Organ transplantation and blood transfusion can be of the potential transmission routes of
T. gondii. These routes of transmission are less common; however, if donors are infected, it will cause acute toxoplasmosis because the recipients are usually immunocompromised patients, with significant clinical consequences such as encephalitis, brain abscess, myocarditis, and chorioretinitis (
10). Despite the serious complications of this parasitic disease, especially in immunocompromised patients, available treatments are not fully effective; moreover, safe and efficacious vaccines are not available; thus, the prevention of parasite transmission is one of the effective strategies for reducing toxoplasmosis (
25). Detecting the source of infection such as infected blood and organs for recipient candidates, especially patients undergoing multiple transfusions or those requiring blood transfusion for transplantation management, can be crucial to control and prevent toxoplasmosis (
16). Currently,
T. gondii screening in blood and blood products of blood donors is not routinely considered in worldwide therefore certainly do not assay the relationship between
T. gondii and blood safety in blood transfusion centers.
In this study, 385 blood samples were collected from healthy blood donors from Chaharmahal and Bakhtiari province, Iran, and were evaluated by serological and molecular methods for T. gondii infection. The results indicated that 154 (40%) samples were seropositive for anti-T. gondii antibodies while 37.9% and 1.56% were positive for IgG and IgM anti-T. gondii antibodies, respectively. These findings showed a considerable prevalence rate of toxoplasmosis in this population. Although seropositivity of IgG (latent infection) was high, the rate of anti-T. gondii IgM antibodies (acute infection) was low.
Previous investigations conducted in Iran showed that the seroprevalence of
T. gondii in volunteer blood donors was reported to be 34.4% (95% CI: 24.9% - 43.9%), ranging from 18.3% in Gonabad city (
26) to 56.4% in Hamedan province (
20). However, different rates were reported for various regions by serological methods for IgG and IgM antibodies respectively as 25% and 0% in Zahedan (Southeast Iran) (
27), 25% and 3.2% in Mashhad (Northeast Iran) (
28), 37.8% and 0% in Urmia (Northwest Iran) (
29), 38.66% and 1.03% in Tabriz (Northwest Iran) (
21), 16.30% and 0.7% in Boyer-Ahmad county (Southwest Iran), 34.47% and 0.5% in Ahvaz (Southwest Iran) (
17), and 28.8% and 3.2%in Kerman (Southeast Iran) (
30), which may be related to living conditions, geographical and environmental factors, sanitary conditions, economic and social situation of blood donors, sample size, and sensitivity of detection methods.
The overall seroepidemiological studies of
T. gondii on blood donors in different regions of the world indicated very different prevalence rates for IgG and IgM antibodies from 0.64% and 0% to 70.29% and 5.81%, respectively (
8). The highest seroprevalence rates were from Brazil (75%) (
31) and Ethiopia (73%) (
32) while low seroprevalence rates of toxoplasmosis in blood donors were observed in Namibia (0.96%) (
33), Thailand (9.6%), Taiwan (9.3%), and Mexico (7.4%) (
17).
In the present study, the obtained results showed that the seroprevalence of
T. gondii was significantly higher in female than in male donors, which may be due to sampling bias because most blood donors were males. Similarly, Mahmoudvand et al. (
30) and Sundar et al. (
34) reported that the seroprevalence of
T. gondii in female donors was significantly higher than that in male donors. However, some studies reported contradictory results (
28,
35).
According to a recently published systematic review of toxoplasmosis in Iranian blood donors, the difference between men and women was not statistically significant (
36). Regarding age groups, IgG positivity was more frequent in donors aged > 45 years that was similar to other studies indicating that the rate of seropositivity increased with age as a consequence of the increased opportunity of acquiring the infection. The obtained findings disclosed that blood donors with blood group B+ had more
Toxoplasma seropositivity than other blood groups; however, no correlation was found between
T. gondii seropositivity and blood groups. Shaapan et al. reported that blood group A (48.7%) had the most frequent
Toxoplasma seropositivity among blood donors from Egypt (
37). However, Mahmoudvand et al., (
30) Shaddel et al., (
38) and Elsheikha et al. (
19) indicated a significant correlation between toxoplasmosis and blood groups AB, A, and O, respectively. Due to the small number of reports of the correlation between toxoplasmosis and blood groups, this hypothesis needs to be confirmed in further investigations.
Although cats are the definitive host of this protozoon and infected cats can infect the environment by defecated oocysts, conflicting findings have been reported concerning the transmission of
T. gondii via contact with cats. However, our study suggested that contact with cats is a potential risk factor for acquiring toxoplasmosis. Concerning food habits, the study exhibited that the seroprevalence rate of toxoplasmosis was higher in blood donors who consumed raw/half-cooked meat than in other blood donors. Therefore, ingesting meat containing tissue cysts seems to be the main route of infection among the other routes. Moreover, some studies such as Mahmoudvand et al. study confirmed this finding (
30). In this study, no significant relationships were found between the consumption of raw vegetables, occupational activities, education level, residence place, blood transfusion, and raw milk/egg consumption (as potential risk factors for acquiring toxoplasmosis) and seropositivity of
T. gondii.
Despite this fact that serological methods such as ELISA are used in many medical diagnostic laboratories for detecting antibodies against
T. gondii, these methods have false-positive results and cannot differentiate past and present infections; therefore, the diagnosis of toxoplasmosis remains unsatisfactory with serological methods. This is while molecular methods can obviate this limitation (
39,
40). Many researchers have used molecular methods such as PCR and real-time PCR for detecting
T. gondii in blood donors. Studies carried out based on the detection of DNA of
T. gondii in blood donors in Iran indicated that 0.9% of IgM-positive samples in Kerman (
30), 6.97% samples in Rafsanjan (
18), 40% of seropositive samples in Ahvaz (
17), and 100% of IgM-positive samples in Razavi Khorasan (
41) contained the DNA of the parasite. Nevertheless, by the PCR method,
T. gondii DNA was not detected in the buffy coat of any of the seropositive cases in Boyer-Ahmad County, Southwest Iran (
42).
Our findings according to the molecular assay demonstrated that six (1.56%) samples had the DNA of
T. gondii. Of these, four (1.04%) were seropositive for both IgG and IgM antibodies and two (0.52%) were positive only for IgG antibody. In line with these findings, Fallahi et al. reported that LAMP is a useful tool for the diagnosis of toxoplasmosis in children with leukemia with high sensitivity and specificity (
24). Loop-mediated isothermal amplification is an attractive DNA amplification method compared to other molecular methods such as PCR because it requires a minimal DNA sample such as a single tachyzoite or 10 copies of recombinant plasmid whereas the PCR method in toxoplasmosis diagnosis needs much more DNA sample (
24,
39). Furthermore, the LAMP assay was very simple, as the reaction would be carried out in a single tube under one isothermal condition and at one-hour reaction time. Therefore, the LAMP method has the advantages of specificity, rapidity, sensitivity, and easiness for the clinical diagnosis of
T. gondii (
43).
5.1. Conclusions
In conclusion, the results demonstrated that the prevalence of T. gondii infection is high among apparently healthy blood donors in Southwest Iran. Thus, there is the possibility of transmission of infection by blood transfusion while screening tests are not used to detect Toxoplasma infection in Blood Transfusion Organizations. Furthermore, serological methods have potential weaknesses such as time-intensiveness and false-positive results. Therefore, it is strongly suggested that appropriate and sensitivity programs be designed for screening of toxoplasmosis by the LAMP method to detect T. gondii DNA in blood donors and prevent the transmission of T. gondii to at-risk people, especially multi-transfused patients.