A case-control study of the association of toxoplasmosis with antirheumatic therapy in rheumatoid arthritis

Background & Objective: Toxoplasmosis is a globally prevalent opportunistic zoonotic infection. Rheumatoid arthritis (RA) is an autoimmune disease which is manifested as joint inflammation, pain, stiffness, and swelling. The patients may contract toxoplasmosis, especially when receiving antirheumatic immunosuppressive therapy. However conflicting results have been reported on toxoplasmosis in RA patients. We aimed to evaluate Toxoplasma gondii positivity and associated risk factors in patients with RA in Duhok province, Iraq, and to assess the role of antirheumatic therapy in toxoplasmosis and the possibility of its reactivation. Methodology: This case-control study was carried out in Duhok, Kurdistan Region, Iraq, from February 2022 to June 2023. A total of 88 RA patients, with and without concurrent antirheumatic therapy, were recruited. The diagnosis of RA was according to the 2010 American College of Rheumatology/European League. RA-patients were categorized into three groups: Group 1 - no-therapy (n = 14); Group 2 - conventional therapy (n = 49) and Group 3 - biologics in combination with conventional medications (n = 25). Healthy subjects (n = 61) were also selected as controls. Plasma samples obtained from the participants were screened for T. gondii infection using Human anti-Toxoplasma gondii antibody IgG. IgG positive samples were tested utilizing human anti-Toxoplasma gondii antibody IgM ELISA Kit and the avidity T. gondii IgG ELISA kit was used to determine the state of infection. Results: Of the 88 RA patients, with or without antirheumatic therapy, 76 (86.36%) were females and 12 (13.64%) were males. Patients on therapy (n = 74) received several conventional antirheumatic drugs of which methotrexate was the most frequently used one (86.36%). Among biological therapies, etanercept, a TNF-alpha inhibitor, was mostly used (13.51%). The toxoplasmosis was significantly less in the older age group (> 50 y) compared to individuals under 30 y. Gender had no significant effect. Toxoplasma IgG positivity was found to be significantly higher in the three groups of RA patients in comparison with healthy controls. Further assessment of anti-Toxoplasma IgM positivity and Toxoplasma IgG avidity results to identify the state of T. gondii infection in anti-Toxoplasma IgG positive subjects revealed that the frequency of reactivation of toxoplasmosis in RA patient groups was not significantly different from that of the control counterparts. Conclusion: The study showed higher seroprevalence of anti-Toxoplasma antibodies in patients with RA irrespective of therapy; therefore, we could consider toxoplasmosis interaction with RA in the pathogenesis of both diseases. This seroprevalence was higher in younger age groups, but with no significant role of gender, duration of disease, duration of therapy and its type. No significant difference was noted in rates of reactivation of latent T. gondii infection among RA patients and healthy controls. Abbreviations: CI - Confidence interval; O - Odds ratio; RA - Rheumatoid arthritis; SD - Standard deviation; T. gondii - Toxoplasma gondii; TNF - Tumor necrosis factor. Keywords: Autoimmune disease; Rheumatoid arthritis; Antirheumatic drugs; Toxoplasma gondii; Toxoplasma seroprevalence; Toxoplasma IgG avidity. Citation: Abdullah RG, Eassa SH, Mohammad FK. A case-control study of the association of toxoplasmosis with antirheumatic therapy in rheumatoid arthritis. Anaesth, pain intensive care 2024;28(4):674−680; DOI: 10.35975/apic.v28i4.2510 Received: May 14, 2024; Reviewed: June 28, 2024; Accepted: June 28, 2024