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K.I. Nijem¹ and S. Al-Amleh¹

معدَّل الانتشار المصلي وعوامل الخطر المرافقة لداء المقوَّسات لدى الحوامل في منطقة الخليل، فلسطين

خلدون عيسى نجم، شفا محمد العملة

الخلاصـة: لقياس معدَّل انتشار داء المقوسات، أجرى الباحثون اختبارات شملت 204 حاملاً للتعرُّف على الأضداد من الغلوبين المناعي G ومن الغلوبين المناعي M للمقوَّسات الغوندية باستخدام المقايسة المناعية المرتبطة بالإنزيم، وذلك في منطقة الخليل خلال عام 2005. وقد وجدوا أن معدَّل الانتشار المصلي للأضداد من الغلوبين المناعي G للمقوسات الغوندية %27.9، وأن معدَّل الانتشار المصلي للأضداد من الغلوبين المناعي M للمقوسات الغوندية 17.6، مع ازدياد في معدل الانتشار المصلي للمقوسات الغوندية مع تقدم العمر. وكانت نسبة النسوة الريفيات اللاتي لديهن معدَّل الانتشار المصلي للأضداد من الغلوبين المناعي G للمقوسات الغوندية (%36.8) أكبر مما هي لدى الحضريات (%21.4). وطرق سراية العدوى المحتملة هي التـراب الملوث، وشرب مياه الأمطار، وتناول الخضراوات النيئة أكثر من أكل اللحم غير المطبوخ أو مخالطة القطط. وقد بلغ معدَّل انتشار إسقاط سابق %37.3 مع ترافق خفيف (ولكن لا يعتد به إحصائياً) مع داء المقوَّسات.

ABSTRACT To measure the prevalence of toxoplasmosis, we tested 204 pregnant women for IgG and IgM antibodies to Toxoplasma gondii using an enzyme-linked immunoassay. The study was conducted in Hebron district during the year 2005. The seroprevalence of IgG antibodies to T. gondii was 27.9% while IgM seroprevalence was 17.6%; the seroprevalence of T. gondii increased with age. More women from rural areas (36.8%) had IgG antibodies to T. gondii than urban women (21.4%). Possible routes of infection were contaminated soil, drinking rainwater and eating raw vegetables rather than eating uncooked meat or contact with cats. The prevalence of previous abortion was 37.3%, with a slight (but not statistically significant) association with toxoplasmosis.

Séroprévalence de la toxoplasmose chez les femmes enceintes du district d’Hébron (Palestine) et facteurs de risque associés

RÉSUMÉ Afin de mesurer la prévalence de la toxoplasmose, nous avons effectué une recherche d’anticorps IgG et IgM anti-Toxoplasma gondii chez 204 femmes enceintes au moyen d’un test immunoenzymatique. Cette étude a été menée dans le district d’Hébron au cours de l’année 2005. La séroprévalence des anticorps IgG anti-T. gondii était de 27,9 %, alors que celle des anticorps IgM était de 17,6 % ; la séroprévalence de T. gondii augmentait avec l’âge. Les femmes vivant en zone rurale qui présentaient des anticorps IgG anti-T. gondii étaient plus nombreuses (36,8 %) que celles vivant en zone urbaine (21,4 %). Les voies d’infection possibles étaient les sols contaminés, la consommation d’eau de pluie et de légumes crus, davantage que la consommation de viande non cuite ou le contact avec des chats. La prévalence d’avortements antérieurs était de 37,3 %, avec une association légère (sans être statistiquement significative) avec la toxoplasmose.

1Department of Biology, Faculty of Science and Technology, Hebron University, Hebron, West Bank, Palestine (Correspondence to K.I. Nijem: This e-mail address is being protected from spambots. You need JavaScript enabled to view it ).
Received: 17/03/07; accepted: 14/05/07
EMHJ, 2009, 15(5):1278-1284

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Introduction

Toxoplasmosis is a very common infection caused by the obligate intracellular protozoan parasite Toxoplasma gondii. Most Toxoplasma infections are asymptomatic, but the implications in pregnant women are manifold. The women may have spontaneous abortions, stillbirths or premature delivery in addition to various fetal anomalies [1,2]. The parasite is transmitted to humans by ingestion of the tissue cysts in raw or undercooked meat, as well as ingestion of food and water contaminated with oocysts from cat faeces [3,4]. Human infection with T. gondii is very frequent throughout the world: the seroprevalence ranges from 15% in the United Kingdom to 80% in South America and certain European countries such as France [5]. In developing countries toxoplasmosis is also very frequent: in Turkey, IgG seroprevalence of T. gondii among pregnant women was 60% [6] while in India it was 45% [7]. Studies among Arab populations have reported the seroprevalence of toxoplasmosis ranging from 22.9% in the United Arab Emirates [8] to 47% in Jordan [9].

The frequency of severe congenital infections can be limited by early screening for specific antibodies to T. gondii in the serum of pregnant women [10]. Many developed countries have implemented a toxo­plasmosis screening programme [11,12], however, such programmes have not been implemented in most developing countries, including Palestine. If seroconversion is documented, therapy by sulfadiazine is offered to pregnant women during the first trimester and to the infant until 1 year of age [13].

Only a few studies have been done in Palestine, but not enough to provide the necessary information about toxoplasmosis. The aim of the present study was, therefore, to determine seroprevalence IgG and IgM antibodies to T. gondii among first trimester pregnant women in Hebron district, Palestine.

Methods

Study population

The study was conducted in Hebron district, 40 km from Jerusalem. The district has 400 000 inhabitants and includes the city of Hebron and many villages engaged in agriculture. According to the 1997 population census, 66% of the population live in rural areas [14].

Sampling procedure

The study was carried out on pregnant women aged 16–43 years in their first trimester of pregnancy. They were recruited on their first prenatal visit to an obstetrics/gynaecology clinic in Hebron city during January–August 2005. We gave out invitations and information letters to pregnant women during their first visit to the clinic and all those meeting the inclusion criteria were invited to participate. All agreed to participate and were asked to provide a blood sample and answer a self-reported questionnaire containing sociodemographic questions, including age, number of children, smoking, occupation and date of marriage as well as questions related to route of exposure to the parasite, abortion and number of dead children.

Immunological tests

IgG and IgM antibodies to T. gondii were measured using a commercial kit (Platelia Toxo IgG, IgM TMB, Bio-Rad Laboratories) according to the manufacturer’s instructions. An aliquot of blood was withdrawn from each woman by a professional clinical laboratory technician. Sera were then separated by centrifugation and stored at –20 °C until analysis. Each blood sample was analysed for the presence of T. gondii by identifying serum IgG and IgM antibodies to T. gondii using an enzyme-linked immunoassay test.

Data and statistical analysis

The seroprevalence IgG and IgM antibodies to T. gondii was calculated among pregnant women in both urban and rural areas. Seroprevalence was also calculated according to different sociodemographic characteristics, including age, occupation and years of marriage, using SPSS, version 12. The association between IgG seropositivity to T. gondii and previous abortion was calculated by logistic regression. Odds ratio (OR) was adjusted for age category (16–22, 23–29, 30–43 years), cigarette smoking (yes, no) and main occupation (housewife, other). Calculated 95% confidence intervals (95% CI) that did not include the null value were considered statistically significant. Frequencies, and means and standard deviations (SD) of sociodemographic and life-style factors were also calculated.

Results

Altogether, all 204 eligible women agreed to participate in the study. The mean age of the sample was 26.4 (SD = 6.1) years; 57.4 % of the sample were from Hebron city (n = 117) with a mean age of 25.5 (SD = 6.0) years. The rest were from the rural area of Hebron district (Table 1). The pregnant women from the villages [mean age 27.7 (SD = 6.0) years] were slightly older than those from the city. The mean age at marriage was 19.3 (range = 12–38; SD 3.7) years. The majority of the participants (80.4%) were housewives (did not work outside the home). Keeping cats and eating raw meat were not common among the women we studied. Sociodemographic and lifestyle characteristics are shown in Table 1.

The overall seroprevalence of IgG antibodies to T. gondii was 27.9%. A higher prevalence of T. gondii IgG antibodies was seen among women from the rural areas (36.8%) compared with those from the city (21.4%). The highest prevalence of T. gondii IgG antibodies (38.2%) was seen in the age stratum 30–43 years, while the age group 16–22 showed the lowest IgG seroprevalence (17.9%). Housewives had a higher IgG seropositivity, 29.3%, compared with others (22.5%) (Table 2).

Few of the women kept cats: only 1 woman kept a cat inside the house, while 14 kept a cat outside (Table 1). Among these, T. gondii IgG seroprevalence was 100.0% (n = 1) and 21.4% (n = 3) respectively.

Previous abortion was reported by 37.3% of the participants, with a slightly higher prevalence in urban women (Table 1). T. gondii IgG seroprevalence was significantly higher among women from rural areas who had previously had an abortion (50.0%) than those from the city (20.5%) (P = 0.007).

Overall, the seroprevalence of IgM antibodies to T. gondii was 17.6%; it was higher among those from rural areas (19.5%), women married at age < 20 years (18.7%), and housewives (18.3%) (Table 2). T. gondii IgM seroprevalence among women who had had an abortion was 18.4% (n = 147) (Table 3). Both IgG and IgM antibodies to T. gondii were found in 6.4% of the sample.

The association between previous abortion and toxoplasmosis was estimated using logistic regression. A slight, but not statistically significant, association was found between previous abortion and T. gondii IgG seropositivity (OR = 1.47; 95% CI: 0.79–2.7). When the OR for abortion was adjusted for age, smoking and occupation, a slightly higher, but still not statistically significant, association was found (adjusted OR = 1.67; 95% CI: 0.88–3.2).

Discussion

In this study overall seropositivity to T. gondii among pregnant women (IgG seroprevalence) was 27.9%, which means that about 72% of pregnant women are at risk of acquiring the infection if they are exposed during pregnancy, and consequently could transmit the infection to the fetus. The IgG seroprevalence of Toxoplasma increased with age: older women are more susceptible to the parasite than younger women as a result of longer exposure time. Our findings are consistent with those of other researchers in Jordan and Turkey [9,15].

Although cats are the main host for Toxoplasma, this is not the main route of infection worldwide [16]. Eating uncooked food was found to be a major factor in transmitting the parasite in a number of countries [16], including the Arab population of Israel [13] and Jordan [17]. However, in Hebron district, keeping cats inside houses as well as eating raw or undercooked meat were not common (Table 1). This might be related to cultural behaviour: meat is usually cooked thoroughly before serving. The possible route of infection in the Hebron population might involve other factors such as contact with contaminated soil, water and vegetables [9]. The IgG seropositvity of Toxoplasma was higher among women from rural areas, which could be related to agricultural activities. Agricultural activities in Hebron district are mainly family-run businesses, where husbands, wives and children (both sexes) help in planting, harvesting and collecting vegetables [18]. During their work they would be susceptible to parasitic infection through direct contact with soil and plants contaminated with Toxoplasma oocysts shed in cat faeces. At the same time, most houses in the city have small gardens where vegetables are grown. These gardens are irrigated by rainwater collected in special containers put beside the houses to collect water during the winter to support families during the water shortages in summer. Collected water is often used for drinking without boiling or addition of chloride for sterilization. Such water is expected to be highly contaminated with different organisms, including Toxoplasma oocysts.

The fact that most of the women in our sample were housewives might increase the seroprevalence of toxoplasmosis since they are usually in direct contact with vegetables during food preparation. These vegetables are usually collected from house gardens (where cats are often seen) and eaten without washing. In the absence of poor hand hygiene, these vegetables could be a main route for infection [19,20]

Overall IgM seroprevalence was 17.6%, the proportion of cases negative for IgG and positive for IgM was 11.3%; this reflects the risk among pregnant women with a recent infection who might transfer the parasite to the fetus. However, the interpretation of IgM positivity as an indication of recent infection requires additional laboratory confirmation, either by the demonstration of a significant rise in the IgM antibody titres in sequential serum samples or by using PCR for the Toxoplasma genome in the amniotic fluid of the fetus [13]. Determining time of infection in pregnant women is particularly important because infection before conception poses no substantial risk for transmission of infection to the fetus, but infection after conception does pose such a risk [21].

There was a slight (but not statistically significant) association between previous abortion and toxoplasmosis. Both IgG and IgM seroprevalence were much higher among women from rural areas who had had previous abortion compared with women from the city, although the actual prevalence of previous abortion was slightly higher among women from the city (37.6%) compared to those from rural areas (36.8%). This could indicate the presence of other factors, such as early marriage, that may contribute to abortion; 63.5% of the urban women married at age < 20 years compared to 57.5% in rural areas. Furthermore, 10.9% of the selected women had married at age ≤ 15 years (data not shown), thus early marriage could be a potential risk factor for previous abortion among studied cases [22].

To conclude, our results showed that women in Hebron district are susceptible to the toxoplasmosis parasite. The implementation of regular serological testing during pregnancy is important to reduce the effects of the disease on mothers as well as on newborn babies.

Acknowledgement

The authors would like to thank the Academy for Educational Development, United States of America for supporting and funding the project.

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