Association between Toxocara Spp. Exposure and Schizophrenia: A Case-Control Study

Toxocariasis is a zoonotic disease caused by the larvae of Toxocara canis or Toxocara cati. Patients with schizophrenia may be at higher risk of infection, possibly due to their cognitive and personal self-care impairments. We aimed to assess the association between Toxocara spp. exposure and schizophrenia.

This case-control study was conducted on 109 patients with schizophrenia admitted to Ibn Sina Hospital, Shiraz, Iran, and 104 age- and gender-matched healthy controls from May to September 2021. A questionnaire was obtained and serum samples were tested for IgG antibodies to Toxocara excretory/secretory (TES) antigens using an enzyme-linked immunosorbent assay (ELISA).

Anti-Toxocara IgG was detected in 12 schizophrenic patients and 10 control subjects, giving respective seroprevalences of 11.0% (95% confidence interval [95% CI]=5.8-18.4%) and 9.6% (95% CI=4.7-17.0%). Univariate logistic analyses estimated an odds ratio (OR) of 1.16 (95% CI=0.44-3.16); however, it was not statistically significant (P=0.915). Individuals with a history of eating unwashed vegetables or fruits (23.1%, 95% CI=9.0-43.6, crude odds ratio [COR]=3.21, 95% CI=1.13-9.13) and rural residency (19.5%, 95% CI=8.8-34.9, COR=2.74, 95% CI=1.06-7.05) had significantly higher rates of seropositivity using the univariate logistic analyses. After multivariate logistic analyses, the differences were not statistically significant.

The toxocariasis seroprevalence among schizophrenic and healthy participants was not significantly different (11% vs. 9.6%). Since the disease severity, onset, and cognitive sequelae are not the same among schizophrenic patients, clinically matched studies with larger samples are required to address the current inconsistency between the studies.