Toxoplasmosis is a Protozoan disease caused by the intracellular protozoan parasite Toxoplasma gondii that can infect humans and various warm-blooded animals. Toxoplasmosis is a highly prevalent infection, and studies have estimated that as many as one-third of the adult worldwide population may be infected with the parasite (1). Despite the high global prevalence, the exact prevalence within any human community is significantly influenced by factors such as geography, climate, dietary habits, and levels of sanitation (2). Felidae species, both pets and wild, are acknowledged as the unique definitive hosts of this parasite.

Transmission primarily occurs via foodborne pathways, including ingesting oocyst-contaminated food or water and consuming raw or undercooked meat harboring tissue cysts. Congenital transmission also poses significant risks, particularly to fetuses (3). The parasite can accomplish its life cycle by transferring from warm-blooded intermediate hosts to the cat as the final host (3, 4). In immunocompetent adults, T. gondii infection is typically asymptomatic or mild, with 10–30% of cases showing symptoms like lymphadenopathy. However, in immunocompromised individuals, it can lead to severe outcomes, including central nervous system (CNS) disorders (5). Moreover, vertical transmission can result in severe consequences like seizures and cognitive impairments in newborns (5). Additionally, recent studies have indicated that latent toxoplasmosis may be considered a significant contributor to various psychotic conditions, such as Parkinson’s disease, Alzheimer’s disease, bipolar disorder, and schizophrenia (6, 7).

Globally, studies report seroprevalence rates from 20% in younger adults to 77% in older populations, reflecting cumulative exposure (8). Occupational exposure, particularly among farmers, and environmental factors such as soil contact are consistently identified as risk factors (8–10). Conversely, traditional risk factors such as cat ownership and raw meat consumption exhibit inconsistent associations across different populations (11, 12). Studies conducted since 2020 have enhanced our understanding of T. gondii epidemiology in Iran. Hamidi et al. synthesized data from 2000 to 2023, highlighting higher rates in rural settings (13). Hassanen et al. (14) investigated cat-human transmission dynamics, while Maleki et al. (10) identified soil as a key reservoir. Also, a systematic review and meta-analysis study estimated a 45.1% prevalence of toxoplasmosis among immunocompromised individuals in Iran (15).

In Iran, toxoplasmosis is a public health concern, and previous research indicates significant variability in seroprevalence, with the average prevalence ranging from 12.5 to 61% in different provinces (13). East Azerbaijan Province in northwestern Iran, with its diverse nomadic, rural, and urban populations, has been the focus of numerous epidemiological studies from 2000 to 2023, reporting provincial rates of around 46% (16). However, the most recent study in East Azerbaijan Province was conducted in 2018 and was limited to Tabriz city (16). Also, the mentioned study did not aim to find risk factors in the general population and focused on the relationship between toxoplasmosis and diabetes. Consequently, a study extending across the whole had to be conducted in the present time to obtain accurate and detailed data; therefore, this study aims to comprehensively understand the seroprevalence and risk factors of toxoplasmosis across the entire East Azerbaijan Province, including urban, rural, and nomadic populations. By doing so, it seeks to identify variations in infection rates and associated risk factors among these different demographic groups, which have not been previously explored in such detail. This approach will contribute valuable insights into the epidemiology of toxoplasmosis in this region and inform targeted public health interventions, building on recent findings such as Arefkhah et al. (17) on nomadic communities in southwestern Iran. It is worth noting that this study uniquely investigates T. gondii across diverse settings, including underrepresented nomadic communities.

In this study, the serum IgG level of the participants was measured using ELISA. Since humoral immunity plays a determining role in immune reactions and protection against infections, the IgG antibody levels may be considered one of the best parameters reflecting the immunological resistance of a given subject to infections. Therefore, enzymatic immunoassay techniques such as ELISA can help assess the immune system level.

The present study is the first to investigate seroprevalence and associated risk factors of toxoplasmosis in East Azerbaijan Province since 2018 (16). Compared to the last published survey, which was only conducted in Tabriz, the present study included four cities from different geographical regions. In contrast to the previous studies, the present study includes all three demographic categories: urban, rural, and nomadic populations. Its originality lies in its inclusion of nomadic populations and broad geographic scope, and it has been updating data since 2018. Although the seroprevalence found in the present cross-sectional study is higher than the average seroprevalence in Iran (32.9%) and East Azerbaijan province (46%), it is within the range of some studies (13). For example, Khalili et al. (16) found that 59% of the healthy adult population tested positive for toxoplasmosis in 2016. In addition, Mahami et al. (22) reported a prevalence of 62% among healthy adults in Tabriz in 2016. Another study reported a prevalence of 33.5% of individuals referred to diagnostic laboratories in Markazi Province (23). These findings suggest significant variability in seroprevalence rates across different regions and populations, highlighting the need for targeted public health interventions and further research to understand the factors contributing to these differences.

In the current study, univariate analysis linked multiple variables to T. gondii infection (Table 1). However, in the multivariate logistic regression analysis, among the risk factors investigated, a significant association was found between toxoplasmosis and three risk factors: age, contact with soil, and occupation. Age-related increases in seropositivity align with global trends, reflecting cumulative exposure (8). Soil contact and farming occupations emerged as key risk factors, supported by recent studies (10), while traditional factors like cat ownership were non-significant, challenging earlier assumptions (11).

Seroepidemiologic studies revealed that prevalence increases with age due to increased exposure to the parasite throughout the lifespan. For example, seroprevalence increased from 20% in 18- to 29-year-olds to up to 77% in 70- to 79-year-olds, showing that infections increase with age (8). Another study found that the infection rate is highest in people over the age of 40, suggesting that this may be due to the sum of interactions with the virus (24). This age-related trend underscores the importance of targeted public health interventions aimed at sensitive groups, such as immunocompromised individuals in older ages, who may be more vulnerable to both exposure and severe outcomes associated with toxoplasmosis.

This statistical analysis showed that contact with soil increases the risk of toxoplasmosis by a large percentage, which is consistent with previous studies on environmental transmission of the T. gondii parasite (9, 10). According to these studies, soil can serve as a source of the parasite’s oocysts, which are excreted in the feces of sick cats. When people use contaminated soil for gardening or play outdoors, they are likely to ingest these oocysts and become infected. Implementing effective educational campaigns about safe gardening practices and hygiene can significantly reduce the risk of infection, thereby protecting vulnerable populations from potential health threats.

This study reveals a strong correlation between occupation and toxoplasmosis rates, and the data collected provides valuable information about the spread of this infection. The prevalence of toxoplasmosis among farmers and ranchers, who were expected to have the highest infection rate due to direct contact with soil, livestock, and other sources of T. gondii oocysts, was 69.4%. These people spend most of their time in places where they may be exposed to T. gondii oocysts. Previous studies have consistently found that people in agriculture often have higher seroprevalence levels for the same reasons as handling soil and animal products (25). Understanding these occupational hazards is crucial for developing targeted prevention strategies, particularly in rural areas where farming practices may inadvertently increase exposure to this parasite.

Another group with a high prevalence rate (62%) is homemakers, possibly due to gardening or handling raw meat without proper hand washing. Oocysts found in contaminated soil or on surfaces can contact with this group. Infection could be prevented if safe food handling and hygiene programs were extended to this group (26, 27).

The unemployed group, which makes up 59.8% of respondents, is interesting; they may not be occupationally contaminated, but if they have come into contact with contaminated surfaces, water, soil, or other objects due to their previous working conditions, they are more likely to handle contaminated objects or surfaces.

Clerks (45.8%) and students (18.5%) have lower prevalence rates and should presumably be exposed to conditions suitable for T. gondii transmission less often. In all likelihood, students may have less contact than those directly involved in some of the tasks described above. At the same time, clerks are indoor people, and their contact with soil or animals is minimal at the most (11, 26).

The findings of this study suggest that toxoplasmosis, as assessed by risk factors, is not associated with gender, household type, education level, income level, owing cats, consumption of raw vegetables, consumption of raw or rare meat, and county of residence. This result means that these commonly hypothesized risk factors may not even significantly impact the transmission patterns of T. gondii in the target population. For example, previous reviews have indicated that cat ownership and consumption of red and processed meat are associated with increased risk, and our findings suggest that these findings do not generalize to all populations. Several studies indicated that seroprevalence could be related to the remaining population’s direct contact with cats or raw meat consumption (11, 14, 28, 29). Several other studies did not support or hesitate the preceding by presenting varying seroprevalence results and the factors above (12, 26, 30). For instance, a study by Karimi et al. (31) supports our finding that there is no significant association with cat ownership. The absence of a significant correlation between owning a cat and toxoplasmosis suggests that cats can roam freely in urban or rural areas without being restricted to their owner’s home or suggests environmental oocyst transmission via soil may overshadow traditional risk factors in this region. Also, the lack of association between dietary (consumption of meat) and toxoplasmosis may reflect local cooking norms, meriting further investigation because a small percentage (11%) of study participants had a history of consuming raw or undercooked meat.

Moreover, the study reveals a notable absence of correlation between educational attainment and income levels, suggesting that other variables may significantly influence susceptibility to toxoplasmosis. This finding highlights the potential impact of environmental and behavioral factors that warrant further investigation. It is essential to delve deeper into these aspects to understand how they might contribute to infection rates beyond the control variables assessed in the current research. Such exploration could uncover critical insights into the multifaceted nature of toxoplasmosis susceptibility and its underlying causes, prompting a more comprehensive approach to prevention and intervention strategies.

In conclusion, the present study provides valuable data regarding toxoplasmosis in East Azerbaijan province to stress the necessity of continuing monitoring and control strategies to mitigate T. gondii exposure hazards among sensitive groups such as pregnant women.