Seasonal variations in acute toxoplasmosis in pregnant women in Slovenia

Anti-Toxoplasma gondii Antibodies in European Residents: A Systematic Review and Meta-Analysis of Studies Published between 2000 and 2020

Toxoplasmosis has a major impact on animal and public health. Information regarding the seroprevalence of human Toxoplasma gondii infections from a European perspective has not yet been compiled to date. Thus, the present review summarized available resident data from the period 2000-2020. The overall seroprevalence of anti-T. gondii IgG was 32.1%, with great variability between countries (n = 30). The subgroup analysis identified different pooled prevalence data depending on the geographic area (p < 0.0001), target population (p = 0.0147), and serological diagnosis assays used (p = 0.0059). A high heterogeneity (I2 = 100%, p < 0.001; Q = 3.5e+05, d.f. = 135, p < 0.001) and degree of publication bias (Egger's test = 6.14, p < 0.001) were observed among the 134 studies considered. The occurrence of anti-T. gondii IgM, which was reported in 64.7% of studies, reached a pooled seroprevalence of 0.6%. In addition, among the eight main risk factors identified, "contact with soil", "consumption of undercooked beef", and "intake of unwashed vegetables" were the most significantly associated with infections. The fact that one-third of the European population has been exposed to T. gondii justifies extra efforts to harmonize surveillance systems and develop additional risk-factor analyses based on detailed source attribution assessment.

High prevalence and diversity of Toxoplasma gondii DNA in feral cat feces from coastal California

Toxoplasma gondii is a zoonotic parasite that can cause severe morbidity and mortality in warm-blooded animals, including marine mammals such as sea otters. Free-ranging cats can shed environmentally resistant T. gondii oocysts in their feces, which are transported through rain-driven runoff from land to sea. Despite their large population sizes and ability to contribute to environmental oocyst contamination, there are limited studies on T. gondii oocyst shedding by free-ranging cats. We aimed to determine the frequency and genotypes of T. gondii oocysts shed by free-ranging domestic cats in central coastal California and evaluate whether genotypes present in feces are similar to those identified in sea otters that died from fatal toxoplasmosis. We utilized a longitudinal field study of four free-ranging cat colonies to assess oocyst shedding prevalence using microscopy and molecular testing with polymerase chain reaction (PCR). T. gondii DNA was confirmed with primers targeting the ITS1 locus and positive samples were genotyped at the B1 locus. While oocysts were not visualized using microscopy (0/404), we detected T. gondii DNA in 25.9% (94/362) of fecal samples. We genotyped 27 samples at the B1 locus and characterized 13 of these samples at one to three additional loci using multi locus sequence typing (MLST). Parasite DNA detection was significantly higher during the wet season (16.3%, 59/362) compared to the dry season (9.7%; 35/362), suggesting seasonal variation in T. gondii DNA presence in feces. High diversity of T. gondii strains was characterized at the B1 locus, including non-archetypal strains previously associated with sea otter mortalities. Free-ranging cats may thus play an important role in the transmission of virulent T. gondii genotypes that cause morbidity and mortality in marine wildlife. Management of free-ranging cat colonies could reduce environmental contamination with oocysts and subsequent T. gondii infection in endangered marine mammals and people.

The epidemiology of patients with toxoplasmosis and its associated risk factors in Taiwan during the 2007-2020 period

BACKGROUND

Toxoplasmosis is a zoonotic parasitic disease caused by the protozoan Toxoplasma gondii (T. gondii), and may cause miscarriage and birth defects during pregnancy. This study aimed to assess the epidemiological features, epidemic trends, and correlations between the before number of confirmed toxoplasmosis cases in Taiwan from 2007 to 2020 in gender, age, season, and residential area, and hypothesized the environmental and climate factors also might affect the disease in Taiwan.

METHODS

This study reviewed publicly available annual summary data on reported toxoplasmosis cases in the Taiwan Centers for Diseases Control (TCDC) between 2007 and 2020.

RESULTS

This study collected 150 confirmed domestic and nine patients with imported toxoplasmosis. There was an increasing trend in the incidence of toxoplasmosis, 0.09-0.89 cases per 1,000,000 people, peaking in 2017. The average annual toxoplasmosis incidence was 4.4, 13, and 18 during 2007-2011, 2012-2016, and 2017-2020, respectively. Comparing sex, age, season, and place of residence, the incidence rate was highest in male, 20-39 years-old patients, summer, and the eastern region, with 1.02, 1.72, 0.38, and 3.63 cases per million population, respectively. Additionally, comparing the distribution of cases by age group in Taiwan, there were significant differences between 40-59 years-old in the northern region (odds ratio (OR) = 0.343, 95% confidence interval (CI) = 0.167-0.705, p = 0.004) and 40-59 years-old in the southern region (OR = 4.488, and 95% CI = 2.149-9.374, p< 0.001), respectively. Linear regression analysis also showed that PM (particulate matter) 2.5 (μg/m3) concentration was positively associated with toxoplasmosis (β = 0.095, p = 0.037). CO concentration was negatively correlated with toxoplasmosis (β = -14.001, p = 0.021).

CONCLUSIONS

This study is the first to report domestic and confirmed cases of imported toxoplasmosis from the surveillance data of the TCDC between 2007 and 2020. It identified that residence and age were associated with an increased risk of toxoplasmosis in Taiwan. This study confirmed that toxoplasmosis remains a prevalent infectious disease in Taiwan, its epidemic is gradually increasing and becoming more severe. These findings might be useful for policy-makers and clinical experts to direct prevention and control activities to patients with T. gondii, which causes the most severe illness and greatest burden to Taiwanese people.

Seasonal variations and public search interests in Toxoplasma: a 16-year retrospective analysis of big data on Google Trends

BACKGROUND

This study aims to understand whether there is a seasonal change in the internet search interest for Toxoplasma by using the data derived from Google Trends (GT).

METHODS

The present study searched for the relative search volume (RSV) for the search term 'Toxoplasma' in GT within six major English-speaking countries (Australia, New Zealand [Southern Hemisphere] and Canada, Ireland, the UK and the USA [Northern Hemisphere] from 1 January 2004 to 31 December 2019, utilizing the category of 'health'. Data regarding the RSV of Toxoplasma was obtained and further statistical analysis was performed in R software using the 'season' package.

RESULTS

There were significantly seasonal patterns for the RSV of the search term 'Toxoplasma' in five countries (all p<0.05), except for the UK. A peak in December-March and a trough in July-September (Canada, Ireland, the UK and the USA) were observed, while a peak in June/August and a trough in December/February (Australia, New Zealand) were also found. Moreover, the presence of seasonal patterns regarding RSV for 'Toxoplasma' between the Southern and Northern Hemispheres was also found (both p<0.05), with a reversed meteorological month.

CONCLUSIONS

Overall, our study revealed the seasonal variation for Toxoplasma in using internet search data from GT, providing additional evidence on seasonal patterns in Toxoplasma.

Large-scale serological screening of slaughter pigs for Toxoplasma gondii infections in The Netherlands during five years (2012-2016): Trends in seroprevalence over years, seasons, regions and farming systems

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The seroprevalence of T. gondii in slaughter pigs was between 1.4% and 2.8%.

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The seroprevalence of T. gondii in slaughter pigs showed a peak in winter.

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Pigs from organic farms had a higher seroprevalence of T. gondii.

Toxoplasma gondii is the causative agent of the parasitic disease toxoplasmosis, which is an important foodborne zoonosis. Eating undercooked meat of infected animals, including pigs, has been considered the major transmission route of T. gondii to humans. Therefore, it is urgent to develop and implement intervention measures in the pork meat chain to reduce risks of acquiring a T. gondii infection. Proposed measures for control of T. gondii in pigs include serological testing of pigs and audits of pig farms on risk factors for T. gondii infection. So far, these ideas have not been tested in practice. In order to generate knowledge about the epidemiology and seroprevalence of T. gondii, as a basis for developing a surveillance system, we studied the long term seroprevalence over years, farming systems and regions, and seasonal patterns of T. gondii seroprevalence in Dutch slaughter pigs. During a five year study period from 2012 to 2016, serum samples were routinely collected in five Dutch pig slaughterhouses. The sera were tested in an ELISA for the presence of antibodies against Toxoplasma. In total 226,340 serum samples were collected and tested during the study period. The observed seroprevalence varied over years, with the highest overall seroprevalence in 2014 (2.8%) and the lowest in 2016 (1.4%). A higher seroprevalence was observed in pigs from organic farms compared to pigs from conventional farms. The overall risk of infection was on average 2.63 times significantly (p < 0.001) higher for organically raised pigs than for conventionally raised pigs. A seasonal pattern in seroprevalence was observed: the results showed a dominant annual periodicity with a seroprevalence peak in winter around week 1 and a minimum seroprevalence in summer around week 27.

To our knowledge, this is the first large scale study on the seroprevalence of T. gondii in slaughter pigs. In comparison to other European serological studies, the observed seroprevalence seems to be relatively low. However, care is needed when comparing the results with other studies because of differences in test setup, the number of samples and time period of sampling. The results can be used as a starting point for developing a surveillance system for T. gondii, and for implementation of intervention measures.

Seasonality of births in horizontal strabismus: comparison with birth seasonality in schizophrenia and other disease conditions

Recent work has implicated one type of horizontal strabismus (exotropia) as a risk factor for schizophrenia. This new insight raises questions about a potential common developmental origin of the two diseases. Seasonality of births is well established for schizophrenia. Seasonal factors such as light exposure affect eye growth and can cause vision abnormalities, but little is known about seasonality of births in strabismus. We examined birth seasonality in people with horizontal strabismus in a retrospective study in Washoe County, Nevada, and re-examined similar previously obtained data from Osaka, Japan. We then compared seasonal patterns of births between strabismus, refractive error, schizophrenia and congenital toxoplasmosis. Patients with esotropia had a significant seasonality of births, with a deficit in March, then increasing to an excess in September, while patients with exotropia had a distinctly different pattern, with an excess of births in July, gradually decreasing to a deficit in November. These seasonalities were statistically significant with either χ2 or Kolmogorov-Smirnov-type statistics. The birth seasonality of esotropia resembled that for hyperopia, with an increase in amplitude, while the seasonality for myopia involved a phase-shift. There was no correlation between seasonality of births between strabismus and congenital toxoplasmosis. The pattern of an excess of summer births for people with exotropia was remarkably similar to the well-established birth seasonality of one schizophrenia subtype, the deficit syndrome, but not schizophrenia as a whole. This suggests a testable hypothesis: that exotropia may be a risk factor primarily for the deficit type of schizophrenia.

Seroprevalence of Toxoplasma gondii in Western Romania

Toxoplasma gondii is an obligate intracellular parasite that most commonly causes asymptomatic infection in immunocompetent hosts, but can have devastating consequences in congenitally infected infants and immunocompromised patients. We evaluated the seroprevalence of T. gondii in the general population in Western Romania. Sera from 304 individuals were analysed with the Pastorex Toxo test, which allows the simultaneous detection of T. gondii IgG and/or IgM antibodies. T. gondii antibodies were demonstrated in 197 individuals (64.8%) and the prevalence increased with age: 35.0% in those < 20 years versus 76.8% in those ≥ 70 years (p < 0.001). There was a higher prevalence of T. gondii antibodies in rural areas (76.9%) than in urban regions (55.3%) (p < 0.001). Our results suggest a high prevalence of T. gondii antibodies in Western Romania.

Seasonal variation of acute toxoplasmic lymphadenopathy in the United States

We describe the seasonal variation of acute toxoplasmosis in the United States. Acute toxoplasmic lymphadenopathy (ATL) can be a surrogate of acute toxoplasmosis in patients in whom the date of onset of lymphadenopathy matches the window of acute infection predicted by serological tests performed at a reference laboratory. We used the electronic database of the Palo Alto Medical Foundation Toxoplasma Serology Laboratory (PAMF-TSL) (1997-2011) to identify cases of ATL. We tested the uniformity of distribution of ATL cases per month, across the 12 calendar months, using circular statistics uniformity tests. We identified 112 consecutive cases of ATL. The distribution of cases was not uniform across the 12 calendar months. We observed the highest peak of cases in December and a second highest peak in September. Similar months were identified in patients with acute toxoplasmosis in rural areas in France. The results were similar when we performed weighted analyses, weighting for the total number of Toxoplasma gondii IgG tests performed per month in the PAMF-TSL laboratory. This is the largest study to date of the seasonal variation of ATL in the United States. Physicians should advise high-risk individuals to avoid risk factors associated with T. gondii infections especially around those months.

Epidemiologic aspects of toxoplasmosis and evaluation of its seroprevalence in pregnant women

INTRODUCTION

The aim of the present study was to analyze the exposure to risk factors for toxoplasmosis disease and the level of knowledge in pregnant women who were treated by the Public Health Care System (SUS) from October 2007 to September 2008 in Divinópolis City, Brazil.

METHODS

We analyzed 2,136 prenatal exams of pregnant women that were treated from October 2007 to September 2008.

RESULTS

Out of the 2,136 pregnant women evaluated, 200 answered a quantitative questionnaire; 49.5% were seropositive for immunoglobulin (Ig) G and 3.6% for IgM. Comparative analysis of congenital toxoplasmosis cases were evaluated in 11 regions and showed an irregular distribution (p < 0.01). This difference was also observed among the pregnant women observed in each location. The results from the questionnaire show that 93% of the pregnant women had no knowledge about toxoplasmosis, and 24% presented with positive serology, but no clinical manifestation. Analysis for pregnant IgG-positive women and the presence of pets showed a statistically significant correlation (p < 0.05), suggesting that the transmission of this disease might occur in the domestic environment.

CONCLUSIONS

We suggest the implementation of a triage program for pregnant women and health education to encourage their use of SUS services.

Methods to assess seasonal effects in epidemiological studies of infectious diseases--exemplified by application to the occurrence of meningococcal disease

Seasonal variation in occurrence is a common feature of many diseases, especially those of infectious origin. Studies of seasonal variation contribute to healthcare planning and to the understanding of the aetiology of infections. In this article, we provide an overview of statistical methods for the assessment and quantification of seasonality of infectious diseases, as exemplified by their application to meningococcal disease in Denmark in 1995-2011. Additionally, we discuss the conditions under which seasonality should be considered as a covariate in studies of infectious diseases. The methods considered range from the simplest comparison of disease occurrence between the extremes of summer and winter, through modelling of the intensity of seasonal patterns by use of a sine curve, to more advanced generalized linear models. All three classes of method have advantages and disadvantages. The choice among analytical approaches should ideally reflect the research question of interest. Simple methods are compelling, but may overlook important seasonal peaks that would have been identified if more advanced methods had been applied. For most studies, we suggest the use of methods that allow estimation of the magnitude and timing of seasonal peaks and valleys, ideally with a measure of the intensity of seasonality, such as the peak-to-low ratio. Seasonality may be a confounder in studies of infectious disease occurrence when it fulfils the three primary criteria for being a confounder, i.e. when both the disease occurrence and the exposure vary seasonally without seasonality being a step in the causal pathway. In these situations, confounding by seasonality should be controlled as for any confounder.

Seasonal variations in acute toxoplasmosis in pregnant women in the Rhône-Alpes region (France)

To search for seasonal variations we analysed data on 1998 acute toxoplasmic infections diagnosed between 1988 and 2009 in pregnant women. Two distinctive transmission profiles were observed: one in rural areas, which was strongly influenced by seasons with significantly fewer infections in the first half of the year but maximal risks at the end of summer and end of autumn, and a stable urban distribution with only moderate peaks. Further studies on individual risks and environmental and climatic factors are needed to understand what prevention message should be given to susceptible pregnant women.

Incidence of maternal Toxoplasma infections in pregnancy in Upper Austria, 2000-2007

Background

Despite three decades of prenatal screening program for toxoplasmosis in Austria, population-based estimates for the incidence of maternal infections with Toxoplasma gondii during pregnancy are lacking. We studied the incidence of primary maternal infections during pregnancy in the Federal State of Upper Austria.

Methods

Screening tests for 63,416 women and over 90,000 pregnancies (more than 84.5% of pregnancies in the studied region) in the time period between 01.01.2000 and 31.12.2007 were analysed. The incidence of toxoplasmosis was estimated indirectly by binomial and directly by interval censored regression.

Results

During the studied period, 66 acute infections (risk of 0.07% per pregnancy) were detected, but only 29.8% of seronegative women were tested at least three times during their pregnancies. The seroprevalence of Toxoplasma antibodies among all tested women was 31%. Indirectly estimated incidence (from differences in prevalence by age) was 0.5% per pregnancy, while directly estimated incidence (interval censored regression) was 0.17% per pregnancy (95% confidence interval: 0.13-0.21%).

Conclusions

Calculating incidence from observed infections results in severe underreporting due to many missed tests and potential diagnostic problems. Using statistical modelling, we estimated primary toxoplasmosis to occur in 0.17% (0.13-0.21%) of all pregnancies in Upper Austria.

Kinetics of Toxoplasma infection in the Balkans

AIM

The kinetics of Toxoplasma infection in the Balkans were reviewed.

SOURCE OF DATA

Published reports on Toxoplasma infection in women of childbearing age in the last 30 years for all Balkan countries.

RESULTS

The dominant feature of Toxoplasma infection in the Balkans is a continuous decrease in the prevalence over time. Systematic monitoring of Toxoplasma infection prevalence in populations of women of childbearing age in Slovenia, Serbia and Greece over the last 30 years has shown a continuous significant decrease in all three countries. Moreover, a decrease has also been shown in Montenegro and Former Yugoslav Republic of Macedonia where Toxoplasma infection has been surveyed only during the past decade. Another region-wide feature is that the prevalence of infection currently does not surpass 50%. Furthermore, a decrease in Toxoplasma prevalence from the north to the south has been shown in the eastern part of the Balkan Peninsula, from southern Hungary (as a region neighbouring the Balkans at the north), over Serbia and FYRoM to northern Greece. Seasonality of infection, with significantly more cases of acute infection in the winter than in the summer, was observed in Slovenia in the west and Serbia in the east. Despite a common decreasing trend, different infection transmission risk factors seem predominant across the region; while contact with cats was discussed as important in Slovenia, consumption of undercooked meat was shown to be the leading risk factor in Serbia and Albania, and contact with soil in FYRoM and in northern Greece.

CONCLUSION

A decreasing trend of Toxoplasma prevalence over time in the Balkans is part of a changing pattern of Toxoplasma infection throughout Europe. Strategies for the prevention of congenital toxoplasmosis should take the infection dynamics into account.

Seasonal variations in human Toxoplasma infection in Serbia

BACKGROUND

Seasonal variations in the occurrence of toxoplasmosis have been studied only sporadically. We thus examined the seasonal distribution of acute toxoplasmosis in Serbia during a 4-year period (2004-2008).

MATERIALS AND METHODS

A total of 391 consecutive symptomatic (recent lymphadenopathy) and 715 asymptomatic (women tested for obstetric reasons) patients were tested for Toxoplasma immunoglobulin G (IgG) (including IgG avidity) and IgM antibodies. The distribution of patients with acute infection, and of all patients from both groups, was analyzed for seasonality. In addition, factors (including undercooked meat consumption, contact with cats and with soil) possibly contributing to seasonality were analyzed in patients with acute infection (cases) matched by age, sex, and time (month and year) of infection (symptomatic) or presentation (asymptomatic) with seronegative patients (controls).

RESULTS

Acute toxoplasmosis was serologically (IgG avidity low, IgM positive) diagnosed in 39 (10.0%) symptomatic and 38 (5.3%) asymptomatic patients. In both groups, monthly distribution of acute infections showed significant (p < 0.0001) seasonality, which was related to the four seasons of the year (p < 0.0001). Importantly, the observed seasonality was not related to the distribution of all examined patients in either group (p < 0.001). In the symptomatic patients, acute infections occurred more often between October and March (p = 0.0486). Although more asymptomatic acute infections were diagnosed between February and July (p = 0.0037), low IgG avidity suggests that infection had occurred within the previous trimester (between November and April). Undercooked meat consumption was shown as a risk factor for symptomatic infection in the October-March period (odds ratio 7.67, 95% confidence interval 1.61-36.45).

CONCLUSION

Seasonality patterns should be taken into account in the health education guidelines for the prevention of toxoplasmosis in pregnant women.