Toxoplasmosis and toxocariasis, caused by the Toxoplasma gondii protozoan and Toxocara spp. nematodes, respectively, have been important parasitic zoonoses of public health concern (1). Both diseases have been highly associated with low socioeconomic conditions (2, 3), with a global overall prevalence of 19% for toxocariasis (4) and 36% for toxoplasmosis (5). Pregnant women have also been highly affected by both infections, with global seroprevalence of 1.9 and 32.9% for anti-T. gondii IgM and IgG, respectively (6), and toxocariasis prevalence of 6.4% worldwide, 7.4% in Brasília, central-western Brazil (7), 9.2% in the Shandong Province, eastern China (8), 14.5% in Caribbean countries (9), 17.2% in Athens and nearby Piraeus, Greece (10), and 21.2% in the Ilam Province, western Iran (11).

Although toxoplasmosis may be asymptomatic in approximately 50% of healthy immunocompetent adults, severe infection with devastating sequelae has been reported in immunocompromised individuals and neonates (12). Thus, pregnant women have been considered the most vulnerable group in need of healthcare attention to prevent and monitor toxoplasmosis infection (5). In addition, transplacental transmission of T. gondii may lead to fetal miscarriage or stillbirth, severe disease in living infants (3), and permanent injuries including neurological damage and blindness (13).

Toxocariasis agents have also been asymptomatic in most human infections, but serious health consequences (14) may occur, including hepatic (15), pulmonary (16), cardiac (17), and urinary (18) lesions in the visceral form, ocular impairment or vision loss (19, 20), and neurological disorders (21, 22). Although rare, congenital transmission of Toxocara spp. was reported to cause ocular lesions in a premature child in Argentina (23) and strabismus in a 5-week-old infant in the USA (24). Vertical transmission has been experimentally reproduced in a murine model for both Toxocara canis (25) and Toxocara cati (26).

Toxoplasmosis and toxocariasis have shared several associated risk factors, particularly due to low socioeconomic aspects (27). In addition to similar human organ targeting, both pathogens have been directly transmitted to the human hosts through the intake of raw or undercooked meat or viscera from intermediate hosts of T. gondii or paratenic hosts of Toxocara spp. (28) and through the ingestion of T. gondii sporulated oocysts (29) or infective Toxocara spp. eggs from soil, vegetables, and water (30, 31).

Despite the similarities of infection, transmission, and associated risks of toxoplasmosis and toxocariasis for pregnant women, the prevalence and impact of co-infection remain to be fully established. Accordingly, the present study has simultaneously assessed infection by T. gondii and Toxocara spp. and the risk factors associated with seropositivity in pregnant women assisted by the Public Health System in southeastern Brazil.

Seroprevalence of Toxocara spp. and Toxoplasma gondii was observed in the present study, with a significant concurrent infection in pregnant women living in low-income areas of southeastern Brazil.

The 20.0% (56/280) seropositivity to toxocariasis herein was higher than the 6.4% found in southern Brazil (33) and the 7.2% observed in central-western Brazil (7), both in pregnant women assisted by the Public Health System (SUS), but similar to the 20.7% observed in a different group of pregnant women in Presidente Prudente (37), the municipality of the present study. Although all these low-income populations were assisted by SUS and presented disadvantaged socioeconomic characteristics, differences in seroprevalence may reflect local infrastructure, habits, and hygiene. Nonetheless, the results herein are similar to the overall global 19.0% toxocariasis seropositivity, which has been associated with lower income levels (4).

The 24.6% (69/280) seropositivity to T. gondii herein is lower than that of other recent Brazilian studies (last 10 years) involving pregnant women attended by SUS, ranging from 51.7% in southern Brazil (38) to 68.4% in northern Brazil (39). Although such variation could be related to the technique used for IgG detection, eating habits and water sources may play a role in transmission, as already reported (13). In addition, such seropositivity divergence between the two pregnant populations may be influenced by the socio-economic and climatic differences. As the northern Tocantins state presents higher rainfall and temperature, favoring the disease cycle, and the southern Paraná shows a very similar climate to the study setting herein, the socio-economic disparities between these two regions may be the main reason for seropositivity differences.

In the present study, a statistically significant concurrent 8.9% seropositivity (25/280, OR: 3.3) to anti-T. gondii and anti-Toxocara spp. differed from previous pregnant women serosurveys, with 7.9% (22/280) in southern Brazil (33), 13.2% (31/235) in China (40), and 9.5% (36/378) in western Iran (41). Co-infection has been shown in pregnant women, as IgG antibodies against T. gondii posed a risk (OR: 2.2, 95% CI: 1.7–2.9) of Toxocara spp. seropositivity in a general population survey of 13,509 individuals between 2011 and 2014 (42). Co-infection has also been reported in children, ranging from 3.2% (17/544) (43) to 27.4% (113/412) (27) in southern Brazil.

Herein, the ratio between toxoplasmosis/toxocariasis seroprevalence (1.23) was higher than 1. It was very close to the 1.17 observed in China (40) and lower than the 4.2 in western Iran (41). This finding possibly indicates increased exposure of pregnant women to T. gondii herein. In Iran, seropositivity in pregnancy was associated with contact with cats (41). In the present study, aging was associated with increased odds of T. gondii seropositivity, as shown in older pregnant women in northeastern (44, 45), southern (46, 47), northern (48), and central-western Brazil (49), Iran (50), and Saudi Arabia (51). This phenomenon has been attributed to lifelong antibody persistence and detection (52), but other causes have been indicated such as prolonged exposure to etiological agents, transmission routes, and lack of public awareness about prevention (50). Although increased odds of Toxocara spp. seropositivity has also been related to antibody persistence following exposure (53), no association between age and seropositivity was observed herein. This outcome differs from a previous study in the same area, in which adolescents were 2.6-fold more likely to be seropositive for toxocariasis than adult pregnant women (37), showing soil contact as an associated risk factor for toxocariasis among pregnant adolescents, but not for pregnant adults.

In Brazil, previous studies have reported risk factors associated with T. gondii infection during pregnancy, such as previous contact with cats in northern (54), northeastern (45, 55), and southern states (46, 56); socioeconomical vulnerability (55, 57), washing vegetables with untreated water (57), dog ownership (57), and homemade water ice consumption in northeastern states (57); living in urban area (48), frequent consumption of vegetables (58), and meat handling in northern states (54); living in rural areas in southern states (38, 47, 59, 60); gardening activities, contact with soil (48, 61), and raw milk consumption in southern and northern states (56, 58); consumption of chicken and meat in northeastern and northern states (57, 58). However, few studies involving co-infection with both parasites in pregnant women have been conducted, limiting the discussion of comparative risk factors. Thus, further retrospective and review studies are necessary to characterize the ratio of co-infection in different pregnant populations.

The similar transmission route of T. gondii and Toxocara spp., including consumption of raw or undercooked meat and the ingestion of embryonated eggs of Toxocara spp. and oocysts of T. gondii, may explain the co-infection in pregnant women observed in southern Brazil (33). Herein, logistic regression revealed that having a higher educational level was a protective factor against toxoplasmosis and toxocariasis co-seropositivity, corroborating with other serosurveys for T. gondii in pregnant women in Brazil (38, 55, 62) and other countries, such as Benin, Africa (63). Pregnant women with a higher educational level were associated with having toxoplasmosis-related knowledge (62), which may increase their awareness and understanding of the importance of hygiene habits to prevent diseases, including toxoplasmosis (64). Although the presence of a sewage system at home herein was also found to be a protective factor for toxocariasis but not for toxoplasmosis, having no public sewer service was previously associated with an increased risk of toxoplasmosis in southern Brazil (65).

In addition, owning cats increased the odds (OR: 2.3) of toxocariasis seropositivity herein, while no influence had previously been reported in that area (37). Despite the pregnant population of both studies being similar, the divergent outcome between studies may have been influenced by the higher number of pregnant women who declared their ownership of cats herein (n = 50) and previously (n = 38), which may have made it difficult to find statistically significant differences due to the low number of positive individuals. Likewise, owning cats has been reported as a risk factor for toxoplasmosis in some (66–69) but not all (27, 45, 70) serosurveys worldwide. Although seropositivity to toxoplasmosis herein was not influenced by the presence of cats in the household, increased odds of Toxocara spp. seropositivity herein due to cat contact should be considered as a potential disease risk when keeping cats at home.

Pregnant women may be directly infected by T. gondii and Toxocara spp. through the consumption of raw or undercooked meat or viscera (28), with high odds (OR: 5.7) of toxoplasmosis observed in pregnant women in northeastern Brazil (67). Although no study has found such a risk for toxocariasis and approximately one-fifth of the pregnant women herein declared the habit of consuming undercooked or raw meat, no association with toxocariasis or toxoplasmosis seropositivity was found. As previously stated, Presidente Prudente has been ranked in the top 2.4% of cities for population nationwide, the top 2.6% for Gross Domestic Product, and the top 0.4% for Human Development Index, with low commercial meat disease risk, mostly slaughtered, traded, and handled under rigorous state and federal sanitary inspections (37).

Pregnancy may be the highest risk time to be infected with T. gondii, as transplacental infection may lead to a wide variety of manifestations including miscarriage, stillbirth, and severe disease in living infants, despite mostly children being asymptomatic at birth (3). In addition, transplacental toxocariasis has been reported in one premature (23) and one 5-week-old (24) baby with ocular lesions. However, no study in pregnant women has found an association between miscarriage history and toxocariasis seropositivity in Brazil (7, 37, 71), including the present study.

A limitation of the present study is that no differentiation between acute and chronic phases was made, as no IgM or antibody avidity tests were performed for either pathogen. Nonetheless, infant mortality associated with congenital toxoplasmosis has been a persistent public health problem in Brazil (72). A surveillance protocol for gestational toxoplasmosis has been recently established by the Brazilian Minister of Health, including systematic serodiagnosis, compulsory notification, and educational and preventive activities coordinated by the Unified Health System (73). Given that serological tests may result in the overestimation of prevalence via false positive results, a second test should be recommended for further confirmation in epidemiological investigations of toxoplasmosis. Accordingly, a meta-analysis revealed that a combination of tests may improve the sensitivity and provide improved accuracy (74). Finally, as knowledge of risk factors for toxoplasmosis and toxocariasis may be helpful during early pregnancy (44), such educational and preventive activities should be taken into consideration as public health policies.

In conclusion, significant co-infection observed herein reinforces the importance of educational programs aimed at the prevention of toxocariasis and toxoplasmosis, particularly in pregnant women at high risk of exposure.

The original contributions presented in the study are included in the article/Supplementary material, further inquiries can be directed to the corresponding author.

The present study was approved for research with human beings by the Ethics Committee at the University of Western São Paulo (UNOESTE), corroborated by the Brazilian National Health Council (protocol number 52817021.0.0000.5515). The studies were conducted in accordance with the local legislation and institutional requirements. Written informed consent for participation in this study was provided by the participants or/and their legal guardians/next of kin.

EP: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Validation, Visualization, Writing – original draft, Writing – review & editing. IF: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Writing – original draft, Writing – review & editing. RV: Data curation, Investigation, Writing – original draft, Writing – review & editing. SL: Formal analysis, Investigation, Methodology, Writing – original draft, Writing – review & editing. RG: Data curation, Formal analysis, Investigation, Software, Validation, Writing – original draft, Writing – review & editing. LK: Investigation, Writing – review & editing. AB: Funding acquisition, Investigation, Writing – review & editing. VS: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing.