Serological screening for toxoplasmosis in pregnancy in Slovenia

Congenital toxoplasmosis: an in-depth density-equalizing mapping analysis to explore its global research architecture

BACKGROUND

Toxoplasmosis endangers the unborn child if its infectious agent--toxoplasma gondii--is transmitted transplacentally during pregnancy. Although this condition occurs in all parts of the world and represents a major public health burden, no detailed knowledge on the global research architecture of congenital toxoplasmosis is available thus far. Hence, it was the aim of this study to assess the related global research activity over the past 110 years.

METHODS

We employed the NewQIS platform, which combines established scientometric and socioeconomic analysis tools with novel visualizing techniques such as density equalizing mapping projections.

RESULTS

In the Web of Science, 13,044 congenital toxoplasmosis-related items published between 1900 and 2012 were identified. These were issued by 26,483 authors originating from 125 countries. The US was the dominating nation (38.7 % of total scientific output), followed by France (10.9 %) and Great Britain (9.2 %). The US also led the ranking in regards to semi-qualitative parameters (total citations, country-specific h-indices and citation rates). When research activity was related to economic figures, the ratio of total toxoplasmosis publications to the total GDP listed Switzerland first with an average of 589.35 toxoplasmosis-related publications per GDP in 1000 Bio US-$, followed by France (545.16), the UK (486.13) and Brazil (431.84) and the US (311.11). The relation of toxoplasmosis-specific publications to the economic power indicator GDP per capita in 1000 US-$ revealed that the US was ranked first with 97.65 toxoplasmosis-related publications/GDP per capita in 1000 US-$, followed by Brazil (85.95). Subject area analysis indicated a relative shortage of studies that addressed pharmacological or public health aspects of congenital toxoplasmosis.

CONCLUSIONS

This study is the first in-depth approach to sketch a global picture of the congenital toxoplasmosis research architecture. In contrast to other fields of biomedical research, not only high-income countries play a major role regarding congenital toxoplasmosis research but also countries such as Brazil that have a high incidence of congenital toxoplasmosis.

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.

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.

Prevention of congenital toxoplasmosis in Slovenia by serological screening of pregnant women

A programme for the prevention of congenital toxoplasmosis in Slovenia involving the screening of pregnant women for Toxoplasma infection is presented. Of 21,270 pregnant women screened for toxoplasmosis between, 1996 and the end of 1999, 13,987 (66%) were seronegative, 7,151 (34%) seropositive and 132 had primary infection; approximately 9/1,000 women were at risk of acquiring the primary infection. One hundred live-born infants of primary infected women were available for follow-up. Nine infected but asymptomatic children were born to mothers who were screened and treated in time and two congenitally infected babies were born to mothers in whom infection was detected too late in pregnancy and who therefore received no adequate treatment. It is suggested that the results obtained in this study outweigh the cost of screening for toxoplasmosis in pregnancy. Pregnant women should always be tested at the beginning of pregnancy and, in cases of seronegativity, should be re-tested in the second and third trimesters of the pregnancy. Toxoplasma primary infected pregnant women and neonates should be treated as soon as possible. However, long-term follow-up of children born to primary infected women would be necessary for an accurate evaluation of the effectiveness of the screening because of the possibility of late onset of symptoms.

Prevalence of antibodies to Toxoplasma gondii in the female population of the County of Split Dalmatia, Croatia

The prevalence of IgG antibodies reactive with Toxoplasma gondii in the female population of the County of Split Dalmatia was investigated by enzyme linked immunosorbent assay. Of a total of 1109 serum samples collected from female subjects, 423 (38.1%) reacted with T. gondii. The frequency of positive sera increased with age. Theoretical incidence of congenital toxoplasmosis was calculated from the annual increase in cumulative prevalence of antibodies between different age groups among the women of childbearing age. The estimated theoretical incidence of congenital toxoplasmosis was 1.4 per 100 pregnancies of adolescents (16-20 years) and decreased to 0.1% in seronegative pregnant women aged 41-45.

Toxoplasma gondii: from animals to humans

Toxoplasmosis is one of the more common parasitic zoonoses world-wide. Its causative agent, Toxoplasma gondii, is a facultatively heteroxenous, polyxenous protozoon that has developed several potential routes of transmission within and between different host species. If first contracted during pregnancy, T. gondii may be transmitted vertically by tachyzoites that are passed to the foetus via the placenta. Horizontal transmission of T. gondii may involve three life-cycle stages, i.e. ingesting infectious oocysts from the environment or ingesting tissue cysts or tachyzoites which are contained in meat or primary offal (viscera) of many different animals. Transmission may also occur via tachyzoites contained in blood products, tissue transplants, or unpasteurised milk. However, it is not known which of these routes is more important epidemiologically. In the past, the consumption of raw or undercooked meat, in particular of pigs and sheep, has been regarded as a major route of transmission to humans. However, recent studies showed that the prevalence of T. gondii in meat-producing animals decreased considerably over the past 20 years in areas with intensive farm management. For example, in several countries of the European Union prevalences of T. gondii in fattening pigs are now <1%. Considering these data it is unlikely that pork is still a major source of infection for humans in these countries. However, it is likely that the major routes of transmission are different in human populations with differences in culture and eating habits. In the Americas, recent outbreaks of acute toxoplasmosis in humans have been associated with oocyst contamination of the environment. Therefore, future epidemiological studies on T. gondii infections should consider the role of oocysts as potential sources of infection for humans, and methods to monitor these are currently being developed. This review presents recent epidemiological data on T. gondii, hypotheses on the major routes of transmission to humans in different populations, and preventive measures that may reduce the risk of contracting a primary infection during pregnancy.

Risk factors for Toxoplasma infection in a reproductive age female population in the area of Belgrade, Yugoslavia

The contribution to Toxoplasma infection of known transmission risk factors such as consumption of undercooked meat, contact with soil, and contact with cats, as well as that of age, degree of education, residence in central vs. suburban city communities, and year of entry into the study, has been investigated in a group of 1157 female residents (age range 15 to 45 years) of a defined geographic area (Belgrade) during a 4-years period (1988-1991). The rate of infection increased with age, ranging from 57% to 93%, with an overall mean of 77%. However, it decreased significantly over the study period (p < 0.01). Of the potential risk factors examined, regression analysis showed that the following: age (relative risk (RR): 1.18, 95% confidence interval (CI): 1.02-1.37, p = 0.022), undercooked meat consumption (RR: 2.22, 95% CI: 1.2-2.86, p = 0.001), and the year of entry into the study (RR: 0.69, 95% CI: 0.6-0.8, p = 0.000) were significantly associated with infection. However, while the consumption of undercooked meat contributed to the frequency of infection in the whole group, its significance increased with the degree of education but decreased with age, and was greater in women residing in the suburbs. In addition, in women below age 20, exposure to soil (farming, gardening) was significantly associated with infection (RR: 1.38, 95% CI: 1.12-1.97, p = 0.037). Since cats are the single source of toxoplasma oocysts, the above finding indicates that cats are an epidemiologically significant source of environmental contamination in Belgrade. However, cat ownership itself as a criterion of contact with cats was not associated with infection (p = 0.326). In the absence of a general screening in pregnancy program in Yugoslavia, these data point out the groups of pregnant women at the highest risk of infection and provide a basis for a region-appropriate educational program to prevent congenital toxoplasmosis.

Screening for toxoplasmosis in pregnancy: what is the evidence of reducing a health problem?

OBJECTIVES

Toxoplasma gondii is a parasite which may give rise to congenital infection. Screening pregnant women for antibodies against toxoplasmosis is being debated in many countries. The preventive impact of toxoplasmosis screening of pregnant women depends on the magnitude of disease caused by congenital toxoplasmosis (incidence x transmission rate to fetus x diseased proportion of infected children), on the one hand, and the preventable proportion of disease (sensitivity of the screening test x efficacy of the treatment x compliance), on the other. In this study the preventive impact of screening pregnant women for toxoplasmosis antibodies is assessed by letting the value for these variables change within reasonable limits.

METHODS

To obtain information on these variables, relevant publications were reviewed in the Medline database from 1983 to February 1996 and the Cochrane Pregnancy and Childbirth Database. References in review articles on congenital toxoplasmosis were also studied.

RESULTS

The literature review showed that no population based prospective studies of the natural history of toxoplasmosis infection during pregnancy, nor any randomised controlled trials of the efficacy of antiparasitic treatment, had been carried out. In the empirical studies which have been performed the values of most variables show considerable differences. According to these values, the estimates in this study of the impact of toxoplasmosis screening in pregnancy may range from 0 to 40 children in whom disease is preventable per 100,000 pregnant women susceptible to toxoplasmosis infection.

CONCLUSION

Sufficient scientific evidence is not yet available to propose screening for toxoplasmosis in pregnant women, and efforts should be made to provide such knowledge. Also, the magnitude of the negative impact of screening, such as induced abortion of healthy fetuses, anxiety in women with false positive screening tests, and side effects of treatment, has not been sufficiently examined.