Association of Maternal Toxoplasma Gondii Molecular and Serological Positivity With Child's Gross-Motor Development and Behavior in Tribal Regions of Gujarat, India: A Prospective Study

Toxoplasma gondii is a protozoan parasite causing toxoplasmosis in humans, with lifelong presence in brain and muscular tissues [1, 2]. Disease is mostly asymptomatic with infection largely correlating with changes in human personality [3, 4]. T. gondii infection can be acquired from environment and during pregnancy when the parasite can be transmitted to the fetus through the placenta resulting in congenital toxoplasmosis. National and international studies including our previous community study have assessed Toxoplasma prevalence in pregnant women through molecular and serological methods [5-8]. Follow-up studies have explored severe or more apparent outcomes among children born to Toxoplasma-positive mothers, such as hearing-vision deficiencies including chorioretinitis [9, 10]. Longer pregnancy, slower fetal development, and slower post-natal gross-motor development have been associated with children born to Toxoplasma-positive mothers [11, 12]. However, similar profiling of development characteristics in a developing country like India is lacking. In addition, temperament characteristics among children born to Toxoplasma-positive mothers are unclear.

Therefore, the objective of this small-scale, exploratory study was to explore the association of maternal Toxoplasma positivity with child's gross-motor development and temperament through structured, well-established, parent-reported questionnaires. This is a nested investigation involving mothers from a previously completed prospective pregnancy cohort study [6].

There were no significant differences in the prevalence of any of the household-associated infection risk factors among the categories of children born to Toxoplasma-positive mothers (IgG+, PCR+IgG+, PCR−IgG+) and Toxoplasma-negative mothers (PCR−IgG−) (Supporting Information: Table S1). Comparing children born to Toxoplasma-positive and Toxoplasma-negative groups, there were no significant differences in bio-parameters such as age, low birth weight status, weight, and height (Table 1). Adjustment for confounders such as gender, low birth weight status, and age did not result in any significant association of mothers' Toxoplasma positivity with the child's weight or height.

In contrast to another study [12], gross motor skill development did not show significant differences between categories of children born to Toxoplasma-positive and Toxoplasma-negative mothers (Table 1). Ages of achieving indicated milestones are within the age cut-offs for normal development as per the Indian Academy of Pediatrics Guidelines [15], except for the median age of holding head which is delayed by a month from the cut-off in all the groups. None of the children had vision and hearing deficiencies.

IBQ-R-VS responses collected from infants (≤ 12 months old) revealed significantly higher levels of negative affect scores in infants born to PCR+IgG+ mothers compared to both infants born to PCR−IgG− mothers, p = 0.01 and infants born to PCR−IgG+ mothers, p = 0.02 (Table 2). No significant changes were observed in other temperament scales.

Our study has identified similar exposure to infection risk factors between the households of Toxoplasma-positive (PCR+IgG+, PCR−IgG+, and IgG+) and Toxoplasma-negative mothers (PCR−IgG−). Given this scenario, our study demonstrates that the higher negative affect scores are associated with infants born to PCR+IgG+ mothers, not with infants born to PCR−IgG+ mothers. Although the biological significance of these subsets is presently unknown, our study indicates the importance of performing both PCR and serological assays for better understanding of the relationship of maternal Toxoplasma positivity during pregnancy with a child's temperament characteristics. Large-scale studies are needed to confirm these findings. In addition, longitudinal studies are needed to assess the temperament of these children as they enter adolescence and adulthood.

High negative affectivity has been identified in children with attention-deficit/hyperactivity disorder (ADHD), a developmental and behavioral disorder [16, 17]. Interestingly, increased levels of severe form of ADHD were correlated with Toxoplasma seropositivity in children [18, 19]. Although we did not clinically evaluate ADHD in this study, future studies will need to explore the predisposition to development of ADHD in children demonstrating both high negative affectivity and Toxoplasma seropositivity to understand the role of Toxoplasma in regulating behavioral functions. Additionally, biological and environmental factors contribute to negative affectivity, including parenting behaviors, household chaos, and maternal emotion expressivity [20], which were not evaluated in the present study.

There was a lack of significant difference in children's bio-parameters between the groups. Although large-scale studies are needed to confirm, inherent similarities including food habits, malnutrition, and anemia [21] need to be considered.

In contrast to a Western study [12], our analysis did not show a significant difference in gross-motor skills such as the age at which the child learned to lift the head and move/turn around independently. It is possible that there are genetic and environmental factors that need to be considered [22]. A limitation of the study is that developmental features were not assessed comprehensively, for example, through questionnaires like “Ages and Stages” (ASQ), and Developmental Assessment Scale for Indian Infants (DASII) which have been established to detect developmental delay in Indian children [23].

There are other limitations in the study that children's Toxoplasma status could not be determined due to resource and logistical constraints, and could not be subsequently correlated with their temperament and corresponding mother's Toxoplasma status. Analyzing these aspects in future studies would provide more insight into the pathophysiological link between a mother's Toxoplasma status during pregnancy and subsequent child's behavior. Potential confounding factors such as parent's educational levels, family's emotional environment, and children's health factors were not evaluated. Another limitation is that the Cronbach's alpha values in the IBQ-R-VS questionnaire were not excellent in our study and future studies need to assess how the scale reliability in Gujarati-translated questionnaires could be further improved. It is possible that there are other cross-cultural nuances that need to be considered.

One of the strengths of this study is that this is a follow-up of a previously conducted large prospective study that assessed the prevalence of TORCH positivity among pregnant women. In the present study, as their children were being evaluated, mothers were enthusiastic in participating and forthcoming in their responses. Furthermore, the participating mothers were not aware of their Toxoplasma status, and therefore no inherent bias was involved while answering the questionnaires. Questionnaires were administered through a data collector belonging to the same study area who ensured that the parents understood the questions. In addition, infection risk factors were not significantly different between the Toxoplasma-positive and -negative mothers, allowing independent interpretation of the child's development and behavioral characteristics.

The study indicates the importance of combinatorial assessment of molecular and serological testing for understanding the implications of Toxoplasma positivity during pregnancy through association with the infant's temperament characteristics. Large-scale studies are needed to determine if the PCR+IgG+ category of maternal Toxoplasma status poses an early increased risk for children to develop altered behavior later in life. Such a questionnaire-based approach involving the parents could directly impact understanding of Toxoplasma infection among the tribal community where currently, there is a lack of awareness about the disease.

Aarthi Sundararajan: conceptualization, methodology, funding acquisition, project administration, writing–original draft, writing–review and editing, supervision, data curation. Kranti Vora: conceptualization, supervision, project administration, writing–review and editing, methodology. Shahin Saiyed: methodology, project administration, writing–review and editing, data curation. Senthilkumar Natesan: conceptualization, writing–review and editing, supervision. Vidhi Vaidya: writing–review and editing, methodology.

The corresponding authors Aarthi Sundararajan and Kranti Vora affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.

The study was approved by the Institutional Ethics Committee of the Indian Institute of Public Health Gandhinagar (approval code: 15/2020-21).

The authors declare no conflicts of interest.