A Rare Case of Congenitally Acquired Ocular Toxocariasis in A Five-Week-Old Infant.

PURPOSE: To report a case of strabismus in a five-week-old infant, likely secondary to a rare occurrence of congenitally acquired ocular toxocariasis. METHODS: Retrospective case report. RESULTS: A five-week-old male infant with left exotropia was referred to pediatric ophthalmology and to a vitreoretinal specialist. Fundoscopic examination revealed a granuloma with associated retinal folds and tractional retinal detachment typical for ocular toxocariasis. Serology revealed positivity for Toxocara antibodies, consistent with the clinical diagnosis of ocular toxocariasis. CONCLUSION: Ocular toxocariasis is typically thought to be secondary to acquired Toxocara infection secondary to fecal-oral transmission. In this case of early-onset strabismus secondary to ocular toxocariasis, it is hypothesized that this is a presentation of congenitally acquired toxocariasis.

A prospective seroepidemiological study of toxocariasis during early childhood in coastal Ecuador: potential for congenital transmission and risk factors for infection.

BACKGROUND: Although Toxocara spp. infection has a worldwide distribution, to our knowledge, no data from birth cohorts have been reported in published studies on the potential for congenital transmission and determinants of infection in early childhood. METHODS: We followed 290 mother-infant pairs from birth to 5 years of age through periodic collection of data and samples at birth, 7 and 13 months and 2, 3 and 5 years of age. Data on potential risk factors and confounders were collected by maternal questionnaire. Blood for plasma was collected from the mother at time of birth and periodically from the child for detection of anti-Toxocara spp. immunoglobulin G (IgG) antibodies using a Toxocara canis larval excretory-secretory antigen-based enzyme-linked immunosorbent assay. Stool samples were collected from the mother around the time of birth and periodically from the child for microscopic detection of soil-transmitted helminths (STH). Associations between potential risk factors and Toxocara spp. seroprevalence and seroconversion were estimated using multivariable logistic regression and generalized estimating equations. RESULTS: Toxocara spp. seroprevalence was 80.7% in mothers and in children was 0%, 9.3%, 48.4%, 64.9%, and 80.9% at 7 months, 13 months, 2, 3 and 5 years, respectively. Risk factors significantly associated with increases in seroprevalence over the first 5 years of life in multivariable analyses were age [Odds ratio (OR) 2.06, 95% confidence interval (CI) 1.39-2.27, P < 0001], male sex (female vs. male: OR 0.66, 95% CI 0.48-0.89, P = 0.006), maternal ethnicity (non-Afro vs. Afro-Ecuadorian: OR 0.65, 95% CI 0.47-0.91, P = 0.011), lower maternal educational and socioeconomic level, and childhood STH (OR 2.29, 95% CI 1.51-3.47, P < 0.001). Seroconversion rates for infection were greatest at 2 years of age (3.8%/month). Factors associated significantly with seroconversion at 2, 3 or 5 years were childhood STH infection, male sex, and more frequent domestic cat exposure. CONCLUSIONS: Our data, from an area of high Toxocara spp. endemicity, indicate no congenital transmission but high rates of seroconversion after 13 months of age reaching maternal levels of seroprevalence by 5 years of age. Factors associated with seroprevalence and seroconversion included STH infections, domestic cats, maternal ethnicity, male sex, STH infections, and markers of greater poverty.

Experimental congenital toxocariasis: effect on foetal future immune response.

Congenital parasitic infections may not lead to any overt clinical effects but could modulate the foetal future immune response to the same parasite depending on whether sensitization or tolerance has occurred in utero. In this study, pregnant female mice were infected with Toxocara canis eggs at different gestational age, then the offspring were next challenged with Toxocara eggs 6 weeks after birth and their immune response was assessed by estimation of the eosinophilic count and serum IgE concentration. The Total larval count (TLC), brain parasitism (BP) and reduction % in (TLC) were used as criteria for the course of infection. It was found that exposure to infection during pregnancy whether early or late led not only to transmission of larvae to the foetus but also to modulation of its immune response and course of infection when next encountered the parasite after birth. The offspring when compared to control from non-infected mothers were hyporesponsive when infection occurred early during pregnancy and they showed high immune responsiveness when infection was induced late in pregnancy. The potential clinical application of these findings was suggested. It is now an established fact that immunocompetence in the mammalian foetus including humans develops very early in utero. Therefore, the foetus is capable of showing some forms of activity against invasion by maternal pathogenic organisms or their antigens (Loke, 1978). Moreover, the early contact with parasitic antigens may affect the foetus future immune response when it next encounters similar organisms after birth. Palmer (1978) reported a rapid secondary immune response in the offspring of Plasmodium berghei infected female rats when challenged with the parasite and compared to control groups from non-infected mothers. An apposite response was reported by Hang et al. (1974) who noticed that massive infection of pregnant mice with Schistosoma mansoni cercariae resulted in offspring hyporesponsive to subsequent challenge assessed by the diameter of the egg granulomas. Considering that toxocariasis is a frequent and potentially serious disease affecting primarily young children, also congenital toxocariasis was well documented since the original studies of Fulleborn (1921), this study was designed to reveal the extent to which the foetus future immune response can be modulated by maternal toxocariasis in experimental animals. The estimation of the immune response included IgE level (antibody mediated mechanism) and the absolute eosinophils count (a manifestation of cell mediated immune response) since eosinophil/IgE/mast cell axis represents a specialized immune mechanism that may contribute directly to parasite damage in toxocariasis (Knight, 1982). Also, (TLC), (B.P) and reduction % in (TLC) were used as criteria for the course of infection.