High prevalence of congenital toxoplasmosis in Brazil estimated in a 3-year prospective neonatal screening study

A Systematic Review to Evaluate a Possible Association Between Congenital Toxoplasmosis and Preterm Labor

BACKGROUND

Congenital toxoplasmosis (CT) is a widespread infection in several countries, and it is defined as an infection of a fetus, newborn, or infant under 1 year of age. Moreover, it represents a thread to pregnant women globally. The objective of our study is to evaluate a potential association between prematurity and CT and whether intrauterine transmission impacts gestational length during pregnancy.

METHODS

PubMed, Cochrane Library and Google Scholar databases were searched from 1950 to 2019. Case-control studies, retrospective, and prospective cohort studies were eligible. Seven studies were included from a total of 314. The Newcastle-Ottawa scale was used to establish the quality of the articles included.

RESULTS

Based on our review, an association between CT and preterm labor was not established, which may reflect heterogeneity in screening, treatments administered, and differing reported incidences of CT across continents over 69 years. A multicenter prospective cohort study powered to investigate a potential association is indicated.

CONCLUSION

Further studies are needed including multicenter prospective cohort studies powered to investigate key clinical associations such as vertical transmission and preterm birth.

Long-Term Outcomes in Children with Congenital Toxoplasmosis-A Systematic Review

Even in the absence of manifestations at birth, children with congenital toxoplasmosis (CT) may develop serious long-term sequelae later in life. This systematic review aims to present the current state of knowledge to base an informed decision on how to optimally manage these pregnancies and children. For this, a systematic literature search was performed on 28 July 2022 in PubMed, CENTRAL, ClinicalTrials.gov, Google Scholar and Scopus to identify all prospective and retrospective studies on congenital toxoplasmosis and its long-term outcomes that were evaluated by the authors. We included 31 research papers from several countries. Virulent parasite strains, low socioeconomic status and any delay of treatment seem to contribute to a worse outcome, whereas an early diagnosis of CT as a consequence of prenatal screening may be beneficial. The rate of ocular lesions in treated children increases over time to 30% in European and over 70% in South American children and can be considerably reduced by early treatment in the first year of life. After treatment, new neurological manifestations are not reported, while ocular recurrences are observed in more than 50% of patients, with a mild to moderate impact on quality of life in European cohorts when compared to a significantly reduced quality of life in the more severely affected South American children. Though CT is rare and less severe in Europe when compared with South America, antenatal screening is the only effective way to diagnose and treat affected individuals at the earliest possible time in order to reduce the burden of disease and achieve satisfying outcomes.

IgG Avidity in Samples Collected on Filter Paper: Importance of The Early Diagnosis of Congenital Toxoplasmosis

OBJECTIVE

 The purpose of the present study is to standardize and evaluate the use of the immunoglobulin G (IgG) antibody avidity test on blood samples from newborns collected on filter paper to perform the heel test aiming at its implementation in ongoing programs.

METHODS

 Blood samples from newborns were collected on filter paper simultaneously with the heel prick test. All samples were subjected to immunoglobulin M IgM and IgG enzyme-linked immunosorbent assays (ELISA). Peripheral blood was collected again in the traditional way and on filter paper from newborns with high IgG levels (³3). Three types of techniques were performed, the standard for measuring IgG in serum, adapted for filter paper and the technique of IgG avidity in serum and on filter paper. The results of the avidity test were classified according to the Rahbari protocol.

RESULTS

 Among the 177 samples, 17 were collected in duplicate from the same child, 1 of peripheral blood and 1 on filter paper. In this analysis, 1 (5.88%) of the 17 samples collected in duplicate also exhibited low IgG avidity, suggesting congenital infection. In addition, the results obtained from serum and filter paper were in agreement, that is, 16 (94.12%) samples presented high avidity, with 100% agreement between the results obtained from serum and from filter paper.

CONCLUSION

 The results of the present study indicate that the avidity test may be another valuable method for the diagnosis of congenital toxoplasmosis in newborns.

Antenatal factors related to congenital toxoplasmosis in Rio De Janeiro, Brazil

BACKGROUND

Toxoplasmosis is one of the main preventable congenital infections in Brazil. This manuscript aims to describe antenatal factors possibly associated with congenital toxoplasmosis (CT).

METHODS

This is a case-control study, with data collected from medical records, from infants admitted under one year of age at the Infectious Diseases Clinic of Instituto de Puericultura e Pediatria Martagão Gesteira, reference center from Rio de Janeiro, exposed to toxoplasmosis during their antenatal period. Patients diagnosed with CT were classified as cases and those exposed without infection as controls.

RESULTS

A total of 289 patients were followed up in 10 years. CT was confirmed in 43 (14.9%) of which six (14%) were asymptomatic, five (12%) had the classic triad (retinochoroiditis, hydrocephalus and intracranial calcifications), 27/42 (64.3%) had reactive IgM. Even after adjusted for prematurity, cases were born with lower weight (OR 0.49 - IC95% 0.33-0.73). There was a 13% increase in chance of CT per gestational week of the maternal diagnosis. Maternal fever, consumption of poorly washed vegetables during pregnancy, and diagnosis in the third trimester were associated with CT (OR: 6.43, 6.55, and 2.16, respectively).

CONCLUSION

Fever during pregnancy, consumption of poorly washed vegetables and diagnosis in the third trimester were associated with CT. Infants with diagnosis of CT were born with lower weight than the controls.

Hearing brain evaluated using near-infrared spectroscopy in congenital toxoplasmosis

Congenital toxoplasmosis (CT) is a known cause of hearing loss directly caused by Toxoplasma gondii. Hearing loss might result from sensory, neural, or sensorineural lesions. Early treated infants rarely develop hearing loss, but retinochoroidal lesions, intracranial calcifications and hydrocephalus are common. In this study, we aimed to evaluate the brain evoked hemodynamic responses of CT and healthy infants during four auditory stimuli: mother infant directed speech, researcher infant directed speech, mother reading and researcher recorded. Children underwent Transitionally Evoked Otoacoustic Emission Auditory Testing and Automated Brainstem Auditory Response tests with normal auditory results, but with a tendency for greater latencies in the CT group compared to the control group. We assessed brain hemodynamics with functional near-infrared spectroscopy (fNIRS) measurements from 61 infants, and we present fNIRS results as frequency maps of activation and deactivation for each stimulus. By evaluating infants in the three first months of life, we observed an individual heterogeneous brain activation pattern in response to all auditory stimuli for both groups. Each channel was activated or deactivated in less than 30% of children for all stimuli. There is a need of prospective studies to evaluate if the neurologic or auditory changes course with compromise of children outcomes.

Seroepidemiology of Toxoplasma gondii in Dairy Cows in Southeastern Brazil: Seropositive Cows on All Farms Investigated

PURPOSE

This study aimed to estimate the prevalence and identify the risk factors associated with the higher in-herd T. gondii seroprevalence in dairy cows in 37 farms in southern Minas Gerais, Southeastern Brazil.

METHODS

Serum samples from 1,105 dairy cows were subjected to an indirect fluorescence antibody test (IFAT 1:64) for anti-T. gondii IgG. The association existing between possible risk factors at the herd level and the seroprevalence were verified through Generalized Estimating Equation (GEE) multiple logistic regression models.

RESULTS

Anti-T. gondii antibodies were observed in 31.4% of the cows (347; 95% CI= 28.7-34.2) and on 100% of the farms (37; 95% CI= 90.6-100.0%), indicating that all properties possessed at least one seropositive animal. For univariate analysis, herds with seroprevalence were categorized as greater and less than 30% as the outcome. The "breeding of Holstein Friesian cows" (p= 0.016, OR= 6.667, 95% CI= 1.500-29.628) and in an "intensive system" (p= 0.013, OR= 6.120, 95% CI= 1.394-26.876) increased the chance of the herd seroprevalence being greater than 30% by approximately six-fold. However, these variables did not exhibit a significant association (p >0.05) in the Generalized Estimating Equations (GEE) logistic regression model.

CONCLUSIONS

The results demonstrate that T. gondii infection is widespread among dairy cows in the south of Minas Gerais, with a wide environmental dispersion of the parasite on farms in this region.

Spiramycin/cotrimoxazole versus pyrimethamine/sulfonamide and spiramycin alone for the treatment of toxoplasmosis in pregnancy

OBJECTIVE

To compare the effectiviness of spiramycin/cotrimoxazole (Sp/C) versus pyrimethamine/sulfonamide (Pyr/Sul) and spiramycin alone (Spy) on mother-to-child transmission of toxoplasmosis infection in pregnancy.

STUDY DESIGN

Retrospective study of pregnant women evaluated for suspected toxoplasmosis between 1992 and 2011.

RESULT

A total of 120 mothers and their 123 newborns were included. Prenatal treatment consisted of spiramycin in 43 mothers (35%), spiramycin/cotrimoxazole in 70 (56.9%) and pyrimethamine/sulfonamide in 10 (8.1%). A trend toward reduction in toxoplasmosis transmission was found when Sp/C was compared with Pyr/Sul and particularly with Spy alone (P=0.014). In particular, Spy increased the risk of congenital infection when compared with Sp/C (odds ratio (OR) 4.368; 95% CI: 1.253 to 15.219), but there was no significant reduction when Sp/C was compared with Pyr/Sul (OR 1.83; 95% CI: 0.184 to 18.274).

CONCLUSION

The treatment based on Sp/C has significant efficacy in reducing maternal-fetal transmission of Toxoplasma gondii when compared with Pyr/Sul and particularly to Spy. Randomized controlled trials would be required.

Animals are key to human toxoplasmosis

Toxoplasma gondii is an extremely sucessfull protozoal parasite which infects almost all mamalian species including humans. Approximately 30% of the human population worldwide is chronically infected with T. gondii. In general, human infection is asymptomatic but the parasite may induce severe disease in fetuses and immunocompromised patients. In addition, T. gondii may cause sight-threatening posterior uveitis in immunocompetent patients. Apart from few exceptions, humans acquire T. gondii from animals. Both, the oral uptake of T. gondii oocysts released by specific hosts, i.e. felidae, and of cysts persisting in muscle cells of animals result in human toxoplasmosis. In the present review, we discuss recent new data on the cell biology of T. gondii and parasite diversity in animals. In addition, we focus on the impact of these various parasite strains and their different virulence on the clinical outcome of human congenital toxoplasmosis and T. gondii uveitis.

Evaluation of a new protocol for retrospective diagnosis of congenital toxoplasmosis by use of Guthrie cards

The aim of this study was to assess the diagnostic value of IgM Western blotting (WB), IgA enzyme immunoassay (EIA), and DNA amplification by real-time PCR on Guthrie cards to retrospectively establish the diagnosis of congenital toxoplasmosis (CT). To this purpose, Guthrie cards were collected from 18 infants born to mothers with primary Toxoplasma gondii infection during pregnancy. Moreover, the analytical sensitivity of T. gondii PCR was assessed by testing mock dried blood specimens set up with several known DNA dilutions. IgM WB was demonstrated to be the most sensitive method. When the results of T. gondii DNA detection and specific IgM recovery were combined, retrospective CT diagnosis by using Guthrie cards was established in 3 out of 6 infected infants (sensitivity, 50%; 95% confidence interval, 26.8% to 73.2%). No positive PCR or serologic results were found in the group of 12 uninfected infants, demonstrating the excellent specificity of the three methods (95% confidence interval, 78.1% to 99.5%). The findings of the present study suggest that, in cases of missed diagnosis of CT at birth, analysis of Guthrie cards for children with compatible clinical findings after the perinatal period, in particular the combination of recovery of specific IgM antibodies and T. gondii DNA amplification, could be helpful. Nevertheless, since suboptimal conditions of storage of dried blood specimens can seriously affect sensitivity, negative results cannot rule out CT diagnosis. In contrast, because of the excellent specificity shown by IgM serologic testing and T. gondii DNA amplification on Guthrie cards, positive results obtained by either of the two methods should be considered diagnostic.

Congenital toxoplasmosis in a reference center of Paraná, Southern Brazil

This study describes the characteristics of 31 children with congenital toxoplasmosis children admitted to the University Hospital of Londrina, Southern Brazil, from 2000 to 2010. In total, 23 (85.2%) of the mothers received prenatal care but only four (13.0%) were treated for toxoplasmosis. Birth weight was <2500 g in 37.9% of the infants. During the first month of life, physical examination was normal in 34.5%, and for those with clinical signs and symptoms, the main manifestations were hepatomegaly and/or splenomegaly (62.1%), jaundice (13.8%), and microcephaly (6.9%). During ophthalmic examination, 74.2% of the children exhibited injuries, 58.1% chorioretinitis, 32.3% strabismus, 19.4% microphthalmia, and 16.2% vitreitis. Anti-Toxoplasma gondii IgM antibodies were detected in 48.3% of the children. Imaging brain evaluation was normal in 44.8%; brain calcifications, hydrocephaly, or both conditions were observed in 27.6%, 10.3%, and 17.2%, respectively, of the patients. Patients with cerebrospinal fluid protein ≥ 200 mg/dL presented more brain calcifications (p = 0.0325). Other sequelae were visual impairment (55.2% of the cases), developmental delay (31.0%), motor deficit (13.8%), convulsion (27.5%), and attention deficit (10.3%). All patients were treated with sulfadiazine, pyrimethamine, and folinic acid, and 55.2% of them exhibited adverse effects. The results demonstrate the significance of the early diagnosis and treatment of toxoplasmosis during pregnancy to reduce congenital toxoplasmosis and its consequences.

Gestational toxoplasmosis in Paraná State, Brazil: prevalence of IgG antibodies and associated risk factors

The aim of the present study was to verify the association between seropositivity for IgG anti-Toxoplasma gondii antibodies and social, economic and environmental variables of pregnant women attending the public health centers of Paraná, Brazil. From January 2007 to July 2010, 2226 pregnant women were interviewed and detection of anti-T. gondii specific IgG and IgM antibodies was performed by chemiluminescence test. Seropositivity for anti-T. gondii IgG was observed in 1151 (51.7%) pregnant women, 29 of which (1.3%) presented IgM reagent with IgG of high avidity. The variables associated with the presence of IgG were residency in the rural area, more than one pregnancy, less than or equal to eight years schooling, low per capita income, age group, raw or poorly cooked meat ingestion, and contact with the soil. There was neither association with raw fruit and vegetable ingestion nor with the presence of cats in the residencies.

Ocular toxoplasmosis: clinical characteristics in pediatric patients

PURPOSE

To describe the clinical features of Ocular Toxoplasmosis in pediatric patients.

METHODS

A retrospective, non-comparative series of cases was studied. We reviewed the clinical records of patients 16 year old or younger diagnosed with Ocular Toxoplasmosis.

RESULTS

Forty patients (56 eyes) were included. The mean age was 9.5 yrs old. Twenty were female. Unilateral involvement was noticed in 60% of patients. The most common symptoms were strabismus (32.1%) and reduced VA in (23.2%). An inactive retinal scar was observed in most cases (71.4%). Panuveitis was found in 8 eyes (14.2%), and posterior uveitis in 7 eyes of 7 patients (12.5%); one eye presented neuroretinitis. The most frequent location of retinochoroidal lesions was the posterior pole (72.7%).

CONCLUSIONS

In children, ocular toxoplasmosis is most commonly diagnosed during the inactive stage. When inflammation is present, it can be severe and frequently associated with other complications such vasculitis and papillitis.

Toxoplasmosis in humans and animals in Brazil: high prevalence, high burden of disease, and epidemiology

Infections by the protozoan parasite Toxoplasma gondii are widely prevalent in humans and animals in Brazil. The burden of clinical toxoplasmosis in humans is considered to be very high. The high prevalence and encouragement of the Brazilian Government provides a unique opportunity for international groups to study the epidemiology and control of toxoplasmosis in Brazil. Many early papers on toxoplasmosis in Brazil were published in Portuguese and often not available to scientists in English-speaking countries. In the present paper we review prevalence, clinical spectrum, molecular epidemiology, and control of T. gondii in humans and animals in Brazil. This knowledge should be useful to biologists, public health workers, veterinarians, and physicians. Brazil has a very high rate of T. gondii infection in humans. Up to 50% of elementary school children and 50-80% of women of child-bearing age have antibodies to T. gondii. The risks for uninfected women to acquire toxoplasmosis during pregnancy and fetal transmission are high because the environment is highly contaminated with oocysts. The burden of toxoplasmosis in congenitally infected children is also very high. From limited data on screening of infants for T. gondii IgM at birth, 5-23 children are born infected per 10 000 live births in Brazil. Based on an estimate of 1 infected child per 1000 births, 2649 children with congenital toxoplasmosis are likely to be born annually in Brazil. Most of these infected children are likely to develop symptoms or signs of clinical toxoplasmosis. Among the congenitally infected children whose clinical data are described in this review, several died soon after birth, 35% had neurological disease including hydrocephalus, microcephaly and mental retardation, 80% had ocular lesions, and in one report 40% of children had hearing loss. The severity of clinical toxoplasmosis in Brazilian children may be associated with the genetic characteristics of T. gondii isolates prevailing in animals and humans in Brazil.

Epidemiology of and diagnostic strategies for toxoplasmosis

The apicomplexan parasite Toxoplasma gondii was discovered a little over 100 years ago, but knowledge of its biological life cycle and its medical importance has grown in the last 40 years. This obligate intracellular parasite was identified early as a pathogen responsible for congenital infection, but its clinical expression and the importance of reactivations of infections in immunocompromised patients were recognized later, in the era of organ transplantation and HIV infection. Recent knowledge of host cell-parasite interactions and of parasite virulence has brought new insights into the comprehension of the pathophysiology of infection. In this review, we focus on epidemiological and diagnostic aspects, putting them in perspective with current knowledge of parasite genotypes. In particular, we provide critical information on diagnostic methods according to the patient's background and discuss the implementation of screening tools for congenital toxoplasmosis according to health policies.

Causes of blindness and visual impairment in Latin America

We review what is known in each country of the Latin American region with regards to blindness and visual impairment and make some comparisons to Hispanic populations in the United States. Prevalence of blindness varied from 1.1% in Argentina to 4.1% in Guatemala in people 50 years of age and older, with the major cause being cataract. Diabetic retinopathy and glaucoma are starting to make serious inroads, although epidemiological data are limited, and age-related macular degeneration is now a concern in some populations. Infectious diseases such as trachoma and onchocerciasis are quickly diminishing. Although progress has been made, retinopathy of prematurity remains the major cause of childhood blindness. If VISION 2020 is to succeed, many more epidemiological studies will be needed to set priorities, although some can be of the Rapid Assessment of Avoidable Blindness design. Developing the infrastructure for screening and treatment of ophthalmic disease in Latin America continues to be a challenge.

Seroprevalence of Toxoplasma gondii infection among pregnant women in Cameroon

Toxoplasmosis is caused by an intracellular protozoan, Toxoplasma gondii, which has a wide geographical distribution. The congenital form results in a gestational form that can present a temporary parasiteamia that will infect the fetus. For this reason early diagnosis in pregnancy is highly desirable, allowing prompt intervention in cases of infection. The aim of this study was to determine the seroprevalence of Toxoplasma gondii antibodies among pregnant women attending the Douala General Hospital. The study was carried out between March and July 2009, whereby 110 pregnant women were tested for IgG and IgM antibodies and information about eating habits and hygienic conditions was collected using a questionnaire. These women's ages ranged from 20–44 years old with an average of 29.9 years; the overall IgG and IgM seroprevalence was 70% and 2.73 % respectively. Seroprevalence was significantly high amongst women who ate raw vegetables (76.39%, P<0.05) and there was a significant trend towards a higher seroprevalence in women who did not have a good source of water (75.58%, P<0.05). This research showed that consumption of raw vegetables and poor quality drinking water are two risk factors associated with Toxoplasma gondii infection amongst pregnant women attending the Douala General Hospital in Cameroon.

Prevalence and risk factors of toxoplasmosis among pregnant women in Fortaleza, Northeastern Brazil

We determined the seroprevalence of Toxoplasma gondii and associated risk factors among 963 pregnant women attending an obstetric hospital in Fortaleza, Brazil. Seroprevalences of IgG and IgM against T. gondii were 68.6% (95% confidence interval [CI] = 65.6-71.6%) and 0.5% (95% CI = 0.06-1.0%), respectively. Seroprevalence of IgG was high in women less than 25 years of age (91.7%) and in low-income women (odds Ratio [OR] = 1.40, 95% CI = 1.02-1.90). Multivariate regression analysis showed that consumption of homemade water ice (adjusted OR = 1.49, 95% CI = 1.09-2.04), vegetables washed with untreated water (adjusted OR = 1.43, 95% CI = 1.05-1.94), consumption of chicken (adjusted OR = 1.49, 95% CI = 1.12-2.0), and dog ownership (adjusted OR= 1.46, 95% CI = 1.07-1.98) were factors associated with IgG seropositivity. Young women in northeastern Brazil living under poor socioeconomic conditions are at highest risk for acquiring infection with T. gondii. Oocyst contamination of water and soil must be addressed in future prevention strategies.

Options for clinical trials of pre and post-natal treatments for congenital toxoplasmosis

Clinical trials comparing different drug regimens and strategies for the treatment of congenital toxoplasmosis and its clinical manifestations in the liveborn child in different clinical settings should aim at formally evaluating the net benefit of existing treatments and at developing new therapeutic options. Currently, there is no ideal drug for congenital toxoplasmosis; future research should focus on the screening of new active drugs and on their pre-clinical and early clinical development, with a focus on pharmacokinetic/dynamic studies and teratogenicity. For the prenatal treatment of congenital toxoplasmosis, a trial comparing spiramycine to pyrimethamine-sulphadiazine and placebo would allow a formal estimation of the effect of both drugs in infected pregnant women. In newborn children, the net benefit of pyrimethamine-sulphadiazine should also be formally assessed. These trials will be implemented in settings where prenatal screening for Toxoplasma gondii is currently implemented. Trials should be carefully designed to allow for translation to other settings and modelling tools like cost-effectiveness analysis should be used to provide clinicians and founders with the best available evidence to establish recommendations.

Tracking transmission of the zoonosis Toxoplasma gondii

Toxoplasma gondii is a highly successful parasite that infects many host species and has colonised a wide range of habitats. Review of the parasite's life cycle demonstrates that it has become adapted to exploit multiple routes of transmission through a sexual cycle in the definitive host and asexually, through carnivory, and by vertical transmission. These alternative routes may operate synergistically to enhance transmission, but they might also provide a vehicle for selection leading to partitioning of strains in the environment. Genetic analysis has shown that parasite population structure varies globally. In South America, there is high strain diversity while in North America, Europe and Africa three clonal strain types predominate. This may imply a shift from sexual to asexual transmission. Mapping of the parasite genome has provided a wealth of markers for strain characterisation. Close genotyping of isolates gives evidence of multiple infection and recombination in natural populations and reveals differences in both the distribution and the phenotype of strains. More intensive epidemiological studies are now required to unravel the networks of transmission operating within defined habitats.

Recovery of anti-Toxoplasma gondii immunoglobulin M in stored guthrie card blood spots

Retrospective testing of neonatal Guthrie card blood spots for specific immunoglobulin M (IgM) can distinguish congenital toxoplasmosis from acquired toxoplasmosis. We determined whether storage temperature reduced IgM detection, using filter paper blood samples "spiked" with anti-Toxoplasma IgM. After 300 days, IgM detection deteriorated with storage at room temperature but not at temperatures of 4 degrees C or lower.

Seroepidemiology of toxoplasmosis in women of childbearing age from a marginal community of Maracaibo, Venezuela

The aim of this study was to determine the prevalence of anti-T. gondii total and IgM antibodies in women of childbearing age. One hundred serum samples of women were studied with age range from 11 to 45 years old. Samples were chosen by random. The determination of total antibodies was carried out through the indirect hemagglutination technique and IgM antibodies by ELISA's technique. The statistical analysis was carried out through the Chi square and the Spearman correlation tests. The theoretical estimated incidence of congenital toxoplasmosis was calculated, according to the annual increment of antibody prevalence among the age groups. The overall prevalence of toxoplasmosis was 33%, while only six individuals (18.2%) were positive to IgM. The highest prevalence was observed in the 11-35 year-old age group. The theoretical estimated incidence was 1.5 for 100 pregnancies in women of 21-25 year-old group; it decreased until 0.1% in the 41-45 year-old age group. The findings show a high prevalence of toxoplasmosis in this community with a high infection risk in women of the studied age group and the high cat population observed, suggesting that the transmission way by contaminated soils may play a main role in the spreading of toxoplasmosis in this community.

Why prevent, diagnose and treat congenital toxoplasmosis?

Evidence that prevention, diagnosis and treatment of toxoplasmosis is beneficial developed as follows: anti-parasitic agents abrogate Toxoplasma gondii tachyzoite growth, preventing destruction of infected, cultured, mammalian cells and cure active infections in experimental animals, including primates. They treat active infections in persons who are immune-compromised, limit destruction of retina by replicating parasites and thereby treat ocular toxoplasmosis and treat active infection in the fetus and infant. Outcomes of untreated congenital toxoplasmosis include adverse ocular and neurologic sequelae described in different countries and decades. Better outcomes are associated with treatment of infected infants throughout their first year of life. Shorter intervals between diagnosis and treatment in utero improve outcomes. A French approach for diagnosis and treatment of congenital toxoplasmosis in the fetus and infant can prevent toxoplasmosis and limit adverse sequelae. In addition, new data demonstrate that this French approach results in favorable outcomes with some early gestation infections. A standardized approach to diagnosis and treatment during gestation has not yet been applied generally in the USA. Nonetheless, a small, similar experience confirms that this French approach is feasible, safe, and results in favorable outcomes in the National Collaborative Chicago-based Congenital Toxoplasmosis Study cohort. Prompt diagnosis, prevention and treatment reduce adverse sequelae of congenital toxoplasmosis.

Vaccination concepts against Toxoplasma gondii

Toxoplasma gondii is a parasite that infects animals and humans worldwide. Despite the current knowledge of immunology, pathology and genetics related to the parasite, a safe vaccine for prevention of the infection in both humans and animals does not exist. Here, we review some aspects concerning vaccination against T. gondii.

Toxoplasmosis screening and risk factors amongst pregnant females in Natal, northeastern Brazil

Toxoplasmosis results in systemic disease, and if the mother is infected for the first time during gestation, the fetus may suffer substantial damage. Relatively little is known about the epidemiology of toxoplasmosis in pregnancy in most states of northeastern Brazil. Seroprevalence of toxoplasmosis among pregnant woman was studied in Natal, capital of Rio Grande do Norte State, in northeastern Brazil, from March to December 2007. The sera were tested for IgM and avidity of IgG antibodies to Toxoplasma by a microparticle enzyme immunoassay. The overall seroprevalence was high [126/190 (66.3%)]; prevalence increased with age indicating that in this setting most infections occur in adulthood (third decade of life). Only one pregnant woman was IgM positive and had high-avidity antibodies. The high percentage of pregnant women who are vulnerable to this parasite (33.1%) favors primary infection during pregnancy. Our studies show that direct contact with cats or dogs was highly associated with toxoplasmosis (odds ratio 2.72, P<0.001, 95% CI 1.46-5.02). The number of years in school (P<0.001), precarious socioeconomic status and limited knowledge about the disease (P<or=0.05 for both) were also associated with toxoplasmosis infection. The pattern of risk factors for infection corroborate other studies in Brazil.

Ocular sequelae of congenital toxoplasmosis in Brazil compared with Europe

Background

Toxoplasmic retinochoroiditis appears to be more severe in Brazil, where it is a leading cause of blindness, than in Europe, but direct comparisons are lacking. Evidence is accumulating that more virulent genotypes of Toxoplasma gondii predominate in South America.

Methods

We compared prospective cohorts of children with congenital toxoplasmosis identified by universal neonatal screening in Brazil and neonatal or prenatal screening in Europe between 1992 and 2003, using the same protocol in both continents.

Results

Three hundred and eleven (311) children had congenital toxoplasmosis: 30 in Brazil and 281 in Europe, where 71 were identified by neonatal screening. Median follow up was 4.1 years in Europe and 3.7 years in Brazil. Relatively more children had retinochoroiditis during the first year in Brazil than in Europe (15/30; 50% versus 29/281; 10%) and the risk of lesions by 4 years of age was much higher: the hazard ratio for Brazil versus Europe was 5.36 (95%CI: 3.17, 9.08). Children in Brazil had larger lesions, which were more likely to be multiple and to affect the posterior pole (p<0.0001). In Brazil, visual impairment (<6/12 Snellen) was predicted for most affected eyes (87%, 27/31), but not in Europe (29%; 20/69, p<0.0001). The size of newly detected lesions decreased with age (p = 0.0007).

Conclusions

T. gondii causes more severe ocular disease in congenitally infected children in Brazil compared with Europe. The marked differences in the frequency, size and multiplicity of retinochoroidal lesions may be due to infection with more virulent genotypes of the parasite that predominate in Brazil but are rarely found in Europe.

Toxoplasma gondii is found throughout the world and is the most common parasitic infection in humans. Infection can cause inflammatory lesions at the back of the eye, which sometimes affect vision. These complications appear to be more common and more severe when people acquire infection in Brazil than in Europe or North America, but there have been no direct comparisons of patients identified and followed up in the same way. In this report, we compare children with congenital toxoplasmosis diagnosed at birth by universal screening in Europe and Brazil and followed up until the age of 4. We found that Brazilian children had a 5 times higher risk than European children of developing eye lesions and their lesions were larger, more numerous and more likely to affect the part of the area of the retina responsible for central vision. Two-thirds of Brazilian children infected with congenital toxoplasmosis had eye lesions by 4 years of age compared with 1 in 6 in Europe. These stark differences are likely to be due to the predominance of more virulent genotypes of the parasite in Brazil, which are rarely found in Europe.

Congenital toxoplasmosis: late pregnancy infections detected by neonatal screening and maternal serological testing at delivery

The first aim of this study was to determine the prevalence of congenital toxoplasmosis in newborn infants treated by the public health system in Porto Alegre, a city in southern Brazil, using neonatal screening for Toxoplasma gondii-specific IgM. The second aim was to investigate whether the cases detected by this approach could have been identified by the prenatal screening for antibodies to T. gondii that was performed in the same population. A fluorometric assay was used to analyse T. gondii-specific IgM in filter paper specimens obtained from newborn infants for routine screening for metabolic diseases. When the specific IgM was positive, serum samples from the infant and the mother were requested for confirmatory serological testing, and the infant underwent clinical examination. Among 10 000 infants screened for T. gondii-specific IgM, seven filter paper samples were positive, and congenital toxoplasmosis was confirmed in six patients. The prevalence of IgM specific for T. gondii was 6/10 000 [95% CI 2/10 000, 13/10 000]. One infected infant had already been identified in the maternity ward before birth, three had been identified by maternal serology at delivery, and two infants with congenital toxoplasmosis were identified solely through neonatal screening. Although four mothers of the patients with congenital toxoplasmosis received prenatal care, and three mothers had one or two serological tests for T. gondii-specific antibodies (one at first trimester, one at first and second trimesters, and the other at second and third trimesters), they were not identified during pregnancy as infected. Neonatal screening identified cases of infection not detected by obtaining only one or two serum samples from pregnant women for T. gondii serology, mainly when infection was acquired and transmitted in late pregnancy. Maternal serology at delivery and neonatal screening were especially useful in the identification of infants with congenital toxoplasmosis when the mother did not receive regular prenatal serological testing or prenatal care.

Serological screening and toxoplasmosis exposure factors among pregnant women in the Democratic Republic of Sao Tome and Principe

The seroprevalence of Toxoplasma gondii infection among pregnant women in the Democratic Republic of Sao Tome and Principe (DRSTP) from November 2003 to March 2004 was determined by detection of serum anti-T. gondii antibodies. A short questionnaire interview for pregnant women was performed to investigate risk factors associated with T. gondii infection, including consumption of raw meat or unwashed vegetables, drinking unboiled water and keeping pets (cats and dogs). The overall seroprevalence of T. gondii infection was high (75.2%; 375/499). The older age group of > or =35 years had a significantly higher seroprevalence (85.7%; 54/63) than that of the younger age group of 15-25 years (70.4%; 178/253) (odds ratio 2.5, 95% CI 1.2-5.4; P=0.01). No significant difference in the seroprevalence of T. gondii infection was found between the pregnant women with and without exposure to the risk factors studied. However, among pregnant women with high antibody titers of > or =1:1024, it seemed likely that continual contact with pets and consumption of oocyst-contaminated water or raw unwashed vegetables rather than tissue cysts in meat was the primary route of infection. The incidence of congenital toxoplasmosis in unborn babies should be intensively monitored in the DRSTP.

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.

Newborn screening for congenital toxoplasmosis: feasible, but benefits are not established

Perspective on the paper by Schmidt et al (see page 661)

Genetic divergence of Toxoplasma gondii strains associated with ocular toxoplasmosis, Brazil

Brazilian strains of T. gondii differ from lineages in North America and Europe; these differences may underlie severe ocular disease.

Previous studies have shown a high prevalence of toxoplasmosis and the frequent occurrence of ocular disease in Brazil. To identify the genotypes of parasite strains associated with ocular disease, we compared 25 clinical and animal isolates of Toxoplasma gondii from Brazil to previously characterized clonal lineages from North America and Europe. Multilocus nested polymerase chain reaction analysis was combined with direct sequencing of a polymorphic intron to classify strains by phylogenetic methods. The genotypes of T. gondii strains isolated from Brazil were highly divergent when compared to the previously described clonal lineages. Several new predominant genotypes were identified from different regions of Brazil, including 2 small outbreaks attributable to foodborne or waterborne infection. These findings show that the genetic makeup of T. gondii is more complex than previously recognized and suggest that unique or divergent genotypes may contribute to different clinical outcomes of toxoplasmosis in different localities.

Symptomatic toxoplasma infection due to congenital and postnatally acquired infection

AIMS

To determine the incidence and severity of symptomatic toxoplasma infection presenting during childhood due to congenital or postnatally acquired infection.

METHODS

Between 2002 and 2004, newly diagnosed children (<16 years) with signs or symptoms of congenital or ocular toxoplasmosis were reported by clinicians to the British Paediatric and Ophthalmic Surveillance Units or by toxoplasma referral laboratories. Confirmed cases were estimated to have a greater than 50% probability of congenital and/or ocular toxoplasmosis, based on clinical and serological findings.

RESULTS

Thirty eight children had confirmed toxoplasma infection. Twenty two (58%) were classified with congenital infection (cumulative incidence for England and Wales 1.62[corrected]/100,000 live births; 95% CI 0.85[corrected] to 2.83[corrected]), of whom 2 (9%) were stillborn, 7 (32%) live births had intracranial abnormalities and/or developmental delay (5 of whom had retinochoroiditis), and 10 (45%) had retinochoroiditis with no other abnormalities reported. A further 16 (42%) children were classified as infected after birth; all had retinochoroiditis.

CONCLUSIONS

The low burden of symptomatic congenital toxoplasmosis combined with the lack of evidence of an effective treatment support current policy not to offer prenatal or neonatal screening for toxoplasma infection. Primary prevention strategies need to address acquisition of infection in childhood which accounts for half the ocular disease due to toxoplasma infection in children in the UK and Ireland.

Biology and epidemiology of Toxoplasma gondii in man and animals

Toxoplasma gondii is a coccidian parasite which utilizes felids as definitive hosts, and which has an unusually wide intermediate host range. The parasite was initially described by Nicolle and Manceaux in 1908 from the rodent, Ctenodactylus gundi. Infection with T. gondii is one of the most common parasitic infections of man and other warm-blooded animals. It has been found worldwide from Alaska to Australia. Nearly one-third of humanity has been exposed to this parasite; serologic surveys indicate that T. gondii infections are common in wild carnivores, including pigs, bears, felids, fox, raccoons, and skunks. Clinical and subclinical toxoplasmosis has been reported from wild cervids, ungulates, marsupials, monkeys, and marine mammals. Southern sea otter populations have been severely impacted by Toxoplasma infections.

Association between congenital toxoplasmosis and parent-reported developmental outcomes, concerns, and impairments, in 3 year old children

Background

Information is lacking on the effects of congenital toxoplasmosis on development, behavior, and impairment in later childhood, as well as on parental concerns and anxiety. This information is important for counselling parents about the prognosis for an infected child and for policy decisions on screening.

Methods

We prospectively studied a cohort of children identified by screening for toxoplasmosis in pregnant women or neonates between 1996 and 2000 in ten European centers. At 3 years of age, parents of children with and without congenital toxoplasmosis were surveyed about their child's development, behavior, and impairment, and about parental concerns and anxiety, using a postal questionnaire.

Results

Parents of 178/223 (80%) infected, and 527/821 (64%) uninfected children responded. We found no evidence that impaired development or behavior were more common in infected children, or that any potential effect of congenital toxoplasmosis was masked by prenatal treatment. Parents of infected children were significantly more anxious and reported more visual problems in their children.

Conclusion

On average, children aged three to four years with congenital toxoplasmosis identified by screening and treated during infancy in this European setting had risks of abnormal development and behavior similar to uninfected children. Parental anxiety about infected children needs to be addressed by clinicians. Future studies with longer follow up and clinician-administered assessments may be better able to detect any subtle differences in child outcomes.

Association between congenital toxoplasmosis and preterm birth, low birthweight and small for gestational age birth

OBJECTIVE

To determine the association between congenital toxoplasmosis and preterm birth, low birthweight and small for gestational age birth.

DESIGN

Multicentre prospective cohort study.

SETTING

Ten European centres offering prenatal screening for toxoplasmosis.

POPULATION

Deliveries after 23 weeks of gestation in 386 women with singleton pregnancies who seroconverted to toxoplasma infection before 20 weeks of gestation. Deliveries after 36 weeks in 234 women who seroconverted at 20 weeks or later, and tested positive before 37 weeks.

METHODS

Comparison of infected and uninfected births, adjusted for parity and country of birth.

MAIN OUTCOME MEASURES

Differences in gestational age at birth, birthweight and birthweight centile.

RESULTS

Infected babies were born or delivered earlier than uninfected babies: the mean difference for seroconverters before 20 weeks was -5.4 days (95% CI: -1.4, -9.4), and at 20 weeks or more, -2.6 days (95% CI: -0.5, -4.7). Congenital infection was associated with an increased risk of preterm delivery when seroconversion occurred before 20 weeks (OR 4.71; 95% CI: 2.03, 10.9). No significant differences were detected for birthweight or birthweight centile.

CONCLUSION

Babies with congenital toxoplasmosis were born earlier than uninfected babies but the mechanism leading to shorter length of gestation is unknown. Congenital infection could precipitate early delivery or prompt caesarean section or induction of delivery. We found no evidence for a significant association between congenital toxoplasmosis and reduced birthweight or small for gestational age birth.

Newborn screening for congenital infectious diseases

To estimate the prevalence of congenital toxoplasmosis, Chagas disease, cytomegalovirus, and rubella, blood samples on dried blood spot (DBS) from neonates (day 3–20 of life) were screened for immunoglobulin (Ig) M against Toxoplasma gondii, cytomegalovirus, rubella virus, and IgG against Trypanosoma cruzi by methods used for serum and adapted for use with DBS. Positive samples were further analyzed for IgM and IgG in serum from neonates and mothers. DBS samples from 364,130 neonates were tested for Toxoplasma gondii–specific IgM, and 15,873 neonates were also tested for IgM against cytomegalovirus and rubella virus and for Trypanosoma cruzi–specific IgG. A total of 195 were diagnosed with congenital toxoplasmosis, 16 with cytomegalovirus, and 11 with congenital rubella. One newborn had a confirmed result for Chagas disease, and 21 mothers had positive serum antibodies. These results suggest that infectious diseases should be considered for future inclusion in programs for newborn screening of metabolic diseases in disease-endemic areas.

Ocular manifestations of toxoplasmosis

PURPOSE OF REVIEW

The concepts of toxoplasmosis and its ocular manifestations in humans have thoroughly changed in the past 3 years. This review addresses new epidemiologic data, specifically the occurrence of ocular disease in postnatal infections, and puts the changed views on the frequency and pathogenesis of toxoplasmic ocular manifestations into historical perspective.

RECENT FINDINGS

Newly described clinical presentations are discussed together with their recent diagnostic possibilities. The new data on congenital or postnatal acquisition of infection and their importance for ocular involvement are presented as well as the high prevalence of 79% of recurrent disease in ocular toxoplasmosis, which cannot be prevented by short-term treatments. Recently published analyses of literature showed, unexpectedly, the lack of efficacy of short-term treatments for ocular disease as well as of the long-term prenatal treatments on fetal transmission rate and the severity of congenital disease.

SUMMARY

The recent guidelines for treatment are included together with the up-to-date recommendations for the treatment of ocular toxoplasmosis in the immunosuppressed host.

Prevalence of IgG antibodies specific to Toxoplasma gondii among blood donors in Recife, Northeast Brazil

A serological survey of Toxoplasma gondii infection in blood donors was carried out in order to identify seroprevalence in Recife, Brazil. Sera from 160 individuals (119 male and 41 female) were evaluated by using a Toxoplasma IgG-antibody enzyme immunoassay (Denka Seiken Co., LTD., Tokyo, Japan). The seropositive percentual for males (79.0%) showed to be higher (p < 0.05) than for females (63.4%). This percentage increases with age, ranging from 18.2% to 92.6% for individuals aging under 20 and 40-50 years old, respectively. For women of childbearing age (18-40 years) it was found a prevalence of 51.6%.

[Prospective study of pregnants and babies with risk of congenital toxoplasmosis in municipal district of Rio Grande do Sul]

This study followed up 2,126 pregnant women cared for at SUS day-care clinics (Public Health Insurance System) of the northwest of the State of Rio Grande do Sul, Brazil. After serological screening we performed a follow up of all pregnant women and their babies. Serologic tests included: IgG, IgM, IgA and IgG avidity levels, mice inoculation and polymerase chain reaction (PCR) also placentas and umbilical materials were tested using immunoperoxidase as well as clinical evaluation. Of all the pregnant women screened, 74.5% were reactive to toxoplasmosis, and 3.6% presented IgM seropositivity. At ophthalmic evaluation ten women had ocular lesions and one infant presented eye lesions and brain calcification. The presence of anti-T.gondii specific IgM throughout the entire pregnancy did not characterize acute phase infection, for this, complementary tests were necessary. The importance is underscored for attendance of the newborn of mothers presenting serology compatible with this infection even in the absence of signs and symptoms of congenital toxoplasmosis.

Incidence of congenital toxoplasmosis in southern Brazil: a prospective study

The study aimed to determine the incidence of congenital infection by Toxoplasma gondii and to describe neonatal and maternal characteristics regarding newborn infants treated at a teaching hospital in the town of Passo Fundo, State of Rio Grande do Sul, Brazil. Cord blood samples collected from 1,250 live newborns were analyzed. The laboratory diagnosis was established by the detection of Toxoplasma gondii IgM using an enzyme linked fluorescent assay. Gestational age, intrauterine growth, anthropometric measures, and prenatal characteristics were assessed. The incidence of congenital toxoplasmosis at birth was 8/10,000 (95%CI 0.2-44.5). Mean birthweight was 3,080 +/- 215.56 grams and mean gestational age was 38.43 +/- 1.88 weeks. With regard to prenatal care, 58% of the pregnant patients visited their doctors five times or more and 38.9% were serologically tested for toxoplasmosis in the first trimester of pregnancy. The incidence of congenital toxoplasmosis was similar to that found in most studies conducted in our country and abroad. Our study sample is representative of the town of Passo Fundo and therefore it is possible to consider the frequency observed as the prevalence of the disease in this town during the study period.

Highly endemic, waterborne toxoplasmosis in north Rio de Janeiro state, Brazil

In Campos dos Goytacazes, northern Rio de Janeiro state, Brazil, reports of uveitis consistent with toxoplasmosis led to a survey of the prevalence and risk factors for Toxoplasma gondii infection in 1997-1999. The survey population was selected randomly from schools, randomly chosen communities, and an army battalion. Serum samples from 1,436 persons were tested. With results adjusted for age, 84% of the population in the lower socioeconomic group was seropositive, compared with 62% and 23% of the middle and upper socioeconomic groups, respectively (p<0.001). When multivariate analysis was performed, drinking unfiltered water was found to increase the risk of seropositivity for the lower socioeconomic (odds ratio [OR]: 3.0, 95% confidence interval [CI] 1.3 to 6.9) and middle socioeconomic (OR: 1.7, 95% CI 1.2 to 2.3) populations. We also found a high T. gondii seroprevalence in this Brazilian community. Drinking unfiltered water increased the risk of T. gondii seropositivity, indicating the potential importance of oocyst transmission in water in this region.

The role of cytokines and their signaling pathways in the regulation of immunity to Toxoplasma gondii

The development of a strong cellular immune response is critical for the control of the intracellular pathogen Toxoplasma gondii. This occurs by activation of a complex, integrated immune response, which utilizes cells of the innate and adaptive immune systems. In the last two decades there have been major advances in our understanding of the role of cytokines in the initiation and maintenance of protective immunity to T. gondii, and IFN-gamma has been identified as the major mediator of resistance to this pathogen. This article provides an overview of the biology of toxoplasmosis and focuses on the pivotal role of cytokines and their signaling pathways during infection. It also addresses the role of cytokines in modulating other immune functions that are critical in determining the balance between a protective and a pathological immune response.