Prevalence of anti-Toxoplasma IgG and IgM in hemodialysis patients comparing to healthy individuals in Sistan area , Iran

Introduction The protozoan, Toxoplasma gondii, is globally prevalent and causes toxoplasmosis, which is an important parasitic disease. A wide range hosts including humans, domesticated mammals, and birds could get infected. Felid family and cats are the final hosts and humans and most vertebrates are taken as the intermediate hosts. The sexual cycle of this parasite is completed in cat’s intestine and results in producing and excretion of oocytes in their feces. Humans and other warm-blooded animals can be infected by indirect ingestion of these oocysts or by ingestion of tissue cysts in the undercooked meat. This protozoan can cause infection in humans through ingestion of contaminated water and vegetables, raw or partly cooked meat, direct contact with the infected cat, blood and leucocyte transfusion, and organ transplantation (1,2). Toxoplasmosis can be seen in healthy adults as an asymptomatic chronic infection and in people with weakened immune system as a severe and fatal disease (3). Infection in people with healthy immune system is Mohammad Dorri1, Mansour Dabirzadeh1*, Yahya Maroufi1, Mahdi Afshari2, Milad Badri Chokamy3


Introduction
The protozoan, Toxoplasma gondii, is globally prevalent and causes toxoplasmosis, which is an important parasitic disease.A wide range hosts including humans, domesticated mammals, and birds could get infected.Felid family and cats are the final hosts and humans and most vertebrates are taken as the intermediate hosts.The sexual cycle of this parasite is completed in cat's intestine and results in producing and excretion of oocytes in their feces.Humans and other warm-blooded animals can be infected by indirect ingestion of these oocysts or by ingestion of tissue cysts in the undercooked meat.This protozoan can cause infection in humans through ingestion of contaminated water and vegetables, raw or partly cooked meat, direct contact with the infected cat, blood and leucocyte transfusion, and organ transplantation (1,2).Toxoplasmosis can be seen in healthy adults as an asymptomatic chronic infection and in people with weakened immune system as a severe and fatal disease (3).Infection in people with healthy immune system is generally without clinical symptom, but for those with immune deficiencies it can cause plenty of symptoms.The risk of activation and relapse of the disease is high in immunocompromised patients.Patients suffering from cancer, patients with organ transplant, on-dialysis patients, and patients who take immunosuppressants are at risk of toxoplasmosis (4)(5)(6).Many studies on patients with renal disorders have shown that these patients also suffer from immune system impairment (7,8).Thus, they are at risk of many infections (7).On the other hand, the most prevalent opportunist protozoan is toxoplasmosis, as the infection may invade central nervous system and cause encephalitis and encephalopathy (5,9).Determination of prevalence of anti-Toxoplasma antibodies can be an indicative for their risk of acquiring the infection.Nowadays, serological method such as enzyme linked immunosorbent assay (ELISA) is easily convenient and can be done in any laboratory.In ELISA test, the concentrations of anti-Toxoplasma IgG and IgM can be determined.

Objectives
This study aimed to determine the prevalence anti-Toxoplasma IgG and IgM seropositivity in on-dialysis patients comparing to the healthy people among who referred to Imam Khomeini hospital located in Zabol and Seyed-Al-Shohada hospital located in Zahak, Iran.

Patients and Methods
In this case control study the patients were 76 on-dialysis patients in Sistan and 76 healthy individuals.These samples were chosen during May to July 2014.The healthy people were chosen with normal blood urea nitrogen (BUN) and creatinine (Cr) tests.The blood samples of exposed and non-exposed people were taken.During the sampling, a questionnaire which includes some questions about their demographic information and dialysis time was filled by the participants.From each taken blood, 2 cc was obtained and the sera were separated by centrifuge with 2000 rpm for 1 minute.The sera were put in suitable micro-tubes and were numbered and kept frozen at -20°C.ELISA test was used for determination of the serum concentrations of anti-Toxoplasma IgG and IgM.The BUN and Cr tests were done by Pars Azmoon kits (Iran) with calorimetric method applied in BT3000 device, for both exposed and non-exposed people.

Ethical issues
The research followed the tenets of the Declaration of Helsinki.Informed consents were obtained.All patients took part in this study voluntary.This study has the ethical code zbmu.1.rec.1393.2issued by the ethic committee of Zabol University of Medical Sciences.

Statistical analysis
This study is a quasi-experimental study that we used all on-dialysis patients as cases and equal number as control.
A P < 0.05 was assumed to be significant.

Results
The anti-Toxoplasma gondii IgG was positive for 56 (73.7%) of exposed patients and 33 (43.4%) of non-exposed ones.All of the people in case and control groups were negative anti-Toxoplasma gondii IgM.The IgG difference among the two studied groups was statistically significant (P < 0.001) (Table 1), but there were no differences regarding age, gender, and education since they were conformed.

Discussion
Toxoplasmosis is a relatively prevalent infection and is among the opportunist infections in patients with deficiencies in immune system.The rates of the infection in countries or in different areas of the same country may vary regarding different factors such as age, gender, occupation, geography, culture, social behaviors, and diet (10)(11)(12).Toxoplasmosis is an intracellular infection in which the cellular immunity is responsible for activation against the infection.The cellular immunity is weakened in ondialysis and uremic patients, as the number of T cells in patients suffering from renal disorders are reduced and suppressors are increased.It should be noted that dialysis does not obviate this problem.Also, the reduction of phagocytic activity and reduction in the number of natural killer cells have been reported in these patients (8,(13)(14)(15) In some studies in Turkey and Egypt, it is reported that the prevalence of anti-Toxoplasma antibodies in the ondialysis patients is higher than the controls and there was a significant positive relationship between the duration of treatment with dialysis and positive cases of anti-Toxoplasma antibodies (16,17).The present study showed higher prevalence of Toxoplasma gondii infection in ondialysis patients.The prevalence of anti-Toxoplasma IgG in the patients group was significantly higher compared to the healthy group, while IgM was negative in the both groups.Ocak et al showed that 76.5% (195 cases) of on-dialysis patients and 48% (42 cases) of controls were infected by Toxoplasma, which were similar to the results of the present study (18).In another study done by Yazar et al in Turkey, from a total of 173 on-dialysis patients, 56.06% (79 cases) and among 40 cases of control group, 20% (8  (20).
The results of the present study showed that on-dialysis patients should be taken as an at-risk group regarding Toxoplasma infection.It is also showed that anti-Toxoplasma IgG in these patients is relatively higher compared to healthy people.Reactivation of bradyzoites can cause active toxoplasmosis in patients with deficiency in immune system and since on-dialysis patients have a weakened immune system, this infection can cause severe problem.Therefore, treatment and prevention of toxoplasmosis seems necessary to attention in these patients.

Conclusion
Toxoplasmosis is more common in hemodialysis patients in comparison with healthy ones and they must be considered as a risk group for toxoplasmosis

Limitations of the study
Due to emigration or death, we excluded some patients contributing to study.

Authors' contribution
Collecting data; MoD.Statistical analysis; MA.Study supervision; MaD and YM.Drafting the manuscript; MBC.

Table 1 .
Anti-Toxoplasma seropositivity among the two studied groups