Seroprevalence and detection of Toxoplasma gondii and Echinococcus granulosus in humans by indirect immunoglobulin G enzyme-linked immunosorbent assays in Baghdad

Document Type : Original Articles

Authors

1 College of Health and Medical, Al-Bayan University

2 Ibn Sina University, College of Medical and Pharmaceutical

3 AL-Mamoun University College.

4 Medical Technical College, Al-Farahidi University

10.32592/ARI.2024.79.3.669

Abstract

The present study was conducted from December 2021 until April 2023 at the College of Health and Medical, Al-Bayan University, Iraq, in Baghdad province, to detect the infection of Toxoplasma gondii in humans and identification by serological methods. Field studies were conducted from 1500 sera samples from hospitals and private medical laboratories. The sera samples were separated and examined by indirect ELISA IgG for the human kit to detect the infection with Toxoplasma gondii serologically. The serological results showed that 62% were positive. The present study recorded a high rate of infection in pregnant women at 70.4% (526/747) and then non-pregnant women at 53.6% (404/753). The serological results in males showed 57%, while the females showed 65.1%. It was noted non-significant difference. According to age groups 30-39 years, the high rate of infection was 90.2% (415/460), whereas the lowest infection among age groups < 20 years was 25.1% (83/330). However, serologically tested sera samples were positive for Echinococcus granuloses; 7.8% of 192 sera samples from humans were tested. Regarding the age group, the rate of infection was 10.2% (5\49) from <20 and >29 years, while from >30 to >39 years was 6.6% (3\45) and >40 years was 14% (7\50) with a high significant difference with Echinococcus. According to gender, the percentage of infestation in males was 5.7% out of (6\104) sera samples, while in females was 10.2% out of (9\88) sera samples with a highly significant difference (P≤0.01). Finally, regarding the months, the peak infection rate was recorded in March.

Keywords

Main Subjects

1. Introduction

T. gondii is an intracellular protozoan infecting around one-third of the world's people. Humans and almost all warm-blooded animals are intermediate hosts of T. gondii, and cats play a crucial role in the epidemiology of T. gondii as the definitive host ( 1 ). Human infection generally occurs through congenital transmission, organ transplantation, food or drink contaminated with oocysts, and tissue cysts from undercooked meat ( 2 ). The dormant form of T. gondii mainly resides in nervous and muscle tissues in infected hosts, and until recently, latent infections in people were expected to be asymptomatic ( 3 ). Symptomatic infection is generally described as congenital infections acquired through the first trimester and more severe than those acquired in the second and third trimesters. Lymphadenopathy, reticular cell hyperplasia, and finally, ocular toxoplasmosis can be observed after congenital or acquired infection as a result of acute infection or reactivation ( 4 ). The tissue cyst-forming coccidium is a polygynous protozoan with a facultative heterogeneous life cycle. Human T. gondii infection is one of the most significant public health challenges, affecting one-third of the world's population ( 5 ). Especially immunocompromised people, such as HIV-positives, cancer patients, and organ transplant recipients. T. gondii, as an opportunistic protozoa, can lead to life-threatening consequences for patients. Moreover, after congenital infection, acute disease and ocular infection can occur ( 6 , 7 , 8 ). Cystic echinococcosis has international prevalence partially due to the capability of worms to adapt to the extensive variability of house and wild middle and final hosts ( 9 , 10 ). This infection severely affects the health of humans and animals and has frequently been observed in countries in moderate regions, including parts of Africa, Australia, South America, Central Asia, and China ( 11 , 12 ). In light of the aforementioned issues, the present study aimed to detect T. gondii and E. granulosus in humans and examine the seroprevalence of the parasite regarding gender, age group, and female gender in humans.

2. Materials and Methods

2.1. Human sample collection

This field study was conducted on 1,500 human blood samples from private clinics in different areas of Baghdad from December 2023 to April 2023. Blood samples were collected from humans (580 males and 920 females) aged between < 20 and ≥ 40 years. E. granulosus was passed out to 192 humans from different regions of Baghdad. Blood tests were collected from humans of both genders and different ages.

2.2. Serological technique

The human blood samples were disrupted in several wells (two for controls and more specimens) and plates in strip containers. Incubation was performed at room temperature (15-25°C) for 10 min; subsequently, 100 ul of enzyme conjugate was washed, enhanced, and stored at room temperature for 5 min. Following that, 100 ul of the chromogen was added to each well. It was mixed well by gently patting the lateral part of the band holder with the directory member for about 15 sec.

2.3. Statistical Analysis

The data were analyzed in SAS software (version 20.1). A two-way ANOVA and least significant differences (LSD) post hoc test were performed to assess significant differences among the means of the groups. The results were expressed as mean ± standard errors, and p-values of < 0.05 were considered statistically significant ( 13 ).

3. Results

A total of 1,500 human blood samples were registered as infected with T. gondii. The total rate of infection was 62% in human immunoglobulin G (IgG). Regarding the age groups, subjects younger than 20 recorded a 25.1% infection rate, while this rate was 88.5% among 20-29-year-old cases. The highest rate of infection was recorded as 90.2% in the 30-39-year-old subjects, followed by the ≥ 40-year age group (33.8%), with significant differences (P≤0.01) (Table 1). In terms of gender, females (16.2%) accounted for the highest infection rate, while the infection rate was 3.7% in males, with non-significant differences (P>0.01) (Table 2). Finally, the present study recorded a high rate of infection in pregnant women (70.4%), with a lower rate in non-pregnant ones (53.6%) (Table 3). The total number of hydatidosis patients was 7.8% in this study (Table 4). In females, there were 9 infections (10.2%), compared to 6 infections (5.7%) in males (Table 5). These cases were in the age range of 20-40 years old. The most infected cases were in the age group of ≥ 40 years (14%), while the 30-39 age group had the lowest rate of infection (6.6%) (Table 6). Regarding gender, the highest infection rate was 10.2% in females, while the infection rate was 5.7% in males.

Age Examined No. Positive No. Percentage (%)
< 20yr 330 83 25.1
20yr-29yr 350 310 88.5
30yr-39yr 460 415 90.2
≥ 40yr 360 122 33.8
Total 1500 930 62
Chi-Square (χ2) --- --- 72.414**
Table 1.Infection rate of Toxoplasma gondi in human according to ages groups by indirect ELISA IgG
Gender No. of examined samples No. of positive samples Percentage (%)
Males 580 331 57
Females 920 599 65.1
Total 1500 930 62
Chi-Square (χ2) --- --- 72.282**
Table 2.Infection rate of Toxoplasma gondi in Human according to genders by indirect ELISA IgG
Female status No. of examined samples No. of positive samples Percentage (%)
Pregnant 747 526 70.4
Non-Pregnant 753 404 53.6
Total 1500 930 62
Chi-Square (χ2) --- --- 8.5824**
Table 3.Seroprevalence of Toxoplasma gondi according to pregnant status by indirect ELISA IgG
Host No. of examined samples No. of positive samples (%) Percentage (%)
Human 192 15 7.8
Table 4.Total infection rate of Echinococcus granuloses in Human by using indirect IgG-ELISA
Age Examined No. Positive No. Percentage (%)
< 20yr 48 0 0.00
20yr-29yr 49 5 10.2
30yr-39yr 45 3 6.6
≥ 40yr 50 7 14
Total 192 15 7.8
Chi-Square (χ2) --- --- 11.802 **
Table 5.Echinococcus granuloses infection in human according to age group by using indirect IgG-ELISA
Gender No. of examined samples No. of positive Samples Percentage (%)
Males 104 6 5.7
Females 88 9 10.2
Total 192 15 7.8
Chi-Square (χ2) --- ---- 7.155 **
Table 6.Echinococcus granuloses infection rate in Human according to gender by using indirect IgG-ELISA

4. Discussion

It is crucial to understand the status of Toxoplasma infection in the general population, especially humans. This study estimated the seroprevalence of T. gondii infection rate in the Iraq population using the serological diagnosis. In this study, 62% of IgG seropositive cases were recorded. The results of this research were inconsistent with those carried out in neighboring countries, such as Pakistan and Qatar. The overall seroprevalence rates of infection were recorded at 29.45% and 29.8%, respectively ( 14 , 15 ).

A related study in Iran demonstrated that the seroprevalence of Toxoplasma infection was 39%. At the same time, Latin America, Central and Eastern Europe, and Southeast Asia have a high seroprevalence of T. gondii infection 75%-85% ( 16 , 17 , 18 ). In another study in Mexico, the seroprevalence of T. gondii infection was reported as 20.26% ( 19 ). In China and India, seroprevalence estimations were 12.5% and 30.9%, respectively. Although some of these risk factors may have the lowest effect on the epidemiological condition, they can alter the epidemiologic pattern of infection in various regions, with geographical and climatic conditions being significant variables ( 20 ). The results of this research are in agreement with those obtained in another study in which the adult age group (≥45 years) had significantly higher serological rates (80%) than the younger one 20% ( 21 ). Our findings revealed that seroprevalence positive cases were predominantly detected in the older age group of ≥ 40 years (55%) than in the younger age groups of 0-19 years (29%) and 20-39 years (44%). Other studies reported similar results ( 22 , 23 ). The reason for the increasing rate of serology in older age groups is unclear. It can be ascribed to their longer exposure to the risk factors, with increased contact with pets and consumption of contaminated food and water being two of the modes of transmission. The study revealed that the prevalence rate was lower in males (57%) than in females (65.1%). However, the two genders exhibited no significant difference in Toxoplasma serological tests.  The results related to Echinococcus infection were in line with those of previous results demonstrating that the age range of 11-40 years had the highest rate of disease incidence ( 24 , 25 ). In disagreement with another study who illustrated that the highest rate of infection pertained to the 20-30 age group ( 26 ). The seroprevalence of E. granulosus infection was obtained at 1.24% in an Uruguayan rural human ( 27 ). The seroprevalence of E. granulosus infection at 4.36% in South Kashmir, India, using an enzyme-linked immunosorbent assay ( 28 ).

In Iran, around 7.4% of cases were reported while the seroprevalence study on antibodies against hydatid cysts from Sarkari showed a rate of 7.2% ( 29 , 30 ). This result can be attributed to the disruption experienced by this group of rural and other social workers, leading to increased exposure to sources of contamination. Clinically, cats are important reservoirs of zoonotic parasites. T. gondii and Echinococcus infections represent a considerable parasitic disease. The dearth of data in this regard highlights the necessity of research on molecular epidemiology and clinical pathology aspects of T. gondii and E. granulosus infection in Iraq. Controlling pets that serve as hosts for zoonotic parasites is essential to reduce the prevalence of the parasite. This involves limiting the number of pets and ensuring they receive veterinary treatment. Toxoplasma and E. granulosus are some of the most common parasites in developed countries and may cause chronic diseases.

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Archives of Razi Institute
Volume 79, Issue 3
May and June 2024
Pages 669-674

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