Toxocariasis and Epilepsy: Systematic Review and Meta-Analysis

<div><h3>Objective</h3><p>Human toxocariasis is a zoonotic infection caused by the larval stages of <em>Toxocara canis</em> (<em>T. canis</em>) and less frequently <em>Toxocara cati (T. cati)</em>. A relationship between toxocariasis and epilepsy has been hypothesized. We conducted a systematic review and a meta-analysis of available data to evaluate the strength of association between epilepsy and <em>Toxocara</em> spp. seropositivity and to propose some guidelines for future surveys.</p> <h3>Data Sources</h3><p>Electronic databases, the database from the Institute of Neuroepidemiology and Tropical Neurology of the University of Limoges (<a href="http://www-ient.unilim.fr/">http://www-ient.unilim.fr/</a>) and the reference lists of all relevant papers and books were screened up to October 2011.</p> <h3>Methods</h3><p>We performed a systematic review of literature on toxocariasis (the exposure) and epilepsy (the outcome). Two authors independently assessed eligibility and study quality and extracted data. A common odds ratio (OR) was estimated using a random-effects meta-analysis model of aggregated published data.</p> <h3>Results</h3><p>Seven case-control studies met the inclusion criteria, for a total of 1867 participants (850 cases and 1017 controls). The percentage of seropositivity (presence of anti-<em>Toxocara</em> spp. antibodies) was higher among people with epilepsy (PWE) in all the included studies even if the association between epilepsy and <em>Toxocara</em> spp. seropositivity was statistically significant in only 4 studies, with crude ORs ranging 2.04–2.85. Another study bordered statistical significance, while in 2 of the included studies no significant association was found. A significant (p<0.001) common OR of 1.92 [95% confidence interval (CI) 1.50–2.44] was estimated. Similar results were found when meta-analysis was restricted to the studies considering an exclusively juvenile population and to surveys using Western Blot as confirmatory or diagnostic serological assay.</p> <h3>Conclusion</h3><p>Our results support the existence of a positive association between <em>Toxocara</em> spp. seropositivity and epilepsy. Further studies, possibly including incident cases, should be performed to better investigate the relationship between toxocariasis and epilepsy.</p>