Eastern Mediterranean Health Journal | All issues | Volume 14, 2008 | Volume 14, issue 1 | Seroepidemiology of toxoplasmosis in primigravida women in Hamadan, Islamic Republic of Iran, 2004

Seroepidemiology of toxoplasmosis in primigravida women in Hamadan, Islamic Republic of Iran, 2004

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M. Fallah,1 S. Rabiee,2 M Matini1 and H Taherkhani1

الوبائيات السيرولوجية لداء المقوَّسات لدى بِكريَّات الحمل في مدينة همدان، جمهورية إيران الإسلامية، 2004

محمد فلاح، صغرا ربيعي، محمد متيني، حشمت طاهر تاحرخاني

الخلاصـة: قام الباحثون في هذه الدراسة بتحديد مدى انتشار أضداد المقوسات لدى 576 امرأة من بِكريَّات الحمل، تم انتقاؤهن عشوائياً من وحدات الرعاية الصحية الأولية في مدينة همدان. وتم تقيـيم العلاقة بين الإيجابية للأضداد وبين بعض عوامل الاختطار. وجُمعت المعطيات عن طريق استبيان، وفُحصت عينات من الدم لتحرِّي أضداد المقوَّسات باستخدام اختبار الضد المتألق غير المباشر. وبيَّنت الدراسة أن هؤلاء النسوة الـ 576 كانت 193 منهن (نسبة 33.5%) إيجابيات لأضداد المقوسات (العيار £ 20:1). وتبيَّن أيضاً أن العمر، وتناوُل اللحم الطازج الناقص الطبخ، وتكرار تناوُل الخضراوات النيِّئة، كل هذه تـترابط ترابُطاً يُعْتَدُّ به إحصائياً مع ارتفاع معدلات العدوى. ولم يثبت وجود أيِّ ترابط بين العدوى وبين مستوى التعليم، ولمس القطط، والتعامل مع اللحم النيِّئ، والنشاط الزراعي، وطريقة غسل الخضراوات، وتناوُل اللبن غير المغلي والبيض غير المطهو.

ABSTRACT: We determined the prevalence of Toxoplasma antibodies in 576 primigravid women randomly selected from health houses in Hamadan. The relationship between positivity and some risk factors was assessed. Data were collected by questionnaire and blood samples examined for Toxoplasma antibodies by indirect fluorescent antibody test. Of the 576 women, 193 (33.5%) were positive for Toxoplasma antibodies (titre ≥ 1:20). Age, consumption of fresh undercooked meat and frequent consumption of raw vegetables were statistically significantly associated with higher infection rates. Educational level, touching cats, handling raw meat, farming, method of washing vegetables and consumption of raw milk and eggs were not associated with infection.

Séroépidémiologie de la toxoplasmose chez la femme primipare à Hamadan (République islamique d'Iran) en 2004

RÉSUMÉ: Nous avons déterminé la prévalence des anticorps antitoxoplasmiques au sein d’un échantillon aléatoire de 576 femmes primipares sélectionnées dans les maisons de santé à Hamadan et évalué la relation existant entre la séropositivité et certains facteurs de risque. Les données ont été collectées par le biais d’un questionnaire, et la recherche d’anticorps anti‑Toxoplasma dans les prélèvements sanguins a été effectuée par immunofluorescence indirecte. Sur les 576 femmes testées, 193 (33,5 %) étaient séropositives pour les anticorps antitoxoplasmiques (titre ≥ 1:20). Il est apparu une association statistiquement significative entre un taux d’infection accru et l’âge, la consommation de viande fraîche mal cuite et la consommation fréquente de légumes crus. Par contre, nous avons constaté l’absence d’association entre l’infection et le niveau d’instruction, le contact des chats, la manipulation de viande crue, le jardinage, la méthode de lavage des légumes ou la consommation de lait et d’œufs crus.

1Department of Parasitology; 2Department of Obstetrics and Gynaecology, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Islamic Republic of Iran (Correspondence to M. Fallah: This e-mail address is being protected from spambots. You need JavaScript enabled to view it )
Received: 21/08/05; accepted: 13/12/05
EMHJ, 2008, 14(1): 163-171


Introduction

Infection by the protozoan parasite Toxoplasma gondii is widely prevalent in animals and humans throughout the world [1]. The ingestion of food and water contaminated with oocysts from infected cat faeces or the ingestion of tissue cysts from ingested meat are 2 major sources of T. gondii infection in humans [2]. Prevalence data for human infection vary from place to place for reasons that remain largely obscure. The importance of toxoplasmosis is primarily in pregnant women, organ transplantation patients and immunodeficient individuals [3–5]. With yearly seroconversion rates of 3%–5%, fetal risk is high because more mothers in the childbearing range of 20 to 30 years become infected. Congenital toxoplasmosis is a major problem in most communities with a high prevalence of T. gondii infection and study of the seroepidemiology of this infection among women of reproductive age could provide appropriate approaches to preventive measures [6,7].

The prevalence of Toxoplasma infection in different population groups and different parts of the Islamic Republic of Iran as reported in different studies is shown in Table 1. It has been reported to be: 49.6% in the south-west region, 55.7% the northern region, 36.4% in the western region, 26% in the southern region and 27.4% in some central areas. Seropositivity in intermediate hosts such as sheep, goats, cattle and birds was: 24.5% to 61% for sheep, 17% to 19% for goats, 11% for cattle and 29% for domestic fowl [8–24].

Results of previous surveys carried out in the Islamic Republic of Iran indicate that Toxoplasma infection is quite high. Despite several reports of Toxoplasma antibody determination in the general population [12,16], few seroepidemiological studies have been performed in pregnant women, particularly in primigravidas. There are certain factors in Hamadan province (west of the country) which may increase the risk of Toxoplasma infection; for example, the large population of stray cats, especially in the capital of the province, the traditional way of preparing certain foods, and the consumption of underdone mutton and chicken (as kebab). The present study was therefore carried out to determine the prevalence of Toxoplasma antibodies in primigravid women admitted to prenatal care units in Hamadan and investigate certain risk factors for infection.

Methods

The investigation was carried out in Hamadan province, in western Islamic Republic of Iran, which has a population of about 1.7 million. Most areas of the province are mountainous (about 1200 m altitude) and the main occupation of the people is agriculture. The average temperature is 9 °C (varying from –28 °C in the winter to 36 °C in the summer) and the annual rainfall varies from 11 to 141 mm.

In the Iranian health system, all pregnant women have a health file in the urban and rural health houses for periodical, prenatal and antenatal check-ups. The study population was all women who had health files in the health houses of the province. The study sample was selected randomly, using a random table, from the health files of the target population. All the files of multiparous and non-pregnant women were excluded and only primigravid women were included for sampling. Sample size was calculated assuming a prevalence of 40% (as reported in similar regions), a degree of precision of 4 and 95% confidence interval. Therefore, the sample size was calculated as 576 primigravid women.

Blood samples were collected from the 576 selected women and sera were separated and stored at –20 °C until analysis in the Department of Parasitology of the School of Medicine. Samples were examined by indirect fluorescent antibody (IFA) test. Antigen was obtained from the Pasteur Institute of the Islamic Republic of Iran, Tehran. Polyvalent anti-human conjugated serum and serum controls were purchased from Baharafshan Company, Tehran. Tests were performed according to Ghorbani [8]. Sera reacting positively at dilutions ≥ 1:20 were considered indicative of previous Toxoplasma exposure and infection.

A questionnaire was used to obtain data on age and education level and exposure to the following main risk factors for Toxoplasma infection: contact with or touching cats, presence of cats in or around the house, consumption of fresh, undercooked meat (i.e. barbecued kebabs or hamburgers which are traditionally undercooked), consumption of raw vegetables, handling raw and fresh meat, vegetable washing method (using water only, using antiseptic solution, using solution of hypertonic salt), and consumption of raw milk and eggs.

The chi-squared test was used for statistical analysis using SPSS, version 10. P < 0.05 was considered significant.

Results

A total of 193 serum samples were positive by IFAT at titre ≥ 1:20 (cut-off), a seroprevalence of 33.5%. The distribution of titre ratios (1:20, 1:50, 1:100, 1:200, 1:400, 1:800) is shown in Table 2.

Only 2.6% of the women had titres ≥ 1:400. Most of the women (55.4%) had a titre of 1:20. For the purposes of statistical analysis, age was divided into 6 groups: 15–18 years (n = 81), 19–22 years (n = 215), 23–26 years (n = 168), 27–30 years (n = 68), 31–34 years (n = 31) and ≥ 35 years (n = 13). Table 3 shows the infection rate according to age distribution, educational status, and certain risk factors for Toxoplasma infection. Seroprevalence was found to differ significantly with age (χ²5 = 8.69, P< 0.001). The highest prevalence rate was also observed in women who were illiterate (61.5%), but the difference was not significant. The prevalence was significantly higher among women who was consumed barbecued meat (Iranian kebab) (P < 0.05), and those who consumed raw vegetables daily (P < 0.001).

In multivariate analysis, the risk of T. gondii infection increased with age. The highest infection rate was found in the age group ≥ 35 years. Striking differences in seropositivity were found between women with illiterate status and those who consumed kebab frequently as well.

Of all the women participating in the survey, none had previously undergone serological testing for the detection of Toxoplasma antibodies.

Discussion

This study showed a moderate seroprevalence (33.5%) of T. gondii antibodies in comparison with other parts of the Islamic Republic of Iran as shown in Table 1. Most of the studies on toxoplasmosis at the community level in the country have been conducted on the general population or some subgroups, like immunodeficient subjects. Few have been conducted on primigravid women.

Because of some reports on congenital toxoplasmosis [25,26], various epidemiological studies have been performed in some parts of the country [10,16]. High prevalence rates have been reported from humid regions like the northern parts of country; 55.7% and 87% seropositivity rates have been documented in eastern and western parts of the Caspian basin respectively [8,11]. Rates from 6% to 23% have been reported in the north-west mountainous region [10] and 9.3% to 26% in the south-west parts of country [10,16].

Regarding the source of infection, pigs and lambs are the important sources in Western countries such as the United States and Europe [27,28], rather than sheep and cattle. In contrast, sheep and cattle appear to be the main sources of T. gondii infection in Islamic countries, such as the Islamic Republic of Iran [9,19,29]. However, other surveys suggest that small animals, especially sheep, play a more important role as a source of toxoplasmosis than cattle [22–24]. Furthermore, since the consumption of mutton is much greater than that of beef or goat, this increases the importance of sheep as source of local infection in the Islamic Republic of Iran. Although meat consumption behaviour did not appear to have a significant association with seropositivity in our study, data collected by questionnaire should be interpreted with caution in countries with low cultural and health-related knowledge.

Seropositivity increased significantly with age while it decreased with higher educational level but the difference was not statistically significant. Increased knowledge through higher education and its impact on behaviour may lead to a decrease in T. gondii infection, and may have an indirect effect on environmental and cultural factors involved in Toxoplasma infection. Our findings are similar to a report from Malayer in the east of this region [12] and slightly higher than the neighbouring province of Kermanshah [14,30].

According to some reports of Toxoplasma infection of intermediate hosts, such as sheep, goats, cattle and birds, especially chicken, it seems that the main route of human infection is ingestion of the undercooked meat of these animals, particularly mutton and lamb, which is the commonest meat consumed in all parts of the country. However, in our study there was no significant correlation between infection rate and the consumption of fresh, undercooked meat.

The role of definitive and intermediate hosts were studied in different parts of the Islamic Republic of Iran [18,31]. The infection rates in cats (definitive host) ranged from 59.4% in Ahwaz to 94% in Tehran. Birds (intermediate host) may also be a potential source of Toxoplasma infection in the country because of the high seropositivity. Similar findings have been reported from other countries [11].

Different investigations performed throughout the world show a wide spectrum of seropositivity for Toxoplasma antibodies among pregnant women (different gravidas), ranging from 14% (Sweden, Stockholm) to 77% (Belgrade, Yugoslavia) [32,33]. The seroprevalence of a group of women of child-bearing age (between 16 and 36 years) in Nepal was 55.4% [34]. A study carried out on primigravidas found a 41.7% seropositivity in Indian women [35]. Lower prevalences are found in North America, South-east Asia and Oceania [36,37]. Regional variation has been attributed to climate, cultural differences and the amount and type of meat consumed. A previous study on prevalence of this infection in this region showed 38.9% seropositivity in women of child-bearing age [13].

Our results indicate that a large number of the study subjects (over 65%) were vulnerable to Toxoplasma infection. If these infections had occurred during the pregnancy the fetuses would have been at risk of infection. There is a need to provide health education to pregnant women in order to prevent primary Toxoplasma infection during pregnancy. Women should be counselled and evaluated before conception. The focus should include questions on contact with pets, especially cats, and whether the cats are confined indoors or allowed outdoors. Other questions should include a woman’s preference about cooked meat and her hygiene habits in the kitchen (washing of fruits, vegetables and utensils) and her work in the garden or farm. If she has any of the above risk factors, then a screening test for toxoplasmosis could be considered.

We recommend further studies to determine the incidence of acute Toxoplasma infection and congenital toxoplasmosis in humans and the prevalence of infection in stray and household cats and intermediate hosts in this region.

Acknowledgements

This work was supported in part by a grant from the Postgraduate Council, Education Deputy, Hamadan University of Medical Sciences.

We thank the staff of the health centres for their kind collaboration.

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