The Potential Association Between Latent Toxoplasma gondii Infection and Opioid Abuse: A Registry-Based Sero-Molecular Case–Control Study

Abstract

Toxoplasma gondii is a ubiquitous parasitic protozoan that can cause neurological and psychiatric disorders, potentially impacting human emotional behavior. This study aimed to explore serological and molecular evidence of T. gondii infection in opioid abusers in northern Iran. In this case–control study, opioid abusers who were referred to substance abuse rehabilitation centers in Mazandaran Province, northern Iran, were enrolled. Blood samples were collected from the participants to perform a serological assay to detect T. gondii IgG and IgM antibodies. A polymerase chain reaction (PCR) test was also conducted on buffy coats of the blood samples. The study comprised a total of 474 participants, with 239 individuals being opioid abusers and 235 healthy individuals serving as the control group. The results indicated that 163 opioid abusers (68.2%) were positive for T. gondii IgG, whereas 76 (31.8%) were negative. Among the control group, 63 individuals (26.8%) tested positive for T. gondii IgG, whereas 172 (73.2%) tested negative. This difference was statistically significant according to p = 0.01, odds ratio (OR) = 2.67, and 95% confidence interval (CI) = 1.03–4.15. In addition, 7.1% (17/239) of the case and 2.1% (5/235) of the control groups were PCR positive for Toxoplasma DNA. This difference was statistically significant (p = 0.01; OR = 2.96; 95%; CI = 0.94–7.01). In contrast, all of the participants were negative for T. gondii IgM antibodies. Our findings demonstrated that the sero-molecular prevalence of latent T. gondii infection in opioid abusers is significantly higher than that in healthy individuals. This suggests a potential correlation between T. gondii IgG antibody positivity and PCR results with opioid abuse.