Ultrastructural morphology of second and third-stage larvae of Toxocara cati inside paratenic host tissue

Background: Toxocara cati is a known cause of a zoonotic infectious illness called toxocariasis. Parathenic hosts are important as they can transmit larvae 2 (L₂) through direct transmission. Scanning electron microscope (SEM) techniques are needed to provide a three-dimensional image of each stage of T. cati larvae. Aim: The aim of this study was to determine the morphology of L₂ and L₃ T. cati in parathenic host tissue for etiological diagnosis using SEM. Methods: Mice were used as suitable paratenic hosts for this experiment. A total of 786 embryonated eggs (16 eggs/ gram body weight) containing L₂ were inoculated into pregnant mice at day 11–13 of its gestation period. After delivery, L₂ was transmitted to the off-spring. After 14 days, L₂ was collected from mice, and L₃ was collected from its off-spring. Data were analyzed descriptively based on ultrastructure examination using SEM. Results: SEM examination results indicate that the size of L₂ is smaller than L₃. Results also showed differences between L₂ and L₃ based on middle and posterior observations. In the middle of the larval body, the number of L₂ body rings was observed to be narrower and more than that of L₃. In addition, the distance between L₂ body rings was much larger than that of L₃. Posteriorly, the tail tip of L₃ was more curved than L₂. Conclusion: Ultrastructural examination using SEM has the ability to show differences in L₂ and L₃ body rings of T. cati by observing the middle and posterior parts of its larvae.