In 2015, the FMJ researchers initiated the Jundiaí Zika cohort (JZC) as a response to the cases of microcephaly and neurological disorders reported in the regions affected by ZIKV in Brazil. The JZC was a comprehensive longitudinal study that monitored pregnant women and their children over time to investigate the consequences of ZIKV exposure.14
A study conducted by JZC focused on pregnant women and their children up to three years of age. The study found that three children had microcephaly due to ZIKV, nine children had developmental delay, three children had mild cognitive delay, three children had speech delay, two children had autism spectrum disorder, and three children had sensorineural hearing loss.15 A study involving 462 newborns in the same cohort revealed that microcephaly prevalence was 4.1%, and ZIKV contamination was not the primary cause.16 Due to the high-risk factor of pregnancy and the vulnerability of families, this study is a continuation of previous work done by JZC investigators.
There is still a limited understanding of the motor development of children above two years of age who were infected with ZIKV during pregnancy. Additionally, there is even less knowledge about those who were infected but did not develop microcephaly or CZS.
This study has shown that children born prematurely had worse scores in the ‘’Manual Dexterity’’ domain, which is a statistically significant result. This finding supports previous research that has found an association between prematurity and poor motor development. Children born prematurely are more at risk of experiencing delays in motor development.17
Low birth weight is a well-known factor in delaying motor development, as recognized by the scientific community.18 The small sample size precluded drawing firm conclusions, but most SGA children consistently remained in the Yellow/Red zone across all components.
There is a statistically significant relationship between maternal age and the manual dexterity score. Surprisingly, children of mothers under 25 scored higher in manual dexterity tests than children of mothers aged 25 or older at the time of birth. This finding contradicts existing studies and highlights the need for further research on this topic.19,20
The results of this research indicate that, overall, children who were exposed to ZIKV had good scores in gross and fine motor skills. This was observed both in the original classification of the MABC-2 assessment instrument and when compared to previous studies conducted in Brazil. Additionally, the exposed children had similar motor skills scores to unexposed children of the same age and region.11,21
According to a study conducted by Hulteen et al.22, the MABC-2 assessment tool is extensively used in various countries. The study also found that many other research works have demonstrated the tool's validity, consistency, and reliability, all classified as "Adequate" to "Very good". Based on these findings, it can be confidently concluded that the MABC-2 is a dependable and valid instrument for evaluating movement difficulties in preschool children.23
The MABC-2, in its second version, is a reliable method for measuring motor performance in children aged three and four. Studies conducted across various countries have demonstrated that most children in this age group can successfully complete the MABC-2 tasks as per the guidelines. Almost 90% of these children are enthusiastic and capable of completing more than 50% of the tasks.25
A version of the MABC-2 test was created and tested for reliability and validity in Brazilian Portuguese. The results showed that the test is accurate and valid for Brazilian children. However, the researchers suggest that the cultural and developmental differences among Brazilian regions should be considered when using the test.21
The average TSS of children aged 44 to 80 months exposed to ZIKV in the urban conglomerate of Jundiaí was consistent with the average TSS of the translation, reliability, and validation study for Brazilian children.21
The results obtained from this research were consistent with the findings of other studies that evaluated the motor development of children exposed to ZIKV. A previous study by Souza et al.25, also from the JZC, showed no significant differences in neurological assessment between children exposed to ZIKV and those not up to 24 months.
Blackmon et al.26 and Díaz-Martínez et al.27 conducted studies that revealed that children without microcephaly who were exposed to ZIKV and were up to 24 months of age did not exhibit any delays in neurodevelopment. Similarly, Sobral da Silva et al.28 showed that their children did not have a significant risk of neurological development impairment up to 42 months.
Some studies have found divergences in children without microcephaly who were exposed to ZIKV, including a high risk of visual impairment, a higher frequency of cognitive delay, and a language deficit.26,27,29 According to this research, most children did not experience any delays or disorders, with only isolated cases in both groups. Additionally, there were no indications of visual or language changes in children who were exposed to ZIKV. However, further studies are required to investigate any possible impairments that congenital ZIKV infection may cause, especially in children exposed to the virus but did not develop CZS.
Souza et al.25 found that children exposed to ZIKV had worse dorsiflexion scores up to 12 months post-exposure. In this study, there was no individual assessment of this disorder, but it did not appear to affect the performance of dynamic balance tasks such as "Walking Heels Raised" and "Jumping on Mats"
Not all children exposed to ZIKV suffer from brain damage or impaired neurological development, as several studies have shown. However, it is necessary to continuously monitor these children as they are still in preschool, as Sobral da Silva et al. point out. A systematic review and meta-analysis by Marban-Castro et al.29 concluded that congenital ZIKV infection is a risk factor for neurodevelopmental delay in children without microcephaly. As these children grow older, it is crucial to conduct more studies to determine the presence of developmental delays.29
It is unclear whether children with certain disorders will continue to be affected by them as they grow, or if these disorders will disappear over time. As a result of the Zika virus outbreak in Brazil, researchers had the opportunity to evaluate the motor development of children who had just started preschool.
The MABC-2 assessment takes into account non-motor factors that may affect movement. Among these, anxiety, impulsivity, distraction, and hyperactivity were the most common behaviors observed in the children in this study. The presence of these behaviors in preschool children highlights the need for monitoring by a multidisciplinary team and the importance of studying these behaviors in affected children.