disorders among children worldwide. This article describes the common pathogens causing intrauterine infections and summarizes the current status of diagnosis, treatment, and prevention.

Brain↗

PubMed1996

Risk factors for recent toxoplasma infection in pregnant women in Naples.

Effective primary prevention of congenital toxoplasmosis requires up to date information on locally relevant risk factors for infection in pregnant women. In Naples, risk factors for toxoplasma infection were compared in recently infected women (as assessed by detection of specific IgM in serum) and susceptible, IgG negative women. Recent infection was strongly associated with frequency of consumption of cured pork and raw meat. Eating cured pork or raw meat at least once a month increased the risk of toxoplasma infection threefold. This simple study design for determining locally relevant sources of toxoplasma infection is the first report of cured pork as a risk factor for infection. Further research is required to determine cyst viability in cured pork products. Our findings suggest that in southern Italy, cured pork and raw meat should be avoided by susceptible pregnant women.

Adult↗

PubMed1998

Congenital toxoplasma gondii infection diagnosed by PCR amplification of peripheral mononuclear blood cells from a child and mother.

A case of congenital toxoplasmosis is presented, where diagnosis by PCR amplification of Toxoplasma gondii DNA from peripheral blood led to early treatment of the infant and seemingly normal brain development despite the presence of intracranial calcifications at birth. The mother, who experienced a subclinical infection during pregnancy, was PCR-positive for toxoplasma DNA in a sample of peripheral blood drawn after delivery.

Animals↗

PubMedDate not supplied

Nonfatal prolonged overdosage of pyrimethamine in an infant: measurement of plasma and urine levels using HPLC with diode-array detection.

A nonfatal case of accidental prolonged overdosage of pyrimethamine (10 times the usual dose for 10 days) in a seven-week-old infant treated for congenital toxoplasmosis is presented. The drug was identified and quantitated in plasma and urine using an HPLC technique with diode-array detection. Initial plasma concentration of pyrimethamine was 6.22 micrograms/mL. Results are discussed in light of the existing literature.

Chromatography, High Pressure Liquid↗

PubMed2006

Prevalence and estimated incidence of Toxoplasma infection among pregnant women in Poland: a decreasing trend in the younger population.

This study investigated the prevalence of specific Toxoplasma gondii IgG in pregnancy, the incidence of congenital toxoplasmosis and the prevalence trend of T. gondii infection among pregnant Polish women between 1998 and 2003. The study population comprised 4916 women who were admitted to the Polish Mother's Memorial Hospital Research Institute in Łódź. Their sera were tested for specific IgG and IgM antibodies to T. gondii, and the incidence of T. gondii infection was calculated from the increase in prevalence rates of IgG antibodies in various age groups. Specific IgG antibody was found in 41.3% (95% CI 39.9-42.7) of pregnant women, and the prevalence of IgG increased with age. The linear trend was significant (p <0.001), with an annual seroconversion rate of 0.7% (95% CI 0.004-0.010). The risk of primary infection was estimated to be 0.5% for 9 months, i.e., an incidence of 5/1000 pregnancies. Assuming a 30% maternofetal transmission rate, 1.5/1000 neonates were infected in utero. Seroprevalence during the 6-year study period decreased from 45.4% in 1998 to 39.4% in 2003, with a yearly decline in prevalence of 1.0% (p 0.02). The most important contributory factor to this decline was the group of women aged 19-29 years, among whom seroprevalence decreased significantly (p 0.007). Specific IgM was found in 244 (4.9%) women.

Adult↗

PubMedDate not supplied

Benign partial epilepsy with centrotemporal (or rolandic) spikes and brain lesion.

We describe three patients with benign partial epilepsy with centrotemporal spikes (BECT) in association with proven brain lesion (agenesis of the corpus callosum, lipoma of the corpus callosum, and congenital toxoplasmosis, respectively). The age of onset, the ictal signs, the interictal electroencephalographic findings and the favorable outcome of epilepsy even after withdrawal of drug therapy led to the diagnosis of BECT although organic brain lesions were present. In such cases, the epilepsy should not be ascribed to the lesions but should be considered benign even though fortuitiously associated with brain lesions.

Action Potentials↗

PubMed1996

A new set of primers for the detection of Toxoplasma gondii in amniotic fluid using polymerase chain reaction.

A new PCR system including a pair of primers, a probe and an internal control were designed from the B1 gene of Toxoplasma gondii. The system described allowed the detection of less than 10 tachyzoites of the RH strain of T. gondii. Among 21 amniotic fluid samples, this system diagnosed the cases of congenital toxoplasmosis which were simultaneously diagnosed using mice inoculation, in vitro culture, and serology from both amniotic fluid and fetal blood. These results show that these new primers allow for a highly sensitive detection of T. gondii DNA.

Amniotic Fluid↗

PubMed1998

A second European collaborative study on polymerase chain reaction for Toxoplasma gondii, involving 15 teams.

In order to investigate the accuracy and practicability of the polymerase chain reaction (PCR) in the antenatal diagnosis of congenital toxoplasmosis, a collaborative study involving 15 European laboratories was performed under the auspices of the Biomed 2 Programme of the European Community. Each team received 12 aliquots (four negative, eight positive) of 'artificial samples' made of amniotic fluid spiked with tachyzoites of the RH strain of Toxoplasma gondii. Each team performed its own PCR protocol (all were different). Nine of the 15 laboratories were able to detect a single parasite, but two of the 15 found all samples negative. Four of the 15 laboratories found one or more control samples to be falsely positive. This study highlights the lack of homogeneity between PCR protocols and performance and underlines the need for an external quality assurance scheme which could provide 'reference' samples that could be used by any laboratory wanting to establish and maintain an accurate diagnostic test based on PCR.

Amniotic Fluid↗

PubMed1994

Optic nerve aplasia associated with macular 'atypical colobomà'.

A 12-year-old patient presenting with absence of the optic disc and retinal blood vessels associated with atrophic macular lesion was studied. A toxoplasma IgG antibody test had been found positive at the age of 4 months. This test and the clinical findings suggested the possibility of optic nerve aplasia with atypical macular coloboma due to congenital toxoplasmosis. The pro's and contra's concerning this hypothesis are discussed by the authors.

Animals↗

PubMed2001

Prevalence of congenital Toxoplasma gondii infection among newborns from the Poznań region of Poland: validation of a new combined enzyme immunoassay for Toxoplasma gondii-specific immunoglobulin A and immunoglobulin M antibodies.

We determined the value of a new serological assay detecting Toxoplasma-specific immunoglobulin M (IgM) and IgA antibodies at birth for use in mass neonatal screening. The incidence of congenital infection in newborns was compared with data from an epidemiological investigation on the seroprevalence of Toxoplasma in the studied population. Peripheral blood was collected on Guthrie cards during the first 3 days of life and tested for anti-Toxoplasma IgA and IgM using a noncommercial immunocapture enzyme-linked immunosorbent assay (ELISA). When the screening assay was positive, serum samples from the child and the mother were collected for use in Western blotting comparative immunological profile analysis and traditional serological tests for determination of specific IgG, IgM, and IgA antibodies. From December 1998 to April 2000, 17,653 filter paper samples from live-born neonates were successively screened. Congenital T. gondii infection was finally confirmed in 19 newborns. In traditional assays, 13 of 19 infants were IgM and IgA positive using filter paper eluates at birth, 1 child was positive only for IgM, 1 patient was positive for IgM and borderline for IgA, 1 had an equivocal level of IgA, and 3 cases were confirmed only by the Western blot assay. The prevalence of Toxoplasma-specific IgA and/or IgM in filter paper samples at birth was 1 per 929 live-born neonates (1.08/1,000) or about 1 per 523 children (1.9/1,000) born to nonimmune women with a potential risk of primary T. gondii infection during pregnancy, compared to the actual seropositivity rate of 43.7%. The diagnostic sensitivity of the combined IgA-IgM ELISA using neonatal filter paper specimens was not more than 95%, the positive predictive value of the test was 82.6%, and the diagnostic specificity was calculated to be 99.9%. The combined IgA-IgM ELISA is a valuable method for the diagnosis of congenital toxoplasmosis at birth and fulfills criteria for neonatal screening programs. The method showed a good diagnostic sensitivity in neonates untreated prenatally who were born in an area of high seroprevalence of T. gondii infection.

Animals↗

PubMed1977

Neonatal hepatic calcification secondary to transplacental infection.

Transplacentally acquired infections which cause prenatal and neonatal hepatitis can cause hepatic calcification in the newborn. Three cases are reported in which congenital toxoplasmosis and herpes simplex viral infections were causes of neonatal hepatic calcification. Autopsies performed in 2 of the cases revealed extensive dystrophic hepatic calcifications.

Calcinosis↗

PubMedDate not supplied

Methods to estimate the optimal threshold for normally or log-normally distributed biological tests.

Putting a screening or a diagnostic test into everyday use requires the determination of its threshold. The authors present methods that yield a point and an interval estimation of the threshold that maximize the population utility whenever the test results are normally or log-normally distributed among healthy and among diseased subjects, with equal variances. These methods were assessed for bias, coverage probability, coverage symmetry, and confidence-interval width using simulation. They proved to be asymptotically nonbiased and to have a satisfactory coverage probability whenever the sample sizes of the healthy and the diseased subjects are equal to or greater than 50. The methods were next applied to determine an optimal threshold for the antibody load used to diagnose congenital toxoplasmosis at birth. The methods are easy to implement and impose few constraints; however, the sample sizes should be carefully determined according to the required accuracy.

Antibodies, Protozoan↗

PubMed2006

Toxoplasma-IgM and IgG-avidity in single samples from areas with a high infection rate can determine the risk of mother-to-child transmission.

Anti-Toxoplasma IgG-avidity was determined in 168 serum samples from IgG- and IgM-positive pregnant women at various times during pregnancy, in order to evaluate the predictive value for risk of mother-to-child transmission in a single sample, taking the limitations of conventional serology into account. The neonatal IgM was considered the serologic marker of transmission. Fluorometric tests for IgG, IgM (immunocapture) and IgG-avidity were performed. Fifty-one of the 128 pregnant women tested gave birth in the hospital and neonatal IgM was obtained. The results showed 32 (62.75%) pregnant women having high avidity, IgM indexes between 0.6 and 2.4, and no infected newborn. Nineteen (37.25%) had low or inconclusive avidity, IgM indexes between 0.6 and 11.9, and five infected newborns and one stillbirth. In two infected newborns and the stillbirth maternal IgM indexes were low and in one infected newborn the only maternal parameter that suggested fetal risk was IgG-avidity. In the present study, IgG-avidity performed in single samples from positive IgM pregnant women helped to determine the risk of transmission at any time during pregnancy, especially when the indexes of the two tests were analysed with respect to gestational age. This model may be less expensive in developing countries where there is a high prevalence of infection than the follow-up of susceptible mothers until childbirth with monthly serology, and it creates a new perspective for the diagnosis of congenital toxoplasmosis.

Animals↗

PubMed2006

Pediatric and adolescent population with visual impairment: study of 385 cases.

OBJECTIVE: To analyze data on the pediatric population attending the Ophthalmologic Clinic's Low Vision Service at the São Paulo University Medical School. METHODS: Low vision ophthalmologic assessment, from April 1998 to December 2003, of 385 children and adolescents with mean age of 7 years; 51.7% males and 48.3% females. The main data analyzed were age, diagnosis, anatomic site of the ocular injury, visual acuity, and prescription of optical aids. RESULTS: 45.4% were below 6 years, and 54.6% were between 6 and 16 years. 35.5% experienced moderate visual impairment, 26% had severe visual impairment, 8.6% had profound visual impairment, 10.6% were near blind, and 1.6% were blind. The main causes of visual impairment included congenital glaucoma (30.6%), macular retinochoroiditis due to congenital toxoplasmosis (16.7%), congenital cataract (12.8%), retinal and macular inherited disorders (11.7%), and optic atrophy (9.8%). Among school-age children, 52.9% received a prescription of optical aids. The most widely used optical aids for distance were 2.8 X 26 (34.4%); 4.2 X 12 (30.3%); and 6 X 17 (26.8%) telescopic systems. The most frequently prescribed optical aid for near vision was the 2x magnifying bar (33.3%). CONCLUSIONS: There is a need for prevention of primary (congenital infections), secondary (congenital glaucoma and retinopathy of prematurity), and tertiary (congenital cataract) visual impairment. The prescription of optical aids for school-age children will help them perform better at school and contribute to their social inclusion.

Adolescent↗